fbpx
Wikipedia

Cephalopod

January 31, 2023

A cephalopod /ˈsɛfələpɒd/ is any member of the molluscan class Cephalopoda /sɛfəˈlɒpədə/ (Greek plural κεφαλόποδες, kephalópodes; "head-feet")[3] such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

Cephalophoda
Temporal range: Late Cambrian – present;[1] possible Early Cambrian presence[2]
Extant and extinct cephalopods; clockwise from top-left: common octopus (Octopus vulgaris), Caribbean reef squid (Sepioteuthis sepioidea), chambered nautilus (Nautilus pompilius), Orthosphynctes, Clarkeiteuthis conocauda, and common cuttlefish (Sepia officinalis)
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Subphylum: Conchifera
Class: Cephalopoda
Cuvier, 1797
Subclasses

Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. Two important extinct taxa are the Ammonoidea (ammonites) and Belemnoidea (belemnites). Extant cephalopods range in size from the 10 mm (0.3 in) Idiosepius thailandicus to the 14 m (45.1 ft) colossal squid, the largest extant invertebrate.

Distribution

 
 
Left: A pair of cuttlefish (Sepia officinalis) in shallow water
Right: An octopus (Benthoctopus sp.) on the Davidson Seamount at 2,422 m depth

There are over 800 extant species of cephalopod,[4] although new species continue to be described. An estimated 11,000 extinct taxa have been described, although the soft-bodied nature of cephalopods means they are not easily fossilised.[5]

Cephalopods are found in all the oceans of Earth. None of them can tolerate fresh water, but the brief squid, Lolliguncula brevis, found in Chesapeake Bay, is a notable partial exception in that it tolerates brackish water.[6] Cephalopods are thought to be unable to live in fresh water due to multiple biochemical constraints, and in their >400 million year existence have never ventured into fully freshwater habitats.[7]

Cephalopods occupy most of the depth of the ocean, from the abyssal plain to the sea surface. Their diversity is greatest near the equator (~40 species retrieved in nets at 11°N by a diversity study) and decreases towards the poles (~5 species captured at 60°N).[8]

Biology

Nervous system and behavior

See also: Cephalopod intelligence, squid giant axon, squid giant synapse, and cephalopod aggression
 
 
Left: An octopus opening a container with a screw cap
Right: Hawaiian bobtail squid, Euprymna scolopes, burying itself in the sand, leaving only the eyes exposed

Cephalopods are widely regarded as the most intelligent of the invertebrates, and have well developed senses and large brains (larger than those of gastropods).[9] The nervous system of cephalopods is the most complex of the invertebrates[10][11] and their brain-to-body-mass ratio falls between that of endothermic and ectothermic vertebrates.[8]: 14  Captive cephalopods have also been known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on the crabs, and return to their own aquarium.[12]

The brain is protected in a cartilaginous cranium. The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology; their large diameter (due to lack of myelination) makes them relatively easy to study compared with other animals.[13]

Many cephalopods are social creatures; when isolated from their own kind, some species have been observed shoaling with fish.[14]

Some cephalopods are able to fly through the air for distances of up to 50 m. While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion; water continues to be expelled from the funnel while the organism is in the air.[15] The animals spread their fins and tentacles to form wings and actively control lift force with body posture.[16] One species, Todarodes pacificus, has been observed spreading tentacles in a flat fan shape with a mucus film between the individual tentacles[16][17] while another, Sepioteuthis sepioidea, has been observed putting the tentacles in a circular arrangement.[18]

Senses

Cephalopods have advanced vision, can detect gravity with statocysts, and have a variety of chemical sense organs.[8]: 34  Octopuses use their arms to explore their environment and can use them for depth perception.[8]

Vision

Main articles: Cephalopod eye and mollusc eye
 
The primitive nautilus eye functions similarly to a pinhole camera.
The W-shaped pupil of the cuttlefish expanding when the lights are turned off

Most cephalopods rely on vision to detect predators and prey, and to communicate with one another.[19] Consequently, cephalopod vision is acute: training experiments have shown that the common octopus can distinguish the brightness, size, shape, and horizontal or vertical orientation of objects. The morphological construction gives cephalopod eyes the same performance as shark eyes, however their construction differs, as cephalopods lack a cornea and have an everted retina.[19] Cephalopods' eyes are also sensitive to the plane of polarization of light.[20] Unlike many other cephalopods, nautiluses do not have good vision; their eye structure is highly developed, but lacks a solid lens. They have a simple "pinhole" eye through which water can pass. Instead of vision, the animal is thought to use olfaction as the primary sense for foraging, as well as locating or identifying potential mates.

 
A cuttlefish with W-shaped pupils which may help them discriminate colors

Surprisingly, given their ability to change color, all octopuses[21] and most cephalopods[22][23] are considered to be color blind. Coleoid cephalopods (octopus, squid, cuttlefish) have a single photoreceptor type and lack the ability to determine color by comparing detected photon intensity across multiple spectral channels. When camouflaging themselves, they use their chromatophores to change brightness and pattern according to the background they see, but their ability to match the specific color of a background may come from cells such as iridophores and leucophores that reflect light from the environment.[24] They also produce visual pigments throughout their body, and may sense light levels directly from their body.[25] Evidence of color vision has been found in the sparkling enope squid (Watasenia scintillans).[22][26] It achieves color vision with three photoreceptors, which are based on the same opsin, but use distinct retinal molecules as chromophores: A1 (retinal), A3 (3-dehydroretinal), and A4 (4-hydroxyretinal). The A1-photoreceptor is most sensitive to green-blue (484 nm), the A2-photoreceptor to blue-green (500 nm), and the A4-photoreceptor to blue (470 nm) light.[27]

In 2015, a novel mechanism for spectral discrimination in cephalopods was described. This relies on the exploitation of chromatic aberration (wavelength-dependence of focal length). Numerical modeling shows that chromatic aberration can yield useful chromatic information through the dependence of image acuity on accommodation. The unusual off-axis slit and annular pupil shapes in cephalopods enhance this ability by acting as prisms which are scattering white light in all directions.[28][29]

Photoreception

In 2015, molecular evidence was published indicating that cephalopod chromatophores are photosensitive; reverse transcription polymerase chain reactions (RT-PCR) revealed transcripts encoding rhodopsin and retinochrome within the retinas and skin of the longfin inshore squid (Doryteuthis pealeii), and the common cuttlefish (Sepia officinalis) and broadclub cuttlefish (Sepia latimanus). The authors claim this is the first evidence that cephalopod dermal tissues may possess the required combination of molecules to respond to light.[30]

Hearing

Some squids have been shown to detect sound using their statocysts,[31] but, in general, cephalopods are deaf.

Use of light

 
This broadclub cuttlefish (Sepia latimanus) can change from camouflage tans and browns (top) to yellow with dark highlights (bottom) in less than a second.
Further information: Counter-illumination

Most cephalopods possess an assemblage of skin components that interact with light. These may include iridophores, leucophores, chromatophores and (in some species) photophores. Chromatophores are colored pigment cells that expand and contract in accordance to produce color and pattern which they can use in a startling array of fashions.[8][30] As well as providing camouflage with their background, some cephalopods bioluminesce, shining light downwards to disguise their shadows from any predators that may lurk below.[8] The bioluminescence is produced by bacterial symbionts; the host cephalopod is able to detect the light produced by these organisms.[32] Bioluminescence may also be used to entice prey, and some species use colorful displays to impress mates, startle predators, or even communicate with one another.[8]

Coloration

Further information: Animal coloration and Animals that can change color

Cephalopods can change their colors and patterns in milliseconds, whether for signalling (both within the species and for warning) or active camouflage,[8] as their chromatophores are expanded or contracted.[33] Although color changes appear to rely primarily on vision input, there is evidence that skin cells, specifically chromatophores, can detect light and adjust to light conditions independently of the eyes.[34] The octopus changes skin color and texture during quiet and active sleep cycles.[35]

Cephalopods can use chromatophores like a muscle, which is why they can change their skin hue as rapidly as they do. Coloration is typically stronger in near-shore species than those living in the open ocean, whose functions tend to be restricted to disruptive camouflage.[8]: 2  These chromatophores are found throughout the body of the octopus, however, they are controlled by the same part of the brain that controls elongation during jet propulsion to reduce drag. As such, jetting octopuses can turn pale because the brain is unable to achieve both controlling elongation and controlling the chromatophores.[36] Most octopuses mimic select structures in their field of view rather than becoming a composite color of their full background.[37]

Evidence of original coloration has been detected in cephalopod fossils dating as far back as the Silurian; these orthoconic individuals bore concentric stripes, which are thought to have served as camouflage.[38] Devonian cephalopods bear more complex color patterns, of unknown function.[39]

Ink

Main articles: Cephalopod ink and ink sac

With the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina,[40] all known cephalopods have an ink sac, which can be used to expel a cloud of dark ink to confuse predators.[21] This sac is a muscular bag which originated as an extension of the hindgut. It lies beneath the gut and opens into the anus, into which its contents – almost pure melanin – can be squirted; its proximity to the base of the funnel means the ink can be distributed by ejected water as the cephalopod uses its jet propulsion.[21] The ejected cloud of melanin is usually mixed, upon expulsion, with mucus, produced elsewhere in the mantle, and therefore forms a thick cloud, resulting in visual (and possibly chemosensory) impairment of the predator, like a smokescreen. However, a more sophisticated behavior has been observed, in which the cephalopod releases a cloud, with a greater mucus content, that approximately resembles the cephalopod that released it (this decoy is referred to as a pseudomorph). This strategy often results in the predator attacking the pseudomorph, rather than its rapidly departing prey.[21] For more information, see Inking behaviors.

The ink sac of cephalopods has led to a common name of "inkfish",[41] formerly the pen-and-ink fish.[42]

 
Viscera of Chtenopteryx sicula
 
Viscera of Ocythoe tuberculata

Circulatory system

Cephalopods are the only molluscs with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts) that move blood through the capillaries of the gills. A single systemic heart then pumps the oxygenated blood through the rest of the body.[43]

Like most molluscs, cephalopods use hemocyanin, a copper-containing protein, rather than hemoglobin, to transport oxygen. As a result, their blood is colorless when deoxygenated and turns blue when bonded to oxygen.[44] In oxygen-rich environments and in acidic water, hemoglobin is more efficient, but in environments with little oxygen and in low temperatures, hemocyanin has the upper hand.[45][46][47] The hemocyanin molecule is much larger than the hemoglobin molecule, allowing it to bond with 96 O2 or CO2 molecules, instead of the hemoglobin's just four. But unlike hemoglobin, which are attached in millions on the surface of a single red blood cell, hemocyanin molecules float freely in the bloodstream.[48]

Respiration

Cephalopods exchange gases with the seawater by forcing water through their gills, which are attached to the roof of the organism.[49]: 488 [50] Water enters the mantle cavity on the outside of the gills, and the entrance of the mantle cavity closes. When the mantle contracts, water is forced through the gills, which lie between the mantle cavity and the funnel. The water's expulsion through the funnel can be used to power jet propulsion. If respiration is used concurrently with jet propulsion, large losses in speed or oxygen generation can be expected.[51][52] The gills, which are much more efficient than those of other mollusks, are attached to the ventral surface of the mantle cavity.[50] There is a trade-off with gill size regarding lifestyle. To achieve fast speeds, gills need to be small – water will be passed through them quickly when energy is needed, compensating for their small size. However, organisms which spend most of their time moving slowly along the bottom do not naturally pass much water through their cavity for locomotion; thus they have larger gills, along with complex systems to ensure that water is constantly washing through their gills, even when the organism is stationary.[49] The water flow is controlled by contractions of the radial and circular mantle cavity muscles.[53]

The gills of cephalopods are supported by a skeleton of robust fibrous proteins; the lack of mucopolysaccharides distinguishes this matrix from cartilage.[54][55] The gills are also thought to be involved in excretion, with NH4+ being swapped with K+ from the seawater.[50]

Locomotion and buoyancy

 
Octopuses swim headfirst, with arms trailing behind

While most cephalopods can move by jet propulsion, this is a very energy-consuming way to travel compared to the tail propulsion used by fish.[56] The efficiency of a propeller-driven waterjet (i.e. Froude efficiency) is greater than a rocket.[57] The relative efficiency of jet propulsion decreases further as animal size increases; paralarvae are far more efficient than juvenile and adult individuals.[58] Since the Paleozoic era, as competition with fish produced an environment where efficient motion was crucial to survival, jet propulsion has taken a back role, with fins and tentacles used to maintain a steady velocity.[5] Whilst jet propulsion is never the sole mode of locomotion,[5]: 208  the stop-start motion provided by the jets continues to be useful for providing bursts of high speed – not least when capturing prey or avoiding predators.[5] Indeed, it makes cephalopods the fastest marine invertebrates,[8]: Preface  and they can out-accelerate most fish.[49] The jet is supplemented with fin motion; in the squid, the fins flap each time that a jet is released, amplifying the thrust; they are then extended between jets (presumably to avoid sinking).[58] Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the hyponome, created by a fold in the mantle. The size difference between the posterior and anterior ends of this organ control the speed of the jet the organism can produce.[59] The velocity of the organism can be accurately predicted for a given mass and morphology of animal.[60] Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions.[61] Some cephalopods accompany this expulsion of water with a gunshot-like popping noise, thought to function to frighten away potential predators.[62]

Cephalopods employ a similar method of propulsion despite their increasing size (as they grow) changing the dynamics of the water in which they find themselves. Thus their paralarvae do not extensively use their fins (which are less efficient at low Reynolds numbers) and primarily use their jets to propel themselves upwards, whereas large adult cephalopods tend to swim less efficiently and with more reliance on their fins.[58]

 
Nautilus belauensis seen from the front, showing the opening of the hyponome

Early cephalopods are thought to have produced jets by drawing their body into their shells, as Nautilus does today.[63] Nautilus is also capable of creating a jet by undulations of its funnel; this slower flow of water is more suited to the extraction of oxygen from the water.[63] When motionless, Nautilus can only extract 20% of oxygen from the water.[51] The jet velocity in Nautilus is much slower than in coleoids, but less musculature and energy is involved in its production.[64] Jet thrust in cephalopods is controlled primarily by the maximum diameter of the funnel orifice (or, perhaps, the average diameter of the funnel)[65]: 440  and the diameter of the mantle cavity.[66] Changes in the size of the orifice are used most at intermediate velocities.[65] The absolute velocity achieved is limited by the cephalopod's requirement to inhale water for expulsion; this intake limits the maximum velocity to eight body-lengths per second, a speed which most cephalopods can attain after two funnel-blows.[65] Water refills the cavity by entering not only through the orifices, but also through the funnel.[65] Squid can expel up to 94% of the fluid within their cavity in a single jet thrust.[57] To accommodate the rapid changes in water intake and expulsion, the orifices are highly flexible and can change their size by a factor of twenty; the funnel radius, conversely, changes only by a factor of around 1.5.[65]

Some octopus species are also able to walk along the seabed. Squids and cuttlefish can move short distances in any direction by rippling of a flap of muscle around the mantle.

While most cephalopods float (i.e. are neutrally buoyant or nearly so; in fact most cephalopods are about 2–3% denser than seawater[14]), they achieve this in different ways.[56] Some, such as Nautilus, allow gas to diffuse into the gap between the mantle and the shell; others allow purer water to ooze from their kidneys, forcing out denser salt water from the body cavity;[56] others, like some fish, accumulate oils in the liver;[56] and some octopuses have a gelatinous body with lighter chloride ions replacing sulfate in the body chemistry.[56]

Squids are the primary sufferers of negative buoyancy in cephalopods. The negative buoyancy means that some squids, especially those whose habitat depths are rather shallow, have to actively regulate their vertical positions. This means that they must expend energy, often through jetting or undulations, in order to maintain the same depth. As such, the cost of transport of many squids are quite high. That being said, squid and other cephalopod that dwell in deep waters tend to be more neutrally buoyant which removes the need to regulate depth and increases their locomotory efficiency.[67][51]

The Macrotritopus defilippi, or the sand-dwelling octopus, was seen mimicking both the coloration and the swimming movements of the sand-dwelling flounder Bothus lunatus to avoid predators. The octopuses were able to flatten their bodies and put their arms back to appear the same as the flounders as well as move with the same speed and movements.[68]

Females of two species, Ocythoe tuberculata and Haliphron atlanticus, have evolved a true swim bladder.[69]

Octopus vs. squid locomotion

Two of the categories of cephalopods, octopus and squid, are vastly different in their movements despite being of the same class. Octopuses are generally not seen as active swimmers; they are often found scavenging the sea floor instead of swimming long distances through the water. Squids, on the other hand, can be found to travel vast distances, with some moving as much as 2000 km in 2.5 months at an average pace of 0.9 body lengths per second.[70] There is a major reason for the difference in movement type and efficiency: anatomy.

Both octopuses and squids have mantles (referenced above) which function towards respiration and locomotion in the form of jetting. The composition of these mantles differs between the two families, however. In octopuses, the mantle is made up of three muscle types: longitudinal, radial, and circular. The longitudinal muscles run parallel to the length of the octopus and they are used in order to keep the mantle the same length throughout the jetting process. Given that they are muscles, it can be noted that this means the octopus must actively flex the longitudinal muscles during jetting in order to keep the mantle at a constant length. The radial muscles run perpendicular to the longitudinal muscles and are used to thicken and thin the wall of the mantle. Finally, the circular muscles are used as the main activators in jetting. They are muscle bands that surround the mantle and expand/contract the cavity. All three muscle types work in unison to produce a jet as a propulsion mechanism.[70]

Squids do not have the longitudinal muscles that octopus do. Instead, they have a tunic.[70] This tunic is made of layers of collagen and it surrounds the top and the bottom of the mantle. Because they are made of collagen and not muscle, the tunics are rigid bodies that are much stronger than the muscle counterparts. This provides the squids some advantages for jet propulsion swimming. The stiffness means that there is no necessary muscle flexing to keep the mantle the same size. In addition, tunics take up only 1% of the squid mantle's wall thickness, whereas the longitudinal muscle fibers take up to 20% of the mantle wall thickness in octopuses.[70] Also because of the rigidity of the tunic, the radial muscles in squid can contract more forcefully.

The mantle is not the only place where squids have collagen. Collagen fibers are located throughout the other muscle fibers in the mantle. These collagen fibers act as elastics and are sometimes named "collagen springs".[70] As the name implies, these fibers act as springs. When the radial and circular muscles in the mantle contract, they reach a point where the contraction is no longer efficient to the forward motion of the creature. In such cases, the excess contraction is stored in the collagen which then efficiently begins or aids in the expansion of the mantle at the end of the jet. In some tests, the collagen has been shown to be able to begin raising mantle pressure up to 50ms before muscle activity is initiated.[70]

These anatomical differences between squid and octopuses can help explain why squid can be found swimming comparably to fish while octopuses usually rely on other forms of locomotion on the sea floor such as bipedal walking, crawling, and non-jetting swimming.[71]

Shell

See also: Cirrate shell, Cuttlebone, Gladius (cephalopod), and Mollusc shell
 
Cross section of Spirula spirula, showing the position of the shell inside the mantle
 
Cuttlebone of Sepia officinalis
 
Gladius of Sepioteuthis lessoniana

Nautiluses are the only extant cephalopods with a true external shell. However, all molluscan shells are formed from the ectoderm (outer layer of the embryo); in cuttlefish (Sepia spp.), for example, an invagination of the ectoderm forms during the embryonic period, resulting in a shell (cuttlebone) that is internal in the adult.[72] The same is true of the chitinous gladius of squid[72] and octopuses.[73] Cirrate octopods have arch-shaped cartilaginous fin supports,[74] which are sometimes referred to as a "shell vestige" or "gladius".[75] The Incirrina have either a pair of rod-shaped stylets or no vestige of an internal shell,[76] and some squid also lack a gladius.[77] The shelled coleoids do not form a clade or even a paraphyletic group.[78] The Spirula shell begins as an organic structure, and is then very rapidly mineralized.[79] Shells that are "lost" may be lost by resorption of the calcium carbonate component.[80]

Females of the octopus genus Argonauta secrete a specialized paper-thin egg case in which they reside, and this is popularly regarded as a "shell", although it is not attached to the body of the animal and has a separate evolutionary origin.

The largest group of shelled cephalopods, the ammonites, are extinct, but their shells are very common as fossils.

The deposition of carbonate, leading to a mineralized shell, appears to be related to the acidity of the organic shell matrix (see Mollusc shell); shell-forming cephalopods have an acidic matrix, whereas the gladius of squid has a basic matrix.[81] The basic arrangement of the cephalopod outer wall is: an outer (spherulitic) prismatic layer, a laminar (nacreous) layer and an inner prismatic layer. The thickness of every layer depends on the taxa.[82] In modern cephalopods, the Ca carbonate is aragonite. As for other mollusc shells or coral skeletons, the smallest visible units are irregular rounded granules.[83]

 
 
Left: A giant squid found in Logy Bay, Newfoundland, in 1873. The two long feeding tentacles are visible on the extreme left and right.
Right: Detail of the tentacular club of Abraliopsis morisi

Head appendages

Main articles: Cephalopod limb and tentacle

Cephalopods, as the name implies, have muscular appendages extending from their heads and surrounding their mouths. These are used in feeding, mobility, and even reproduction. In coleoids they number eight or ten. Decapods such as cuttlefish and squid have five pairs. The longer two, termed tentacles, are actively involved in capturing prey;[1]: 225  they can lengthen rapidly (in as little as 15 milliseconds[1]: 225 ). In giant squid they may reach a length of 8 metres. They may terminate in a broadened, sucker-coated club.[1]: 225  The shorter four pairs are termed arms, and are involved in holding and manipulating the captured organism.[1]: 225  They too have suckers, on the side closest to the mouth; these help to hold onto the prey.[1]: 226  Octopods only have four pairs of sucker-coated arms, as the name suggests, though developmental abnormalities can modify the number of arms expressed.[84]

The tentacle consists of a thick central nerve cord (which must be thick to allow each sucker to be controlled independently)[85] surrounded by circular and radial muscles. Because the volume of the tentacle remains constant, contracting the circular muscles decreases the radius and permits the rapid increase in length. Typically a 70% lengthening is achieved by decreasing the width by 23%.[1]: 227  The shorter arms lack this capability.

The size of the tentacle is related to the size of the buccal cavity; larger, stronger tentacles can hold prey as small bites are taken from it; with more numerous, smaller tentacles, prey is swallowed whole, so the mouth cavity must be larger.[86]

Externally shelled nautilids (Nautilus and Allonautilus) have on the order of 90 finger-like appendages, termed tentacles, which lack suckers but are sticky instead, and are partly retractable.

Feeding

 
The two-part beak of the giant squid, Architeuthis sp.

All living cephalopods have a two-part beak;[8]: 7  most have a radula, although it is reduced in most octopus and absent altogether in Spirula.[8]: 7 [87]: 110  They feed by capturing prey with their tentacles, drawing it into their mouth and taking bites from it.[21] They have a mixture of toxic digestive juices, some of which are manufactured by symbiotic algae, which they eject from their salivary glands onto their captured prey held in their mouths. These juices separate the flesh of their prey from the bone or shell.[21] The salivary gland has a small tooth at its end which can be poked into an organism to digest it from within.[21]

The digestive gland itself is rather short.[21] It has four elements, with food passing through the crop, stomach and caecum before entering the intestine. Most digestion, as well as the absorption of nutrients, occurs in the digestive gland, sometimes called the liver. Nutrients and waste materials are exchanged between the gut and the digestive gland through a pair of connections linking the gland to the junction of the stomach and caecum.[21] Cells in the digestive gland directly release pigmented excretory chemicals into the lumen of the gut, which are then bound with mucus passed through the anus as long dark strings, ejected with the aid of exhaled water from the funnel.[21] Cephalopods tend to concentrate ingested heavy metals in their body tissue.[88] However, octopus arms use a family of cephalopod-specific chemotactile receptors (CRs) to be their "taste by touch" system.[89]

Radula

See also: Radula § In cephalopods
 
Amphioctopus marginatus eating a crab

The cephalopod radula consists of multiple symmetrical rows of up to nine teeth[90] – thirteen in fossil classes.[91] The organ is reduced or even vestigial in certain octopus species and is absent in Spirula.[91] The teeth may be homodont (i.e. similar in form across a row), heterodont (otherwise), or ctenodont (comb-like).[91] Their height, width and number of cusps is variable between species.[91] The pattern of teeth repeats, but each row may not be identical to the last; in the octopus, for instance, the sequence repeats every five rows.[91]: 79 

Cephalopod radulae are known from fossil deposits dating back to the Ordovician.[92] They are usually preserved within the cephalopod's body chamber, commonly in conjunction with the mandibles; but this need not always be the case;[93] many radulae are preserved in a range of settings in the Mason Creek.[94] Radulae are usually difficult to detect, even when they are preserved in fossils, as the rock must weather and crack in exactly the right fashion to expose them; for instance, radulae have only been found in nine of the 43 ammonite genera,[95][clarification needed] and they are rarer still in non-ammonoid forms: only three pre-Mesozoic species possess one.[92]

Excretory system

Most cephalopods possess a single pair of large nephridia. Filtered nitrogenous waste is produced in the pericardial cavity of the branchial hearts, each of which is connected to a nephridium by a narrow canal. The canal delivers the excreta to a bladder-like renal sac, and also resorbs excess water from the filtrate. Several outgrowths of the lateral vena cava project into the renal sac, continuously inflating and deflating as the branchial hearts beat. This action helps to pump the secreted waste into the sacs, to be released into the mantle cavity through a pore.[96]

Nautilus, unusually, possesses four nephridia, none of which are connected to the pericardial cavities.

The incorporation of ammonia is important for shell formation in terrestrial molluscs and other non-molluscan lineages.[97] Because protein (i.e. flesh) is a major constituent of the cephalopod diet, large amounts of ammonium ions are produced as waste. The main organs involved with the release of this excess ammonium are the gills.[98] The rate of release is lowest in the shelled cephalopods Nautilus and Sepia as a result of their using nitrogen to fill their shells with gas to increase buoyancy.[98] Other cephalopods use ammonium in a similar way, storing the ions (as ammonium chloride) to reduce their overall density and increase buoyancy.[98]

Reproduction and life cycle

 
Female Argonauta argo with eggcase and eggs
 
Detail of the hectocotylus of Ocythoe tuberculata
 
A dissected male specimen of Onykia ingens, showing a non-erect penis (the white tubular structure located below most of the other organs)
 
A specimen of the same species exhibiting an elongation of the penis to 67 cm in length

Cephalopods are a diverse group of species, but share common life history traits, for example, they have a rapid growth rate and short life spans.[99] Stearns (1992) suggested that in order to produce the largest possible number of viable offspring, spawning events depend on the ecological environmental factors of the organism. The majority of cephalopods do not provide parental care to their offspring, except, for example, octopus, which helps this organism increase the survival rate of their offspring.[99] Marine species' life cycles are affected by various environmental conditions.[100] The development of a cephalopod embryo can be greatly affected by temperature, oxygen saturation, pollution, light intensity, and salinity.[99] These factors are important to the rate of embryonic development and the success of hatching of the embryos. Food availability also plays an important role in the reproductive cycle of cephalopods. A limitation of food influences the timing of spawning along with their function and growth.[100] Spawning time and spawning vary among marine species; it's correlated with temperature, though cephalopods in shallow water spawn in cold months so that the offspring would hatch at warmer temperatures. Breeding can last from several days to a month.[99]

Sexual maturity

Cephalopods that are sexually mature and of adult size begin spawning and reproducing. After the transfer of genetic material to the following generation, the adult cephalopods then die.[99] Sexual maturation in male and female cephalopods can be observed internally by the enlargement of gonads and accessory glands.[101] Mating would be a poor indicator of sexual maturation in females; they can receive sperm when not fully reproductively mature and store them until they are ready to fertilize the eggs.[100] Males are more aggressive in their pre-mating competition when in the presence of immature females than when competing for a sexually mature female.[102] Most cephalopod males develop a hectocotylus, an arm tip which is capable of transferring their spermatozoa into the female mantle cavity. Though not all species use a hectocotylus; for example, the adult nautilus releases a spadix.[103] An indication of sexual maturity of females is the development of brachial photophores to attract mates.[104]

Fertilization

Cephalopods are not broadcast spawners. During the process of fertilization, the females use sperm provided by the male via external fertilization. Internal fertilization is seen only in octopuses.[101] The initiation of copulation begins when the male catches a female and wraps his arm around her, either in a "male to female neck" position or mouth to mouth position, depending on the species. The males then initiate the process of fertilization by contracting their mantle several times to release the spermatozoa.[105] Cephalopods often mate several times, which influences males to mate longer with females that have previously, nearly tripling the number of contractions of the mantle.[105] To ensure the fertilization of the eggs, female cephalopods release a sperm-attracting peptide through the gelatinous layers of the egg to direct the spermatozoa. Female cephalopods lay eggs in clutches; each egg is composed of a protective coat to ensure the safety of the developing embryo when released into the water column. Reproductive strategies differ between cephalopod species. In giant Pacific octopus, large eggs are laid in a den; it will often take several days to lay all of them.[101] Once the eggs are released and attached to a sheltered substrate, the females then die,[101] making them semelparous. In some species of cephalopods, egg clutches are anchored to substrates by a mucilaginous adhesive substance. These eggs are swelled with perivitelline fluid (PVF), a hypertonic fluid that prevents premature hatching.[106] Fertilized egg clusters are neutrally buoyant depending on the depth that they were laid, but can also be found in substrates such as sand, a matrix of corals, or seaweed.[100] Because these species do not provide parental care for their offspring, egg capsules can be injected with ink by the female in order to camouflage the embryos from predators.[100]

Male–male competition

Most cephalopods engage in aggressive sex: a protein in the male capsule sheath stimulates this behavior. They also engage in male–male aggression, where larger males tend to win the interactions.[99] When a female is near, the males charge one another continuously and flail their arms. If neither male backs away, the arms extend to the back, exposing the mouth, followed by the biting of arm tips.[107] During mate competition males also participate in a technique called flushing. This technique is used by the second male attempting to mate with a female. Flushing removes spermatophores in the buccal cavity that was placed there by the first mate by forcing water into the cavity.[99] Another behavior that males engage in is sneaker mating or mimicry – smaller males adjust their behavior to that of a female in order to reduce aggression. By using this technique, they are able to fertilize the eggs while the larger male is distracted by a different male.[107] During this process, the sneaker males quickly insert drop-like sperm into the seminal receptacle.[108]

Mate choice

Mate choice is seen in cuttlefish species, where females prefer some males over others, though characteristics of the preferred males are unknown.[99] A hypothesis states that females reject males by olfactory cues rather than visual cues.[99] Several cephalopod species are polyandrous – accepting and storing multiple male spermatophores, which has been identified by DNA fingerprinting.[105] Females are no longer receptive to mating attempts when holding their eggs in their arms. Females can store sperm in two places (1) the buccal cavity where recently mated males place their spermatophores, and (2) the internal sperm-storage receptacles where sperm packages from previous males are stored.[99] Spermatophore storage results in sperm competition; which states that the female controls which mate fertilizes the eggs. In order to reduce this sort of competition, males develop agonistic behaviors like mate guarding and flushing.[99] The Hapalochlaena lunulata, or the blue-ringed octopus, readily mates with both males and females.[109]

Sexual dimorphism

In a variety of marine organisms, it is seen that females are larger in size compared to the males in some closely related species. In some lineages, such as the blanket octopus, males become structurally smaller and smaller resembling a term, "dwarfism" dwarf males usually occurs at low densities.[110] The blanket octopus male is an example of sexual-evolutionary dwarfism; females grow 10,000 to 40,000 times larger than the males and the sex ratio between males and females can be distinguished right after hatching of the eggs.[110]

 
Egg cases laid by a female squid

Embryology

Cephalopod eggs span a large range of sizes, from 1 to 30 mm in diameter.[111] The fertilised ovum initially divides to produce a disc of germinal cells at one pole, with the yolk remaining at the opposite pole. The germinal disc grows to envelop and eventually absorb the yolk, forming the embryo. The tentacles and arms first appear at the hind part of the body, where the foot would be in other molluscs, and only later migrate towards the head.[96][112]

The funnel of cephalopods develops on the top of their head, whereas the mouth develops on the opposite surface.[113]: 86  The early embryological stages are reminiscent of ancestral gastropods and extant Monoplacophora.[112]

The shells develop from the ectoderm as an organic framework which is subsequently mineralized.[72] In Sepia, which has an internal shell, the ectoderm forms an invagination whose pore is sealed off before this organic framework is deposited.[72]

Development

 
Chtenopteryx sicula paralarvae. Left: Two very young paralarvae. The circular tentacular clubs bear approximately 20 irregularly arranged suckers. Two chromatophores are present on each side of the mantle. Centre: Ventral, dorsal and side views of a more advanced paralarva. An equatorial circulet of seven large yellow-brown chromatophores is present on the mantle. Posteriorly the expanded vanes of the gladius are visible in the dorsal view. Right: Ventral and dorsal views of a very advanced paralarva.
 
 
Left: Immature specimens of Chiroteuthis veranyi. In this paralarval form, known as the doratopsis stage, the pen is longer than the mantle and 'neck' combined
Right: A mature Chiroteuthis veranyi. This species has some of the longest tentacles in proportion to its size of any known cephalopod.

The length of time before hatching is highly variable; smaller eggs in warmer waters are the fastest to hatch, and newborns can emerge after as little as a few days. Larger eggs in colder waters can develop for over a year before hatching.[111]

The process from spawning to hatching follows a similar trajectory in all species, the main variable being the amount of yolk available to the young and when it is absorbed by the embryo.[111]

Unlike most other molluscs, cephalopods do not have a morphologically distinct larval stage. Instead, the juveniles are known as paralarvae. They quickly learn how to hunt, using encounters with prey to refine their strategies.[111]

Growth in juveniles is usually allometric, whilst adult growth is isometric.[114]

Evolution

Main article: Evolution of cephalopods

The traditional view of cephalopod evolution holds that they evolved in the Late Cambrian from a monoplacophoran-like ancestor[115] with a curved, tapering shell,[116] which was closely related to the gastropods (snails).[117] The similarity of the early shelled cephalopod Plectronoceras to some gastropods was used in support of this view. The development of a siphuncle would have allowed the shells of these early forms to become gas-filled (thus buoyant) in order to support them and keep the shells upright while the animal crawled along the floor, and separated the true cephalopods from putative ancestors such as Knightoconus, which lacked a siphuncle.[117] Neutral or positive buoyancy (i.e. the ability to float) would have come later, followed by swimming in the Plectronocerida and eventually jet propulsion in more derived cephalopods.[118]

Possible early Cambrian remains have been found in the Avalon Peninsula, matching genetic data for a pre-Cambrian origin.[2]

However, some morphological evidence is difficult to reconcile with this view, and the redescription of Nectocaris pteryx, which did not have a shell and appeared to possess jet propulsion in the manner of "derived" cephalopods, complicated the question of the order in which cephalopod features developed – provided Nectocaris is a cephalopod at all.[119]

Early cephalopods were likely predators near the top of the food chain.[21] After the late Cambrian extinction led to the disappearance of many Anomalocaridids, predatory niches became available for other animals.[120] During the Ordovician period the primitive cephalopods underwent pulses of diversification[121] to become diverse and dominant in the Paleozoic and Mesozoic seas.[122]

In the Early Palaeozoic, their range was far more restricted than today; they were mainly constrained to sublittoral regions of shallow shelves of the low latitudes, and usually occurred in association with thrombolites.[123] A more pelagic habit was gradually adopted as the Ordovician progressed.[123] Deep-water cephalopods, whilst rare, have been found in the Lower Ordovician – but only in high-latitude waters.[123] The mid-Ordovician saw the first cephalopods with septa strong enough to cope with the pressures associated with deeper water, and could inhabit depths greater than 100–200 m.[121] The direction of shell coiling would prove to be crucial to the future success of the lineages; endogastric coiling would only permit large size to be attained with a straight shell, whereas exogastric coiling – initially rather rare – permitted the spirals familiar from the fossil record to develop, with their corresponding large size and diversity.[124] (Endogastric means the shell is curved so as the ventral or lower side is longitudinally concave (belly in); exogastric means the shell is curved so as the ventral side is longitudinally convex (belly out) allowing the funnel to be pointed backward beneath the shell.)[124]

 
An ammonoid with the body chamber missing, showing the septal surface (especially at right) with its undulating lobes and saddles

The ancestors of coleoids (including most modern cephalopods) and the ancestors of the modern nautilus, had diverged by the Floian Age of the Early Ordovician Period, over 470 million years ago.[123][125] The Bactritida, a Silurian–Triassic group of orthocones, are widely held to be paraphyletic without the coleoids and ammonoids, that is, the latter groups arose from within the Bactritida.[126]: 393  An increase in the diversity of the coleoids and ammonoids is observed around the start of the Devonian period and corresponds with a profound increase in fish diversity. This could represent the origin of the two derived groups.[126]

Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species. Competitive pressure from fish is thought to have forced the shelled forms into deeper water, which provided an evolutionary pressure towards shell loss and gave rise to the modern coleoids, a change which led to greater metabolic costs associated with the loss of buoyancy, but which allowed them to recolonize shallow waters.[117]: 36  However, some of the straight-shelled nautiloids evolved into belemnites, out of which some evolved into squid and cuttlefish.[verification needed] The loss of the shell may also have resulted from evolutionary pressure to increase maneuverability, resulting in a more fish-like habit.[1]: 289 

There has been debate on the embryological origin of cephalopod appendages.[127] Until the mid-twentieth century, the "Arms as Head" hypothesis was widely recognized. In this theory, the arms and tentacles of cephalopods look similar to the head appendages of gastropods, suggesting that they might be homologous structures. Cephalopod appendages surround the mouth, so logically they could be derived from embryonic head tissues.[128] However, the "Arms as Foot" hypothesis, proposed by Adolf Naef in 1928, has increasingly been favoured;[127] for example, fate mapping of limb buds in the chambered nautilus indicates that limb buds originate from "foot" embryonic tissues.[129]

Genetics

The sequencing of a full Cephalopod genome has remained challenging to researchers due to the length and repetition of their DNA.[130] The characteristics of Cephalopod genomes were initially hypothesized to be the result of entire genome duplications. Following the full sequencing of a California two-spot octopus, the genome showed similar patterns to other marine invertebrates with significant additions to the genome assumed to be unique to Cephalopods. No evidence of full genome duplication was found.[131]

Within the California two-spot octopus genome there are substantial replications of two gene families. Significantly, the expanded gene families were only previously known to exhibit replicative behaviour within vertebrates.[131] The first gene family was identified as the Protocadherins which are attributed to neuron development. Protocadherins function as cell adhesion molecules, essential for synaptic specificity. The mechanism for Protocadherin gene family replication in vertebrates is attributed to complex splicing, or cutting and pasting, from a locus. Following the sequencing of the California two-spot octopus, researchers found that the Prorocadherin gene family in Cephalopods has expanded in the genome due to tandem gene duplication. The different replication mechanisms for Protocadherin genes indicate an independent evolution of Protocadherin gene expansion in vertebrates and invertebrates.[131] Analysis of individual Cephalopod Protocadherin genes indicate independent evolution between species of Cephalopod. A species of shore squid Doryteuthis pealeii with expanded Protocadherin gene families differ significantly from those of the California two-spot octopus suggesting gene expansion did not occur before speciation within Cephalopods. Despite different mechanisms for gene expansion, the two-spot octopus Protocadherin genes were more similar to vertebrates than squid, suggesting a convergent evolution mechanism. The second gene family known as C2H2 are small proteins that function as zinc transcription factors. C2H2 are understood to moderate DNA, RNA and protein functions within the cell.[130]

The sequenced California two spot octopus genome also showed a significant presence of transposable elements as well as transposon expression. Although the role of transposable elements in marine vertebrates is still relatively unknown, significant expression of transposons in nervous system tissues have been observed.[132] In a study conducted on vertebrates, the expression of transposons during development in the fruitfly Drosophila melanogaster activated genomic diversity between neurons.[133] This diversity has been linked to increased memory and learning in mammals. The connection between transposons and increased neuron capability may provide insight into the observed intelligence, memory and function of Cephalopods.[132]

Using long-read sequencing, researchers have decoded the cephalopod genomes and discovered they have been churned and scrambled. The genes were compared to those of thousands of other species and while blocks of three or more genes co-occurred between squid and octopus, the blocks of genes were not found together in any other animals'. Many of the groupings were in the nervous tissue, suggesting the course they adapted their intelligence.[134][135]

Phylogeny

The approximate consensus of extant cephalopod phylogeny, after Strugnell et al. 2007, is shown in the cladogram.[78] Mineralized taxa are in bold. The attachment of the clade including Sepia and Spirula is unclear; either of the points marked with an asterisk may represent the root of this clade.

Cephalopoda
Nautiloids  
Coleoids

Basal octopods (e.g. Argonautidae)  

Octopodiformes  
Decapodiformes  

Sepiolida (bobtail squid)  

  *  

Sepiida (cuttlefish)  

Idiosepiidae  

Myopsida  

Spirulida  

  *  

Certain benthic squids (e.g. Bathyteuthoidea)  

The internal phylogeny of the cephalopods is difficult to constrain; many molecular techniques have been adopted, but the results produced are conflicting.[78][136] Nautilus tends to be considered an outgroup, with Vampyroteuthis forming an outgroup to other squid; however in one analysis the nautiloids, octopus and teuthids plot as a polytomy.[78] Some molecular phylogenies do not recover the mineralized coleoids (Spirula, Sepia, and Metasepia) as a clade; however, others do recover this more parsimonious-seeming clade, with Spirula as a sister group to Sepia and Metasepia in a clade that had probably diverged before the end of the Triassic.[137][138]

Molecular estimates for clade divergence vary. One 'statistically robust' estimate has Nautilus diverging from Octopus at 415 ± 24 million years ago.[139]

Taxonomy

 
Chambered nautilus (Nautilus pompilius)
 
Common cuttlefish (Sepia officinalis)
 
Atlantic bobtail (Sepiola atlantica)
 
European squid (Loligo vulgaris)
 
Common octopus (Octopus vulgaris)

The classification presented here, for recent cephalopods, follows largely from Current Classification of Recent Cephalopoda (May 2001), for fossil cephalopods takes from Arkell et al. 1957, Teichert and Moore 1964, Teichert 1988, and others. The three subclasses are traditional, corresponding to the three orders of cephalopods recognized by Bather.[140]

Class Cephalopoda († indicates extinct groups)

Other classifications differ, primarily in how the various decapod orders are related, and whether they should be orders or families.

Suprafamilial classification of the Treatise

This is the older classification that combines those found in parts K and L of the Treatise on Invertebrate Paleontology, which forms the basis for and is retained in large part by classifications that have come later.

Nautiloids in general (Teichert and Moore, 1964) sequence as given.

Subclass † Endoceratoidea. Not used by Flower, e.g. Flower and Kummel 1950, interjocerids included in the Endocerida.
Order † Endocerida
Order † Intejocerida
Subclass † Actinoceratoidea Not used by Flower, ibid
Order † Actinocerida
Subclass Nautiloidea Nautiloidea in the restricted sense.
Order † Ellesmerocerida Plectronocerida subsequently split off as separate order.
Order † Orthocerida Includes orthocerids and pseudorthocerids
Order † Ascocerida
Order † Oncocerida
Order † Discosorida
Order † Tarphycerida
Order † Barrandeocerida A polyphyletic group now included in the Tarphycerida
Order Nautilida
Subclass † Bactritoidea
Order † Bactritida

Paleozoic Ammonoidea (Miller, Furnish and Schindewolf, 1957)

Suborder † Anarcestina
Suborder † Clymeniina
Suborder † Goniatitina
Suborder † Prolecanitina

Mesozoic Ammonoidea (Arkel et al., 1957)

Suborder † Ceratitina
Suborder † Phylloceratina
Suborder † Lytoceratina
Suborder † Ammonitina

Subsequent revisions include the establishment of three Upper Cambrian orders, the Plectronocerida, Protactinocerida, and Yanhecerida; separation of the pseudorthocerids as the Pseudorthocerida, and elevating orthoceratid as the Subclass Orthoceratoidea.

Shevyrev classification

Shevyrev (2005) suggested a division into eight subclasses, mostly comprising the more diverse and numerous fossil forms,[141][142] although this classification has been criticized as arbitrary, lacking evidence, and based on misinterpretations of other papers.[143]

 
Gyronaedyceras eryx, a nautiloid from the Devonian of Wisconsin
 
Various species of ammonites
 
Holotype of Ostenoteuthis siroi from family Ostenoteuthidae
 
A fossilised belemnite

Class Cephalopoda

Cladistic classification

 
Pyritized fossil of Vampyronassa rhodanica, a vampyromorphid from the Lower Callovian (165.3 million years ago)

Another recent system divides all cephalopods into two clades. One includes nautilus and most fossil nautiloids. The other clade (Neocephalopoda or Angusteradulata) is closer to modern coleoids, and includes belemnoids, ammonoids, and many orthocerid families. There are also stem group cephalopods of the traditional Ellesmerocerida that belong to neither clade.[145][146]

The coleoids, despite some doubts,[1]: 289  appear from molecular data to be monophyletic.[147]

In culture

Further information: Cephalopods in popular culture
 
Pen and wash drawing of an imagined colossal octopus attacking a ship, by the malacologist Pierre de Montfort, 1801

Ancient seafaring people were aware of cephalopods, as evidenced by artworks such as a stone carving found in the archaeological recovery from Bronze Age Minoan Crete at Knossos (1900 – 1100 BC) has a depiction of a fisherman carrying an octopus.[148] The terrifyingly powerful Gorgon of Greek mythology may have been inspired by the octopus or squid, the octopus's body representing the severed head of Medusa, the beak as the protruding tongue and fangs, and its tentacles as the snakes.[149]

 
The NROL-39 mission patch, depicting the National Reconnaissance Office as an octopus with a long reach

The Kraken are legendary sea monsters of giant proportions said to dwell off the coasts of Norway and Greenland, usually portrayed in art as giant cephalopods attacking ships. Linnaeus included it in the first edition of his 1735 Systema Naturae.[150][151] A Hawaiian creation myth says that the present cosmos is the last of a series which arose in stages from the ruins of the previous universe. In this account, the octopus is the lone survivor of the previous, alien universe.[152] The Akkorokamui is a gigantic tentacled monster from Ainu folklore.[153]

A battle with an octopus plays a significant role in Victor Hugo's book Travailleurs de la mer (Toilers of the Sea), relating to his time in exile on Guernsey.[154]Ian Fleming's 1966 short story collection Octopussy and The Living Daylights, and the 1983 James Bond film were partly inspired by Hugo's book.[155]

Japanese erotic art, shunga, includes ukiyo-e woodblock prints such as Katsushika Hokusai's 1814 print Tako to ama (The Dream of the Fisherman's Wife), in which an ama diver is sexually intertwined with a large and a small octopus.[156][157] The print is a forerunner of tentacle erotica.[158] The biologist P. Z. Myers noted in his science blog, Pharyngula, that octopuses appear in "extraordinary" graphic illustrations involving women, tentacles, and bare breasts.[159][160]

Its many arms that emanate from a common center means that the octopus is sometimes used to symbolize a powerful and manipulative organization.[161]

See also

References

  1. ^ a b c d e f g h i Wilbur, Karl M.; Trueman, E.R.; Clarke, M.R., eds. (1985), The Mollusca, vol. 11. Form and Function, New York: Academic Press, ISBN 0-12-728702-7
  2. ^ a b Hildenbrand, Anne; Austermann, Gregor; Fuchs, Dirk; Bengtson, Peter; Stinnesbeck, Wolfgang (2021). "A potential cephalopod from the early Cambrian of eastern Newfoundland, Canada". Communications Biology. 4 (1): 388. doi:10.1038/s42003-021-01885-w. PMC 7987959. PMID 33758350.
  3. ^ Queiroz, K.; Cantino, P. D.; Gauthier, J. A. (2020). Phylonyms: A Companion to the PhyloCode. CRC Press. p. 1843. ISBN 978-1-138-33293-5.
  4. ^ . CephBase. Archived from the original on 12 January 2016. Retrieved 29 January 2016.
  5. ^ a b c d Wilbur, Karl M.; Clarke, M.R.; Trueman, E.R., eds. (1985), The Mollusca, vol. 12. Paleontology and neontology of Cephalopods, New York: Academic Press, ISBN 0-12-728702-7
  6. ^ Bartol, I. K.; Mann, R.; Vecchione, M. (2002). "Distribution of the euryhaline squid Lolliguncula brevis in Chesapeake Bay: effects of selected abiotic factors". Marine Ecology Progress Series. 226: 235–247. Bibcode:2002MEPS..226..235B. doi:10.3354/meps226235.
  7. ^ "Are there any freshwater cephalopods?". ABC Science. 16 January 2013.
  8. ^ a b c d e f g h i j k l Nixon, Marion; Young, J. Z. (2003). The Brains and Lives of Cephalopods. New York: Oxford University Press. ISBN 978-0-19-852761-9.
  9. ^ Tricarico, E.; Amodio, P.; Ponte, G.; Fiorito, G. (2014). "Cognition and recognition in the cephalopod mollusc Octopus vulgaris: coordinating interaction with environment and conspecifics". In Witzany, G. (ed.). Biocommunication of Animals. Springer. pp. 337–349. ISBN 978-94-007-7413-1.
  10. ^ Budelmann, B. U. (1995). "The cephalopod nervous system: What evolution has made of the molluscan design". In Breidbach, O.; Kutsch, W. (eds.). The nervous systems of invertebrates: An evolutionary and comparative approach. ISBN 978-3-7643-5076-5.
  11. ^ Chung, Wen-Sung; Kurniawan, Nyoman D.; Marshall, N. Justin (2020). "Toward an MRI-Based Mesoscale Connectome of the Squid Brain". iScience. 23 (1): 100816. Bibcode:2020iSci...23j0816C. doi:10.1016/j.isci.2019.100816. PMC 6974791. PMID 31972515.
  12. ^ Raven, Peter et al. (2003). Biology, p. 669. McGraw-Hill Education, New York. ISBN 9780073383071.
  13. ^ Tasaki, I.; Takenaka, T. (1963). "Resting and action potential of squid giant axons intracellularly perfused with sodium-rich solutions". Proceedings of the National Academy of Sciences of the United States of America. 50 (4): 619–626. Bibcode:1963PNAS...50..619T. doi:10.1073/pnas.50.4.619. PMC 221236. PMID 14077488.
  14. ^ a b Packard, A. (1972). "Cephalopods and fish: the limits of convergence". Biological Reviews. 47 (2): 241–307. doi:10.1111/j.1469-185X.1972.tb00975.x. S2CID 85088231.
  15. ^ Macia, Silvia; Robinson, Michael P.; Craze, Paul; Dalton, Robert; Thomas, James D. (2004). "New observations on airborne jet propulsion (flight) in squid, with a review of previous reports". Journal of Molluscan Studies. 70 (3): 297–299. doi:10.1093/mollus/70.3.297.
  16. ^ a b Muramatsu, K.; Yamamoto, J.; Abe, T.; Sekiguchi, K.; Hoshi, N.; Sakurai, Y. (2013). "Oceanic squid do fly". Marine Biology. 160 (5): 1171–1175. doi:10.1007/s00227-013-2169-9. S2CID 84388744.
  17. ^ "Scientists Unravel Mystery of Flying Squid". Ocean Views. National Geographic. 20 February 2013.
  18. ^ Jabr, Ferris (2 August 2010). "Fact or Fiction: Can a Squid Fly out of Water?". Scientific American.
  19. ^ a b Serb, J. M.; Eernisse, D. J. (2008). "Charting Evolution's Trajectory: Using Molluscan Eye Diversity to Understand Parallel and Convergent Evolution". Evolution: Education and Outreach. 1 (4): 439–447. doi:10.1007/s12052-008-0084-1. S2CID 2881223.
  20. ^ Wells, Martin J. (2011). . Treatise Online. Lawrence, Kansas, USA. doi:10.17161/to.v0i0.4226. Archived from the original on 2016-08-22. Retrieved 2013-05-10.(subscription required)
  21. ^ a b c d e f g h i j k Boyle, Peter; Rodhouse, Paul (2004). Cephalopods : ecology and fisheries. Blackwell. doi:10.1002/9780470995310.ch2. ISBN 978-0-632-06048-1.
  22. ^ a b Messenger, John B.; Hanlon, Roger T. (1998). Cephalopod Behaviour. Cambridge: Cambridge University Press. pp. 17–21. ISBN 978-0-521-64583-6.
  23. ^ Chung, Wen-Sung; Marshall, N. Justin (2016-09-14). "Comparative visual ecology of cephalopods from different habitats". Proceedings of the Royal Society B: Biological Sciences. 283 (1838): 20161346. doi:10.1098/rspb.2016.1346. ISSN 0962-8452. PMC 5031660. PMID 27629028.
  24. ^ Hanlon and Messenger, 68.
  25. ^ Mäthger, L.; Roberts, S.; Hanlon, R. (2010). "Evidence for distributed light sensing in the skin of cuttlefish, Sepia officinalis". Biology Letters. 6 (5): 600–603. doi:10.1098/rsbl.2010.0223. PMC 2936158. PMID 20392722.
  26. ^ Michinomae, M.; Masuda, H.; Seidou, M.; Kito, Y. (1994). "Structural basis for wavelength discrimination in the banked retina of the firefly squid Watasenia scintillans". Journal of Experimental Biology. 193 (1): 1–12. doi:10.1242/jeb.193.1.1. PMID 9317205.
  27. ^ Seidou, M.; Sugahara, M.; Uchiyama, H.; Hiraki, K.; Hamanaka, T.; Michinomae, M.; Yoshihara, K.; Kito, Y. (1990). "On the three visual pigments in the retina of the firefly squid, Watasenia scintillans". Journal of Comparative Physiology A. 166 (6). doi:10.1007/BF00187321. S2CID 25707481.
  28. ^ Stubbs, A. L.; Stubbs, C. W. (2015). "A novel mechanism for color vision: Pupil shape and chromatic aberration can provide spectral discrimination for 'color blind' organisms". bioRxiv 10.1101/017756.
  29. ^ Octopus Eyes Are Crazier Than We Imagined
  30. ^ a b Kingston, A. C.; Kuzirian, A. M.; Hanlon, R. T.; Cronin, T. W. (2015). "Visual phototransduction components in cephalopod chromatophores suggest dermal photoreception". Journal of Experimental Biology. 218 (10): 1596–1602. doi:10.1242/jeb.117945. PMID 25994635. S2CID 25431963.
  31. ^ "The cephalopods can hear you". BBC News. 2009-06-15. Retrieved 2010-04-28.
  32. ^ Tong, D.; Rozas, S.; Oakley, H.; Mitchell, J.; Colley, J.; Mcfall-Ngai, J. (Jun 2009). "Evidence for light perception in a bioluminescent organ". Proceedings of the National Academy of Sciences of the United States of America. 106 (24): 9836–9841. Bibcode:2009PNAS..106.9836T. doi:10.1073/pnas.0904571106. ISSN 0027-8424. PMC 2700988. PMID 19509343.
  33. ^ "Integument (mollusks)". Encyclopædia Britannica. 2009. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD.
  34. ^ Ramirez, M. D.; Oakley, T. H (2015). "Eye-independent, light-activated chromatophore expansion (LACE) and expression of phototransduction genes in the skin of Octopus bimaculoides" (PDF). Journal of Experimental Biology. 218 (10): 1513–1520. doi:10.1242/jeb.110908. PMC 4448664. PMID 25994633. (PDF) from the original on 2016-08-09.
  35. ^ Sylvia Lima de Souza Medeiros; et al. (2021). "Cyclic alternation of quiet and active sleep states in the octopus". iScience. doi:10.1016/j.isci.2021.102223. PMC 8101055. {{cite journal}}: Cite journal requires |journal= (help)
  36. ^ Huffard, Christine L. (2006-10-01). "Locomotion by Abdopus aculeatus (Cephalopoda: Octopodidae):walking the line between primary and secondary defenses". Journal of Experimental Biology. 209 (19): 3697–3707. doi:10.1242/jeb.02435. ISSN 0022-0949. PMID 16985187. S2CID 26862414.
  37. ^ Josef, Noam; Amodio, Piero; Fiorito, Graziano; Shashar, Nadav (2012-05-23). "Camouflaging in a Complex Environment—Octopuses Use Specific Features of Their Surroundings for Background Matching". PLOS ONE. 7 (5): e37579. Bibcode:2012PLoSO...737579J. doi:10.1371/journal.pone.0037579. ISSN 1932-6203. PMC 3359305. PMID 22649542.
  38. ^ Manda, Štěpán; Turek, Vojtěch (2009). "Minute Silurian oncocerid nautiloids with unusual color patterns". Acta Palaeontologica Polonica. 54 (3): 503–512. doi:10.4202/app.2008.0062. S2CID 54043278.
  39. ^ Turek, Vojtěch (2009). "Colour patterns in Early Devonian cephalopods from the Barrandian Area: Taphonomy and taxonomy". Acta Palaeontologica Polonica. 54 (3): 491–502. doi:10.4202/app.2007.0064. S2CID 55851070.
  40. ^ Hanlon, Roger T.; Messenger, John B. (1999). Cephalopod Behaviour. Cambridge University Press. p. 2. ISBN 978-0-521-64583-6.
  41. ^ "inkfish". Merriam-Webster. Retrieved 1 February 2018.
  42. ^ Bickerdyke, John (1895). Sea Fishing. London: Longmans, Green, and Co. p. 114. the common squid or calamary (Loligo vulgaris). It is sometimes called the pen-and-ink fish, on account of its ink bag, and the delicate elongated shell which is found within it.
  43. ^ Wells, M.J. (1 April 1980). "Nervous control of the heartbeat in octopus". Journal of Experimental Biology. 85 (1): 111–28. doi:10.1242/jeb.85.1.111. PMID 7373208.
  44. ^ Ghiretti-Magaldi, A. (October 1992). "The Pre-history of Hemocyanin. The Discovery of Copper in the Blood of Molluscs". Cellular and Molecular Life Sciences. 48 (10): 971–972. doi:10.1007/BF01919143. S2CID 33290596.
  45. ^ How many hearts does an octopus have? - New Scientist
  46. ^ Why Do Octopuses Have Three Hearts? - Science ABC
  47. ^ Where Would We Be Without Blood? - Illinois Science Council
  48. ^ Why is Octopus Blood Blue? | Science | Wilstar.com
  49. ^ a b c Gilbert, Daniel L.; Adelman, William J.; Arnold, John M. (1990). Squid as Experimental Animals (illustrated ed.). Springer. ISBN 978-0-306-43513-3.
  50. ^ a b c Schipp, Rudolf; Mollenhauer, Stephan; Boletzky, Sigurd (1979). "Electron Microscopical and Histochemical Studies of Differentiation and Function of the Cephalopod Gill (Sepia Officinalis L.)". Zoomorphologie. 93 (3): 193–207. doi:10.1007/BF00993999. S2CID 20214206.
  51. ^ a b c Wells, M. J.; O'Dor, R. K. (1991-09-01). "Jet Propulsion and the Evolution of the Cephalopods". Bulletin of Marine Science. 49 (1–2): 419–432.
  52. ^ Packard, A.; Trueman, E. R. (October 1974). "Muscular activity of the mantle of Sepia and Loligo (Cephalopoda) during respiratory movements and jetting, and its physiological interpretation". The Journal of Experimental Biology. 61 (2): 411–419. doi:10.1242/jeb.61.2.411. ISSN 0022-0949. PMID 4443736.
  53. ^ Bone, Q.; Brown, E. R.; Travers, G. (1994). "On the respiratory flow in the cuttlefish Sepia Officinalis" (PDF). Journal of Experimental Biology. 194 (1): 153–165. doi:10.1242/jeb.194.1.153. PMID 9317534. (PDF) from the original on 2009-03-04.
  54. ^ Cole, A.; Hall, B. (2009). "Cartilage differentiation in cephalopod molluscs". Zoology. 112 (1): 2–15. doi:10.1016/j.zool.2008.01.003. PMID 18722759.
  55. ^ See also http://tolweb.org/articles/?article_id=4200 2010-06-16 at the Wayback Machine
  56. ^ a b c d e Wilbur, Karl M.; Clarke, M.R.; Trueman, E.R., eds. (1985), "11: Evolution of Buoyancy and Locomotion in recent cephalopods", The Mollusca, vol. 12. Paleontology and neontology of Cephalopods, New York: Academic Press, ISBN 0-12-728702-7
  57. ^ a b Anderson, E.; Demont, M. (2000). "The mechanics of locomotion in the squid Loligo pealei: Locomotory function and unsteady hydrodynamics of the jet and intramantle pressure". Journal of Experimental Biology. 203 (18): 2851–2863. doi:10.1242/jeb.203.18.2851. PMID 10952883.
  58. ^ a b c Bartol, I. K.; Krueger, P. S.; Thompson, J. T.; Stewart, W. J. (2008). "Swimming dynamics and propulsive efficiency of squids throughout ontogeny". Integrative and Comparative Biology. 48 (6): 720–733. doi:10.1093/icb/icn043. PMID 21669828.
  59. ^ Shea, E.; Vecchione, M. (2002). "Quantification of ontogenetic discontinuities in three species of oegopsid squids using model II piecewise linear regression". Marine Biology. 140 (5): 971–979. doi:10.1007/s00227-001-0772-7. S2CID 84822175.
  60. ^ Johnson, W.; Soden, P. D.; Trueman, E. R. (February 1972). "A study in jet propulsion: an analysis of the motion of the squid, Loligo vulgaris". Journal of Experimental Biology. 56 (1972): 155–165. doi:10.1242/jeb.56.1.155.
  61. ^ Campbell, Reece & Mitchell (1999), p. 612.
  62. ^ Guerra, A.; Martinell, X.; González, A. F.; Vecchione, M.; Gracia, J.; Martinell, J. (2007). "A new noise detected in the ocean". Journal of the Marine Biological Association of the United Kingdom. 87 (5): 1255–1256. doi:10.1017/S0025315407058225. hdl:10261/27009. S2CID 85770435.
  63. ^ a b Wells, Martin J.; O'Dor, R. K. (July 1991). "Jet Propulsion and the Evolution of the Cephalopods". Bulletin of Marine Science. 49 (1): 419–432(14).
  64. ^ Chamberlain, J. Jr. (1993). "Locomotion in ancient seas: Constraint and opportunity in cephalopod adaptive design". Geobios. 26 (Suppl. 1): 49–61. doi:10.1016/S0016-6995(06)80360-8.
  65. ^ a b c d e O'Dor, R. K. (1988). "The forces acting on swimming squid". Journal of Experimental Biology. 137: 421–442. doi:10.1242/jeb.137.1.421.
  66. ^ O'Dor, R. K.; Hoar, J. A. (2000). "Does geometry limit squid growth?". ICES Journal of Marine Science. 57: 8–14. doi:10.1006/jmsc.1999.0502.
  67. ^ Seibel, B. A.; Thuesen, E. V.; Childress, J. J.; Gorodezky, L. A. (April 1997). "Decline in Pelagic Cephalopod Metabolism With Habitat Depth Reflects Differences in Locomotory Efficiency". The Biological Bulletin. 192 (2): 262–278. doi:10.2307/1542720. ISSN 1939-8697. JSTOR 1542720. PMID 28581868.
  68. ^ Hanlon, Roger T.; Watson, Anya C.; Barbosa, Alexandra (2010-02-01). "A 'Mimic Octopus' in the Atlantic: Flatfish Mimicry and Camouflage by Macrotritopus defilippi". The Biological Bulletin. 218 (1): 15–24. doi:10.1086/BBLv218n1p15. hdl:1912/4811. ISSN 0006-3185. PMID 20203250. S2CID 12935620.
  69. ^ "The argonaut shell: Gas-mediated buoyancy control in a pelagic octopus".
  70. ^ a b c d e f Gosline, John M.; de Mont, M. Edwin (1985). "Jet-propelled swimming in squids". Scientific American. Vol. 252, no. 1. pp. 96–103. doi:10.1038/scientificamerican0185-96. ISSN 0036-8733. JSTOR 24967551.
  71. ^ Huffard, Christine L. (2006-10-01). "Locomotion by Abdopus aculeatus (Cephalopoda: Octopodidae): Walking the line between primary and secondary defenses". Journal of Experimental Biology. 209 (19): 3697–3707. doi:10.1242/jeb.02435. ISSN 0022-0949. PMID 16985187. S2CID 26862414.
  72. ^ a b c d Baratte, S.; Andouche, A.; Bonnaud, L. (2007). "Engrailed in cephalopods: a key gene related to the emergence of morphological novelties". Development Genes and Evolution. 217 (5): 353–362. doi:10.1007/s00427-007-0147-2. PMID 17394016. S2CID 22241391.
  73. ^ von Boletzky, S. (2004). "'Ammonoïdes nus': un défi pour la phylogénie des céphalopodes ?" ['Nude ammonoids': a challenge to cephalopod phylogeny?]. Geobios. 37: 117–118. doi:10.1016/j.geobios.2003.01.009.
  74. ^ Gibson, R. N.; Atkinson, R. J. A.; Gordon, J. D. M., eds. (2006). Oceanography and Marine Biology: An Annual Review. CRC Press. p. 288. ISBN 978-1420006391.
  75. ^ Aldred, R. G.; Nixon, M.; Young, J. Z. (1983). "Cirrothauma murrayi Chun, a finned octopod". Philosophical Transactions of the Royal Society B: Biological Sciences. 301 (1103): 1–54. Bibcode:1983RSPTB.301....1A. doi:10.1098/rstb.1983.0021.
  76. ^ Fuchs, D.; Ifrim, C.; Stinnesbeck, W. (2008). "A new Palaeoctopus (Cephalopoda: Coleoidea) from the Late Cretaceous of Vallecillo, north-eastern Mexico, and implications for the evolution of Octopoda". Palaeontology. 51 (5): 1129–1139. doi:10.1111/j.1475-4983.2008.00797.x.
  77. ^ von Boletzky, Sigurd (July 1991). "The terminal spine of sepiolid hatchlings: its development and functional morphology (Mollusca, Cephalopoda)". Bulletin of Marine Science. 49: 107–112.
  78. ^ a b c d Strugnell, J.; Nishiguchi, M. K. (2007). "Molecular phylogeny of coleoid cephalopods (Mollusca: Cephalopoda) inferred from three mitochondrial and six nuclear loci: a comparison of alignment, implied alignment and analysis methods". Journal of Molluscan Studies. 73 (4): 399–410. doi:10.1093/mollus/eym038.
  79. ^ Warnke, K.; Keupp, H. (2005). "Spirula – a window to the embryonic development of ammonoids? Morphological and molecular indications for a palaeontological hypothesis" (PDF). Facies. 51 (1–4): 60–65. doi:10.1007/s10347-005-0054-9. S2CID 85026080.
  80. ^ Furuhashi, T.; Schwarzinger, C.; Miksik, I.; Smrz, M.; Beran, A. (2009). "Molluscan shell evolution with review of shell calcification hypothesis". Comparative Biochemistry and Physiology B. 154 (3): 351–371. doi:10.1016/j.cbpb.2009.07.011. PMID 19665573.
  81. ^ Dauphin, Y. (1996). "The organic matrix of coleoid cephalopod shells: molecular weights and isoelectric properties of the soluble matrix in relation to biomineralization processes". Marine Biology. 125 (3): 525–529. doi:10.1007/BF00353265. S2CID 83400480.
  82. ^ Dauphin, Y. (1983). Les subdivisions majeures de la classe des céphalopodes : bases de la systématique actuelle : apport de l'analyse microstructurale. These Doct. Etat, Université Paris Sud. OCLC 972899981.
  83. ^ Dauphin, Y. (2001). "Nanostructures de la nacre des tests de céphalopodes actuels". Paläontologische Zeitschrift. 75 (1): 113–122. doi:10.1007/bf03022601. ISSN 0031-0220. S2CID 126900936.
  84. ^ Toll, R. B.; Binger, L. C. (1991). "Arm anomalies: Cases of supernumerary development and bilateral agenesis of arm pairs in Octopoda (Mollusca, Cephalopoda)". Zoomorphology. 110 (6): 313–316. doi:10.1007/BF01668021. S2CID 34858474.
  85. ^ Anatomy of the Common Squid. 1912.
  86. ^ Nixon 1988 in Wippich, M. G. E.; Lehmann, J. (2004). "Allocrioceras from the Cenomanian (mid-Cretaceous) of the Lebanon and its bearing on the palaeobiological interpretation of heteromorphic ammonites". Palaeontology. 47 (5): 1093–1107. doi:10.1111/j.0031-0239.2004.00408.x.
  87. ^ Wilbur, Karl M.; Clarke, M.R.; Trueman, E.R., eds. (1985), "5", The Mollusca, vol. 12. Paleontology and neontology of Cephalopods, New York: Academic Press, ISBN 0-12-728702-7
  88. ^ C.Michael Hogan. 2011. Celtic Sea. eds. P.Saundry & C.Cleveland. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC.
  89. ^ Lena van Giesen; et al. (2020). "Molecular Basis of Chemotactile Sensation in Octopus". Vol. 183, no. 3. Cell. pp. 594–604. doi:10.1016/j.cell.2020.09.008.
  90. ^ "Cephalopod radula". Tree of Life web project.
  91. ^ a b c d e Nixon, M. (1995). "A nomenclature for the radula of the Cephalopoda (Mollusca) – living and fossil". Journal of Zoology. 236: 73–81. doi:10.1111/j.1469-7998.1995.tb01785.x.
  92. ^ a b Gabbott, S. E. (1999). "Orthoconic cephalopods and associated fauna from the late Ordovician Soom Shale Lagerstatte, South Africa". Palaeontology. 42: 123–148. doi:10.1111/1475-4983.00065.
  93. ^ Landman, Neil H.; Davis, Richard Arnold; Mapes, Royal H., eds. (2007). Cephalopods present and past: new insights and fresh perspectives. Springer. ISBN 978-1-4020-6461-6.
  94. ^ Richardson & ... (1977). Fossils of the Mason Creek.
  95. ^ Kruta, I.; Landman, N.; Rouget, I.; Cecca, F.; Tafforeau, P. (2011). "The role of ammonites in the Mesozoic marine food web revealed by jaw preservation". Science. 331 (6013): 70–72. Bibcode:2011Sci...331...70K. doi:10.1126/science.1198793. PMID 21212354. S2CID 206530342.
  96. ^ a b Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 450–460. ISBN 978-0-03-056747-6.
  97. ^ Loest, R. A. (1979). "Ammonia Volatilization and Absorption by Terrestrial Gastropods_ a Comparison between Shelled and Shell-Less Species". Physiological Zoology. 52 (4): 461–469. doi:10.1086/physzool.52.4.30155937. JSTOR 30155937. S2CID 87142440.
  98. ^ a b c Boucher-Rodoni, R.; Mangold, K. (1994). "Ammonia production in cephalopods, physiological and evolutionary aspects". Marine and Freshwater Behaviour and Physiology. 25 (1–3): 53–60. doi:10.1080/10236249409378907.
  99. ^ a b c d e f g h i j k Vidal, Erica A. G. Advances in Cephalopod Science: Biology, Ecology, Cultivation and Fisheries.
  100. ^ a b c d e Rodrigues, M.; Guerra; Troncoso (2010). "The embryonic phase and its implication in the hatchling size and condition of Atlantic bobtail squid Sepiola Atlantica". Helgoland Marine Research. 65 (2): 211–216. Bibcode:2011HMR....65..211R. doi:10.1007/s10152-010-0217-0. S2CID 41577834.
  101. ^ a b c d Arkhipkin, A. I. (1992). "Reproductive system structure, development and function in cephalopods with a new general scale for maturity stages". Journal of Northwest Atlantic Fishery Science. 12: 63–74. doi:10.2960/j.v12.a7.
  102. ^ Mohanty, Sobhi; Ojanguren, Alfredo F.; Fuiman, Lee A. (2014-07-01). "Aggressive male mating behavior depends on female maturity in Octopus bimaculoides". Marine Biology. 161 (7): 1521–1530. doi:10.1007/s00227-014-2437-3. ISSN 0025-3162. S2CID 85256742.
  103. ^ Saunders, W. B; Spinosa, C. (1978). "Sexual dimorphism in Nautilus from Palau". Paleobiology. 4 (3): 349–358. doi:10.1017/S0094837300006047. S2CID 85899974.
  104. ^ Young, R. B. (1975). "A Systematic Approach to Planning Occupational Programs". Community College Review. 3 (2): 19–25. doi:10.1177/009155217500300204. S2CID 145374345.
  105. ^ a b c Squires, Z. E; Norman, M. D; Stuart-Fox, D. (2013). "Mating behaviour and general spawning patterns of the southern dumpling squid Euprymna tasmanica". Journal of Molluscan Studies. 79 (3): 263–269. doi:10.1093/mollus/eyt025.
  106. ^ Marthy, H. J.; Hauser, R; Scholl, A. (1976). "Natural tranquilizer in cephalopod eggs". Nature. 261 (5560): 496–7. Bibcode:1976Natur.261..496M. doi:10.1038/261496a0. PMID 945466. S2CID 8693207.
  107. ^ a b Norman, M. D.; Lu, C. C. (1997). "Redescription of the southern dumpling squid Euprymna tasmanica and a revision of the genus Euprymna (Cephalopoda: Sepiolidae)". Journal of the Marine Biological Association of the United Kingdom. 77 (4): 1109–1137. doi:10.1017/s0025315400038662. S2CID 85748957.
  108. ^ Iwata, Y.; Ito, K.; Sakurai, Y. (2008). "Effect of low temperature on mating behavior of squid Loligo bleekeri". Fisheries Science. 74 (6): 1345–1347. doi:10.1111/j.1444-2906.2008.01664.x. S2CID 43094931.
  109. ^ Cheng, Mary W.; Caldwell, Roy L. (July 2000). "Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulata". Animal Behaviour. 60 (1): 27–33. doi:10.1006/anbe.2000.1447. ISSN 0003-3472. PMID 10924200. S2CID 32899443.
  110. ^ a b Fairbairn, D. (2013). "Blanket Octopus: Drifting Females and Dwarf Males". Odd couples: Extraordinary differences between the sexes in the animal kingdom. Princeton University Press. pp. 104–115.
  111. ^ a b c d Von Boletzky, S. (2003). Biology of early life stages in cephalopod molluscs. Advances in Marine Biology. Vol. 44. pp. 143–203. doi:10.1016/S0065-2881(03)44003-0. ISBN 978-0-12-026144-4. PMID 12846042.
  112. ^ a b Shigeno, S.; Sasaki, T.; Moritaki, T.; Kasugai, T.; Vecchione, M.; Agata, K. (Jan 2008). "Evolution of the cephalopod head complex by assembly of multiple molluscan body parts: Evidence from Nautilus embryonic development". Journal of Morphology. 269 (1): 1–17. doi:10.1002/jmor.10564. PMID 17654542. S2CID 13109195.
  113. ^ Gilbert, Daniel L.; Adelman, William J.; Arnold, John M. (1990). Squid as experimental animals. New York: Plenum Press. ISBN 978-0-306-43513-3.
  114. ^ Moltschaniwskyj, Natalie A. (2004). "Understanding the process of growth in cephalopods". Marine and Freshwater Research. 55 (4): 379–386. doi:10.1071/MF03147.
  115. ^ Lemche, H.; Wingstrand, K. G. (1959). "The anatomy of Neopilina galatheae Lemche, 1957 (Mollusca, Tryblidiacea)" (Link to free full text + plates). Galathea Report. 3: 9–73.
  116. ^ Wingstrand, K. G. (1985). . Galathea Report. 16: 7–94. Archived from the original (Link to free full text + plates) on 2016-03-03. Retrieved 2009-03-23.
  117. ^ a b c Boyle, P.; Rodhouse, P. (2005). "Origin and Evolution". Cephalopods. p. 36. doi:10.1002/9780470995310.ch3. ISBN 9780470995310.
  118. ^ Kröger, B. R. (2007). "Some Lesser Known Features of the Ancient Cephalopod Order Ellesmerocerida (Nautiloidea, Cephalopoda)". Palaeontology. 50 (3): 565–572. doi:10.1111/j.1475-4983.2007.00644.x.
  119. ^ Smith, Martin R.; Caron, Jean-Bernard (2010). "Primitive soft-bodied cephalopods from the Cambrian". Nature. 465 (7297): 427–428. Bibcode:2010Natur.465..427B. doi:10.1038/465427a. PMID 20505713. S2CID 205055896.
  120. ^ Jain, Sreepat (2016). Fundamentals of Invertebrate Palaeontology: Macrofossils. Springer. p. 73. ISBN 978-81-322-3658-0.
  121. ^ a b Kröger, B.; Yun-bai, Y. B. (2009). "Pulsed cephalopod diversification during the Ordovician". Palaeogeography, Palaeoclimatology, Palaeoecology. 273 (1–2): 174–201. Bibcode:2009PPP...273..174K. doi:10.1016/j.palaeo.2008.12.015.
  122. ^ Dzik, J. (1981). "Origin of the Cephalopoda" (PDF). Acta Palaeontologica Polonica. 26 (2): 161–191. (PDF) from the original on 2008-12-16.
  123. ^ a b c d Kröger, B. R.; Servais, T.; Zhang, Y.; Kosnik, M. (2009). "The origin and initial rise of pelagic cephalopods in the Ordovician". PLOS ONE. 4 (9): e7262. Bibcode:2009PLoSO...4.7262K. doi:10.1371/journal.pone.0007262. PMC 2749442. PMID 19789709.
  124. ^ a b Holland, C. H. (1987). "The nautiloid cephalopods: a strange success: President's anniversary address 1986". Journal of the Geological Society. 144 (1): 1–15. Bibcode:1987JGSoc.144....1H. doi:10.1144/gsjgs.144.1.0001. S2CID 128629737.
  125. ^ Kröger, Björn (2006). "Early growth-stages and classification of orthoceridan cephalopods of the Darriwillian (Middle Ordovician) of Baltoscandia". Lethaia. 39 (2): 129–139. doi:10.1080/00241160600623749.
  126. ^ a b Young, R. E.; Vecchione, M.; Donovan, D. T. (1998). "The evolution of coleoid cephalopods and their present biodiversity and ecology". South African Journal of Marine Science. 20 (1): 393–420. doi:10.2989/025776198784126287.
  127. ^ a b Tanabe, K. (2008). Cephalopods – Present and Past. Tokyo: Tokai University Press.[page needed]
  128. ^ Basil, Jennifer; Bahctinova, Irina; Kuroiwa, Kristine; Lee, Nandi; Mims, Desiree; Preis, Michael; Soucier, Christian (2005-09-01). "The function of the rhinophore and the tentacles of Nautilus pompilius L. (Cephalopoda, Nautiloidea) in orientation to odor". Marine and Freshwater Behaviour and Physiology. 38 (3): 209–221. doi:10.1080/10236240500310096. S2CID 33835096.
  129. ^ Shigeno, Shuichi; Sasaki, Takenori; Moritaki, Takeya; Kasugai, Takashi; Vecchione, Michael; Agata, Kiyokazu (January 2008). "Evolution of the cephalopod head complex by assembly of multiple molluscan body parts: Evidence from Nautilus embryonic development". Journal of Morphology. 269 (1): 1–17. doi:10.1002/jmor.10564. PMID 17654542. S2CID 13109195.
  130. ^ a b O'Brien, Caitlin E.; Roumbedakis, Katina; Winkelmann, Inger E. (2018-06-06). "The Current State of Cephalopod Science and Perspectives on the Most Critical Challenges Ahead From Three Early-Career Researchers". Frontiers in Physiology. 9: 700. doi:10.3389/fphys.2018.00700. ISSN 1664-042X. PMC 6014164. PMID 29962956.
  131. ^ a b c Albertin, Caroline B.; Simakov, Oleg; Mitros, Therese; Wang, Z. Yan; Pungor, Judit R.; Edsinger-Gonzales, Eric; Brenner, Sydney; Ragsdale, Clifton W.; Rokhsar, Daniel S. (August 2015). "The octopus genome and the evolution of cephalopod neural and morphological novelties". Nature. 524 (7564): 220–224. Bibcode:2015Natur.524..220A. doi:10.1038/nature14668. ISSN 0028-0836. PMC 4795812. PMID 26268193.
  132. ^ a b Gehring, Mary A. (2013-02-04). "Imprinted Gene Expression and the Contribution of Transposable Elements". Plant Transposons and Genome Dynamics in Evolution. Wiley-Blackwell. pp. 117–142. doi:10.1002/9781118500156.ch7. ISBN 978-1-118-50015-6.
  133. ^ Erwin, Jennifer A.; Marchetto, Maria C.; Gage, Fred H. (August 2014). "Mobile DNA elements in the generation of diversity and complexity in the brain". Nature Reviews Neuroscience. 15 (8): 497–506. doi:10.1038/nrn3730. ISSN 1471-003X. PMC 4443810. PMID 25005482.
  134. ^ Caroline B. Albertin et al. May 4th, 2022 "Genome and transcriptome mechanisms driving cephalopod evolution" Nature Communications
  135. ^ Hannah Schimdbour et al. April 21, 2022 "Emergence of novel cephalopod gene regulation and expression through large-scale genome reorganization" Nature Communications
  136. ^ Strugnell, J.; Norman, M.; Jackson, J.; Drummond, A.; Cooper, A. (2005). "Molecular phylogeny of coleoid cephalopods (Mollusca: Cephalopoda) using a multigene approach; the effect of data partitioning on resolving phylogenies in a Bayesian framework". Molecular Phylogenetics and Evolution. 37 (2): 426–441. doi:10.1016/j.ympev.2005.03.020. PMID 15935706.
  137. ^ Strugnell, J.; Jackson, J.; Drummond, A. J.; Cooper, A. (2006). "Divergence time estimates for major cephalopod groups: evidence from multiple genes". Cladistics. 22 (1): 89–96. doi:10.1111/j.1096-0031.2006.00086.x. PMID 34892892. S2CID 84743000.
  138. ^ Carlini, D. B.; Reece, K. S.; Graves, J. E. (2000). "Actin gene family evolution and the phylogeny of coleoid cephalopods (Mollusca: Cephalopoda)". Molecular Biology and Evolution. 17 (9): 1353–1370. doi:10.1093/oxfordjournals.molbev.a026419. PMID 10958852.
  139. ^ Bergmann, S.; Lieb, B.; Ruth, P.; Markl, J. (2006). "The hemocyanin from a living fossil, the cephalopod Nautilus pompilius: protein structure, gene organization, and evolution". Journal of Molecular Evolution. 62 (3): 362–374. Bibcode:2006JMolE..62..362B. doi:10.1007/s00239-005-0160-x. PMID 16501879. S2CID 4389953.
  140. ^ Bather, F.A. (1888b). "Professor Blake and Shell-Growth in Cephalopoda". Annals and Magazine of Natural History. 6. 1 (6): 421–426. doi:10.1080/00222938809460761.
  141. ^ Shevyrev, A. A. (2005). "The Cephalopod Macrosystem: A Historical Review, the Present State of Knowledge, and Unsolved Problems: 1. Major Features and Overall Classification of Cephalopod Mollusks". Paleontological Journal. 39 (6): 606–614. Translated from Paleontologicheskii Zhurnal No. 6, 2005, 33–42.
  142. ^ Shevyrev, A. A. (2006). "The cephalopod macrosystem; a historical review, the present state of knowledge, and unsolved problems; 2, Classification of nautiloid cephalopods". Paleontological Journal. 40 (1): 46–54. doi:10.1134/S0031030106010059. S2CID 84616115.
  143. ^ Kroger, B. . Archived from the original on 2009-08-31.
  144. ^ Bather, F.A. (1888a). "Shell-growth in Cephalopoda (Siphonopoda)". Annals and Magazine of Natural History. 6. 1 (4): 298–310. doi:10.1080/00222938809460727.
  145. ^ Berthold, Thomas; Engeser, Theo (1987). "Phylogenetic analysis and systematization of the Cephalopoda (Mollusca)". Verhandlungen Naturwissenschaftlichen Vereins in Hamburg. 29: 187–220.
  146. ^ Engeser, Theo (1997). . Archived from the original on 2006-09-25.
  147. ^ Lindgren, A. R.; Giribet, G.; Nishiguchi, M. K. (2004). "A combined approach to the phylogeny of Cephalopoda (Mollusca)". Cladistics. 20 (5): 454–486. CiteSeerX 10.1.1.693.2026. doi:10.1111/j.1096-0031.2004.00032.x. PMID 34892953. S2CID 85975284.
  148. ^ Hogan, C. Michael (22 December 2007). "Knossos fieldnotes". The Modern Antiquarian.
  149. ^ Wilk, Stephen R. (2000). Medusa: Solving the Mystery of the Gorgon. Oxford University Press. ISBN 978-0-19-988773-6.
  150. ^ "Caroli Linnaei Systema naturae sistens regna tria naturae". google.com.
  151. ^ Smedley, Edward; Rose, Hugh James; Rose, Henry John (1845). Encyclopaedia Metropolitana, Or, Universal Dictionary of Knowledge: Comprising the Twofold Advantage of a Philosophical and an Alphabetical Arrangement, with Appropriate Engravings. B. Fellowes. pp. 255–.
  152. ^ Dixon, Roland Burrage (1916). Oceanic. The Mythology of All Races. Vol. 9. Marshall Jones Company. pp. 2–.
  153. ^ Batchelor, John (1901). The Ainu and Their Folklore. London: The Religious Tract Society.
  154. ^ Chisholm, Hugh, ed. (1911). "Octopus" . Encyclopædia Britannica (11th ed.). Cambridge University Press.
  155. ^ Cohen-Vrignaud, Gerard (2012). "On Octopussies, or the Anatomy of Female Power". Differences. 23 (2): 32–61. doi:10.1215/10407391-1533520.
  156. ^ Fritze, Sointu; Suojoki, Saara (2000). Forbidden Images: Erotic Art from Japan's Edo Period (in Finnish). Helsingin kaupungin taidemuseo. pp. 23–28. ISBN 978-951-8965-54-4.
  157. ^ Uhlenbeck, Chris; Margarita Winkel; Ellis Tinios; Amy Reigle Newland (2005). Japanese Erotic Fantasies: Sexual Imagery of the Edo Period. Hotei. p. 161. ISBN 978-90-74822-66-4.
  158. ^ Briel, Holger (2010). Berninger, Mark; Ecke, Jochen; Haberkorn, Gideon (eds.). The Roving Eye Meets Traveling Pictures: The Field of Vision and the Global Rise of Adult Manga. Comics As a Nexus of Cultures: Essays on the Interplay of Media, Disciplines. McFarland. p. 203. ISBN 978-0-7864-3987-4.
  159. ^ Myers, P. Z. (17 May 2017). "Extraordinary Octopus Illustrations". Pharyngula. Retrieved 18 March 2017.
  160. ^ Myers, P. Z. (29 October 2006). "Definitely not safe for work". Pharyngula. Retrieved 18 March 2017.
  161. ^ Smith, S. (26 February 2010). "Why Mark Zuckerberg Octopus Cartoon Evokes 'Nazi Propaganda,' German Paper Apologizes". iMediaEthics. Retrieved 31 May 2017.

Further reading

  • Barskov, I. S.; Boiko, M. S.; Konovalova, V. A.; Leonova, T. B.; Nikolaeva, S. V. (2008). "Cephalopods in the marine ecosystems of the Paleozoic". Paleontological Journal. 42 (11): 1167–1284. doi:10.1134/S0031030108110014. S2CID 83608661. A comprehensive overview of Paleozoic cephalopods.
  • Campbell, Neil A.; Reece, Jane B.; Mitchell, Lawrence G. (1999). Biology, fifth edition. Menlo Park, California: Addison Wesley Longman, Inc. ISBN 978-0-8053-6566-5.
  • Felley, J., Vecchione, M., Roper, C. F. E., Sweeney, M. & Christensen, T., 2001–2003: Current Classification of Recent Cephalopoda. National Museum of Natural History: Department of Systematic Biology: Invertebrate Zoology: Cephalopods
  • Hanlon, Roger; Vecchione, Mike; Allcock, Louise (2018). Octopus, Squid, and Cuttlefish: A Visual, Scientific Guide to the Oceans' Most Advanced Invertebrates. University of Chicago Press. ISBN 978-0226459561.
  • N. Joan Abbott, Roddy Williamson, Linda Maddock. Cephalopod Neurobiology. Oxford University Press, 1995. ISBN 0-19-854790-0
  • Marion Nixon & John Z. Young. The brains and lives of Cephalopods. Oxford University Press, 2003. ISBN 0-19-852761-6
  • Hanlon, Roger T. & John B. Messenger. Cephalopod Behaviour. Cambridge University Press, 1996. ISBN 0-521-42083-0
  • Martin Stevens & Sami Merilaita. Animal camouflage: mechanisms and function. Cambridge University Press, 2011. ISBN 0-521-19911-5
  • Rodhouse, P. G.; Nigmatullin, Ch. M. (1996). "Role as Consumers". Philosophical Transactions of the Royal Society B: Biological Sciences. 351 (1343): 1003–1022. doi:10.1098/rstb.1996.0090.
  • Classification key to modern cephalopods: ftp://ftp.fao.org/docrep/fao/009/a0150e/a0150e03.pdf[permanent dead link]

External links

 
Wikispecies has information related to Cephalopoda.
 
The Wikibook Dichotomous Key has a page on the topic of: Cephalopoda
 
Wikisource has the text of the 1911 Encyclopædia Britannica article "Cephalopoda".
  • Fish vs. Cephalopods
  • TONMO.COM – The Octopus News Magazine Online – cephalopod articles and discussion
  • Scientific American: Can a Squid Fly Out of the Water?
  • Roger Hanlon's Seminar: "Rapid Adaptive Camouflage and Signaling in Cephalopods"
  • Deep Sea Dwelling Bristle Worms
 
Wikimedia Commons has media related to
Cephalopoda.

January 31, 2023
cephalopod, cephalopod, member, molluscan, class, greek, plural, κεφαλόποδες, kephalópodes, head, feet, such, squid, octopus, cuttlefish, nautilus, these, exclusively, marine, animals, characterized, bilateral, body, symmetry, prominent, head, arms, tentacles,. A cephalopod ˈ s ɛ f e l e p ɒ d is any member of the molluscan class Cephalopoda s ɛ f e ˈ l ɒ p e d e Greek plural kefalopodes kephalopodes head feet 3 such as a squid octopus cuttlefish or nautilus These exclusively marine animals are characterized by bilateral body symmetry a prominent head and a set of arms or tentacles muscular hydrostats modified from the primitive molluscan foot Fishers sometimes call cephalopods inkfish referring to their common ability to squirt ink The study of cephalopods is a branch of malacology known as teuthology CephalophodaTemporal range Late Cambrian present 1 possible Early Cambrian presence 2 PreꞒ Ꞓ O S D C P T J K Pg NExtant and extinct cephalopods clockwise from top left common octopus Octopus vulgaris Caribbean reef squid Sepioteuthis sepioidea chambered nautilus Nautilus pompilius Orthosphynctes Clarkeiteuthis conocauda and common cuttlefish Sepia officinalis Scientific classificationKingdom AnimaliaPhylum MolluscaSubphylum ConchiferaClass CephalopodaCuvier 1797SubclassesNautiloidea sensu lato paraphyletic Plectronoceratoidea paraphyletic Multiceratoidea paraphyletic Nautiloidea sensu stricto Endoceratoidea Orthoceratoidea paraphyletic Bactritoidea paraphyletic Ammonoidea ColeoideaCephalopods became dominant during the Ordovician period represented by primitive nautiloids The class now contains two only distantly related extant subclasses Coleoidea which includes octopuses squid and cuttlefish and Nautiloidea represented by Nautilus and Allonautilus In the Coleoidea the molluscan shell has been internalized or is absent whereas in the Nautiloidea the external shell remains About 800 living species of cephalopods have been identified Two important extinct taxa are the Ammonoidea ammonites and Belemnoidea belemnites Extant cephalopods range in size from the 10 mm 0 3 in Idiosepius thailandicus to the 14 m 45 1 ft colossal squid the largest extant invertebrate Contents 1 Distribution 2 Biology 2 1 Nervous system and behavior 2 2 Senses 2 2 1 Vision 2 2 2 Photoreception 2 2 3 Hearing 2 3 Use of light 2 4 Coloration 2 5 Ink 2 6 Circulatory system 2 7 Respiration 2 8 Locomotion and buoyancy 2 8 1 Octopus vs squid locomotion 2 9 Shell 2 10 Head appendages 2 11 Feeding 2 11 1 Radula 2 12 Excretory system 2 13 Reproduction and life cycle 2 13 1 Sexual maturity 2 13 2 Fertilization 2 13 3 Male male competition 2 13 4 Mate choice 2 13 5 Sexual dimorphism 2 13 6 Embryology 2 13 7 Development 3 Evolution 3 1 Genetics 3 2 Phylogeny 3 3 Taxonomy 3 3 1 Suprafamilial classification of the Treatise 3 3 2 Shevyrev classification 3 4 Cladistic classification 4 In culture 5 See also 6 References 7 Further reading 8 External linksDistribution Edit Left A pair of cuttlefish Sepia officinalis in shallow waterRight An octopus Benthoctopus sp on the Davidson Seamount at 2 422 m depth There are over 800 extant species of cephalopod 4 although new species continue to be described An estimated 11 000 extinct taxa have been described although the soft bodied nature of cephalopods means they are not easily fossilised 5 Cephalopods are found in all the oceans of Earth None of them can tolerate fresh water but the brief squid Lolliguncula brevis found in Chesapeake Bay is a notable partial exception in that it tolerates brackish water 6 Cephalopods are thought to be unable to live in fresh water due to multiple biochemical constraints and in their gt 400 million year existence have never ventured into fully freshwater habitats 7 Cephalopods occupy most of the depth of the ocean from the abyssal plain to the sea surface Their diversity is greatest near the equator 40 species retrieved in nets at 11 N by a diversity study and decreases towards the poles 5 species captured at 60 N 8 Biology EditNervous system and behavior Edit See also Cephalopod intelligence squid giant axon squid giant synapse and cephalopod aggression Left An octopus opening a container with a screw capRight Hawaiian bobtail squid Euprymna scolopes burying itself in the sand leaving only the eyes exposed Cephalopods are widely regarded as the most intelligent of the invertebrates and have well developed senses and large brains larger than those of gastropods 9 The nervous system of cephalopods is the most complex of the invertebrates 10 11 and their brain to body mass ratio falls between that of endothermic and ectothermic vertebrates 8 14 Captive cephalopods have also been known to climb out of their aquaria maneuver a distance of the lab floor enter another aquarium to feed on the crabs and return to their own aquarium 12 The brain is protected in a cartilaginous cranium The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology their large diameter due to lack of myelination makes them relatively easy to study compared with other animals 13 Many cephalopods are social creatures when isolated from their own kind some species have been observed shoaling with fish 14 Some cephalopods are able to fly through the air for distances of up to 50 m While cephalopods are not particularly aerodynamic they achieve these impressive ranges by jet propulsion water continues to be expelled from the funnel while the organism is in the air 15 The animals spread their fins and tentacles to form wings and actively control lift force with body posture 16 One species Todarodes pacificus has been observed spreading tentacles in a flat fan shape with a mucus film between the individual tentacles 16 17 while another Sepioteuthis sepioidea has been observed putting the tentacles in a circular arrangement 18 Senses Edit Cephalopods have advanced vision can detect gravity with statocysts and have a variety of chemical sense organs 8 34 Octopuses use their arms to explore their environment and can use them for depth perception 8 Vision Edit Main articles Cephalopod eye and mollusc eye The primitive nautilus eye functions similarly to a pinhole camera source source source source source source source source source source source source source source The W shaped pupil of the cuttlefish expanding when the lights are turned off Most cephalopods rely on vision to detect predators and prey and to communicate with one another 19 Consequently cephalopod vision is acute training experiments have shown that the common octopus can distinguish the brightness size shape and horizontal or vertical orientation of objects The morphological construction gives cephalopod eyes the same performance as shark eyes however their construction differs as cephalopods lack a cornea and have an everted retina 19 Cephalopods eyes are also sensitive to the plane of polarization of light 20 Unlike many other cephalopods nautiluses do not have good vision their eye structure is highly developed but lacks a solid lens They have a simple pinhole eye through which water can pass Instead of vision the animal is thought to use olfaction as the primary sense for foraging as well as locating or identifying potential mates A cuttlefish with W shaped pupils which may help them discriminate colors Surprisingly given their ability to change color all octopuses 21 and most cephalopods 22 23 are considered to be color blind Coleoid cephalopods octopus squid cuttlefish have a single photoreceptor type and lack the ability to determine color by comparing detected photon intensity across multiple spectral channels When camouflaging themselves they use their chromatophores to change brightness and pattern according to the background they see but their ability to match the specific color of a background may come from cells such as iridophores and leucophores that reflect light from the environment 24 They also produce visual pigments throughout their body and may sense light levels directly from their body 25 Evidence of color vision has been found in the sparkling enope squid Watasenia scintillans 22 26 It achieves color vision with three photoreceptors which are based on the same opsin but use distinct retinal molecules as chromophores A1 retinal A3 3 dehydroretinal and A4 4 hydroxyretinal The A1 photoreceptor is most sensitive to green blue 484 nm the A2 photoreceptor to blue green 500 nm and the A4 photoreceptor to blue 470 nm light 27 In 2015 a novel mechanism for spectral discrimination in cephalopods was described This relies on the exploitation of chromatic aberration wavelength dependence of focal length Numerical modeling shows that chromatic aberration can yield useful chromatic information through the dependence of image acuity on accommodation The unusual off axis slit and annular pupil shapes in cephalopods enhance this ability by acting as prisms which are scattering white light in all directions 28 29 Photoreception Edit In 2015 molecular evidence was published indicating that cephalopod chromatophores are photosensitive reverse transcription polymerase chain reactions RT PCR revealed transcripts encoding rhodopsin and retinochrome within the retinas and skin of the longfin inshore squid Doryteuthis pealeii and the common cuttlefish Sepia officinalis and broadclub cuttlefish Sepia latimanus The authors claim this is the first evidence that cephalopod dermal tissues may possess the required combination of molecules to respond to light 30 Hearing Edit Some squids have been shown to detect sound using their statocysts 31 but in general cephalopods are deaf Use of light Edit This broadclub cuttlefish Sepia latimanus can change from camouflage tans and browns top to yellow with dark highlights bottom in less than a second Further information Counter illumination Most cephalopods possess an assemblage of skin components that interact with light These may include iridophores leucophores chromatophores and in some species photophores Chromatophores are colored pigment cells that expand and contract in accordance to produce color and pattern which they can use in a startling array of fashions 8 30 As well as providing camouflage with their background some cephalopods bioluminesce shining light downwards to disguise their shadows from any predators that may lurk below 8 The bioluminescence is produced by bacterial symbionts the host cephalopod is able to detect the light produced by these organisms 32 Bioluminescence may also be used to entice prey and some species use colorful displays to impress mates startle predators or even communicate with one another 8 Coloration Edit Further information Animal coloration and Animals that can change color Cephalopods can change their colors and patterns in milliseconds whether for signalling both within the species and for warning or active camouflage 8 as their chromatophores are expanded or contracted 33 Although color changes appear to rely primarily on vision input there is evidence that skin cells specifically chromatophores can detect light and adjust to light conditions independently of the eyes 34 The octopus changes skin color and texture during quiet and active sleep cycles 35 Cephalopods can use chromatophores like a muscle which is why they can change their skin hue as rapidly as they do Coloration is typically stronger in near shore species than those living in the open ocean whose functions tend to be restricted to disruptive camouflage 8 2 These chromatophores are found throughout the body of the octopus however they are controlled by the same part of the brain that controls elongation during jet propulsion to reduce drag As such jetting octopuses can turn pale because the brain is unable to achieve both controlling elongation and controlling the chromatophores 36 Most octopuses mimic select structures in their field of view rather than becoming a composite color of their full background 37 Evidence of original coloration has been detected in cephalopod fossils dating as far back as the Silurian these orthoconic individuals bore concentric stripes which are thought to have served as camouflage 38 Devonian cephalopods bear more complex color patterns of unknown function 39 Ink Edit Main articles Cephalopod ink and ink sac With the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina 40 all known cephalopods have an ink sac which can be used to expel a cloud of dark ink to confuse predators 21 This sac is a muscular bag which originated as an extension of the hindgut It lies beneath the gut and opens into the anus into which its contents almost pure melanin can be squirted its proximity to the base of the funnel means the ink can be distributed by ejected water as the cephalopod uses its jet propulsion 21 The ejected cloud of melanin is usually mixed upon expulsion with mucus produced elsewhere in the mantle and therefore forms a thick cloud resulting in visual and possibly chemosensory impairment of the predator like a smokescreen However a more sophisticated behavior has been observed in which the cephalopod releases a cloud with a greater mucus content that approximately resembles the cephalopod that released it this decoy is referred to as a pseudomorph This strategy often results in the predator attacking the pseudomorph rather than its rapidly departing prey 21 For more information see Inking behaviors The ink sac of cephalopods has led to a common name of inkfish 41 formerly the pen and ink fish 42 Viscera of Chtenopteryx sicula Viscera of Ocythoe tuberculata Circulatory system Edit Cephalopods are the only molluscs with a closed circulatory system Coleoids have two gill hearts also known as branchial hearts that move blood through the capillaries of the gills A single systemic heart then pumps the oxygenated blood through the rest of the body 43 Like most molluscs cephalopods use hemocyanin a copper containing protein rather than hemoglobin to transport oxygen As a result their blood is colorless when deoxygenated and turns blue when bonded to oxygen 44 In oxygen rich environments and in acidic water hemoglobin is more efficient but in environments with little oxygen and in low temperatures hemocyanin has the upper hand 45 46 47 The hemocyanin molecule is much larger than the hemoglobin molecule allowing it to bond with 96 O2 or CO2 molecules instead of the hemoglobin s just four But unlike hemoglobin which are attached in millions on the surface of a single red blood cell hemocyanin molecules float freely in the bloodstream 48 Respiration Edit Cephalopods exchange gases with the seawater by forcing water through their gills which are attached to the roof of the organism 49 488 50 Water enters the mantle cavity on the outside of the gills and the entrance of the mantle cavity closes When the mantle contracts water is forced through the gills which lie between the mantle cavity and the funnel The water s expulsion through the funnel can be used to power jet propulsion If respiration is used concurrently with jet propulsion large losses in speed or oxygen generation can be expected 51 52 The gills which are much more efficient than those of other mollusks are attached to the ventral surface of the mantle cavity 50 There is a trade off with gill size regarding lifestyle To achieve fast speeds gills need to be small water will be passed through them quickly when energy is needed compensating for their small size However organisms which spend most of their time moving slowly along the bottom do not naturally pass much water through their cavity for locomotion thus they have larger gills along with complex systems to ensure that water is constantly washing through their gills even when the organism is stationary 49 The water flow is controlled by contractions of the radial and circular mantle cavity muscles 53 The gills of cephalopods are supported by a skeleton of robust fibrous proteins the lack of mucopolysaccharides distinguishes this matrix from cartilage 54 55 The gills are also thought to be involved in excretion with NH4 being swapped with K from the seawater 50 Locomotion and buoyancy Edit Octopuses swim headfirst with arms trailing behind While most cephalopods can move by jet propulsion this is a very energy consuming way to travel compared to the tail propulsion used by fish 56 The efficiency of a propeller driven waterjet i e Froude efficiency is greater than a rocket 57 The relative efficiency of jet propulsion decreases further as animal size increases paralarvae are far more efficient than juvenile and adult individuals 58 Since the Paleozoic era as competition with fish produced an environment where efficient motion was crucial to survival jet propulsion has taken a back role with fins and tentacles used to maintain a steady velocity 5 Whilst jet propulsion is never the sole mode of locomotion 5 208 the stop start motion provided by the jets continues to be useful for providing bursts of high speed not least when capturing prey or avoiding predators 5 Indeed it makes cephalopods the fastest marine invertebrates 8 Preface and they can out accelerate most fish 49 The jet is supplemented with fin motion in the squid the fins flap each time that a jet is released amplifying the thrust they are then extended between jets presumably to avoid sinking 58 Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity the spent water is expelled through the hyponome created by a fold in the mantle The size difference between the posterior and anterior ends of this organ control the speed of the jet the organism can produce 59 The velocity of the organism can be accurately predicted for a given mass and morphology of animal 60 Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome but direction can be controlled somewhat by pointing it in different directions 61 Some cephalopods accompany this expulsion of water with a gunshot like popping noise thought to function to frighten away potential predators 62 Cephalopods employ a similar method of propulsion despite their increasing size as they grow changing the dynamics of the water in which they find themselves Thus their paralarvae do not extensively use their fins which are less efficient at low Reynolds numbers and primarily use their jets to propel themselves upwards whereas large adult cephalopods tend to swim less efficiently and with more reliance on their fins 58 Nautilus belauensis seen from the front showing the opening of the hyponome Early cephalopods are thought to have produced jets by drawing their body into their shells as Nautilus does today 63 Nautilus is also capable of creating a jet by undulations of its funnel this slower flow of water is more suited to the extraction of oxygen from the water 63 When motionless Nautilus can only extract 20 of oxygen from the water 51 The jet velocity in Nautilus is much slower than in coleoids but less musculature and energy is involved in its production 64 Jet thrust in cephalopods is controlled primarily by the maximum diameter of the funnel orifice or perhaps the average diameter of the funnel 65 440 and the diameter of the mantle cavity 66 Changes in the size of the orifice are used most at intermediate velocities 65 The absolute velocity achieved is limited by the cephalopod s requirement to inhale water for expulsion this intake limits the maximum velocity to eight body lengths per second a speed which most cephalopods can attain after two funnel blows 65 Water refills the cavity by entering not only through the orifices but also through the funnel 65 Squid can expel up to 94 of the fluid within their cavity in a single jet thrust 57 To accommodate the rapid changes in water intake and expulsion the orifices are highly flexible and can change their size by a factor of twenty the funnel radius conversely changes only by a factor of around 1 5 65 Some octopus species are also able to walk along the seabed Squids and cuttlefish can move short distances in any direction by rippling of a flap of muscle around the mantle While most cephalopods float i e are neutrally buoyant or nearly so in fact most cephalopods are about 2 3 denser than seawater 14 they achieve this in different ways 56 Some such as Nautilus allow gas to diffuse into the gap between the mantle and the shell others allow purer water to ooze from their kidneys forcing out denser salt water from the body cavity 56 others like some fish accumulate oils in the liver 56 and some octopuses have a gelatinous body with lighter chloride ions replacing sulfate in the body chemistry 56 Squids are the primary sufferers of negative buoyancy in cephalopods The negative buoyancy means that some squids especially those whose habitat depths are rather shallow have to actively regulate their vertical positions This means that they must expend energy often through jetting or undulations in order to maintain the same depth As such the cost of transport of many squids are quite high That being said squid and other cephalopod that dwell in deep waters tend to be more neutrally buoyant which removes the need to regulate depth and increases their locomotory efficiency 67 51 The Macrotritopus defilippi or the sand dwelling octopus was seen mimicking both the coloration and the swimming movements of the sand dwelling flounder Bothus lunatus to avoid predators The octopuses were able to flatten their bodies and put their arms back to appear the same as the flounders as well as move with the same speed and movements 68 Females of two species Ocythoe tuberculata and Haliphron atlanticus have evolved a true swim bladder 69 Octopus vs squid locomotion Edit Two of the categories of cephalopods octopus and squid are vastly different in their movements despite being of the same class Octopuses are generally not seen as active swimmers they are often found scavenging the sea floor instead of swimming long distances through the water Squids on the other hand can be found to travel vast distances with some moving as much as 2000 km in 2 5 months at an average pace of 0 9 body lengths per second 70 There is a major reason for the difference in movement type and efficiency anatomy Both octopuses and squids have mantles referenced above which function towards respiration and locomotion in the form of jetting The composition of these mantles differs between the two families however In octopuses the mantle is made up of three muscle types longitudinal radial and circular The longitudinal muscles run parallel to the length of the octopus and they are used in order to keep the mantle the same length throughout the jetting process Given that they are muscles it can be noted that this means the octopus must actively flex the longitudinal muscles during jetting in order to keep the mantle at a constant length The radial muscles run perpendicular to the longitudinal muscles and are used to thicken and thin the wall of the mantle Finally the circular muscles are used as the main activators in jetting They are muscle bands that surround the mantle and expand contract the cavity All three muscle types work in unison to produce a jet as a propulsion mechanism 70 Squids do not have the longitudinal muscles that octopus do Instead they have a tunic 70 This tunic is made of layers of collagen and it surrounds the top and the bottom of the mantle Because they are made of collagen and not muscle the tunics are rigid bodies that are much stronger than the muscle counterparts This provides the squids some advantages for jet propulsion swimming The stiffness means that there is no necessary muscle flexing to keep the mantle the same size In addition tunics take up only 1 of the squid mantle s wall thickness whereas the longitudinal muscle fibers take up to 20 of the mantle wall thickness in octopuses 70 Also because of the rigidity of the tunic the radial muscles in squid can contract more forcefully The mantle is not the only place where squids have collagen Collagen fibers are located throughout the other muscle fibers in the mantle These collagen fibers act as elastics and are sometimes named collagen springs 70 As the name implies these fibers act as springs When the radial and circular muscles in the mantle contract they reach a point where the contraction is no longer efficient to the forward motion of the creature In such cases the excess contraction is stored in the collagen which then efficiently begins or aids in the expansion of the mantle at the end of the jet In some tests the collagen has been shown to be able to begin raising mantle pressure up to 50ms before muscle activity is initiated 70 These anatomical differences between squid and octopuses can help explain why squid can be found swimming comparably to fish while octopuses usually rely on other forms of locomotion on the sea floor such as bipedal walking crawling and non jetting swimming 71 Shell Edit See also Cirrate shell Cuttlebone Gladius cephalopod and Mollusc shell Cross section of Spirula spirula showing the position of the shell inside the mantle Cuttlebone of Sepia officinalis Gladius of Sepioteuthis lessoniana Nautiluses are the only extant cephalopods with a true external shell However all molluscan shells are formed from the ectoderm outer layer of the embryo in cuttlefish Sepia spp for example an invagination of the ectoderm forms during the embryonic period resulting in a shell cuttlebone that is internal in the adult 72 The same is true of the chitinous gladius of squid 72 and octopuses 73 Cirrate octopods have arch shaped cartilaginous fin supports 74 which are sometimes referred to as a shell vestige or gladius 75 The Incirrina have either a pair of rod shaped stylets or no vestige of an internal shell 76 and some squid also lack a gladius 77 The shelled coleoids do not form a clade or even a paraphyletic group 78 The Spirula shell begins as an organic structure and is then very rapidly mineralized 79 Shells that are lost may be lost by resorption of the calcium carbonate component 80 Females of the octopus genus Argonauta secrete a specialized paper thin egg case in which they reside and this is popularly regarded as a shell although it is not attached to the body of the animal and has a separate evolutionary origin The largest group of shelled cephalopods the ammonites are extinct but their shells are very common as fossils The deposition of carbonate leading to a mineralized shell appears to be related to the acidity of the organic shell matrix see Mollusc shell shell forming cephalopods have an acidic matrix whereas the gladius of squid has a basic matrix 81 The basic arrangement of the cephalopod outer wall is an outer spherulitic prismatic layer a laminar nacreous layer and an inner prismatic layer The thickness of every layer depends on the taxa 82 In modern cephalopods the Ca carbonate is aragonite As for other mollusc shells or coral skeletons the smallest visible units are irregular rounded granules 83 Left A giant squid found in Logy Bay Newfoundland in 1873 The two long feeding tentacles are visible on the extreme left and right Right Detail of the tentacular club of Abraliopsis morisi Head appendages Edit Main articles Cephalopod limb and tentacle Cephalopods as the name implies have muscular appendages extending from their heads and surrounding their mouths These are used in feeding mobility and even reproduction In coleoids they number eight or ten Decapods such as cuttlefish and squid have five pairs The longer two termed tentacles are actively involved in capturing prey 1 225 they can lengthen rapidly in as little as 15 milliseconds 1 225 In giant squid they may reach a length of 8 metres They may terminate in a broadened sucker coated club 1 225 The shorter four pairs are termed arms and are involved in holding and manipulating the captured organism 1 225 They too have suckers on the side closest to the mouth these help to hold onto the prey 1 226 Octopods only have four pairs of sucker coated arms as the name suggests though developmental abnormalities can modify the number of arms expressed 84 The tentacle consists of a thick central nerve cord which must be thick to allow each sucker to be controlled independently 85 surrounded by circular and radial muscles Because the volume of the tentacle remains constant contracting the circular muscles decreases the radius and permits the rapid increase in length Typically a 70 lengthening is achieved by decreasing the width by 23 1 227 The shorter arms lack this capability The size of the tentacle is related to the size of the buccal cavity larger stronger tentacles can hold prey as small bites are taken from it with more numerous smaller tentacles prey is swallowed whole so the mouth cavity must be larger 86 Externally shelled nautilids Nautilus and Allonautilus have on the order of 90 finger like appendages termed tentacles which lack suckers but are sticky instead and are partly retractable Feeding Edit The two part beak of the giant squid Architeuthis sp All living cephalopods have a two part beak 8 7 most have a radula although it is reduced in most octopus and absent altogether in Spirula 8 7 87 110 They feed by capturing prey with their tentacles drawing it into their mouth and taking bites from it 21 They have a mixture of toxic digestive juices some of which are manufactured by symbiotic algae which they eject from their salivary glands onto their captured prey held in their mouths These juices separate the flesh of their prey from the bone or shell 21 The salivary gland has a small tooth at its end which can be poked into an organism to digest it from within 21 The digestive gland itself is rather short 21 It has four elements with food passing through the crop stomach and caecum before entering the intestine Most digestion as well as the absorption of nutrients occurs in the digestive gland sometimes called the liver Nutrients and waste materials are exchanged between the gut and the digestive gland through a pair of connections linking the gland to the junction of the stomach and caecum 21 Cells in the digestive gland directly release pigmented excretory chemicals into the lumen of the gut which are then bound with mucus passed through the anus as long dark strings ejected with the aid of exhaled water from the funnel 21 Cephalopods tend to concentrate ingested heavy metals in their body tissue 88 However octopus arms use a family of cephalopod specific chemotactile receptors CRs to be their taste by touch system 89 Radula Edit See also Radula In cephalopods Amphioctopus marginatus eating a crab The cephalopod radula consists of multiple symmetrical rows of up to nine teeth 90 thirteen in fossil classes 91 The organ is reduced or even vestigial in certain octopus species and is absent in Spirula 91 The teeth may be homodont i e similar in form across a row heterodont otherwise or ctenodont comb like 91 Their height width and number of cusps is variable between species 91 The pattern of teeth repeats but each row may not be identical to the last in the octopus for instance the sequence repeats every five rows 91 79 Cephalopod radulae are known from fossil deposits dating back to the Ordovician 92 They are usually preserved within the cephalopod s body chamber commonly in conjunction with the mandibles but this need not always be the case 93 many radulae are preserved in a range of settings in the Mason Creek 94 Radulae are usually difficult to detect even when they are preserved in fossils as the rock must weather and crack in exactly the right fashion to expose them for instance radulae have only been found in nine of the 43 ammonite genera 95 clarification needed and they are rarer still in non ammonoid forms only three pre Mesozoic species possess one 92 Excretory system Edit Most cephalopods possess a single pair of large nephridia Filtered nitrogenous waste is produced in the pericardial cavity of the branchial hearts each of which is connected to a nephridium by a narrow canal The canal delivers the excreta to a bladder like renal sac and also resorbs excess water from the filtrate Several outgrowths of the lateral vena cava project into the renal sac continuously inflating and deflating as the branchial hearts beat This action helps to pump the secreted waste into the sacs to be released into the mantle cavity through a pore 96 Nautilus unusually possesses four nephridia none of which are connected to the pericardial cavities The incorporation of ammonia is important for shell formation in terrestrial molluscs and other non molluscan lineages 97 Because protein i e flesh is a major constituent of the cephalopod diet large amounts of ammonium ions are produced as waste The main organs involved with the release of this excess ammonium are the gills 98 The rate of release is lowest in the shelled cephalopods Nautilus and Sepia as a result of their using nitrogen to fill their shells with gas to increase buoyancy 98 Other cephalopods use ammonium in a similar way storing the ions as ammonium chloride to reduce their overall density and increase buoyancy 98 Reproduction and life cycle Edit Female Argonauta argo with eggcase and eggs Detail of the hectocotylus of Ocythoe tuberculata A dissected male specimen of Onykia ingens showing a non erect penis the white tubular structure located below most of the other organs A specimen of the same species exhibiting an elongation of the penis to 67 cm in length Cephalopods are a diverse group of species but share common life history traits for example they have a rapid growth rate and short life spans 99 Stearns 1992 suggested that in order to produce the largest possible number of viable offspring spawning events depend on the ecological environmental factors of the organism The majority of cephalopods do not provide parental care to their offspring except for example octopus which helps this organism increase the survival rate of their offspring 99 Marine species life cycles are affected by various environmental conditions 100 The development of a cephalopod embryo can be greatly affected by temperature oxygen saturation pollution light intensity and salinity 99 These factors are important to the rate of embryonic development and the success of hatching of the embryos Food availability also plays an important role in the reproductive cycle of cephalopods A limitation of food influences the timing of spawning along with their function and growth 100 Spawning time and spawning vary among marine species it s correlated with temperature though cephalopods in shallow water spawn in cold months so that the offspring would hatch at warmer temperatures Breeding can last from several days to a month 99 Sexual maturity Edit Cephalopods that are sexually mature and of adult size begin spawning and reproducing After the transfer of genetic material to the following generation the adult cephalopods then die 99 Sexual maturation in male and female cephalopods can be observed internally by the enlargement of gonads and accessory glands 101 Mating would be a poor indicator of sexual maturation in females they can receive sperm when not fully reproductively mature and store them until they are ready to fertilize the eggs 100 Males are more aggressive in their pre mating competition when in the presence of immature females than when competing for a sexually mature female 102 Most cephalopod males develop a hectocotylus an arm tip which is capable of transferring their spermatozoa into the female mantle cavity Though not all species use a hectocotylus for example the adult nautilus releases a spadix 103 An indication of sexual maturity of females is the development of brachial photophores to attract mates 104 Fertilization Edit Cephalopods are not broadcast spawners During the process of fertilization the females use sperm provided by the male via external fertilization Internal fertilization is seen only in octopuses 101 The initiation of copulation begins when the male catches a female and wraps his arm around her either in a male to female neck position or mouth to mouth position depending on the species The males then initiate the process of fertilization by contracting their mantle several times to release the spermatozoa 105 Cephalopods often mate several times which influences males to mate longer with females that have previously nearly tripling the number of contractions of the mantle 105 To ensure the fertilization of the eggs female cephalopods release a sperm attracting peptide through the gelatinous layers of the egg to direct the spermatozoa Female cephalopods lay eggs in clutches each egg is composed of a protective coat to ensure the safety of the developing embryo when released into the water column Reproductive strategies differ between cephalopod species In giant Pacific octopus large eggs are laid in a den it will often take several days to lay all of them 101 Once the eggs are released and attached to a sheltered substrate the females then die 101 making them semelparous In some species of cephalopods egg clutches are anchored to substrates by a mucilaginous adhesive substance These eggs are swelled with perivitelline fluid PVF a hypertonic fluid that prevents premature hatching 106 Fertilized egg clusters are neutrally buoyant depending on the depth that they were laid but can also be found in substrates such as sand a matrix of corals or seaweed 100 Because these species do not provide parental care for their offspring egg capsules can be injected with ink by the female in order to camouflage the embryos from predators 100 Male male competition Edit Most cephalopods engage in aggressive sex a protein in the male capsule sheath stimulates this behavior They also engage in male male aggression where larger males tend to win the interactions 99 When a female is near the males charge one another continuously and flail their arms If neither male backs away the arms extend to the back exposing the mouth followed by the biting of arm tips 107 During mate competition males also participate in a technique called flushing This technique is used by the second male attempting to mate with a female Flushing removes spermatophores in the buccal cavity that was placed there by the first mate by forcing water into the cavity 99 Another behavior that males engage in is sneaker mating or mimicry smaller males adjust their behavior to that of a female in order to reduce aggression By using this technique they are able to fertilize the eggs while the larger male is distracted by a different male 107 During this process the sneaker males quickly insert drop like sperm into the seminal receptacle 108 Mate choice Edit Mate choice is seen in cuttlefish species where females prefer some males over others though characteristics of the preferred males are unknown 99 A hypothesis states that females reject males by olfactory cues rather than visual cues 99 Several cephalopod species are polyandrous accepting and storing multiple male spermatophores which has been identified by DNA fingerprinting 105 Females are no longer receptive to mating attempts when holding their eggs in their arms Females can store sperm in two places 1 the buccal cavity where recently mated males place their spermatophores and 2 the internal sperm storage receptacles where sperm packages from previous males are stored 99 Spermatophore storage results in sperm competition which states that the female controls which mate fertilizes the eggs In order to reduce this sort of competition males develop agonistic behaviors like mate guarding and flushing 99 The Hapalochlaena lunulata or the blue ringed octopus readily mates with both males and females 109 Sexual dimorphism Edit In a variety of marine organisms it is seen that females are larger in size compared to the males in some closely related species In some lineages such as the blanket octopus males become structurally smaller and smaller resembling a term dwarfism dwarf males usually occurs at low densities 110 The blanket octopus male is an example of sexual evolutionary dwarfism females grow 10 000 to 40 000 times larger than the males and the sex ratio between males and females can be distinguished right after hatching of the eggs 110 Egg cases laid by a female squid Embryology Edit Cephalopod eggs span a large range of sizes from 1 to 30 mm in diameter 111 The fertilised ovum initially divides to produce a disc of germinal cells at one pole with the yolk remaining at the opposite pole The germinal disc grows to envelop and eventually absorb the yolk forming the embryo The tentacles and arms first appear at the hind part of the body where the foot would be in other molluscs and only later migrate towards the head 96 112 The funnel of cephalopods develops on the top of their head whereas the mouth develops on the opposite surface 113 86 The early embryological stages are reminiscent of ancestral gastropods and extant Monoplacophora 112 The shells develop from the ectoderm as an organic framework which is subsequently mineralized 72 In Sepia which has an internal shell the ectoderm forms an invagination whose pore is sealed off before this organic framework is deposited 72 Development Edit Chtenopteryx sicula paralarvae Left Two very young paralarvae The circular tentacular clubs bear approximately 20 irregularly arranged suckers Two chromatophores are present on each side of the mantle Centre Ventral dorsal and side views of a more advanced paralarva An equatorial circulet of seven large yellow brown chromatophores is present on the mantle Posteriorly the expanded vanes of the gladius are visible in the dorsal view Right Ventral and dorsal views of a very advanced paralarva Left Immature specimens of Chiroteuthis veranyi In this paralarval form known as the doratopsis stage the pen is longer than the mantle and neck combinedRight A mature Chiroteuthis veranyi This species has some of the longest tentacles in proportion to its size of any known cephalopod The length of time before hatching is highly variable smaller eggs in warmer waters are the fastest to hatch and newborns can emerge after as little as a few days Larger eggs in colder waters can develop for over a year before hatching 111 The process from spawning to hatching follows a similar trajectory in all species the main variable being the amount of yolk available to the young and when it is absorbed by the embryo 111 Unlike most other molluscs cephalopods do not have a morphologically distinct larval stage Instead the juveniles are known as paralarvae They quickly learn how to hunt using encounters with prey to refine their strategies 111 Growth in juveniles is usually allometric whilst adult growth is isometric 114 Evolution EditMain article Evolution of cephalopods The traditional view of cephalopod evolution holds that they evolved in the Late Cambrian from a monoplacophoran like ancestor 115 with a curved tapering shell 116 which was closely related to the gastropods snails 117 The similarity of the early shelled cephalopod Plectronoceras to some gastropods was used in support of this view The development of a siphuncle would have allowed the shells of these early forms to become gas filled thus buoyant in order to support them and keep the shells upright while the animal crawled along the floor and separated the true cephalopods from putative ancestors such as Knightoconus which lacked a siphuncle 117 Neutral or positive buoyancy i e the ability to float would have come later followed by swimming in the Plectronocerida and eventually jet propulsion in more derived cephalopods 118 Possible early Cambrian remains have been found in the Avalon Peninsula matching genetic data for a pre Cambrian origin 2 However some morphological evidence is difficult to reconcile with this view and the redescription of Nectocaris pteryx which did not have a shell and appeared to possess jet propulsion in the manner of derived cephalopods complicated the question of the order in which cephalopod features developed provided Nectocaris is a cephalopod at all 119 Early cephalopods were likely predators near the top of the food chain 21 After the late Cambrian extinction led to the disappearance of many Anomalocaridids predatory niches became available for other animals 120 During the Ordovician period the primitive cephalopods underwent pulses of diversification 121 to become diverse and dominant in the Paleozoic and Mesozoic seas 122 In the Early Palaeozoic their range was far more restricted than today they were mainly constrained to sublittoral regions of shallow shelves of the low latitudes and usually occurred in association with thrombolites 123 A more pelagic habit was gradually adopted as the Ordovician progressed 123 Deep water cephalopods whilst rare have been found in the Lower Ordovician but only in high latitude waters 123 The mid Ordovician saw the first cephalopods with septa strong enough to cope with the pressures associated with deeper water and could inhabit depths greater than 100 200 m 121 The direction of shell coiling would prove to be crucial to the future success of the lineages endogastric coiling would only permit large size to be attained with a straight shell whereas exogastric coiling initially rather rare permitted the spirals familiar from the fossil record to develop with their corresponding large size and diversity 124 Endogastric means the shell is curved so as the ventral or lower side is longitudinally concave belly in exogastric means the shell is curved so as the ventral side is longitudinally convex belly out allowing the funnel to be pointed backward beneath the shell 124 An ammonoid with the body chamber missing showing the septal surface especially at right with its undulating lobes and saddles The ancestors of coleoids including most modern cephalopods and the ancestors of the modern nautilus had diverged by the Floian Age of the Early Ordovician Period over 470 million years ago 123 125 The Bactritida a Silurian Triassic group of orthocones are widely held to be paraphyletic without the coleoids and ammonoids that is the latter groups arose from within the Bactritida 126 393 An increase in the diversity of the coleoids and ammonoids is observed around the start of the Devonian period and corresponds with a profound increase in fish diversity This could represent the origin of the two derived groups 126 Unlike most modern cephalopods most ancient varieties had protective shells These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species Competitive pressure from fish is thought to have forced the shelled forms into deeper water which provided an evolutionary pressure towards shell loss and gave rise to the modern coleoids a change which led to greater metabolic costs associated with the loss of buoyancy but which allowed them to recolonize shallow waters 117 36 However some of the straight shelled nautiloids evolved into belemnites out of which some evolved into squid and cuttlefish verification needed The loss of the shell may also have resulted from evolutionary pressure to increase maneuverability resulting in a more fish like habit 1 289 There has been debate on the embryological origin of cephalopod appendages 127 Until the mid twentieth century the Arms as Head hypothesis was widely recognized In this theory the arms and tentacles of cephalopods look similar to the head appendages of gastropods suggesting that they might be homologous structures Cephalopod appendages surround the mouth so logically they could be derived from embryonic head tissues 128 However the Arms as Foot hypothesis proposed by Adolf Naef in 1928 has increasingly been favoured 127 for example fate mapping of limb buds in the chambered nautilus indicates that limb buds originate from foot embryonic tissues 129 Genetics Edit The sequencing of a full Cephalopod genome has remained challenging to researchers due to the length and repetition of their DNA 130 The characteristics of Cephalopod genomes were initially hypothesized to be the result of entire genome duplications Following the full sequencing of a California two spot octopus the genome showed similar patterns to other marine invertebrates with significant additions to the genome assumed to be unique to Cephalopods No evidence of full genome duplication was found 131 Within the California two spot octopus genome there are substantial replications of two gene families Significantly the expanded gene families were only previously known to exhibit replicative behaviour within vertebrates 131 The first gene family was identified as the Protocadherins which are attributed to neuron development Protocadherins function as cell adhesion molecules essential for synaptic specificity The mechanism for Protocadherin gene family replication in vertebrates is attributed to complex splicing or cutting and pasting from a locus Following the sequencing of the California two spot octopus researchers found that the Prorocadherin gene family in Cephalopods has expanded in the genome due to tandem gene duplication The different replication mechanisms for Protocadherin genes indicate an independent evolution of Protocadherin gene expansion in vertebrates and invertebrates 131 Analysis of individual Cephalopod Protocadherin genes indicate independent evolution between species of Cephalopod A species of shore squid Doryteuthis pealeii with expanded Protocadherin gene families differ significantly from those of the California two spot octopus suggesting gene expansion did not occur before speciation within Cephalopods Despite different mechanisms for gene expansion the two spot octopus Protocadherin genes were more similar to vertebrates than squid suggesting a convergent evolution mechanism The second gene family known as C2H2 are small proteins that function as zinc transcription factors C2H2 are understood to moderate DNA RNA and protein functions within the cell 130 The sequenced California two spot octopus genome also showed a significant presence of transposable elements as well as transposon expression Although the role of transposable elements in marine vertebrates is still relatively unknown significant expression of transposons in nervous system tissues have been observed 132 In a study conducted on vertebrates the expression of transposons during development in the fruitfly Drosophila melanogaster activated genomic diversity between neurons 133 This diversity has been linked to increased memory and learning in mammals The connection between transposons and increased neuron capability may provide insight into the observed intelligence memory and function of Cephalopods 132 Using long read sequencing researchers have decoded the cephalopod genomes and discovered they have been churned and scrambled The genes were compared to those of thousands of other species and while blocks of three or more genes co occurred between squid and octopus the blocks of genes were not found together in any other animals Many of the groupings were in the nervous tissue suggesting the course they adapted their intelligence 134 135 Phylogeny Edit The approximate consensus of extant cephalopod phylogeny after Strugnell et al 2007 is shown in the cladogram 78 Mineralized taxa are in bold The attachment of the clade including Sepia and Spirula is unclear either of the points marked with an asterisk may represent the root of this clade Cephalopoda Nautiloids Nautilida Coleoids Basal octopods e g Argonautidae Octopodiformes Vampyromorphida Octopoda Decapodiformes Sepiolida bobtail squid Sepiida cuttlefish Idiosepiidae Myopsida Spirulida Certain benthic squids e g Bathyteuthoidea The internal phylogeny of the cephalopods is difficult to constrain many molecular techniques have been adopted but the results produced are conflicting 78 136 Nautilus tends to be considered an outgroup with Vampyroteuthis forming an outgroup to other squid however in one analysis the nautiloids octopus and teuthids plot as a polytomy 78 Some molecular phylogenies do not recover the mineralized coleoids Spirula Sepia and Metasepia as a clade however others do recover this more parsimonious seeming clade with Spirula as a sister group to Sepia and Metasepia in a clade that had probably diverged before the end of the Triassic 137 138 Molecular estimates for clade divergence vary One statistically robust estimate has Nautilus diverging from Octopus at 415 24 million years ago 139 Taxonomy Edit Chambered nautilus Nautilus pompilius Common cuttlefish Sepia officinalis Atlantic bobtail Sepiola atlantica European squid Loligo vulgaris Common octopus Octopus vulgaris The classification presented here for recent cephalopods follows largely from Current Classification of Recent Cephalopoda May 2001 for fossil cephalopods takes from Arkell et al 1957 Teichert and Moore 1964 Teichert 1988 and others The three subclasses are traditional corresponding to the three orders of cephalopods recognized by Bather 140 Class Cephalopoda indicates extinct groups Subclass Nautiloidea Fundamental ectocochliate cephalopods that provided the source for the Ammonoidea and Coleoidea Order Plectronocerida the ancestral cephalopods from the Cambrian Period Order Ellesmerocerida 500 to 470 Ma Order Endocerida 485 to 430 Ma Order Actinocerida 480 to 312 Ma Order Discosorida 482 to 392 Ma Order Pseudorthocerida 432 to 272 Ma Order Tarphycerida 485 to 386 Ma Order Oncocerida 478 5 to 324 Ma Order Nautilida extant 410 5 Ma to present Order Orthocerida 482 5 to 211 5 Ma Order Ascocerida 478 to 412 Ma Order Bactritida 418 1 to 260 5 Ma Subclass Ammonoidea Ammonites 479 to 66 Ma Order Goniatitida 388 5 to 252 Ma Order Ceratitida 254 to 200 Ma Order Ammonitida 215 to 66 Ma Subclass Coleoidea 410 0 Ma Rec Cohort Belemnoidea Belemnites and kin Genus Jeletzkya Order Aulacocerida 265 to 183 Ma Order Phragmoteuthida 189 6 to 183 Ma Order Hematitida 339 4 to 318 1 Ma Order Belemnitida 339 4 to 66 Ma Genus Belemnoteuthis 189 6 to 183 Ma Cohort Neocoleoidea Superorder Decapodiformes also known as Decabrachia or Decembranchiata Order Spirulida Ram s horn squid Order Sepiida cuttlefish Order Sepiolida pygmy bobtail and bottletail squid Order Teuthida squid Superorder Octopodiformes also known as Vampyropoda Family Trachyteuthididae Order Vampyromorphida Vampire squid Order Octopoda octopus Superorder Palaeoteuthomorpha Order BoletzkyidaOther classifications differ primarily in how the various decapod orders are related and whether they should be orders or families Suprafamilial classification of the Treatise Edit This is the older classification that combines those found in parts K and L of the Treatise on Invertebrate Paleontology which forms the basis for and is retained in large part by classifications that have come later Nautiloids in general Teichert and Moore 1964 sequence as given Subclass Endoceratoidea Not used by Flower e g Flower and Kummel 1950 interjocerids included in the Endocerida Order Endocerida Order Intejocerida dd Subclass Actinoceratoidea Not used by Flower ibidOrder Actinocerida dd Subclass Nautiloidea Nautiloidea in the restricted sense Order Ellesmerocerida Plectronocerida subsequently split off as separate order Order Orthocerida Includes orthocerids and pseudorthocerids Order Ascocerida Order Oncocerida Order Discosorida Order Tarphycerida Order Barrandeocerida A polyphyletic group now included in the Tarphycerida Order Nautilida dd Subclass BactritoideaOrder Bactritida dd Paleozoic Ammonoidea Miller Furnish and Schindewolf 1957 Suborder Anarcestina Suborder Clymeniina Suborder Goniatitina Suborder Prolecanitina dd Mesozoic Ammonoidea Arkel et al 1957 Suborder Ceratitina Suborder Phylloceratina Suborder Lytoceratina Suborder Ammonitina dd Subsequent revisions include the establishment of three Upper Cambrian orders the Plectronocerida Protactinocerida and Yanhecerida separation of the pseudorthocerids as the Pseudorthocerida and elevating orthoceratid as the Subclass Orthoceratoidea Shevyrev classification Edit Shevyrev 2005 suggested a division into eight subclasses mostly comprising the more diverse and numerous fossil forms 141 142 although this classification has been criticized as arbitrary lacking evidence and based on misinterpretations of other papers 143 Gyronaedyceras eryx a nautiloid from the Devonian of Wisconsin Various species of ammonites Holotype of Ostenoteuthis siroi from family Ostenoteuthidae A fossilised belemnite Class Cephalopoda Subclass Ellesmeroceratoidea Order Plectronocerida 501 to 490 Ma Order Protactinocerida Order Yanhecerida Order Ellesmerocerida 500 to 470 Ma Subclass Endoceratoidea 485 to 430 Ma Order Endocerida 485 to 430 Ma Order Intejocerida 485 to 480 Ma Subclass Actinoceratoidea Order Actinocerida 480 to 312 Ma Subclass Nautiloidea 490 0 Ma Rec Order Basslerocerida 490 to 480 Ma Order Tarphycerida 485 to 386 Ma Order Lituitida 485 to 480 Ma Order Discosorida 482 to 392 Ma Order Oncocerida 478 5 to 324 Ma Order Nautilida 410 5 Ma Rec Subclass Orthoceratoidea 482 5 to 211 5 Ma Order Orthocerida 482 5 to 211 5 Ma Order Ascocerida 478 to 412 Ma Order Dissidocerida 479 to 457 5 Ma Order Bajkalocerida Subclass Bactritoidea 422 to 252 Ma Subclass Ammonoidea 410 to 66 Ma Subclass Coleoidea 410 0 Ma rec 144 Cladistic classification Edit Pyritized fossil of Vampyronassa rhodanica a vampyromorphid from the Lower Callovian 165 3 million years ago Another recent system divides all cephalopods into two clades One includes nautilus and most fossil nautiloids The other clade Neocephalopoda or Angusteradulata is closer to modern coleoids and includes belemnoids ammonoids and many orthocerid families There are also stem group cephalopods of the traditional Ellesmerocerida that belong to neither clade 145 146 The coleoids despite some doubts 1 289 appear from molecular data to be monophyletic 147 In culture EditFurther information Cephalopods in popular culture Pen and wash drawing of an imagined colossal octopus attacking a ship by the malacologist Pierre de Montfort 1801 Ancient seafaring people were aware of cephalopods as evidenced by artworks such as a stone carving found in the archaeological recovery from Bronze Age Minoan Crete at Knossos 1900 1100 BC has a depiction of a fisherman carrying an octopus 148 The terrifyingly powerful Gorgon of Greek mythology may have been inspired by the octopus or squid the octopus s body representing the severed head of Medusa the beak as the protruding tongue and fangs and its tentacles as the snakes 149 The NROL 39 mission patch depicting the National Reconnaissance Office as an octopus with a long reach The Kraken are legendary sea monsters of giant proportions said to dwell off the coasts of Norway and Greenland usually portrayed in art as giant cephalopods attacking ships Linnaeus included it in the first edition of his 1735 Systema Naturae 150 151 A Hawaiian creation myth says that the present cosmos is the last of a series which arose in stages from the ruins of the previous universe In this account the octopus is the lone survivor of the previous alien universe 152 The Akkorokamui is a gigantic tentacled monster from Ainu folklore 153 A battle with an octopus plays a significant role in Victor Hugo s book Travailleurs de la mer Toilers of the Sea relating to his time in exile on Guernsey 154 Ian Fleming s 1966 short story collection Octopussy and The Living Daylights and the 1983 James Bond film were partly inspired by Hugo s book 155 Japanese erotic art shunga includes ukiyo e woodblock prints such as Katsushika Hokusai s 1814 print Tako to ama The Dream of the Fisherman s Wife in which an ama diver is sexually intertwined with a large and a small octopus 156 157 The print is a forerunner of tentacle erotica 158 The biologist P Z Myers noted in his science blog Pharyngula that octopuses appear in extraordinary graphic illustrations involving women tentacles and bare breasts 159 160 Its many arms that emanate from a common center means that the octopus is sometimes used to symbolize a powerful and manipulative organization 161 See also EditCephalopod size Cephalopod eye Cephalopod intelligence Pain in cephalopods Kraken List of nautiloids List of ammonitesReferences Edit a b c d e f g h i Wilbur Karl M Trueman E R Clarke M R eds 1985 The Mollusca vol 11 Form and Function New York Academic Press ISBN 0 12 728702 7 a b Hildenbrand Anne Austermann Gregor Fuchs Dirk Bengtson Peter Stinnesbeck Wolfgang 2021 A potential cephalopod from the early Cambrian of eastern Newfoundland Canada Communications Biology 4 1 388 doi 10 1038 s42003 021 01885 w PMC 7987959 PMID 33758350 Queiroz K Cantino P D Gauthier J A 2020 Phylonyms A Companion to the PhyloCode CRC Press p 1843 ISBN 978 1 138 33293 5 Welcome to CephBase CephBase Archived from the original on 12 January 2016 Retrieved 29 January 2016 a b c d Wilbur Karl M Clarke M R Trueman E R eds 1985 The Mollusca vol 12 Paleontology and neontology of Cephalopods New York Academic Press ISBN 0 12 728702 7 Bartol I K Mann R Vecchione M 2002 Distribution of the euryhaline squid Lolliguncula brevis in Chesapeake Bay effects of selected abiotic factors Marine Ecology Progress Series 226 235 247 Bibcode 2002MEPS 226 235B doi 10 3354 meps226235 Are there any freshwater cephalopods ABC Science 16 January 2013 a b c d e f g h i j k l Nixon Marion Young J Z 2003 The Brains and Lives of Cephalopods New York Oxford University Press ISBN 978 0 19 852761 9 Tricarico E Amodio P Ponte G Fiorito G 2014 Cognition and recognition in the cephalopod mollusc Octopus vulgaris coordinating interaction with environment and conspecifics In Witzany G ed Biocommunication of Animals Springer pp 337 349 ISBN 978 94 007 7413 1 Budelmann B U 1995 The cephalopod nervous system What evolution has made of the molluscan design In Breidbach O Kutsch W eds The nervous systems of invertebrates An evolutionary and comparative approach ISBN 978 3 7643 5076 5 Chung Wen Sung Kurniawan Nyoman D Marshall N Justin 2020 Toward an MRI Based Mesoscale Connectome of the Squid Brain iScience 23 1 100816 Bibcode 2020iSci 23j0816C doi 10 1016 j isci 2019 100816 PMC 6974791 PMID 31972515 Raven Peter et al 2003 Biology p 669 McGraw Hill Education New York ISBN 9780073383071 Tasaki I Takenaka T 1963 Resting and action potential of squid giant axons intracellularly perfused with sodium rich solutions Proceedings of the National Academy of Sciences of the United States of America 50 4 619 626 Bibcode 1963PNAS 50 619T doi 10 1073 pnas 50 4 619 PMC 221236 PMID 14077488 a b Packard A 1972 Cephalopods and fish the limits of convergence Biological Reviews 47 2 241 307 doi 10 1111 j 1469 185X 1972 tb00975 x S2CID 85088231 Macia Silvia Robinson Michael P Craze Paul Dalton Robert Thomas James D 2004 New observations on airborne jet propulsion flight in squid with a review of previous reports Journal of Molluscan Studies 70 3 297 299 doi 10 1093 mollus 70 3 297 a b Muramatsu K Yamamoto J Abe T Sekiguchi K Hoshi N Sakurai Y 2013 Oceanic squid do fly Marine Biology 160 5 1171 1175 doi 10 1007 s00227 013 2169 9 S2CID 84388744 Scientists Unravel Mystery of Flying Squid Ocean Views National Geographic 20 February 2013 Jabr Ferris 2 August 2010 Fact or Fiction Can a Squid Fly out of Water Scientific American a b Serb J M Eernisse D J 2008 Charting Evolution s Trajectory Using Molluscan Eye Diversity to Understand Parallel and Convergent Evolution Evolution Education and Outreach 1 4 439 447 doi 10 1007 s12052 008 0084 1 S2CID 2881223 Wells Martin J 2011 Part M Chapter 4 Physiology of Coleoids Treatise Online Lawrence Kansas USA doi 10 17161 to v0i0 4226 Archived from the original on 2016 08 22 Retrieved 2013 05 10 subscription required a b c d e f g h i j k Boyle Peter Rodhouse Paul 2004 Cephalopods ecology and fisheries Blackwell doi 10 1002 9780470995310 ch2 ISBN 978 0 632 06048 1 a b Messenger John B Hanlon Roger T 1998 Cephalopod Behaviour Cambridge Cambridge University Press pp 17 21 ISBN 978 0 521 64583 6 Chung Wen Sung Marshall N Justin 2016 09 14 Comparative visual ecology of cephalopods from different habitats Proceedings of the Royal Society B Biological Sciences 283 1838 20161346 doi 10 1098 rspb 2016 1346 ISSN 0962 8452 PMC 5031660 PMID 27629028 Hanlon and Messenger 68 Mathger L Roberts S Hanlon R 2010 Evidence for distributed light sensing in the skin of cuttlefish Sepia officinalis Biology Letters 6 5 600 603 doi 10 1098 rsbl 2010 0223 PMC 2936158 PMID 20392722 Michinomae M Masuda H Seidou M Kito Y 1994 Structural basis for wavelength discrimination in the banked retina of the firefly squid Watasenia scintillans Journal of Experimental Biology 193 1 1 12 doi 10 1242 jeb 193 1 1 PMID 9317205 Seidou M Sugahara M Uchiyama H Hiraki K Hamanaka T Michinomae M Yoshihara K Kito Y 1990 On the three visual pigments in the retina of the firefly squid Watasenia scintillans Journal of Comparative Physiology A 166 6 doi 10 1007 BF00187321 S2CID 25707481 Stubbs A L Stubbs C W 2015 A novel mechanism for color vision Pupil shape and chromatic aberration can provide spectral discrimination for color blind organisms bioRxiv 10 1101 017756 Octopus Eyes Are Crazier Than We Imagined a b Kingston A C Kuzirian A M Hanlon R T Cronin T W 2015 Visual phototransduction components in cephalopod chromatophores suggest dermal photoreception Journal of Experimental Biology 218 10 1596 1602 doi 10 1242 jeb 117945 PMID 25994635 S2CID 25431963 The cephalopods can hear you BBC News 2009 06 15 Retrieved 2010 04 28 Tong D Rozas S Oakley H Mitchell J Colley J Mcfall Ngai J Jun 2009 Evidence for light perception in a bioluminescent organ Proceedings of the National Academy of Sciences of the United States of America 106 24 9836 9841 Bibcode 2009PNAS 106 9836T doi 10 1073 pnas 0904571106 ISSN 0027 8424 PMC 2700988 PMID 19509343 Integument mollusks Encyclopaedia Britannica 2009 Encyclopaedia Britannica 2006 Ultimate Reference Suite DVD Ramirez M D Oakley T H 2015 Eye independent light activated chromatophore expansion LACE and expression of phototransduction genes in the skin of Octopus bimaculoides PDF Journal of Experimental Biology 218 10 1513 1520 doi 10 1242 jeb 110908 PMC 4448664 PMID 25994633 Archived PDF from the original on 2016 08 09 Sylvia Lima de Souza Medeiros et al 2021 Cyclic alternation of quiet and active sleep states in the octopus iScience doi 10 1016 j isci 2021 102223 PMC 8101055 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Huffard Christine L 2006 10 01 Locomotion by Abdopus aculeatus Cephalopoda Octopodidae walking the line between primary and secondary defenses Journal of Experimental Biology 209 19 3697 3707 doi 10 1242 jeb 02435 ISSN 0022 0949 PMID 16985187 S2CID 26862414 Josef Noam Amodio Piero Fiorito Graziano Shashar Nadav 2012 05 23 Camouflaging in a Complex Environment Octopuses Use Specific Features of Their Surroundings for Background Matching PLOS ONE 7 5 e37579 Bibcode 2012PLoSO 737579J doi 10 1371 journal pone 0037579 ISSN 1932 6203 PMC 3359305 PMID 22649542 Manda Stepan Turek Vojtech 2009 Minute Silurian oncocerid nautiloids with unusual color patterns Acta Palaeontologica Polonica 54 3 503 512 doi 10 4202 app 2008 0062 S2CID 54043278 Turek Vojtech 2009 Colour patterns in Early Devonian cephalopods from the Barrandian Area Taphonomy and taxonomy Acta Palaeontologica Polonica 54 3 491 502 doi 10 4202 app 2007 0064 S2CID 55851070 Hanlon Roger T Messenger John B 1999 Cephalopod Behaviour Cambridge University Press p 2 ISBN 978 0 521 64583 6 inkfish Merriam Webster Retrieved 1 February 2018 Bickerdyke John 1895 Sea Fishing London Longmans Green and Co p 114 the common squid or calamary Loligo vulgaris It is sometimes called the pen and ink fish on account of its ink bag and the delicate elongated shell which is found within it Wells M J 1 April 1980 Nervous control of the heartbeat in octopus Journal of Experimental Biology 85 1 111 28 doi 10 1242 jeb 85 1 111 PMID 7373208 Ghiretti Magaldi A October 1992 The Pre history of Hemocyanin The Discovery of Copper in the Blood of Molluscs Cellular and Molecular Life Sciences 48 10 971 972 doi 10 1007 BF01919143 S2CID 33290596 How many hearts does an octopus have New Scientist Why Do Octopuses Have Three Hearts Science ABC Where Would We Be Without Blood Illinois Science Council Why is Octopus Blood Blue Science Wilstar com a b c Gilbert Daniel L Adelman William J Arnold John M 1990 Squid as Experimental Animals illustrated ed Springer ISBN 978 0 306 43513 3 a b c Schipp Rudolf Mollenhauer Stephan Boletzky Sigurd 1979 Electron Microscopical and Histochemical Studies of Differentiation and Function of the Cephalopod Gill Sepia Officinalis L Zoomorphologie 93 3 193 207 doi 10 1007 BF00993999 S2CID 20214206 a b c Wells M J O Dor R K 1991 09 01 Jet Propulsion and the Evolution of the Cephalopods Bulletin of Marine Science 49 1 2 419 432 Packard A Trueman E R October 1974 Muscular activity of the mantle of Sepia and Loligo Cephalopoda during respiratory movements and jetting and its physiological interpretation The Journal of Experimental Biology 61 2 411 419 doi 10 1242 jeb 61 2 411 ISSN 0022 0949 PMID 4443736 Bone Q Brown E R Travers G 1994 On the respiratory flow in the cuttlefish Sepia Officinalis PDF Journal of Experimental Biology 194 1 153 165 doi 10 1242 jeb 194 1 153 PMID 9317534 Archived PDF from the original on 2009 03 04 Cole A Hall B 2009 Cartilage differentiation in cephalopod molluscs Zoology 112 1 2 15 doi 10 1016 j zool 2008 01 003 PMID 18722759 See also http tolweb org articles article id 4200 Archived 2010 06 16 at the Wayback Machine a b c d e Wilbur Karl M Clarke M R Trueman E R eds 1985 11 Evolution of Buoyancy and Locomotion in recent cephalopods The Mollusca vol 12 Paleontology and neontology of Cephalopods New York Academic Press ISBN 0 12 728702 7 a b Anderson E Demont M 2000 The mechanics of locomotion in the squid Loligo pealei Locomotory function and unsteady hydrodynamics of the jet and intramantle pressure Journal of Experimental Biology 203 18 2851 2863 doi 10 1242 jeb 203 18 2851 PMID 10952883 a b c Bartol I K Krueger P S Thompson J T Stewart W J 2008 Swimming dynamics and propulsive efficiency of squids throughout ontogeny Integrative and Comparative Biology 48 6 720 733 doi 10 1093 icb icn043 PMID 21669828 Shea E Vecchione M 2002 Quantification of ontogenetic discontinuities in three species of oegopsid squids using model II piecewise linear regression Marine Biology 140 5 971 979 doi 10 1007 s00227 001 0772 7 S2CID 84822175 Johnson W Soden P D Trueman E R February 1972 A study in jet propulsion an analysis of the motion of the squid Loligo vulgaris Journal of Experimental Biology 56 1972 155 165 doi 10 1242 jeb 56 1 155 Campbell Reece amp Mitchell 1999 p 612 Guerra A Martinell X Gonzalez A F Vecchione M Gracia J Martinell J 2007 A new noise detected in the ocean Journal of the Marine Biological Association of the United Kingdom 87 5 1255 1256 doi 10 1017 S0025315407058225 hdl 10261 27009 S2CID 85770435 a b Wells Martin J O Dor R K July 1991 Jet Propulsion and the Evolution of the Cephalopods Bulletin of Marine Science 49 1 419 432 14 Chamberlain J Jr 1993 Locomotion in ancient seas Constraint and opportunity in cephalopod adaptive design Geobios 26 Suppl 1 49 61 doi 10 1016 S0016 6995 06 80360 8 a b c d e O Dor R K 1988 The forces acting on swimming squid Journal of Experimental Biology 137 421 442 doi 10 1242 jeb 137 1 421 O Dor R K Hoar J A 2000 Does geometry limit squid growth ICES Journal of Marine Science 57 8 14 doi 10 1006 jmsc 1999 0502 Seibel B A Thuesen E V Childress J J Gorodezky L A April 1997 Decline in Pelagic Cephalopod Metabolism With Habitat Depth Reflects Differences in Locomotory Efficiency The Biological Bulletin 192 2 262 278 doi 10 2307 1542720 ISSN 1939 8697 JSTOR 1542720 PMID 28581868 Hanlon Roger T Watson Anya C Barbosa Alexandra 2010 02 01 A Mimic Octopus in the Atlantic Flatfish Mimicry and Camouflage by Macrotritopus defilippi The Biological Bulletin 218 1 15 24 doi 10 1086 BBLv218n1p15 hdl 1912 4811 ISSN 0006 3185 PMID 20203250 S2CID 12935620 The argonaut shell Gas mediated buoyancy control in a pelagic octopus a b c d e f Gosline John M de Mont M Edwin 1985 Jet propelled swimming in squids Scientific American Vol 252 no 1 pp 96 103 doi 10 1038 scientificamerican0185 96 ISSN 0036 8733 JSTOR 24967551 Huffard Christine L 2006 10 01 Locomotion by Abdopus aculeatus Cephalopoda Octopodidae Walking the line between primary and secondary defenses Journal of Experimental Biology 209 19 3697 3707 doi 10 1242 jeb 02435 ISSN 0022 0949 PMID 16985187 S2CID 26862414 a b c d Baratte S Andouche A Bonnaud L 2007 Engrailed in cephalopods a key gene related to the emergence of morphological novelties Development Genes and Evolution 217 5 353 362 doi 10 1007 s00427 007 0147 2 PMID 17394016 S2CID 22241391 von Boletzky S 2004 Ammonoides nus un defi pour la phylogenie des cephalopodes Nude ammonoids a challenge to cephalopod phylogeny Geobios 37 117 118 doi 10 1016 j geobios 2003 01 009 Gibson R N Atkinson R J A Gordon J D M eds 2006 Oceanography and Marine Biology An Annual Review CRC Press p 288 ISBN 978 1420006391 Aldred R G Nixon M Young J Z 1983 Cirrothauma murrayi Chun a finned octopod Philosophical Transactions of the Royal Society B Biological Sciences 301 1103 1 54 Bibcode 1983RSPTB 301 1A doi 10 1098 rstb 1983 0021 Fuchs D Ifrim C Stinnesbeck W 2008 A new Palaeoctopus Cephalopoda Coleoidea from the Late Cretaceous of Vallecillo north eastern Mexico and implications for the evolution of Octopoda Palaeontology 51 5 1129 1139 doi 10 1111 j 1475 4983 2008 00797 x von Boletzky Sigurd July 1991 The terminal spine of sepiolid hatchlings its development and functional morphology Mollusca Cephalopoda Bulletin of Marine Science 49 107 112 a b c d Strugnell J Nishiguchi M K 2007 Molecular phylogeny of coleoid cephalopods Mollusca Cephalopoda inferred from three mitochondrial and six nuclear loci a comparison of alignment implied alignment and analysis methods Journal of Molluscan Studies 73 4 399 410 doi 10 1093 mollus eym038 Warnke K Keupp H 2005 Spirula a window to the embryonic development of ammonoids Morphological and molecular indications for a palaeontological hypothesis PDF Facies 51 1 4 60 65 doi 10 1007 s10347 005 0054 9 S2CID 85026080 Furuhashi T Schwarzinger C Miksik I Smrz M Beran A 2009 Molluscan shell evolution with review of shell calcification hypothesis Comparative Biochemistry and Physiology B 154 3 351 371 doi 10 1016 j cbpb 2009 07 011 PMID 19665573 Dauphin Y 1996 The organic matrix of coleoid cephalopod shells molecular weights and isoelectric properties of the soluble matrix in relation to biomineralization processes Marine Biology 125 3 525 529 doi 10 1007 BF00353265 S2CID 83400480 Dauphin Y 1983 Les subdivisions majeures de la classe des cephalopodes bases de la systematique actuelle apport de l analyse microstructurale These Doct Etat Universite Paris Sud OCLC 972899981 Dauphin Y 2001 Nanostructures de la nacre des tests de cephalopodes actuels Palaontologische Zeitschrift 75 1 113 122 doi 10 1007 bf03022601 ISSN 0031 0220 S2CID 126900936 Toll R B Binger L C 1991 Arm anomalies Cases of supernumerary development and bilateral agenesis of arm pairs in Octopoda Mollusca Cephalopoda Zoomorphology 110 6 313 316 doi 10 1007 BF01668021 S2CID 34858474 Anatomy of the Common Squid 1912 Nixon 1988 in Wippich M G E Lehmann J 2004 Allocrioceras from the Cenomanian mid Cretaceous of the Lebanon and its bearing on the palaeobiological interpretation of heteromorphic ammonites Palaeontology 47 5 1093 1107 doi 10 1111 j 0031 0239 2004 00408 x Wilbur Karl M Clarke M R Trueman E R eds 1985 5 The Mollusca vol 12 Paleontology and neontology of Cephalopods New York Academic Press ISBN 0 12 728702 7 C Michael Hogan 2011 Celtic Sea eds P Saundry amp C Cleveland Encyclopedia of Earth National Council for Science and the Environment Washington DC Lena van Giesen et al 2020 Molecular Basis of Chemotactile Sensation in Octopus Vol 183 no 3 Cell pp 594 604 doi 10 1016 j cell 2020 09 008 Cephalopod radula Tree of Life web project a b c d e Nixon M 1995 A nomenclature for the radula of the Cephalopoda Mollusca living and fossil Journal of Zoology 236 73 81 doi 10 1111 j 1469 7998 1995 tb01785 x a b Gabbott S E 1999 Orthoconic cephalopods and associated fauna from the late Ordovician Soom Shale Lagerstatte South Africa Palaeontology 42 123 148 doi 10 1111 1475 4983 00065 Landman Neil H Davis Richard Arnold Mapes Royal H eds 2007 Cephalopods present and past new insights and fresh perspectives Springer ISBN 978 1 4020 6461 6 Richardson amp 1977 Fossils of the Mason Creek Kruta I Landman N Rouget I Cecca F Tafforeau P 2011 The role of ammonites in the Mesozoic marine food web revealed by jaw preservation Science 331 6013 70 72 Bibcode 2011Sci 331 70K doi 10 1126 science 1198793 PMID 21212354 S2CID 206530342 a b Barnes Robert D 1982 Invertebrate Zoology Philadelphia PA Holt Saunders International pp 450 460 ISBN 978 0 03 056747 6 Loest R A 1979 Ammonia Volatilization and Absorption by Terrestrial Gastropods a Comparison between Shelled and Shell Less Species Physiological Zoology 52 4 461 469 doi 10 1086 physzool 52 4 30155937 JSTOR 30155937 S2CID 87142440 a b c Boucher Rodoni R Mangold K 1994 Ammonia production in cephalopods physiological and evolutionary aspects Marine and Freshwater Behaviour and Physiology 25 1 3 53 60 doi 10 1080 10236249409378907 a b c d e f g h i j k Vidal Erica A G Advances in Cephalopod Science Biology Ecology Cultivation and Fisheries a b c d e Rodrigues M Guerra Troncoso 2010 The embryonic phase and its implication in the hatchling size and condition of Atlantic bobtail squid Sepiola Atlantica Helgoland Marine Research 65 2 211 216 Bibcode 2011HMR 65 211R doi 10 1007 s10152 010 0217 0 S2CID 41577834 a b c d Arkhipkin A I 1992 Reproductive system structure development and function in cephalopods with a new general scale for maturity stages Journal of Northwest Atlantic Fishery Science 12 63 74 doi 10 2960 j v12 a7 Mohanty Sobhi Ojanguren Alfredo F Fuiman Lee A 2014 07 01 Aggressive male mating behavior depends on female maturity in Octopus bimaculoides Marine Biology 161 7 1521 1530 doi 10 1007 s00227 014 2437 3 ISSN 0025 3162 S2CID 85256742 Saunders W B Spinosa C 1978 Sexual dimorphism in Nautilus from Palau Paleobiology 4 3 349 358 doi 10 1017 S0094837300006047 S2CID 85899974 Young R B 1975 A Systematic Approach to Planning Occupational Programs Community College Review 3 2 19 25 doi 10 1177 009155217500300204 S2CID 145374345 a b c Squires Z E Norman M D Stuart Fox D 2013 Mating behaviour and general spawning patterns of the southern dumpling squid Euprymna tasmanica Journal of Molluscan Studies 79 3 263 269 doi 10 1093 mollus eyt025 Marthy H J Hauser R Scholl A 1976 Natural tranquilizer in cephalopod eggs Nature 261 5560 496 7 Bibcode 1976Natur 261 496M doi 10 1038 261496a0 PMID 945466 S2CID 8693207 a b Norman M D Lu C C 1997 Redescription of the southern dumpling squid Euprymna tasmanica and a revision of the genus Euprymna Cephalopoda Sepiolidae Journal of the Marine Biological Association of the United Kingdom 77 4 1109 1137 doi 10 1017 s0025315400038662 S2CID 85748957 Iwata Y Ito K Sakurai Y 2008 Effect of low temperature on mating behavior of squid Loligo bleekeri Fisheries Science 74 6 1345 1347 doi 10 1111 j 1444 2906 2008 01664 x S2CID 43094931 Cheng Mary W Caldwell Roy L July 2000 Sex identification and mating in the blue ringed octopus Hapalochlaena lunulata Animal Behaviour 60 1 27 33 doi 10 1006 anbe 2000 1447 ISSN 0003 3472 PMID 10924200 S2CID 32899443 a b Fairbairn D 2013 Blanket Octopus Drifting Females and Dwarf Males Odd couples Extraordinary differences between the sexes in the animal kingdom Princeton University Press pp 104 115 a b c d Von Boletzky S 2003 Biology of early life stages in cephalopod molluscs Advances in Marine Biology Vol 44 pp 143 203 doi 10 1016 S0065 2881 03 44003 0 ISBN 978 0 12 026144 4 PMID 12846042 a b Shigeno S Sasaki T Moritaki T Kasugai T Vecchione M Agata K Jan 2008 Evolution of the cephalopod head complex by assembly of multiple molluscan body parts Evidence from Nautilus embryonic development Journal of Morphology 269 1 1 17 doi 10 1002 jmor 10564 PMID 17654542 S2CID 13109195 Gilbert Daniel L Adelman William J Arnold John M 1990 Squid as experimental animals New York Plenum Press ISBN 978 0 306 43513 3 Moltschaniwskyj Natalie A 2004 Understanding the process of growth in cephalopods Marine and Freshwater Research 55 4 379 386 doi 10 1071 MF03147 Lemche H Wingstrand K G 1959 The anatomy of Neopilina galatheae Lemche 1957 Mollusca Tryblidiacea Link to free full text plates Galathea Report 3 9 73 Wingstrand K G 1985 On the anatomy and relationships of Recent Monoplacophora Galathea Report 16 7 94 Archived from the original Link to free full text plates on 2016 03 03 Retrieved 2009 03 23 a b c Boyle P Rodhouse P 2005 Origin and Evolution Cephalopods p 36 doi 10 1002 9780470995310 ch3 ISBN 9780470995310 Kroger B R 2007 Some Lesser Known Features of the Ancient Cephalopod Order Ellesmerocerida Nautiloidea Cephalopoda Palaeontology 50 3 565 572 doi 10 1111 j 1475 4983 2007 00644 x Smith Martin R Caron Jean Bernard 2010 Primitive soft bodied cephalopods from the Cambrian Nature 465 7297 427 428 Bibcode 2010Natur 465 427B doi 10 1038 465427a PMID 20505713 S2CID 205055896 Jain Sreepat 2016 Fundamentals of Invertebrate Palaeontology Macrofossils Springer p 73 ISBN 978 81 322 3658 0 a b Kroger B Yun bai Y B 2009 Pulsed cephalopod diversification during the Ordovician Palaeogeography Palaeoclimatology Palaeoecology 273 1 2 174 201 Bibcode 2009PPP 273 174K doi 10 1016 j palaeo 2008 12 015 Dzik J 1981 Origin of the Cephalopoda PDF Acta Palaeontologica Polonica 26 2 161 191 Archived PDF from the original on 2008 12 16 a b c d Kroger B R Servais T Zhang Y Kosnik M 2009 The origin and initial rise of pelagic cephalopods in the Ordovician PLOS ONE 4 9 e7262 Bibcode 2009PLoSO 4 7262K doi 10 1371 journal pone 0007262 PMC 2749442 PMID 19789709 a b Holland C H 1987 The nautiloid cephalopods a strange success President s anniversary address 1986 Journal of the Geological Society 144 1 1 15 Bibcode 1987JGSoc 144 1H doi 10 1144 gsjgs 144 1 0001 S2CID 128629737 Kroger Bjorn 2006 Early growth stages and classification of orthoceridan cephalopods of the Darriwillian Middle Ordovician of Baltoscandia Lethaia 39 2 129 139 doi 10 1080 00241160600623749 a b Young R E Vecchione M Donovan D T 1998 The evolution of coleoid cephalopods and their present biodiversity and ecology South African Journal of Marine Science 20 1 393 420 doi 10 2989 025776198784126287 a b Tanabe K 2008 Cephalopods Present and Past Tokyo Tokai University Press page needed Basil Jennifer Bahctinova Irina Kuroiwa Kristine Lee Nandi Mims Desiree Preis Michael Soucier Christian 2005 09 01 The function of the rhinophore and the tentacles of Nautilus pompilius L Cephalopoda Nautiloidea in orientation to odor Marine and Freshwater Behaviour and Physiology 38 3 209 221 doi 10 1080 10236240500310096 S2CID 33835096 Shigeno Shuichi Sasaki Takenori Moritaki Takeya Kasugai Takashi Vecchione Michael Agata Kiyokazu January 2008 Evolution of the cephalopod head complex by assembly of multiple molluscan body parts Evidence from Nautilus embryonic development Journal of Morphology 269 1 1 17 doi 10 1002 jmor 10564 PMID 17654542 S2CID 13109195 a b O Brien Caitlin E Roumbedakis Katina Winkelmann Inger E 2018 06 06 The Current State of Cephalopod Science and Perspectives on the Most Critical Challenges Ahead From Three Early Career Researchers Frontiers in Physiology 9 700 doi 10 3389 fphys 2018 00700 ISSN 1664 042X PMC 6014164 PMID 29962956 a b c Albertin Caroline B Simakov Oleg Mitros Therese Wang Z Yan Pungor Judit R Edsinger Gonzales Eric Brenner Sydney Ragsdale Clifton W Rokhsar Daniel S August 2015 The octopus genome and the evolution of cephalopod neural and morphological novelties Nature 524 7564 220 224 Bibcode 2015Natur 524 220A doi 10 1038 nature14668 ISSN 0028 0836 PMC 4795812 PMID 26268193 a b Gehring Mary A 2013 02 04 Imprinted Gene Expression and the Contribution of Transposable Elements Plant Transposons and Genome Dynamics in Evolution Wiley Blackwell pp 117 142 doi 10 1002 9781118500156 ch7 ISBN 978 1 118 50015 6 Erwin Jennifer A Marchetto Maria C Gage Fred H August 2014 Mobile DNA elements in the generation of diversity and complexity in the brain Nature Reviews Neuroscience 15 8 497 506 doi 10 1038 nrn3730 ISSN 1471 003X PMC 4443810 PMID 25005482 Caroline B Albertin et al May 4th 2022 Genome and transcriptome mechanisms driving cephalopod evolution Nature Communications Hannah Schimdbour et al April 21 2022 Emergence of novel cephalopod gene regulation and expression through large scale genome reorganization Nature Communications Strugnell J Norman M Jackson J Drummond A Cooper A 2005 Molecular phylogeny of coleoid cephalopods Mollusca Cephalopoda using a multigene approach the effect of data partitioning on resolving phylogenies in a Bayesian framework Molecular Phylogenetics and Evolution 37 2 426 441 doi 10 1016 j ympev 2005 03 020 PMID 15935706 Strugnell J Jackson J Drummond A J Cooper A 2006 Divergence time estimates for major cephalopod groups evidence from multiple genes Cladistics 22 1 89 96 doi 10 1111 j 1096 0031 2006 00086 x PMID 34892892 S2CID 84743000 Carlini D B Reece K S Graves J E 2000 Actin gene family evolution and the phylogeny of coleoid cephalopods Mollusca Cephalopoda Molecular Biology and Evolution 17 9 1353 1370 doi 10 1093 oxfordjournals molbev a026419 PMID 10958852 Bergmann S Lieb B Ruth P Markl J 2006 The hemocyanin from a living fossil the cephalopod Nautilus pompilius protein structure gene organization and evolution Journal of Molecular Evolution 62 3 362 374 Bibcode 2006JMolE 62 362B doi 10 1007 s00239 005 0160 x PMID 16501879 S2CID 4389953 Bather F A 1888b Professor Blake and Shell Growth in Cephalopoda Annals and Magazine of Natural History 6 1 6 421 426 doi 10 1080 00222938809460761 Shevyrev A A 2005 The Cephalopod Macrosystem A Historical Review the Present State of Knowledge and Unsolved Problems 1 Major Features and Overall Classification of Cephalopod Mollusks Paleontological Journal 39 6 606 614 Translated from Paleontologicheskii Zhurnal No 6 2005 33 42 Shevyrev A A 2006 The cephalopod macrosystem a historical review the present state of knowledge and unsolved problems 2 Classification of nautiloid cephalopods Paleontological Journal 40 1 46 54 doi 10 1134 S0031030106010059 S2CID 84616115 Kroger B Peer review in the Russian Paleontological Journal Archived from the original on 2009 08 31 Bather F A 1888a Shell growth in Cephalopoda Siphonopoda Annals and Magazine of Natural History 6 1 4 298 310 doi 10 1080 00222938809460727 Berthold Thomas Engeser Theo 1987 Phylogenetic analysis and systematization of the Cephalopoda Mollusca Verhandlungen Naturwissenschaftlichen Vereins in Hamburg 29 187 220 Engeser Theo 1997 Fossil Nautiloidea Page Archived from the original on 2006 09 25 Lindgren A R Giribet G Nishiguchi M K 2004 A combined approach to the phylogeny of Cephalopoda Mollusca Cladistics 20 5 454 486 CiteSeerX 10 1 1 693 2026 doi 10 1111 j 1096 0031 2004 00032 x PMID 34892953 S2CID 85975284 Hogan C Michael 22 December 2007 Knossos fieldnotes The Modern Antiquarian Wilk Stephen R 2000 Medusa Solving the Mystery of the Gorgon Oxford University Press ISBN 978 0 19 988773 6 Caroli Linnaei Systema naturae sistens regna tria naturae google com Smedley Edward Rose Hugh James Rose Henry John 1845 Encyclopaedia Metropolitana Or Universal Dictionary of Knowledge Comprising the Twofold Advantage of a Philosophical and an Alphabetical Arrangement with Appropriate Engravings B Fellowes pp 255 Dixon Roland Burrage 1916 Oceanic The Mythology of All Races Vol 9 Marshall Jones Company pp 2 Batchelor John 1901 The Ainu and Their Folklore London The Religious Tract Society Chisholm Hugh ed 1911 Octopus Encyclopaedia Britannica 11th ed Cambridge University Press Cohen Vrignaud Gerard 2012 On Octopussies or the Anatomy of Female Power Differences 23 2 32 61 doi 10 1215 10407391 1533520 Fritze Sointu Suojoki Saara 2000 Forbidden Images Erotic Art from Japan s Edo Period in Finnish Helsingin kaupungin taidemuseo pp 23 28 ISBN 978 951 8965 54 4 Uhlenbeck Chris Margarita Winkel Ellis Tinios Amy Reigle Newland 2005 Japanese Erotic Fantasies Sexual Imagery of the Edo Period Hotei p 161 ISBN 978 90 74822 66 4 Briel Holger 2010 Berninger Mark Ecke Jochen Haberkorn Gideon eds The Roving Eye Meets Traveling Pictures The Field of Vision and the Global Rise of Adult Manga Comics As a Nexus of Cultures Essays on the Interplay of Media Disciplines McFarland p 203 ISBN 978 0 7864 3987 4 Myers P Z 17 May 2017 Extraordinary Octopus Illustrations Pharyngula Retrieved 18 March 2017 Myers P Z 29 October 2006 Definitely not safe for work Pharyngula Retrieved 18 March 2017 Smith S 26 February 2010 Why Mark Zuckerberg Octopus Cartoon Evokes Nazi Propaganda German Paper Apologizes iMediaEthics Retrieved 31 May 2017 Further reading EditBarskov I S Boiko M S Konovalova V A Leonova T B Nikolaeva S V 2008 Cephalopods in the marine ecosystems of the Paleozoic Paleontological Journal 42 11 1167 1284 doi 10 1134 S0031030108110014 S2CID 83608661 A comprehensive overview of Paleozoic cephalopods Campbell Neil A Reece Jane B Mitchell Lawrence G 1999 Biology fifth edition Menlo Park California Addison Wesley Longman Inc ISBN 978 0 8053 6566 5 Felley J Vecchione M Roper C F E Sweeney M amp Christensen T 2001 2003 Current Classification of Recent Cephalopoda National Museum of Natural History Department of Systematic Biology Invertebrate Zoology Cephalopods Hanlon Roger Vecchione Mike Allcock Louise 2018 Octopus Squid and Cuttlefish A Visual Scientific Guide to the Oceans Most Advanced Invertebrates University of Chicago Press ISBN 978 0226459561 N Joan Abbott Roddy Williamson Linda Maddock Cephalopod Neurobiology Oxford University Press 1995 ISBN 0 19 854790 0 Marion Nixon amp John Z Young The brains and lives of Cephalopods Oxford University Press 2003 ISBN 0 19 852761 6 Hanlon Roger T amp John B Messenger Cephalopod Behaviour Cambridge University Press 1996 ISBN 0 521 42083 0 Martin Stevens amp Sami Merilaita Animal camouflage mechanisms and function Cambridge University Press 2011 ISBN 0 521 19911 5 Rodhouse P G Nigmatullin Ch M 1996 Role as Consumers Philosophical Transactions of the Royal Society B Biological Sciences 351 1343 1003 1022 doi 10 1098 rstb 1996 0090 Classification key to modern cephalopods ftp ftp fao org docrep fao 009 a0150e a0150e03 pdf permanent dead link External links Edit Wikispecies has information related to Cephalopoda The Wikibook Dichotomous Key has a page on the topic of Cephalopoda Wikisource has the text of the 1911 Encyclopaedia Britannica article Cephalopoda Fish vs Cephalopods TONMO COM The Octopus News Magazine Online cephalopod articles and discussion Scientific American Can a Squid Fly Out of the Water Roger Hanlon s Seminar Rapid Adaptive Camouflage and Signaling in Cephalopods Deep Sea Dwelling Bristle Worms Wikimedia Commons has media related to Cephalopoda Retrieved from https en wikipedia org w index php title Cephalopod amp oldid 1136391495, wikipedia, wiki, book, books, library,

article

, read, download, free, free download, mp3, video, mp4, 3gp, jpg, jpeg, gif, png, picture, music, song, movie, book, game, games.