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Octopus

December 31, 2022

This article is about the order of cephalopod. For other uses, see Octopus (disambiguation).

An octopus (PL: octopuses or octopodes, see below for variants) is a soft-bodied, eight-limbed mollusc of the order Octopoda (/ɒkˈtɒpədə/, ok-TOP-ə-də[3]). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the center point of the eight limbs.[a] The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps. They trail their eight appendages behind them as they swim. The siphon is used both for respiration and for locomotion, by expelling a jet of water. Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse of all invertebrates.

Octopus
Temporal range: Middle Jurassic – recent
Common octopus
(Octopus vulgaris)
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
(unranked): Neocoleoidea
Clade: Vampyropoda
Superorder: Octopodiformes
Order: Octopoda
Leach, 1818[1]
Suborders

(traditional)

See § Evolution for families

Synonyms
  • Octopoida
    Leach, 1817[2]

Octopuses inhabit various regions of the ocean, including coral reefs, pelagic waters, and the seabed; some live in the intertidal zone and others at abyssal depths. Most species grow quickly, mature early, and are short-lived. In most species, the male uses a specially adapted arm to deliver a bundle of sperm directly into the female's mantle cavity, after which he becomes senescent and dies, while the female deposits fertilised eggs in a den and cares for them until they hatch, after which she also dies. Strategies to defend themselves against predators include the expulsion of ink, the use of camouflage and threat displays, the ability to jet quickly through the water and hide, and even deceit. All octopuses are venomous, but only the blue-ringed octopuses are known to be deadly to humans.

Octopuses appear in mythology as sea monsters like the Kraken of Norway and the Akkorokamui of the Ainu, and probably the Gorgon of ancient Greece. A battle with an octopus appears in Victor Hugo's book Toilers of the Sea, inspiring other works such as Ian Fleming's Octopussy. Octopuses appear in Japanese erotic art, shunga. They are eaten and considered a delicacy by humans in many parts of the world, especially the Mediterranean and the Asian seas.

Etymology and pluralisation

See also: Plural form of words ending in -us

The scientific Latin term octopus was derived from Ancient Greek ὀκτώπους, a compound form of ὀκτώ (oktō, "eight") and πούς (pous, "foot"), itself a variant form of ὀκτάπους, a word used for example by Alexander of Tralles (c. 525–c. 605) for the common octopus.[5][6][7] The standard pluralised form of "octopus" in English is "octopuses";[8] the Ancient Greek plural ὀκτώποδες, "octopodes" (/ɒkˈtɒpədiːz/), has also been used historically.[9] The alternative plural "octopi" is considered grammatically incorrect because it wrongly assumes that octopus is a Latin second declension "-us" noun or adjective when, in either Greek or Latin, it is a third declension noun.[10][11]

Historically, the first plural to commonly appear in English language sources, in the early 19th century, is the latinate form "octopi",[12] followed by the English form "octopuses" in the latter half of the same century. The Hellenic plural is roughly contemporary in usage, although it is also the rarest.[13]

Fowler's Modern English Usage states that the only acceptable plural in English is "octopuses", that "octopi" is misconceived, and "octopodes" pedantic;[14][15][16] the last is nonetheless used frequently enough to be acknowledged by the descriptivist Merriam-Webster 11th Collegiate Dictionary and Webster's New World College Dictionary. The Oxford English Dictionary lists "octopuses", "octopi", and "octopodes", in that order, reflecting frequency of use, calling "octopodes" rare and noting that "octopi" is based on a misunderstanding.[17] The New Oxford American Dictionary (3rd Edition, 2010) lists "octopuses" as the only acceptable pluralisation, and indicates that "octopodes" is still occasionally used, but that "octopi" is incorrect.[18]

Anatomy and physiology

Size

See also: Cephalopod size
 
A giant Pacific octopus at Echizen Matsushima Aquarium, Japan

The giant Pacific octopus (Enteroctopus dofleini) is often cited as the largest known octopus species. Adults usually weigh around 15 kg (33 lb), with an arm span of up to 4.3 m (14 ft).[19] The largest specimen of this species to be scientifically documented was an animal with a live mass of 71 kg (156.5 lb).[20] Much larger sizes have been claimed for the giant Pacific octopus:[21] one specimen was recorded as 272 kg (600 lb) with an arm span of 9 m (30 ft).[22] A carcass of the seven-arm octopus, Haliphron atlanticus, weighed 61 kg (134 lb) and was estimated to have had a live mass of 75 kg (165 lb).[23][24] The smallest species is Octopus wolfi, which is around 2.5 cm (1 in) and weighs less than 1 g (0.035 oz).[25]

External characteristics

The octopus is bilaterally symmetrical along its dorso-ventral (back to belly) axis; the head and foot are at one end of an elongated body and function as the anterior (front) of the animal. The head includes the mouth and brain. The foot has evolved into a set of flexible, prehensile appendages, known as "arms", that surround the mouth and are attached to each other near their base by a webbed structure.[26] The arms can be described based on side and sequence position (such as L1, R1, L2, R2) and divided into four pairs.[27][26] The two rear appendages are generally used to walk on the sea floor, while the other six are used to forage for food.[28] The bulbous and hollow mantle is fused to the back of the head and is known as the visceral hump; it contains most of the vital organs.[29][30] The mantle cavity has muscular walls and contains the gills; it is connected to the exterior by a funnel or siphon.[26][31] The mouth of an octopus, located underneath the arms, has a sharp hard beak.[30]

 
Diagram of octopus from side, with gills, funnel, eye, ocellus (eyespot), web, arms, suckers, hectocotylus and ligula labelled.

The skin consists of a thin outer epidermis with mucous cells and sensory cells, and a connective tissue dermis consisting largely of collagen fibres and various cells allowing colour change.[26] Most of the body is made of soft tissue allowing it to lengthen, contract, and contort itself. The octopus can squeeze through tiny gaps; even the larger species can pass through an opening close to 2.5 cm (1 in) in diameter.[30] Lacking skeletal support, the arms work as muscular hydrostats and contain longitudinal, transverse and circular muscles around a central axial nerve. They can extend and contract, twist to left or right, bend at any place in any direction or be held rigid.[32][33]

The interior surfaces of the arms are covered with circular, adhesive suckers. The suckers allow the octopus to anchor itself or to manipulate objects. Each sucker is usually circular and bowl-like and has two distinct parts: an outer shallow cavity called an infundibulum and a central hollow cavity called an acetabulum, both of which are thick muscles covered in a protective chitinous cuticle. When a sucker attaches to a surface, the orifice between the two structures is sealed. The infundibulum provides adhesion while the acetabulum remains free, and muscle contractions allow for attachment and detachment.[34][35] Each of the eight arms senses and responds to light, allowing the octopus to control the limbs even if its head is obscured.[36]

 
A finned Grimpoteuthis species with its atypical octopus body plan

The eyes of the octopus are large and at the top of the head. They are similar in structure to those of a fish, and are enclosed in a cartilaginous capsule fused to the cranium. The cornea is formed from a translucent epidermal layer; the slit-shaped pupil forms a hole in the iris just behind the cornea. The lens is suspended behind the pupil; photoreceptive retinal cells cover the back of the eye. The pupil can be adjusted in size; a retinal pigment screens incident light in bright conditions.[26]

Some species differ in form from the typical octopus body shape. Basal species, the Cirrina, have stout gelatinous bodies with webbing that reaches near the tip of their arms, and two large fins above the eyes, supported by an internal shell. Fleshy papillae or cirri are found along the bottom of the arms, and the eyes are more developed.[37][38]

Circulatory system

Octopuses have a closed circulatory system, in which the blood remains inside blood vessels. Octopuses have three hearts; a systemic or main heart that circulates blood around the body and two branchial or gill hearts that pump it through each of the two gills. The systemic heart is inactive when the animal is swimming and thus it tires quickly and prefers to crawl.[39][40] Octopus blood contains the copper-rich protein haemocyanin to transport oxygen. This makes the blood very viscous and it requires considerable pressure to pump it around the body; octopuses' blood pressures can exceed 75 mmHg (10 kPa).[39][40][41] In cold conditions with low oxygen levels, haemocyanin transports oxygen more efficiently than haemoglobin. The haemocyanin is dissolved in the plasma instead of being carried within blood cells, and gives the blood a bluish colour.[39][40]

The systemic heart has muscular contractile walls and consists of a single ventricle and two atria, one for each side of the body. The blood vessels consist of arteries, capillaries and veins and are lined with a cellular endothelium which is quite unlike that of most other invertebrates. The blood circulates through the aorta and capillary system, to the vena cavae, after which the blood is pumped through the gills by the branchial hearts and back to the main heart. Much of the venous system is contractile, which helps circulate the blood.[26]

Respiration

 
Octopus with open siphon. The siphon is used for respiration, waste disposal and discharging ink.

Respiration involves drawing water into the mantle cavity through an aperture, passing it through the gills, and expelling it through the siphon. The ingress of water is achieved by contraction of radial muscles in the mantle wall, and flapper valves shut when strong circular muscles force the water out through the siphon.[42] Extensive connective tissue lattices support the respiratory muscles and allow them to expand the respiratory chamber.[43] The lamella structure of the gills allows for a high oxygen uptake, up to 65% in water at 20 °C (68 °F).[44] Water flow over the gills correlates with locomotion, and an octopus can propel its body when it expels water out of its siphon.[43][41]

The thin skin of the octopus absorbs additional oxygen. When resting, around 41% of an octopus's oxygen absorption is through the skin. This decreases to 33% when it swims, as more water flows over the gills; skin oxygen uptake also increases. When it is resting after a meal, absorption through the skin can drop to 3% of its total oxygen uptake.[45]

Digestion and excretion

The digestive system of the octopus begins with the buccal mass which consists of the mouth with its chitinous beak, the pharynx, radula and salivary glands.[46] The radula is a spiked, muscular tongue-like organ with multiple rows of tiny teeth.[30] Food is broken down and is forced into the oesophagus by two lateral extensions of the esophageal side walls in addition to the radula. From there it is transferred to the gastrointestinal tract, which is mostly suspended from the roof of the mantle cavity by numerous membranes. The tract consists of a crop, where the food is stored; a stomach, where food is ground down; a caecum where the now sludgy food is sorted into fluids and particles and which plays an important role in absorption; the digestive gland, where liver cells break down and absorb the fluid and become "brown bodies"; and the intestine, where the accumulated waste is turned into faecal ropes by secretions and blown out of the funnel via the rectum.[46]

During osmoregulation, fluid is added to the pericardia of the branchial hearts. The octopus has two nephridia (equivalent to vertebrate kidneys) which are associated with the branchial hearts; these and their associated ducts connect the pericardial cavities with the mantle cavity. Before reaching the branchial heart, each branch of the vena cava expands to form renal appendages which are in direct contact with the thin-walled nephridium. The urine is first formed in the pericardial cavity, and is modified by excretion, chiefly of ammonia, and selective absorption from the renal appendages, as it is passed along the associated duct and through the nephridiopore into the mantle cavity.[26][47]

A common octopus (Octopus vulgaris) moving around. Its nervous system allows the arms to move with some autonomy.

Nervous system and senses

Octopuses (along with cuttlefish) have the highest brain-to-body mass ratios of all invertebrates;[48] this is greater than that of many vertebrates.[49] Octopuses have the same jumping genes that are active in the human brain, implying an evolutionary convergence at molecular level.[50] The nervous system is complex, only part of which is localised in its brain, which is contained in a cartilaginous capsule.[51] Two-thirds of an octopus's neurons are in the nerve cords of its arms; these are capable of complex reflex actions without input from the brain.[52] Unlike vertebrates, the complex motor skills of octopuses are not organised in their brains via internal somatotopic maps of their bodies.[53]

 
Eye of common octopus

Like other cephalopods, octopuses have camera-like eyes,[48] and can distinguish the polarisation of light. Colour vision appears to vary from species to species, for example being present in O. aegina but absent in O. vulgaris.[54]Opsins in the skin respond to different wavelengths of light and help the animals choose a coloration that camouflages them; the chromatophores in the skin can respond to light independently of the eyes.[55][56] An alternative hypothesis is that cephalopod eyes in species which only have a single photoreceptor protein may use chromatic aberration to turn monochromatic vision into colour vision, though this sacrifices image quality. This would explain pupils shaped like the letter U, the letter W, or a dumbbell, as well as explaining the need for colourful mating displays.[57]

Attached to the brain are two organs called statocysts (sac-like structures containing a mineralised mass and sensitive hairs), that allow the octopus to sense the orientation of its body. They provide information on the position of the body relative to gravity and can detect angular acceleration. An autonomic response keeps the octopus's eyes oriented so that the pupil is always horizontal.[26] Octopuses may also use the statocyst to hear sound. The common octopus can hear sounds between 400 Hz and 1000 Hz, and hears best at 600 Hz.[58]

Octopuses have an excellent somatosensory system. Their suction cups are equipped with chemoreceptors so they can taste what they touch. Octopus arms move easily because the sensors recognise octopus skin and prevent self-attachment.[59] Octopuses appear to have poor proprioceptive sense and must observe the arms visually to keep track of their position.[60][61]

Ink sac

The ink sac of an octopus is located under the digestive gland. A gland attached to the sac produces the ink, and the sac stores it. The sac is close enough to the funnel for the octopus to shoot out the ink with a water jet. Before it leaves the funnel, the ink passes through glands which mix it with mucus, creating a thick, dark blob which allows the animal to escape from a predator.[62] The main pigment in the ink is melanin, which gives it its black colour.[63] Cirrate octopuses usually lack the ink sac.[37]

Lifecycle

Reproduction

Octopuses are gonochoric and have a single, posteriorly-located gonad which is associated with the coelom. The testis in males and the ovary in females bulges into the gonocoel and the gametes are released here. The gonocoel is connected by the gonoduct to the mantle cavity, which it enters at the gonopore.[26] An optic gland creates hormones that cause the octopus to mature and age and stimulate gamete production. The gland may be triggered by environmental conditions such as temperature, light and nutrition, which thus control the timing of reproduction and lifespan.[64][65]

When octopuses reproduce, the male uses a specialised arm called a hectocotylus to transfer spermatophores (packets of sperm) from the terminal organ of the reproductive tract (the cephalopod "penis") into the female's mantle cavity.[66] The hectocotylus in benthic octopuses is usually the third right arm, which has a spoon-shaped depression and modified suckers near the tip. In most species, fertilisation occurs in the mantle cavity.[26]

The reproduction of octopuses has been studied in only a few species. One such species is the giant Pacific octopus, in which courtship is accompanied, especially in the male, by changes in skin texture and colour. The male may cling to the top or side of the female or position himself beside her. There is some speculation that he may first use his hectocotylus to remove any spermatophore or sperm already present in the female. He picks up a spermatophore from his spermatophoric sac with the hectocotylus, inserts it into the female's mantle cavity, and deposits it in the correct location for the species, which in the giant Pacific octopus is the opening of the oviduct. Two spermatophores are transferred in this way; these are about one metre (yard) long, and the empty ends may protrude from the female's mantle.[67] A complex hydraulic mechanism releases the sperm from the spermatophore, and it is stored internally by the female.[26]

 
Female giant Pacific octopus guarding strings of eggs

About forty days after mating, the female giant Pacific octopus attaches strings of small fertilised eggs (10,000 to 70,000 in total) to rocks in a crevice or under an overhang. Here she guards and cares for them for about five months (160 days) until they hatch.[67] In colder waters, such as those off Alaska, it may take up to ten months for the eggs to completely develop.[68]: 74  The female aerates them and keeps them clean; if left untended, many will die.[69] She does not feed during this time and dies soon after. Males become senescent and die a few weeks after mating.[64]

The eggs have large yolks; cleavage (division) is superficial and a germinal disc develops at the pole. During gastrulation, the margins of this grow down and surround the yolk, forming a yolk sac, which eventually forms part of the gut. The dorsal side of the disc grows upward and forms the embryo, with a shell gland on its dorsal surface, gills, mantle and eyes. The arms and funnel develop as part of the foot on the ventral side of the disc. The arms later migrate upward, coming to form a ring around the funnel and mouth. The yolk is gradually absorbed as the embryo develops.[26]

 
Octopus paralarva, a planktonic hatchling

Most young octopuses hatch as paralarvae and are planktonic for weeks to months, depending on the species and water temperature. They feed on copepods, arthropod larvae and other zooplankton, eventually settling on the ocean floor and developing directly into adults with no distinct metamorphoses that are present in other groups of mollusc larvae.[26] Octopus species that produce larger eggs – including the southern blue-ringed, Caribbean reef, California two-spot, Eledone moschata[70] and deep sea octopuses – instead hatch as benthic animals similar to the adults.[68]: 74–75 

In the argonaut (paper nautilus), the female secretes a fine, fluted, papery shell in which the eggs are deposited and in which she also resides while floating in mid-ocean. In this she broods the young, and it also serves as a buoyancy aid allowing her to adjust her depth. The male argonaut is minute by comparison and has no shell.[71]

Lifespan

Octopuses have a relatively short lifespan; some species live for as little as six months. The Giant Pacific octopus, one of the two largest species of octopus, may live for as much as five years. Octopus lifespan is limited by reproduction.[72] For most octopuses the last stage of their life is called senescence. It is the breakdown of cellular function without repair or replacement. For males, this typically begins after mating. Senescence may last from weeks to a few months, at most. For females, it begins when they lay a clutch of eggs. Females will spend all their time aerating and protecting their eggs until they are ready to hatch. During senescence, an octopus does not feed and quickly weakens. Lesions begin to form and the octopus literally degenerates. Unable to defend themselves, octopuses often fall prey to predators.[73] The larger Pacific striped octopus (LPSO) is an exception, as it can reproduce repeatedly over a life of around two years.[72]

Octopus reproductive organs mature due to the hormonal influence of the optic gland but result in the inactivation of their digestive glands. Unable to feed, the octopus typically dies of starvation.[74] Experimental removal of both optic glands after spawning was found to result in the cessation of broodiness, the resumption of feeding, increased growth, and greatly extended lifespans. It has been proposed that the naturally short lifespan may be functional to prevent rapid overpopulation.[75]

Distribution and habitat

 
Octopus cyanea in Kona, Hawaii

Octopuses live in every ocean, and different species have adapted to different marine habitats. As juveniles, common octopuses inhabit shallow tide pools. The Hawaiian day octopus (Octopus cyanea) lives on coral reefs; argonauts drift in pelagic waters. Abdopus aculeatus mostly lives in near-shore seagrass beds. Some species are adapted to the cold, ocean depths. The spoon-armed octopus (Bathypolypus arcticus) is found at depths of 1,000 m (3,300 ft), and Vulcanoctopus hydrothermalis lives near hydrothermal vents at 2,000 m (6,600 ft).[29] The cirrate species are often free-swimming and live in deep-water habitats.[38] Although several species are known to live at bathyal and abyssal depths, there is only a single indisputable record of an octopus in the hadal zone; a species of Grimpoteuthis (dumbo octopus) photographed at 6,957 m (22,825 ft).[76] No species are known to live in fresh water.[77]

Behaviour and ecology

Most species are solitary when not mating,[78] though a few are known to occur in high densities and with frequent interactions, signaling, mate defending and eviction of individuals from dens. This is likely the result of abundant food supplies combined with limited den sites.[79] The LPSO has been described as particularly social, living in groups of up to 40 individuals.[80][81] Octopuses hide in dens, which are typically crevices in rocky outcrops or other hard structures, though some species burrow into sand or mud. Octopuses are not territorial but generally remain in a home range; they may leave in search of food. They can navigate back to a den without having to retrace their outward route.[82] They are not migratory.[83]

Octopuses bring captured prey to the den, where they can eat it safely. Sometimes the octopus catches more prey than it can eat, and the den is often surrounded by a midden of dead and uneaten food items. Other creatures, such as fish, crabs, molluscs and echinoderms, often share the den with the octopus, either because they have arrived as scavengers, or because they have survived capture.[84] On rare occasions, octopuses hunt cooperatively with other species, with fish as their partners. They regulate the species composition of the hunting group — and the behavior of their partners — by punching them.[85]

Feeding

 
Veined octopus eating a crab

Nearly all octopuses are predatory; bottom-dwelling octopuses eat mainly crustaceans, polychaete worms, and other molluscs such as whelks and clams; open-ocean octopuses eat mainly prawns, fish and other cephalopods.[86] Major items in the diet of the giant Pacific octopus include bivalve molluscs such as the cockle Clinocardium nuttallii, clams and scallops and crustaceans such as crabs and spider crabs. Prey that it is likely to reject include moon snails because they are too large and limpets, rock scallops, chitons and abalone, because they are too securely fixed to the rock.[84]

A benthic (bottom-dwelling) octopus typically moves among the rocks and feels through the crevices. The creature may make a jet-propelled pounce on prey and pull it toward the mouth with its arms, the suckers restraining it. Small prey may be completely trapped by the webbed structure. Octopuses usually inject crustaceans like crabs with a paralysing saliva then dismember them with their beaks.[86][87] Octopuses feed on shelled molluscs either by forcing the valves apart, or by drilling a hole in the shell to inject a nerve toxin.[88][87] It used to be thought that the hole was drilled by the radula, but it has now been shown that minute teeth at the tip of the salivary papilla are involved, and an enzyme in the toxic saliva is used to dissolve the calcium carbonate of the shell. It takes about three hours for O. vulgaris to create a 0.6 mm (0.024 in) hole. Once the shell is penetrated, the prey dies almost instantaneously, its muscles relax, and the soft tissues are easy for the octopus to remove. Crabs may also be treated in this way; tough-shelled species are more likely to be drilled, and soft-shelled crabs are torn apart.[89]

Some species have other modes of feeding. Grimpoteuthis has a reduced or non-existent radula and swallows prey whole.[37] In the deep-sea genus Stauroteuthis, some of the muscle cells that control the suckers in most species have been replaced with photophores which are believed to fool prey by directing them to the mouth, making them one of the few bioluminescent octopuses.[90]

Locomotion

 
Octopuses swim with their arms trailing behind.

Octopuses mainly move about by relatively slow crawling with some swimming in a head-first position. Jet propulsion or backward swimming, is their fastest means of locomotion, followed by swimming and crawling.[91] When in no hurry, they usually crawl on either solid or soft surfaces. Several arms are extended forward, some of the suckers adhere to the substrate and the animal hauls itself forward with its powerful arm muscles, while other arms may push rather than pull. As progress is made, other arms move ahead to repeat these actions and the original suckers detach. During crawling, the heart rate nearly doubles, and the animal requires ten or fifteen minutes to recover from relatively minor exercise.[32]

Most octopuses swim by expelling a jet of water from the mantle through the siphon into the sea. The physical principle behind this is that the force required to accelerate the water through the orifice produces a reaction that propels the octopus in the opposite direction.[92] The direction of travel depends on the orientation of the siphon. When swimming, the head is at the front and the siphon is pointed backward but, when jetting, the visceral hump leads, the siphon points at the head and the arms trail behind, with the animal presenting a fusiform appearance. In an alternative method of swimming, some species flatten themselves dorso-ventrally, and swim with the arms held out sideways, and this may provide lift and be faster than normal swimming. Jetting is used to escape from danger, but is physiologically inefficient, requiring a mantle pressure so high as to stop the heart from beating, resulting in a progressive oxygen deficit.[91]

 
Movements of the finned species Cirroteuthis muelleri

Cirrate octopuses cannot produce jet propulsion and rely on their fins for swimming. They have neutral buoyancy and drift through the water with the fins extended. They can also contract their arms and surrounding web to make sudden moves known as "take-offs". Another form of locomotion is "pumping", which involves symmetrical contractions of muscles in their webs producing peristaltic waves. This moves the body slowly.[37]

In 2005, Adopus aculeatus and veined octopus (Amphioctopus marginatus) were found to walk on two arms, while at the same time mimicking plant matter.[93] This form of locomotion allows these octopuses to move quickly away from a potential predator without being recognised.[91] Some species of octopus can crawl out of the water briefly, which they may do between tide pools.[94][95] "Stilt walking" is used by the veined octopus when carrying stacked coconut shells. The octopus carries the shells underneath it with two arms, and progresses with an ungainly gait supported by its remaining arms held rigid.[96]

Intelligence

Main article: Cephalopod intelligence
 
Octopus opening a container by unscrewing its cap

Octopuses are highly intelligent.[97] Maze and problem-solving experiments have shown evidence of a memory system that can store both short- and long-term memory.[98] Young octopuses learn nothing from their parents, as adults provide no parental care beyond tending to their eggs until the young octopuses hatch.[68]: 75 

In laboratory experiments, octopuses can readily be trained to distinguish between different shapes and patterns. They have been reported to practise observational learning,[99] although the validity of these findings is contested.[97] Octopuses have also been observed in what has been described as play: repeatedly releasing bottles or toys into a circular current in their aquariums and then catching them.[100] Octopuses often break out of their aquariums and sometimes into others in search of food.[94][101][102] The veined octopus collects discarded coconut shells, then uses them to build a shelter, an example of tool use.[96]

Camouflage and colour change

Video of Octopus cyanea moving and changing its colour, shape and texture

Octopuses use camouflage when hunting and to avoid predators. To do this they use specialised skin cells which change the appearance of the skin by adjusting its colour, opacity, or reflectivity. Chromatophores contain yellow, orange, red, brown, or black pigments; most species have three of these colours, while some have two or four. Other colour-changing cells are reflective iridophores and white leucophores.[103] This colour-changing ability is also used to communicate with or warn other octopuses.[104]

Octopuses can create distracting patterns with waves of dark coloration across the body, a display known as the "passing cloud". Muscles in the skin change the texture of the mantle to achieve greater camouflage. In some species, the mantle can take on the spiky appearance of algae; in others, skin anatomy is limited to relatively uniform shades of one colour with limited skin texture. Octopuses that are diurnal and live in shallow water have evolved more complex skin than their nocturnal and deep-sea counterparts.[104]

A "moving rock" trick involves the octopus mimicking a rock and then inching across the open space with a speed matching that of the surrounding water.[105]

Defence

 
Warning display of greater blue-ringed octopus (Hapalochlaena lunulata)

Aside from humans, octopuses may be preyed on by fishes, seabirds, sea otters, pinnipeds, cetaceans, and other cephalopods.[106] Octopuses typically hide or disguise themselves by camouflage and mimicry; some have conspicuous warning coloration (aposematism) or deimatic behaviour.[104] An octopus may spend 40% of its time hidden away in its den. When the octopus is approached, it may extend an arm to investigate. 66% of Enteroctopus dofleini in one study had scars, with 50% having amputated arms.[106] The blue rings of the highly venomous blue-ringed octopus are hidden in muscular skin folds which contract when the animal is threatened, exposing the iridescent warning.[107] The Atlantic white-spotted octopus (Callistoctopus macropus) turns bright brownish red with oval white spots all over in a high contrast display.[108] Displays are often reinforced by stretching out the animal's arms, fins or web to make it look as big and threatening as possible.[109]

Once they have been seen by a predator, they commonly try to escape but can also use distraction with an ink cloud ejected from the ink sac. The ink is thought to reduce the efficiency of olfactory organs, which would aid evasion from predators that employ smell for hunting, such as sharks. Ink clouds of some species might act as pseudomorphs, or decoys that the predator attacks instead.[110]

When under attack, some octopuses can perform arm autotomy, in a manner similar to the way skinks and other lizards detach their tails. The crawling arm may distract would-be predators. Such severed arms remain sensitive to stimuli and move away from unpleasant sensations.[111] Octopuses can replace lost limbs.[112]

Some octopuses, such as the mimic octopus, can combine their highly flexible bodies with their colour-changing ability to mimic other, more dangerous animals, such as lionfish, sea snakes, and eels.[113][114]

Pathogens and parasites

The diseases and parasites that affect octopuses have been little studied, but cephalopods are known to be the intermediate or final hosts of various parasitic cestodes, nematodes and copepods; 150 species of protistan and metazoan parasites have been recognised.[115] The Dicyemidae are a family of tiny worms that are found in the renal appendages of many species;[116] it is unclear whether they are parasitic or endosymbionts. Coccidians in the genus Aggregata living in the gut cause severe disease to the host. Octopuses have an innate immune system; their haemocytes respond to infection by phagocytosis, encapsulation, infiltration, or cytotoxic activities to destroy or isolate the pathogens. The haemocytes play an important role in the recognition and elimination of foreign bodies and wound repair. Captive animals are more susceptible to pathogens than wild ones.[117] A gram-negative bacterium, Vibrio lentus, can cause skin lesions, exposure of muscle and sometimes death.[118]

Evolution

Further information: Evolution of cephalopods

The scientific name Octopoda was first coined and given as the order of octopuses in 1818 by English biologist William Elford Leach,[119] who classified them as Octopoida the previous year.[2] The Octopoda consists of around 300 known species[120] and were historically divided into two suborders, the Incirrina and the Cirrina.[38] More recent evidence suggests Cirrina is merely the most basal species, not a unique clade.[121] The incirrate octopuses (the majority of species) lack the cirri and paired swimming fins of the cirrates.[38] In addition, the internal shell of incirrates is either present as a pair of stylets or absent altogether.[122]

Fossil history and phylogeny

 
The octopuses evolved from the Muensterelloidea (fossil pictured) in the Jurassic period.[123]

The Cephalopoda evolved from a mollusc resembling the Monoplacophora in the Cambrian some 530 million years ago. The Coleoidea diverged from the nautiloids in the Devonian some 416 million years ago. In turn, the coleoids (including the squids and octopods) brought their shells inside the body and some 276 million years ago, during the Permian, split into the Vampyropoda and the Decabrachia.[124] The octopuses arose from the Muensterelloidea within the Vampyropoda in the Jurassic. The earliest octopus likely lived near the sea floor (benthic to demersal) in shallow marine environments.[124][125][123] Octopuses consist mostly of soft tissue, and so fossils are relatively rare. As soft-bodied cephalopods, they lack the external shell of most molluscs, including other cephalopods like the nautiloids and the extinct Ammonoidea.[126] They have eight limbs like other Coleoidea, but lack the extra specialised feeding appendages known as tentacles which are longer and thinner with suckers only at their club-like ends.[127] The vampire squid (Vampyroteuthis) also lacks tentacles but has sensory filaments.[128]

The cladograms are based on Sanchez et al., 2018, who created a molecular phylogeny based on mitochondrial and nuclear DNA marker sequences.[121] The position of the Eledonidae is from Ibáñez et al., 2020, with a similar methodology.[129] Dates of divergence are from Kröger et al., 2011 and Fuchs et al, 2019.[124][123]

Cephalopods
Nautiloids

Nautilus  

Coleoids
Decabrachia

Squids and cuttlefish  

Vampyropoda
Vampyromorphida

 

Octopods

 

155 mya
276 mya
416 mya
530 mya

The molecular analysis of the octopods shows that the suborder Cirrina (Cirromorphida) and the superfamily Argonautoidea are paraphyletic and are broken up; these names are shown in quotation marks and italics on the cladogram.

RNA editing and the genome

Octopuses, like other coleoid cephalopods but unlike more basal cephalopods or other molluscs, are capable of greater RNA editing, changing the nucleic acid sequence of the primary transcript of RNA molecules, than any other organisms. Editing is concentrated in the nervous system, and affects proteins involved in neural excitability and neuronal morphology. More than 60% of RNA transcripts for coleoid brains are recoded by editing, compared to less than 1% for a human or fruit fly. Coleoids rely mostly on ADAR enzymes for RNA editing, which requires large double-stranded RNA structures to flank the editing sites. Both the structures and editing sites are conserved in the coleoid genome and the mutation rates for the sites are severely hampered. Hence, greater transcriptome plasticity has come at the cost of slower genome evolution.[130][131]

The octopus genome is unremarkably bilaterian except for large developments of two gene families: protocadherins, which regulate the development of neurons; and the C2H2 zinc-finger transcription factors. Many genes specific to cephalopods are expressed in the animals' skin, suckers, and nervous system.[48]

Relationship to humans

 
Minoan clay vase with octopus decoration, c. 1500 BC

In culture

Ancient seafaring people were aware of the octopus, as evidenced by artworks and designs. For example, a stone carving found in the archaeological recovery from Bronze Age Minoan Crete at Knossos (1900–1100 BC) depicts a fisherman carrying an octopus.[132] The terrifyingly powerful Gorgon of Greek mythology may have been inspired by the octopus or squid, the octopus itself representing the severed head of Medusa, the beak as the protruding tongue and fangs, and its tentacles as the snakes.[133] 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 octopuses attacking ships. Linnaeus included it in the first edition of his 1735 Systema Naturae.[134][135] One translation of the Hawaiian creation myth the Kumulipo suggests that the octopus is the lone survivor of a previous age.[136][137][138] The Akkorokamui is a gigantic octopus-like monster from Ainu folklore, worshipped in Shinto.[139]

A battle with an octopus plays a significant role in Victor Hugo's 1866 book Travailleurs de la mer (Toilers of the Sea).[140] 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.[141] 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.[142][143] The print is a forerunner of tentacle erotica.[144] The biologist P. Z. Myers noted in his science blog, Pharyngula, that octopuses appear in "extraordinary" graphic illustrations involving women, tentacles, and bare breasts.[145][146]

Since it has numerous arms emanating from a common centre, the octopus is often used as a symbol for a powerful and manipulative organisation, company, or country.[147]

Danger

 
Pen and wash drawing of an imagined colossal octopus attacking a ship, by the malacologist Pierre de Montfort, 1801

Octopuses generally avoid humans, but incidents have been verified. For example, a 2.4-metre (8 ft) Pacific octopus, said to be nearly perfectly camouflaged, "lunged" at a diver and "wrangled" over his camera before it let go. Another diver recorded the encounter on video.[148] All species are venomous, but only blue-ringed octopuses have venom that is lethal to humans.[149] Bites are reported each year across the animals' range from Australia to the eastern Indo-Pacific Ocean. They bite only when provoked or accidentally stepped upon; bites are small and usually painless. The venom appears to be able to penetrate the skin without a puncture, given prolonged contact. It contains tetrodotoxin, which causes paralysis by blocking the transmission of nerve impulses to the muscles. This causes death by respiratory failure leading to cerebral anoxia. No antidote is known, but if breathing can be kept going artificially, patients recover within 24 hours.[150][151] Bites have been recorded from captive octopuses of other species; they leave swellings which disappear in a day or two.[152]

Fisheries

Main article: Octopus as food

Octopus fisheries exist around the world with total catches varying between 245,320 and 322,999 metric tons from 1986 to 1995.[153] The world catch peaked in 2007 at 380,000 tons, and had fallen by a tenth by 2012.[154] Methods to capture octopuses include pots, traps, trawls, snares, drift fishing, spearing, hooking and hand collection.[153] Octopus is eaten in many cultures, such as on the Mediterranean and Asian coasts.[155] The arms and sometimes other body parts are prepared in various ways, often varying by species or geography. Live octopuses are eaten in several countries around the world, including the US.[156][157] Animal welfare groups have objected to this practice on the basis that octopuses can experience pain.[158] Octopuses have a food conversion efficiency greater than that of chickens, making octopus aquaculture a possibility.[159] Octopuses compete with human fisheries targeting other species, and even rob traps and nets for their catch; they may, themselves, be caught as bycatch if they cannot get away.[160]

In science and technology

In classical Greece, Aristotle (384–322 BC) commented on the colour-changing abilities of the octopus, both for camouflage and for signalling, in his Historia animalium: "The octopus ... seeks its prey by so changing its colour as to render it like the colour of the stones adjacent to it; it does so also when alarmed."[161] Aristotle noted that the octopus had a hectocotyl arm and suggested it might be used in sexual reproduction. This claim was widely disbelieved until the 19th century. It was described in 1829 by the French zoologist Georges Cuvier, who supposed it to be a parasitic worm, naming it as a new species, Hectocotylus octopodis.[162][163] Other zoologists thought it a spermatophore; the German zoologist Heinrich Müller believed it was "designed" to detach during copulation. In 1856 the Danish zoologist Japetus Steenstrup demonstrated that it is used to transfer sperm, and only rarely detaches.[164]

 
Flexible biomimetic 'Octopus' robotics arm. The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, 2011[165]

Octopuses offer many possibilities in biological research, including their ability to regenerate limbs, change the colour of their skin, behave intelligently with a distributed nervous system, and make use of 168 kinds of protocadherins (humans have 58), the proteins that guide the connections neurons make with each other. The California two-spot octopus has had its genome sequenced, allowing exploration of its molecular adaptations.[48] Having independently evolved mammal-like intelligence, octopuses have been compared by the philosopher Peter Godfrey-Smith, who has studied the nature of intelligence,[166] to hypothetical intelligent extraterrestrials.[167] Their problem-solving skills, along with their mobility and lack of rigid structure enable them to escape from supposedly secure tanks in laboratories and public aquariums.[168]

Due to their intelligence, octopuses are listed in some countries as experimental animals on which surgery may not be performed without anesthesia, a protection usually extended only to vertebrates. In the UK from 1993 to 2012, the common octopus (Octopus vulgaris) was the only invertebrate protected under the Animals (Scientific Procedures) Act 1986.[169] In 2012, this legislation was extended to include all cephalopods[170] in accordance with a general EU directive.[171]

Some robotics research is exploring biomimicry of octopus features. Octopus arms can move and sense largely autonomously without intervention from the animal's central nervous system. In 2015 a team in Italy built soft-bodied robots able to crawl and swim, requiring only minimal computation.[172][173] In 2017 a German company made an arm with a soft pneumatically controlled silicone gripper fitted with two rows of suckers. It is able to grasp objects such as a metal tube, a magazine, or a ball, and to fill a glass by pouring water from a bottle.[174]

See also

Notes

  1. ^ "Tentacle" is a common umbrella term for cephalopod limbs. In teuthological context, octopuses have "arms" with suckers along their entire length while "tentacle" is reserved for appendages with suckers only near the end of the limb, which octopuses lack.[4]

References

  1. ^ "ITIS Report: Octopoda Leach, 1818". Itis.gov. 10 April 2013. Retrieved 4 February 2014.
  2. ^ a b "Coleoidea – Recent cephalopods". Mikko's Phylogeny Archive.
  3. ^ "Octopoda". Merriam-Webster Dictionary. Retrieved 12 July 2021.
  4. ^ Scully, Caitlin (11 October 2018). "Get to Know th Four Types of Cephalopod". U CSan Diego.
  5. ^ Harper, Douglas. "octopus". Online Etymology Dictionary.
  6. ^ "Octopus". Dictionary.reference.com. Retrieved 4 February 2014.
  7. ^ ὀκτάπους, ὀκτώπους. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
  8. ^ Michel, Jean-Baptiste; Shen, Yuan; Aiden, Aviva; Veres, Adrian; Gray, Matthew; Pickett, Joseph; Hoiberg, Dale; Clancy, Dan; Norvig, Peter; Orwant, Jon; Pinker, Steven; Nowak, Martin (2011). "Quantitative Analysis of Culture Using Millions of Digitized Books". Science. 331 (6014): 176–182. Bibcode:2011Sci...331..176M. doi:10.1126/science.1199644. PMC 3279742. PMID 21163965. Relevant data at Google Ngram Viewer.
  9. ^ . Oxforddictionaries.com. 2014. Archived from the original on 30 October 2012. Retrieved 4 February 2014.
  10. ^ Peters, Pam (2004). The Cambridge Guide to English Usage. Cambridge: Cambridge University Press. ISBN 0-521-62181-X, p. 388.
  11. ^ Fowler, Henry Watson (1994). A Dictionary of Modern English Usage. p. 316. ISBN 9781853263187. In Latin plurals there are some traps for non-Latinists; the termination of the singular is no sure guide to that of the plural. Most Latin words in -us have plural in -i, but not all, & so zeal not according to knowledge issues in such oddities as...octopi...; as caution the following list may be useful:...octopus, -podes
  12. ^ Tuckey, James Hingston; Smith, Christen (1818). Narrative of an Expedition to Explore the River Zaire. Kirk & Mercein.
  13. ^ "The Many Plurals of 'Octopus'". www.merriam-webster.com.
  14. ^ Butterfield, Jeremy (2015). Fowler's Dictionary of Modern English Usage. Oxford University Press. ISBN 9780191744532. The only correct plural in English is octopuses. The Greek original is ὀκτώπους, -ποδ- (which would lead to a pedantic English pl. form octopodes). The pl. form octopi, which is occasionally heard (mostly in jocular use), though based on modL octopus, is misconceived
  15. ^ Chambers 21st Century Dictionary 24 November 2007 at the Wayback Machine (retrieved 19 October 2007 )
  16. ^ Stamper, Kory. . Merriam-Webster. Archived from the original on 30 April 2013. Retrieved 26 June 2013.
  17. ^ "octopus". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  18. ^ Stevenson, Angus; Lindberg, Christine A., eds. (2010). New Oxford American Dictionary (3rd ed.). Oxford University Press. ISBN 978-0-19-539288-3.
  19. ^ . Nationalzoo.si.edu. Archived from the original on 23 February 2014. Retrieved 4 February 2014.
  20. ^ Cosgrove, J.A. 1987. Aspects of the Natural History of Octopus dofleini, the Giant Pacific Octopus. MSc Thesis. Department of Biology, University of Victoria (Canada), 101 pp.
  21. ^ Norman, M. 2000. Cephalopods: A World Guide. ConchBooks, Hackenheim. p. 214.
  22. ^ High, William L. (1976). "The giant Pacific octopus" (PDF). Marine Fisheries Review. 38 (9): 17–22.
  23. ^ O'Shea, S. (2004). "The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters". New Zealand Journal of Zoology. 31 (1): 7–13. doi:10.1080/03014223.2004.9518353. S2CID 84954869.
  24. ^ O'Shea, S. (2002). "Haliphron atlanticus – a giant gelatinous octopus" (PDF). Biodiversity Update. 5: 1.
  25. ^ Bradford, Alina (21 July 2016). "Octopus Facts". Live Science. Retrieved 26 April 2017.
  26. ^ a b c d e f g h i j k l m Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2008). Invertebrate Zoology. Cengage Learning. pp. 363–364. ISBN 978-81-315-0104-7.
  27. ^ Wells (1978), pp. 11–12.
  28. ^ Ruth A., Byrne; Kuba, Michael J.; Meisel, Daniela V.; Griebel, Ulrike; Mather, Jennifer A. (August 2006). "Does Octopus vulgaris have preferred arms?". Journal of Comparative Psychology. 120 (3): 198–204. doi:10.1037/0735-7036.120.3.198. PMID 16893257.
  29. ^ a b Mather, Anderson & Wood (2010), pp. 13–15.
  30. ^ a b c d Courage (2013), pp. 40–41.
  31. ^ Semmens (2004). "Understanding octopus growth: patterns, variability and physiology". Marine and Freshwater Research. 55 (4): 367. doi:10.1071/MF03155. S2CID 84208773.
  32. ^ a b Carefoot, Thomas. . A Snail's Odyssey. Archived from the original on 22 May 2013. Retrieved 19 April 2017.
  33. ^ Zelman, I.; Titon, M.; Yekutieli, Y.; Hanassy, S.; Hochner, B.; Flash, T. (2013). "Kinematic decomposition and classification of octopus arm movements". Frontiers in Computational Neuroscience. 7: 60. doi:10.3389/fncom.2013.00060. PMC 3662989. PMID 23745113.
  34. ^ Tramacere, F.; Beccai, L.; Kuba, M.; Gozzi, A.; Bifone, A.; Mazzolai, B. (2013). "The morphology and adhesion mechanism of Octopus vulgaris suckers". PLOS ONE. 8 (6): e65074. Bibcode:2013PLoSO...865074T. doi:10.1371/journal.pone.0065074. PMC 3672162. PMID 23750233.
  35. ^ Kier, W. M.; Smith, A. M. (2002). "The structure and adhesive mechanism of octopus suckers". Integrative and Comparative Biology. 42 (6): 1146–1153. CiteSeerX 10.1.1.512.2605. doi:10.1093/icb/42.6.1146. PMID 21680399. S2CID 15997762.
  36. ^ Katz, Itamar; Shomrat, Tal; Nesher, Nir (1 January 2021). "Feel the light – sight independent negative phototactic response in octopus' arms". Journal of Experimental Biology. 224 (5). doi:10.1242/jeb.237529. ISSN 0022-0949. PMID 33536305.
  37. ^ a b c d "Finned Deep-sea Octopuses, Grimpoteuthis spp". MarineBio. 18 May 2017. Retrieved 14 May 2021.
  38. ^ a b c d Marshall Cavendish Corporation (2004). Encyclopedia of the Aquatic World. Marshall Cavendish. p. 764. ISBN 978-0-7614-7424-1.
  39. ^ a b c Wells (1978), pp. 31–35.
  40. ^ a b c Courage (2013), pp. 42–43.
  41. ^ a b Schmidt-Nielsen, Knut (1997). Animal Physiology: Adaptation and Environment. Cambridge University Press. p. 117. ISBN 978-0-521-57098-5.
  42. ^ Carefoot, Thomas. . A Snail's Odyssey. Archived from the original on 28 April 2017. Retrieved 26 April 2017.
  43. ^ a b Wells (1978), pp. 24–26.
  44. ^ Wells, M. J.; Wells, J. (1995). "The control of ventilatory and cardiac responses to changes in ambient oxygen tension and oxygen demand in Octopus". The Journal of Experimental Biology. 198 (Pt 8): 1717–1727. doi:10.1242/jeb.198.8.1717. PMID 9319626.
  45. ^ Wells, J. (1996). "Cutaneous respiration in Octopus vulgaris". The Journal of Experimental Biology. 199 (Pt 11): 2477–2483. doi:10.1242/jeb.199.11.2477. PMID 9320405.
  46. ^ a b Wells (1978), pp. 73–79.
  47. ^ Wells (1978), pp. 54–56.
  48. ^ a b c d Albertin, Caroline B.; Simakov, Oleg; Mitros, Therese; Wang, Z. Yan; Pungor, Judit R.; Edsinger-Gonzales, Eric; Brenner, Sydney; Ragsdale, Clifton W.; Rokhsar, Daniel S. (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.
  49. ^ Pilleri, Georg (1984). Investigations on Cetacea. Vol. 16–17. Hirnanatomisches Institut der Universität. p. 161. Retrieved 30 July 2018.
  50. ^ Petrosino, Giuseppe; Ponte, Giovanna; Volpe, Massimiliano; et al. (18 May 2022). "Identification of LINE retrotransposons and long non-coding RNAs expressed in the octopus brain". BMC Biology. 20 (1). doi:10.1186/s12915-022-01303-5.
  51. ^ Hochner, B. (2012). "An Embodied View of Octopus Neurobiology". Current Biology. 22 (20): R887–R892. doi:10.1016/j.cub.2012.09.001. PMID 23098601.
  52. ^ Yekutieli, Y.; Sagiv-Zohar, R.; Aharonov, R.; Engel, Y.; Hochner, B.; Flash, T. (2005). "Dynamic model of the octopus arm. I. Biomechanics of the octopus reaching movement". Journal of Neurophysiology. 94 (2): 1443–1458. doi:10.1152/jn.00684.2004. PMID 15829594. S2CID 14711055.
  53. ^ Zullo, L.; Sumbre, G.; Agnisola, C.; Flash, T.; Hochner, B. (2009). "Nonsomatotopic organization of the higher motor centers in Octopus". Current Biology. 19 (19): 1632–1636. doi:10.1016/j.cub.2009.07.067. PMID 19765993. S2CID 15852956.
  54. ^ Kawamura, G.; et al. (2001). "Color Discrimination Conditioning in Two Octopus Octopus aegina and O. vulgaris". Nippon Suisan Gakkaishi. 67 (1): 35–39. doi:10.2331/suisan.67.35.
  55. ^ Kingston, Alexandra C. N.; Kuzirian, Alan M.; Hanlon, Roger T.; Cronin, Thomas W. (2015). "Visual phototransduction components in cephalopod chromatophores suggest dermal photoreception". Journal of Experimental Biology. 218 (10): 1596–1602. doi:10.1242/jeb.117945. ISSN 1477-9145. PMID 25994635.
  56. ^ Ramirez, M. Desmond; Oakley, Todd H. (2015). "Eye-independent, light-activated chromatophore expansion (LACE) and expression of phototransduction genes in the skin of Octopus bimaculoides". Journal of Experimental Biology. 218 (10): 1513–1520. doi:10.1242/jeb.110908. ISSN 1477-9145. PMC 4448664. PMID 25994633.
  57. ^ Stubbs, Alexander L.; Stubbs, Christopher W. (2016). "Spectral discrimination in color blind animals via chromatic aberration and pupil shape". Proceedings of the National Academy of Sciences. 113 (29): 8206–8211. Bibcode:2016PNAS..113.8206S. doi:10.1073/pnas.1524578113. ISSN 0027-8424. PMC 4961147. PMID 27382180.
  58. ^ Hu, Marian Y.; Yan, Hong Young; Chung, Wen-Sung; Shiao, Jen-Chieh; Hwang, Pung-Pung (2009). "Acoustically evoked potentials in two cephalopods inferred using the auditory brainstem response (ABR) approach". Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology. 153 (3): 278–283. doi:10.1016/j.cbpa.2009.02.040. ISSN 1095-6433. PMID 19275944.
  59. ^ Nesher, Nir; Levy, Guy; Grasso, Frank W.; Hochner, Binyamin (2014). "Self-Recognition Mechanism between Skin and Suckers Prevents Octopus Arms from Interfering with Each Other". Current Biology. 24 (11): 1271–1275. doi:10.1016/j.cub.2014.04.024. ISSN 0960-9822. PMID 24835454. S2CID 16140159.
  60. ^ Gutnick, Tamar; Byrne, Ruth A.; Hochner, Binyamin; Kuba, Michael (2011). "Octopus vulgaris Uses Visual Information to Determine the Location of Its Arm". Current Biology. 21 (6): 460–462. doi:10.1016/j.cub.2011.01.052. PMID 21396818. S2CID 10152089.
  61. ^ Kennedy, E. B. Lane; Buresch, Kendra C.; Boinapally, Preethi; Hanlon, Roger T. (2020). "Octopus arms exhibit exceptional flexibility". Scientific Reports. 10 (1): 20872. doi:10.1038/s41598-020-77873-7. PMC 7704652. PMID 33257824.
  62. ^ Mather, Anderson & Wood (2010), p. 107.
  63. ^ Derby, C. D. (2014). "Cephalopod Ink: Production, Chemistry, Functions and Applications". Marine Drugs. 12 (5): 2700–2730. doi:10.3390/md12052700. PMC 4052311. PMID 24824020.
  64. ^ a b Mather, Anderson & Wood (2010), p. 147.
  65. ^ Wells, Martin J.; Wells, J. (1972). "Optic glands and the state of the testis in Octopus". Marine Behaviour and Physiology. 1 (1–4): 71–83. doi:10.1080/10236247209386890.
  66. ^ Young, R. E.; Vecchione, M.; Mangold, K. M. (1999). "Cephalopoda Glossary". Tree of Life web project.
  67. ^ a b Carefoot, Thomas. . A Snail's Odyssey. Archived from the original on 22 April 2017. Retrieved 11 April 2017.
  68. ^ a b c "Giant Pacific Octopus (Enteroctopus dofleini) Care Manual" (PDF). AZA (Association of Zoos and Aquariums) Aquatic Invertebrate Taxonomic Advisory Group in association with AZA Animal Welfare Committee. 9 September 2014. Retrieved 31 May 2016.
  69. ^ Scheel, David. . Alaska Pacific University. Archived from the original on 15 November 2012. Retrieved 9 April 2017.
  70. ^ Forsythe, J. W.; Hanlon, R. T. (1980). "A closed marine culture system for rearing Octopus joubini and other large-egged benthic octopods". Laboratory Animals. 14 (2): 137–142. doi:10.1258/002367780780942737. PMID 7431823. S2CID 19492476.
  71. ^ Simon, Matt (16 January 2015). "Absurd Creature of the Week: The Beautiful Octopus Whose Sex Is All About Dismemberment". Wired: Science. Retrieved 20 May 2017.
  72. ^ a b Hooper, Rowan (21 December 2019). "Octopuses were thought to be solitary until a social species turned up". New Scientist.
  73. ^ Anderson, Roland C.; Wood, James B.; Byrne, Ruth A. (2002). "Octopus Senescence: The Beginning of the End". Journal of Applied Animal Welfare Science. 5 (4): 275–283. CiteSeerX 10.1.1.567.3108. doi:10.1207/S15327604JAWS0504_02. PMID 16221078. S2CID 28355735.
  74. ^ Anderson, Roland C.; Wood, James B.; Byrne, Ruth A. (2002). "Octopus Senescence: The Beginning of the End". Journal of Applied Animal Welfare Science. 5 (4): 275–283. CiteSeerX 10.1.1.567.3108. doi:10.1207/S15327604JAWS0504_02. PMID 16221078. S2CID 28355735.
  75. ^ Wodinsky, Jerome (1977). "Hormonal Inhibition of Feeding and Death in Octopus: Control by Optic Gland Secretion". Science. 198 (4320): 948–951. Bibcode:1977Sci...198..948W. doi:10.1126/science.198.4320.948. PMID 17787564. S2CID 22649186.
  76. ^ Jamieson, A.J.; Vecchione, M. (2020). "First in situ observation of Cephalopoda at hadal depths (Octopoda: Opisthoteuthidae: Grimpoteuthis sp.)". Marine Biology. 167 (82). doi:10.1007/s00227-020-03701-1.
  77. ^ Norman, Mark (16 January 2013). "Ask an expert: Are there any freshwater cephalopods?". ABC Science. Retrieved 26 April 2017.
  78. ^ Edmonds, Patricia (April 2016). "What's Odd About That Octopus? It's Mating Beak to Beak". National Geographic.
  79. ^ Scheel, D.; et al. (2017). "A second site occupied by Octopus tetricus at high densities, with notes on their ecology and behavior". Marine and Freshwater Behaviour and Physiology. 50 (4): 285–291. doi:10.1080/10236244.2017.1369851. S2CID 89738642.
  80. ^ Rodaniche, Arcadio F. (1991). "Notes on the behavior of the Larger Pacific Striped Octopus, an undescribed species of the genus Octopus". Bulletin of Marine Science. 49: 667.
  81. ^ Caldwell, Roy L.; Ross, Richard; Rodaniche, Arcadio; Huffard, Christine L. (2015). "Behavior and Body Patterns of the Larger Pacific Striped Octopus". PLOS ONE. 10 (8): e0134152. Bibcode:2015PLoSO..1034152C. doi:10.1371/journal.pone.0134152. ISSN 1932-6203. PMC 4534201. PMID 26266543.
  82. ^ Goldman, Jason G. (24 May 2012). "How do octopuses navigate?". Scientific American. 168 (4): 491–497. doi:10.1007/BF00199609. S2CID 41369931. Retrieved 8 June 2017.
  83. ^ Courage (2013), pp. 45–46.
  84. ^ a b Carefoot, Thomas. . A Snail's Odyssey. Archived from the original on 8 May 2017. Retrieved 13 April 2017.
  85. ^ Sampaio, Eduardo; Seco, Martim Costa; Rosa, Rui; Gingins, Simon (18 December 2020). "Octopuses punch fishes during collaborative interspecific hunting events". Ecology. Ecological Society of America/Wiley Publishing. 102 (3): e03266. doi:10.1002/ecy.3266. ISSN 0012-9658. PMID 33338268.
  86. ^ a b Wassilieff, Maggy; O'Shea, Steve (2 March 2009). "Octopus and squid – Feeding and predation". Te Ara – the Encyclopedia of New Zealand.
  87. ^ a b Wells (1978), pp. 74–75.
  88. ^ Wodinsky, Jerome (1969). "Penetration of the Shell and Feeding on Gastropods by Octopus" (PDF). American Zoologist. 9 (3): 997–1010. doi:10.1093/icb/9.3.997.
  89. ^ Carefoot, Thomas. . A Snail's Odyssey. Archived from the original on 6 June 2017. Retrieved 21 April 2017.
  90. ^ Johnsen, S.; Balser, E. J.; Fisher, E. C.; Widder, E. A. (1999). (PDF). The Biological Bulletin. 197 (1): 26–39. doi:10.2307/1542994. JSTOR 1542994. PMID 28296499. Archived from the original (PDF) on 5 March 2011.
  91. ^ a b c Huffard, Christine L. (2006). "Locomotion by Abdopus aculeatus (Cephalopoda: Octopodidae): walking the line between primary and secondary defenses". Journal of Experimental Biology. 209 (Pt 19): 3697–3707. doi:10.1242/jeb.02435. PMID 16985187.
  92. ^ Kassim, I.; Phee, L.; Ng, W. S.; Gong, F.; Dario, P.; Mosse, C. A. (2006). "Locomotion techniques for robotic colonoscopy". IEEE Engineering in Medicine and Biology Magazine. 25 (3): 40–56. doi:10.1109/MEMB.2006.1636351. PMID 16764431. S2CID 9124611.
  93. ^ Huffard, C. L.; Boneka, F.; Full, R. J. (2005). "Underwater Bipedal Locomotion by Octopuses in Disguise". Science. 307 (5717): 1927. doi:10.1126/science.1109616. PMID 15790846. S2CID 21030132.
  94. ^ a b Wood, J. B; Anderson, R. C (2004). "Interspecific Evaluation of Octopus Escape Behavior" (PDF). Journal of Applied Animal Welfare Science. 7 (2): 95–106. CiteSeerX 10.1.1.552.5888. doi:10.1207/s15327604jaws0702_2. PMID 15234886. S2CID 16639444. Retrieved 11 September 2015.
  95. ^ Mather, Anderson & Wood (2010), p. 183.
  96. ^ a b Finn, J. K.; Tregenza, T.; Norman, M. D. (2009). "Defensive tool use in a coconut-carrying octopus". Current Biology. 19 (23): R1069–70. doi:10.1016/j.cub.2009.10.052. PMID 20064403. S2CID 26835945.
  97. ^ a b Stewart, Doug (1997). "Armed but not dangerous: Is the octopus really the invertebrate intellect of the sea". National Wildlife. 35 (2).
  98. ^ Zarrella, Ilaria; Ponte, Giovanna; Baldascino, Elena; Fiorito, Graziano (2015). "Learning and memory in Octopus vulgaris: a case of biological plasticity". Current Opinion in Neurobiology. 35: 74–79. doi:10.1016/j.conb.2015.06.012. ISSN 0959-4388. PMID 26186237. S2CID 31682363.
  99. ^ "Octopus intelligence: Jar opening". BBC News. 25 February 2003. Retrieved 4 February 2014.
  100. ^ Mather, J. A.; Anderson, R. C. (1998). Wood, J. B. (ed.). "What behavior can we expect of octopuses?". The Cephalopod Page.
  101. ^ Lee, Henry (1875). "V: The octopus out of water". Aquarium Notes – The Octopus; or, the "devil-fish" of fiction and of fact. London: Chapman and Hall. pp. 38–39. OCLC 1544491. Retrieved 11 September 2015. The marauding rascal had occasionally issued from the water in his tank, and clambered up the rocks, and over the wall into the next one; there he had helped himself to a young lump-fish, and, having devoured it, returned demurely to his own quarters by the same route, with well-filled stomach and contented mind.
  102. ^ Ainge Roy, Eleanor (14 April 2016). "The great escape: Inky the octopus legs it to freedom from aquarium". The Guardian (Australia).
  103. ^ Meyers, Nadia. "Tales from the Cryptic: The Common Atlantic Octopus". Southeastern Regional Taxonomic Centre. Retrieved 27 July 2006.
  104. ^ a b c Mather, Anderson & Wood (2010), pp. 90–97.
  105. ^ Hanlon, R. T.; Messenger, J. B. (2018). Cephalopod Behaviour (2nd ed.). Cambridge University Press. pp. 110–111. ISBN 978-0521723701.
  106. ^ a b Carefoot, Thomas. . A Snail's Odyssey. Archived from the original on 21 April 2017. Retrieved 13 April 2017.
  107. ^ Mäthger, L. M.; Bell, G. R.; Kuzirian, A. M.; Allen, J. J.; Hanlon, R. T. (2012). "How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?". Journal of Experimental Biology. 215 (21): 3752–3757. doi:10.1242/jeb.076869. PMID 23053367.
  108. ^ Wigton, Rachel; Wood, James B. . Marine Invertebrates of Bermuda. Bermuda Institute of Ocean Sciences. Archived from the original on 19 January 2016. Retrieved 10 August 2018.
  109. ^ Hanlon, R. T.; Messenger, J. B. (1998). Cephalopod Behaviour (1st ed.). Cambridge University Press. pp. 80–81, 111. ISBN 978-0-521-64583-6.
  110. ^ Caldwell, R. L. (2005). "An Observation of Inking Behavior Protecting Adult Octopus bocki from Predation by Green Turtle (Chelonia mydas) Hatchlings" (PDF). Pacific Science. 59 (1): 69–72. doi:10.1353/psc.2005.0004. hdl:10125/24161. S2CID 54223984.
  111. ^ Harmon, Katherine (27 August 2013). "Even Severed Octopus Arms Have Smart Moves". Octopus Chronicles. Scientific American.
  112. ^ Mather, Anderson & Wood (2010), p. 85.
  113. ^ Norman, M. D.; Finn, J.; Tregenza, T. (2001). (PDF). Proceedings of the Royal Society. 268 (1478): 1755–8. doi:10.1098/rspb.2001.1708. PMC 1088805. PMID 11522192. Archived from the original (PDF) on 10 February 2012. Retrieved 1 October 2008.
  114. ^ Norman, M. D. (2005). "The 'Mimic Octopus' (Thaumoctopus mimicus n. gen. et sp.), a new octopus from the tropical Indo-West Pacific (Cephalopoda: Octopodidae)". Molluscan Research. 25 (2): 57–70.
  115. ^ Pascal, Santiago; Gestal, Camino; Estevez, J.; Arias, Christian Andrés (1996). "Parasites in commercially-exploited cephalopods (Mollusca, Cephalopoda) in Spain: An updated perspective". Aquaculture. 142 (1–2): 1–10. doi:10.1016/0044-8486(96)01254-9.
  116. ^ Furuya, Hidetaka; Tsuneki, Kazuhiko (2003). "Biology of Dicyemid Mesozoans". Zoological Science. 20 (5): 519–532. doi:10.2108/zsj.20.519. PMID 12777824. S2CID 29839345.
  117. ^ Castellanos-Martínez, Sheila; Gestal, Camino (2013). "Pathogens and immune response of cephalopods". Journal of Experimental Marine Biology and Ecology. 447: 14–22. doi:10.1016/j.jembe.2013.02.007.
  118. ^ Farto, R.; Armada, S. P.; Montes, M.; Guisande, J. A.; Pérez, M. J.; Nieto, T. P. (2003). "Vibrio lentus associated with diseased wild octopus (Octopus vulgaris)". Journal of Invertebrate Pathology. 83 (2): 149–156. doi:10.1016/S0022-2011(03)00067-3. PMID 12788284.
  119. ^ Gofas, S. (2009). "Octopoda". WoRMS. World Register of Marine Species. Retrieved 5 May 2017.
  120. ^ Mather, Anderson & Wood (2010), p. 145.
  121. ^ a b Sanchez, Gustavo; Setiamarga, Davin H. E.; Tuanapaya, Surangkana; Tongtherm, Kittichai; Winkelmann, Inger E.; Schmidbaur, Hannah; Umino, Tetsuya; Albertin, Caroline; Allcock, Louise; Perales-Raya, Catalina; Gleadall, Ian; Strugnell, Jan M.; Simakov, Oleg; Nabhitabhata, Jaruwat (2018). "Genus-level phylogeny of cephalopods using molecular markers: current status and problematic areas". PeerJ. 6: e4331. doi:10.7717/peerj.4331. PMC 5813590. PMID 29456885.
  122. ^ 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.
  123. ^ a b c Fuchs, Dirk; Iba, Yasuhiro; Heyng, Alexander; Iijima, Masaya; Klug, Christian; Larson, Neal L.; Schweigert, Günter; Brayard, Arnaud (2019). "The Muensterelloidea: phylogeny and character evolution of Mesozoic stem octopods". Papers in Palaeontology. 6 (1): 31–92. doi:10.1002/spp2.1254. ISSN 2056-2802. S2CID 198256507.
  124. ^ a b c Kröger, Björn; Vinther, Jakob; Fuchs, Dirk (2011). "Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules". BioEssays. 33 (8): 602–613. doi:10.1002/bies.201100001. ISSN 0265-9247. PMID 21681989. S2CID 2767810.
  125. ^ Fuchs, Dirk; Schweigert, Günter (2018). "First Middle–Late Jurassic gladius vestiges provide new evidence on the detailed origin of incirrate and cirrate octopuses (Coleoidea)". PalZ. 92 (2): 203–217. doi:10.1007/s12542-017-0399-8. ISSN 0031-0220. S2CID 135245479.
  126. ^ "A Broad Brush History of the Cephalopoda". The Cephalopod Group. Retrieved 27 March 2017.
  127. ^ Young, R. E.; Vecchione, M.; Mangold, K. M. (1999). "Cephalopoda Glossary". Tree of Life web project. Retrieved 30 May 2017.
  128. ^ Seibel, B. "Vampyroteuthis infernalis, Deep-sea Vampire squid". The Cephalopod Page. Retrieved 31 May 2017.
  129. ^ Ibáñez, Christian M.; Fenwick, Mark; Ritchie, Peter A.; Carrasco, Sergio A.; Pardo-Gandarillas, M. Cecilia (2020). "Systematics and Phylogenetic Relationships of New Zealand Benthic Octopuses (Cephalopoda: Octopodoidea)". Frontiers in Marine Science. 7. doi:10.3389/fmars.2020.00182. ISSN 2296-7745.
  130. ^ Courage (2013), pp. 46–49.
  131. ^ Liscovitch-Brauer, N.; Alon, S.; Porath, H. T.; Elstein, B.; Unger, R.; Ziv, T.; Admon, A.; Levanon, E. Y.; Rosenthal, J. J. C.; Eisenberg, E. (2017). "Trade-off between transcriptome plasticity and genome evolution in cephalopods". Cell. 169 (2): 191–202. doi:10.1016/j.cell.2017.03.025. PMC 5499236. PMID 28388405.
  132. ^ Hogan, C. Michael (22 December 2007). "Knossos fieldnotes". The Modern Antiquarian.
  133. ^ Wilk, Stephen R. (2000). Medusa: Solving the Mystery of the Gorgon. Oxford University Press. ISBN 978-0-19-988773-6.
  134. ^ Linnaeus, Carl (1735). Systema Naturae. Laurentius Salvius.
  135. ^ 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–.
  136. ^ Dixon, Roland Burrage (1916). Oceanic. The Mythology of All Races. Vol. 9. Marshall Jones Company. pp. 2–.
  137. ^ Bastian, Adolf (1881). Die heilige Sage der Polynesier: Kosmogonie und Theogonie. Oxford University. Leipzig: F. A. Brockhaus. pp. 107–108.
  138. ^ Beckwith, Martha Warren (1981). The Kumulipo: A Hawaiian Creation Chant. University of Hawaii Press. pp. 52–53. ISBN 978-0824807719.
  139. ^ Srinivasan, A. (2017). "The Sucker, the Sucker! [Review]" (PDF). London Review of Books. 39 (17): 23–25.
  140. ^ "[Review] The Toilers of the Sea by Victor Hugo & Translated by James Hogarth". Kirkus Reviews. 2002. Retrieved 14 May 2021.
  141. ^ Cohen-Vrignaud, Gerard (2012). "On Octopussies, or the Anatomy of Female Power". Differences. 23 (2): 32–61. doi:10.1215/10407391-1533520.
  142. ^ 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.
  143. ^ Uhlenbeck, Chris; Winkel, Margarita; Tinios, Ellis; Newland, Amy Reigle (2005). Japanese Erotic Fantasies: Sexual Imagery of the Edo Period. Hotei. p. 161. ISBN 978-90-74822-66-4.
  144. ^ 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.
  145. ^ Myers, Paul Zachary (17 May 2017). "Extraordinary Octopus Illustrations". Pharyngula. Retrieved 18 March 2017.
  146. ^ Myers, Paul Zachary (29 October 2006). "Definitely not safe for work". Pharyngula. Retrieved 18 March 2017.
  147. ^ Smith, S. (26 February 2010). "Why Mark Zuckerberg Octopus Cartoon Evokes 'Nazi Propaganda,' German Paper Apologizes". iMediaEthics. Retrieved 31 May 2017.
  148. ^ Ross, Philip (18 February 2014). "8-Foot Octopus Wrestles Diver Off California Coast, Rare Encounter Caught on Camera". International Business Times.
  149. ^ Fry, B. G.; Roelants, K.; Norman, J. A. (2009). "Tentacles of Venom: Toxic Protein Convergence in the Kingdom Animalia". Journal of Molecular Evolution. 68 (4): 311–321. Bibcode:2009JMolE..68..311F. doi:10.1007/s00239-009-9223-8. ISSN 0022-2844. PMID 19294452. S2CID 13354905.
  150. ^ . The MarineBio Conservation Society. Archived from the original on 16 February 2017. Retrieved 12 April 2017.
  151. ^ Caldwell, Roy. "What makes blue-rings so deadly? Blue-ringed octopus have tetrodotoxin". The Cephalopod Page. Retrieved 12 April 2017.
  152. ^ Wells (1978), pp. 68.
  153. ^ a b Gillespie, G. E.; Parker, G.; Morrison, J. (1998). "A Review of Octopus Fisheries Biology and British Columbia Octopus Fisheries" (PDF). Canadian Stock Assessment Secretariat.
  154. ^ Rocliffe, S.; Harris, A. (2016). "The status of octopus fisheries in the Western Indian Ocean". Retrieved 18 June 2017.
  155. ^ . Monterey Bay Aquarium. 2017. Archived from the original on 4 July 2018. Retrieved 1 August 2015.
  156. ^ Eriksen, L. (10 November 2010). "Live and let dine". The Guardian. Retrieved 15 April 2015.
  157. ^ Killingsworth, Silvia (3 October 2014). "Why not eat octopus?". The New Yorker. Retrieved 15 April 2016.
  158. ^ Ferrier, M. (30 May 2010). "Macho foodies in New York develop a taste for notoriety". The Guardian. Retrieved 15 April 2015.
  159. ^ Wells, Martin (1983). "Cephalopods do it differently". New Scientist. Vol. 100, no. 1382. pp. 333–334. ISSN 0262-4079.
  160. ^ Sauer, Warwick H. H.; Gleadall, Ian G.; et al. (6 December 2019). "World Octopus Fisheries". Reviews in Fisheries Science & Aquaculture. Taylor & Francis. 29 (3): 279–429. doi:10.1080/23308249.2019.1680603. hdl:10261/227068. ISSN 2330-8249. S2CID 210266167.
  161. ^ Aristotle (c. 350 BC). Historia animalium. IX, 622a: 2–10. Cited in Borrelli, Luciana; Gherardi, Francesca; Fiorito, Graziano (2006). A catalogue of body patterning in Cephalopoda. Firenze University Press. ISBN 978-88-8453-377-7. Abstract
  162. ^ Leroi, Armand Marie (2014). The Lagoon: How Aristotle Invented Science. Bloomsbury. pp. 71–72. ISBN 978-1-4088-3622-4.
  163. ^ "The Cephalopoda". University of California Museum of Paleontology. Retrieved 27 March 2017.
  164. ^ Mann, T. (2012). Spermatophores: Development, Structure, Biochemical Attributes and Role in the Transfer of Spermatozoa. Springer. p. 28. ISBN 978-3-642-82308-4.
  165. ^ Laschi, Cecilia; Cianchetti, Matteo; Mazzolai, Barbara; Margheri, Laura; Follador, Maurizio; Dario, Paolo (2012). "Soft Robot Arm Inspired by the Octopus". Advanced Robotics. 26 (7): 709–727. doi:10.1163/156855312X626343. ISSN 0169-1864. S2CID 6104200.
  166. ^ Godfrey-Smith, Peter (2018). Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. William Collins. pp. 77–105, 137–157. ISBN 978-0-00-822629-9.
  167. ^ Baer, Drake (20 December 2016). "Octopuses Are 'the Closest We Will Come to Meeting an Intelligent Alien'". Science of Us. Retrieved 26 April 2017.
  168. ^ Brulliard, Karin (13 April 2016). "Octopus slips out of aquarium tank, crawls across floor, escapes down pipe to ocean". The Washington Post. Retrieved 20 February 2017.
  169. ^ "The Animals (Scientific Procedures) Act (Amendment) Order 1993". The National Archives. Retrieved 18 February 2015.
  170. ^ "The Animals (Scientific Procedures) Act 1986 Amendment Regulations 2012". The National Archives. Retrieved 18 February 2015.
  171. ^ "Directive 2010/63/EU of the European Parliament and of the Council". Official Journal of the European Union. Article 1, 3(b) (see page 276/39). Retrieved 18 February 2015.
  172. ^ "PoseiDRONE". The BioRobotics Institute, Scuola Superiore Sant'Anna. Retrieved 14 May 2021.
  173. ^ Laschi, Cecilia (2015). "Soft Robotics Research, Challenges, and Innovation Potential, Through Showcases". Soft Robotics: 255–264. doi:10.1007/978-3-662-44506-8_21. ISBN 978-3-662-44505-1.
  174. ^ Burgess, Matt (27 March 2017). "This robotic octopus tentacle isn't creepy at all". Wired.

Bibliography

Further reading

  • "Studying the creativity and intelligence of the octopus". CBS News. 30 August 2020.
  • "Untangling the Mysteries of the Octopus" (Video 7:10). CBS News. 12 January 2020.

External links

 
The Wikibook Dichotomous Key has a page on the topic of: Octopoda
 
Wikimedia Commons has media related to Octopoda.

December 31, 2022
octopus, this, article, about, order, cephalopod, other, uses, disambiguation, octopus, octopuses, octopodes, below, variants, soft, bodied, eight, limbed, mollusc, order, octopoda, order, consists, some, species, grouped, within, class, cephalopoda, with, squ. This article is about the order of cephalopod For other uses see Octopus disambiguation An octopus PL octopuses or octopodes see below for variants is a soft bodied eight limbed mollusc of the order Octopoda ɒ k ˈ t ɒ p e d e ok TOP e de 3 The order consists of some 300 species and is grouped within the class Cephalopoda with squids cuttlefish and nautiloids Like other cephalopods an octopus is bilaterally symmetric with two eyes and a beaked mouth at the center point of the eight limbs a The soft body can radically alter its shape enabling octopuses to squeeze through small gaps They trail their eight appendages behind them as they swim The siphon is used both for respiration and for locomotion by expelling a jet of water Octopuses have a complex nervous system and excellent sight and are among the most intelligent and behaviourally diverse of all invertebrates OctopusTemporal range Middle Jurassic recent PreꞒ Ꞓ O S D C P T J K Pg NCommon octopus Octopus vulgaris Scientific classificationKingdom AnimaliaPhylum MolluscaClass Cephalopoda unranked NeocoleoideaClade VampyropodaSuperorder OctopodiformesOrder OctopodaLeach 1818 1 Suborders traditional Cirrina IncirrinaSee Evolution for familiesSynonymsOctopoidaLeach 1817 2 Octopuses inhabit various regions of the ocean including coral reefs pelagic waters and the seabed some live in the intertidal zone and others at abyssal depths Most species grow quickly mature early and are short lived In most species the male uses a specially adapted arm to deliver a bundle of sperm directly into the female s mantle cavity after which he becomes senescent and dies while the female deposits fertilised eggs in a den and cares for them until they hatch after which she also dies Strategies to defend themselves against predators include the expulsion of ink the use of camouflage and threat displays the ability to jet quickly through the water and hide and even deceit All octopuses are venomous but only the blue ringed octopuses are known to be deadly to humans Octopuses appear in mythology as sea monsters like the Kraken of Norway and the Akkorokamui of the Ainu and probably the Gorgon of ancient Greece A battle with an octopus appears in Victor Hugo s book Toilers of the Sea inspiring other works such as Ian Fleming s Octopussy Octopuses appear in Japanese erotic art shunga They are eaten and considered a delicacy by humans in many parts of the world especially the Mediterranean and the Asian seas Contents 1 Etymology and pluralisation 2 Anatomy and physiology 2 1 Size 2 2 External characteristics 2 3 Circulatory system 2 4 Respiration 2 5 Digestion and excretion 2 6 Nervous system and senses 2 7 Ink sac 3 Lifecycle 3 1 Reproduction 3 2 Lifespan 4 Distribution and habitat 5 Behaviour and ecology 5 1 Feeding 5 2 Locomotion 5 3 Intelligence 5 4 Camouflage and colour change 5 5 Defence 5 6 Pathogens and parasites 6 Evolution 6 1 Fossil history and phylogeny 6 2 RNA editing and the genome 7 Relationship to humans 7 1 In culture 7 2 Danger 7 3 Fisheries 7 4 In science and technology 8 See also 9 Notes 10 References 10 1 Bibliography 11 Further reading 12 External linksEtymology and pluralisationSee also Plural form of words ending in us The scientific Latin term octopus was derived from Ancient Greek ὀktwpoys a compound form of ὀktw oktō eight and poys pous foot itself a variant form of ὀktapoys a word used for example by Alexander of Tralles c 525 c 605 for the common octopus 5 6 7 The standard pluralised form of octopus in English is octopuses 8 the Ancient Greek plural ὀktwpodes octopodes ɒ k ˈ t ɒ p e d iː z has also been used historically 9 The alternative plural octopi is considered grammatically incorrect because it wrongly assumes that octopus is a Latin second declension us noun or adjective when in either Greek or Latin it is a third declension noun 10 11 Historically the first plural to commonly appear in English language sources in the early 19th century is the latinate form octopi 12 followed by the English form octopuses in the latter half of the same century The Hellenic plural is roughly contemporary in usage although it is also the rarest 13 Fowler s Modern English Usage states that the only acceptable plural in English is octopuses that octopi is misconceived and octopodes pedantic 14 15 16 the last is nonetheless used frequently enough to be acknowledged by the descriptivist Merriam Webster 11th Collegiate Dictionary and Webster s New World College Dictionary The Oxford English Dictionary lists octopuses octopi and octopodes in that order reflecting frequency of use calling octopodes rare and noting that octopi is based on a misunderstanding 17 The New Oxford American Dictionary 3rd Edition 2010 lists octopuses as the only acceptable pluralisation and indicates that octopodes is still occasionally used but that octopi is incorrect 18 Anatomy and physiologySize See also Cephalopod size A giant Pacific octopus at Echizen Matsushima Aquarium Japan The giant Pacific octopus Enteroctopus dofleini is often cited as the largest known octopus species Adults usually weigh around 15 kg 33 lb with an arm span of up to 4 3 m 14 ft 19 The largest specimen of this species to be scientifically documented was an animal with a live mass of 71 kg 156 5 lb 20 Much larger sizes have been claimed for the giant Pacific octopus 21 one specimen was recorded as 272 kg 600 lb with an arm span of 9 m 30 ft 22 A carcass of the seven arm octopus Haliphron atlanticus weighed 61 kg 134 lb and was estimated to have had a live mass of 75 kg 165 lb 23 24 The smallest species is Octopus wolfi which is around 2 5 cm 1 in and weighs less than 1 g 0 035 oz 25 External characteristics The octopus is bilaterally symmetrical along its dorso ventral back to belly axis the head and foot are at one end of an elongated body and function as the anterior front of the animal The head includes the mouth and brain The foot has evolved into a set of flexible prehensile appendages known as arms that surround the mouth and are attached to each other near their base by a webbed structure 26 The arms can be described based on side and sequence position such as L1 R1 L2 R2 and divided into four pairs 27 26 The two rear appendages are generally used to walk on the sea floor while the other six are used to forage for food 28 The bulbous and hollow mantle is fused to the back of the head and is known as the visceral hump it contains most of the vital organs 29 30 The mantle cavity has muscular walls and contains the gills it is connected to the exterior by a funnel or siphon 26 31 The mouth of an octopus located underneath the arms has a sharp hard beak 30 Diagram of octopus from side with gills funnel eye ocellus eyespot web arms suckers hectocotylus and ligula labelled The skin consists of a thin outer epidermis with mucous cells and sensory cells and a connective tissue dermis consisting largely of collagen fibres and various cells allowing colour change 26 Most of the body is made of soft tissue allowing it to lengthen contract and contort itself The octopus can squeeze through tiny gaps even the larger species can pass through an opening close to 2 5 cm 1 in in diameter 30 Lacking skeletal support the arms work as muscular hydrostats and contain longitudinal transverse and circular muscles around a central axial nerve They can extend and contract twist to left or right bend at any place in any direction or be held rigid 32 33 The interior surfaces of the arms are covered with circular adhesive suckers The suckers allow the octopus to anchor itself or to manipulate objects Each sucker is usually circular and bowl like and has two distinct parts an outer shallow cavity called an infundibulum and a central hollow cavity called an acetabulum both of which are thick muscles covered in a protective chitinous cuticle When a sucker attaches to a surface the orifice between the two structures is sealed The infundibulum provides adhesion while the acetabulum remains free and muscle contractions allow for attachment and detachment 34 35 Each of the eight arms senses and responds to light allowing the octopus to control the limbs even if its head is obscured 36 A finned Grimpoteuthis species with its atypical octopus body plan The eyes of the octopus are large and at the top of the head They are similar in structure to those of a fish and are enclosed in a cartilaginous capsule fused to the cranium The cornea is formed from a translucent epidermal layer the slit shaped pupil forms a hole in the iris just behind the cornea The lens is suspended behind the pupil photoreceptive retinal cells cover the back of the eye The pupil can be adjusted in size a retinal pigment screens incident light in bright conditions 26 Some species differ in form from the typical octopus body shape Basal species the Cirrina have stout gelatinous bodies with webbing that reaches near the tip of their arms and two large fins above the eyes supported by an internal shell Fleshy papillae or cirri are found along the bottom of the arms and the eyes are more developed 37 38 Circulatory system Octopuses have a closed circulatory system in which the blood remains inside blood vessels Octopuses have three hearts a systemic or main heart that circulates blood around the body and two branchial or gill hearts that pump it through each of the two gills The systemic heart is inactive when the animal is swimming and thus it tires quickly and prefers to crawl 39 40 Octopus blood contains the copper rich protein haemocyanin to transport oxygen This makes the blood very viscous and it requires considerable pressure to pump it around the body octopuses blood pressures can exceed 75 mmHg 10 kPa 39 40 41 In cold conditions with low oxygen levels haemocyanin transports oxygen more efficiently than haemoglobin The haemocyanin is dissolved in the plasma instead of being carried within blood cells and gives the blood a bluish colour 39 40 The systemic heart has muscular contractile walls and consists of a single ventricle and two atria one for each side of the body The blood vessels consist of arteries capillaries and veins and are lined with a cellular endothelium which is quite unlike that of most other invertebrates The blood circulates through the aorta and capillary system to the vena cavae after which the blood is pumped through the gills by the branchial hearts and back to the main heart Much of the venous system is contractile which helps circulate the blood 26 Respiration Octopus with open siphon The siphon is used for respiration waste disposal and discharging ink Respiration involves drawing water into the mantle cavity through an aperture passing it through the gills and expelling it through the siphon The ingress of water is achieved by contraction of radial muscles in the mantle wall and flapper valves shut when strong circular muscles force the water out through the siphon 42 Extensive connective tissue lattices support the respiratory muscles and allow them to expand the respiratory chamber 43 The lamella structure of the gills allows for a high oxygen uptake up to 65 in water at 20 C 68 F 44 Water flow over the gills correlates with locomotion and an octopus can propel its body when it expels water out of its siphon 43 41 The thin skin of the octopus absorbs additional oxygen When resting around 41 of an octopus s oxygen absorption is through the skin This decreases to 33 when it swims as more water flows over the gills skin oxygen uptake also increases When it is resting after a meal absorption through the skin can drop to 3 of its total oxygen uptake 45 Digestion and excretion The digestive system of the octopus begins with the buccal mass which consists of the mouth with its chitinous beak the pharynx radula and salivary glands 46 The radula is a spiked muscular tongue like organ with multiple rows of tiny teeth 30 Food is broken down and is forced into the oesophagus by two lateral extensions of the esophageal side walls in addition to the radula From there it is transferred to the gastrointestinal tract which is mostly suspended from the roof of the mantle cavity by numerous membranes The tract consists of a crop where the food is stored a stomach where food is ground down a caecum where the now sludgy food is sorted into fluids and particles and which plays an important role in absorption the digestive gland where liver cells break down and absorb the fluid and become brown bodies and the intestine where the accumulated waste is turned into faecal ropes by secretions and blown out of the funnel via the rectum 46 During osmoregulation fluid is added to the pericardia of the branchial hearts The octopus has two nephridia equivalent to vertebrate kidneys which are associated with the branchial hearts these and their associated ducts connect the pericardial cavities with the mantle cavity Before reaching the branchial heart each branch of the vena cava expands to form renal appendages which are in direct contact with the thin walled nephridium The urine is first formed in the pericardial cavity and is modified by excretion chiefly of ammonia and selective absorption from the renal appendages as it is passed along the associated duct and through the nephridiopore into the mantle cavity 26 47 source source source source source source source source source source A common octopus Octopus vulgaris moving around Its nervous system allows the arms to move with some autonomy Nervous system and senses Octopuses along with cuttlefish have the highest brain to body mass ratios of all invertebrates 48 this is greater than that of many vertebrates 49 Octopuses have the same jumping genes that are active in the human brain implying an evolutionary convergence at molecular level 50 The nervous system is complex only part of which is localised in its brain which is contained in a cartilaginous capsule 51 Two thirds of an octopus s neurons are in the nerve cords of its arms these are capable of complex reflex actions without input from the brain 52 Unlike vertebrates the complex motor skills of octopuses are not organised in their brains via internal somatotopic maps of their bodies 53 Eye of common octopus Like other cephalopods octopuses have camera like eyes 48 and can distinguish the polarisation of light Colour vision appears to vary from species to species for example being present in O aegina but absent in O vulgaris 54 Opsins in the skin respond to different wavelengths of light and help the animals choose a coloration that camouflages them the chromatophores in the skin can respond to light independently of the eyes 55 56 An alternative hypothesis is that cephalopod eyes in species which only have a single photoreceptor protein may use chromatic aberration to turn monochromatic vision into colour vision though this sacrifices image quality This would explain pupils shaped like the letter U the letter W or a dumbbell as well as explaining the need for colourful mating displays 57 Attached to the brain are two organs called statocysts sac like structures containing a mineralised mass and sensitive hairs that allow the octopus to sense the orientation of its body They provide information on the position of the body relative to gravity and can detect angular acceleration An autonomic response keeps the octopus s eyes oriented so that the pupil is always horizontal 26 Octopuses may also use the statocyst to hear sound The common octopus can hear sounds between 400 Hz and 1000 Hz and hears best at 600 Hz 58 Octopuses have an excellent somatosensory system Their suction cups are equipped with chemoreceptors so they can taste what they touch Octopus arms move easily because the sensors recognise octopus skin and prevent self attachment 59 Octopuses appear to have poor proprioceptive sense and must observe the arms visually to keep track of their position 60 61 Ink sac The ink sac of an octopus is located under the digestive gland A gland attached to the sac produces the ink and the sac stores it The sac is close enough to the funnel for the octopus to shoot out the ink with a water jet Before it leaves the funnel the ink passes through glands which mix it with mucus creating a thick dark blob which allows the animal to escape from a predator 62 The main pigment in the ink is melanin which gives it its black colour 63 Cirrate octopuses usually lack the ink sac 37 LifecycleReproduction Adult male Tremoctopus violaceus with hectocotylus Octopuses are gonochoric and have a single posteriorly located gonad which is associated with the coelom The testis in males and the ovary in females bulges into the gonocoel and the gametes are released here The gonocoel is connected by the gonoduct to the mantle cavity which it enters at the gonopore 26 An optic gland creates hormones that cause the octopus to mature and age and stimulate gamete production The gland may be triggered by environmental conditions such as temperature light and nutrition which thus control the timing of reproduction and lifespan 64 65 When octopuses reproduce the male uses a specialised arm called a hectocotylus to transfer spermatophores packets of sperm from the terminal organ of the reproductive tract the cephalopod penis into the female s mantle cavity 66 The hectocotylus in benthic octopuses is usually the third right arm which has a spoon shaped depression and modified suckers near the tip In most species fertilisation occurs in the mantle cavity 26 The reproduction of octopuses has been studied in only a few species One such species is the giant Pacific octopus in which courtship is accompanied especially in the male by changes in skin texture and colour The male may cling to the top or side of the female or position himself beside her There is some speculation that he may first use his hectocotylus to remove any spermatophore or sperm already present in the female He picks up a spermatophore from his spermatophoric sac with the hectocotylus inserts it into the female s mantle cavity and deposits it in the correct location for the species which in the giant Pacific octopus is the opening of the oviduct Two spermatophores are transferred in this way these are about one metre yard long and the empty ends may protrude from the female s mantle 67 A complex hydraulic mechanism releases the sperm from the spermatophore and it is stored internally by the female 26 Female giant Pacific octopus guarding strings of eggs About forty days after mating the female giant Pacific octopus attaches strings of small fertilised eggs 10 000 to 70 000 in total to rocks in a crevice or under an overhang Here she guards and cares for them for about five months 160 days until they hatch 67 In colder waters such as those off Alaska it may take up to ten months for the eggs to completely develop 68 74 The female aerates them and keeps them clean if left untended many will die 69 She does not feed during this time and dies soon after Males become senescent and die a few weeks after mating 64 The eggs have large yolks cleavage division is superficial and a germinal disc develops at the pole During gastrulation the margins of this grow down and surround the yolk forming a yolk sac which eventually forms part of the gut The dorsal side of the disc grows upward and forms the embryo with a shell gland on its dorsal surface gills mantle and eyes The arms and funnel develop as part of the foot on the ventral side of the disc The arms later migrate upward coming to form a ring around the funnel and mouth The yolk is gradually absorbed as the embryo develops 26 Octopus paralarva a planktonic hatchling Most young octopuses hatch as paralarvae and are planktonic for weeks to months depending on the species and water temperature They feed on copepods arthropod larvae and other zooplankton eventually settling on the ocean floor and developing directly into adults with no distinct metamorphoses that are present in other groups of mollusc larvae 26 Octopus species that produce larger eggs including the southern blue ringed Caribbean reef California two spot Eledone moschata 70 and deep sea octopuses instead hatch as benthic animals similar to the adults 68 74 75 In the argonaut paper nautilus the female secretes a fine fluted papery shell in which the eggs are deposited and in which she also resides while floating in mid ocean In this she broods the young and it also serves as a buoyancy aid allowing her to adjust her depth The male argonaut is minute by comparison and has no shell 71 Lifespan Octopuses have a relatively short lifespan some species live for as little as six months The Giant Pacific octopus one of the two largest species of octopus may live for as much as five years Octopus lifespan is limited by reproduction 72 For most octopuses the last stage of their life is called senescence It is the breakdown of cellular function without repair or replacement For males this typically begins after mating Senescence may last from weeks to a few months at most For females it begins when they lay a clutch of eggs Females will spend all their time aerating and protecting their eggs until they are ready to hatch During senescence an octopus does not feed and quickly weakens Lesions begin to form and the octopus literally degenerates Unable to defend themselves octopuses often fall prey to predators 73 The larger Pacific striped octopus LPSO is an exception as it can reproduce repeatedly over a life of around two years 72 Octopus reproductive organs mature due to the hormonal influence of the optic gland but result in the inactivation of their digestive glands Unable to feed the octopus typically dies of starvation 74 Experimental removal of both optic glands after spawning was found to result in the cessation of broodiness the resumption of feeding increased growth and greatly extended lifespans It has been proposed that the naturally short lifespan may be functional to prevent rapid overpopulation 75 Distribution and habitat Octopus cyanea in Kona Hawaii Octopuses live in every ocean and different species have adapted to different marine habitats As juveniles common octopuses inhabit shallow tide pools The Hawaiian day octopus Octopus cyanea lives on coral reefs argonauts drift in pelagic waters Abdopus aculeatus mostly lives in near shore seagrass beds Some species are adapted to the cold ocean depths The spoon armed octopus Bathypolypus arcticus is found at depths of 1 000 m 3 300 ft and Vulcanoctopus hydrothermalis lives near hydrothermal vents at 2 000 m 6 600 ft 29 The cirrate species are often free swimming and live in deep water habitats 38 Although several species are known to live at bathyal and abyssal depths there is only a single indisputable record of an octopus in the hadal zone a species of Grimpoteuthis dumbo octopus photographed at 6 957 m 22 825 ft 76 No species are known to live in fresh water 77 Behaviour and ecologyMost species are solitary when not mating 78 though a few are known to occur in high densities and with frequent interactions signaling mate defending and eviction of individuals from dens This is likely the result of abundant food supplies combined with limited den sites 79 The LPSO has been described as particularly social living in groups of up to 40 individuals 80 81 Octopuses hide in dens which are typically crevices in rocky outcrops or other hard structures though some species burrow into sand or mud Octopuses are not territorial but generally remain in a home range they may leave in search of food They can navigate back to a den without having to retrace their outward route 82 They are not migratory 83 Octopuses bring captured prey to the den where they can eat it safely Sometimes the octopus catches more prey than it can eat and the den is often surrounded by a midden of dead and uneaten food items Other creatures such as fish crabs molluscs and echinoderms often share the den with the octopus either because they have arrived as scavengers or because they have survived capture 84 On rare occasions octopuses hunt cooperatively with other species with fish as their partners They regulate the species composition of the hunting group and the behavior of their partners by punching them 85 Feeding Veined octopus eating a crab Nearly all octopuses are predatory bottom dwelling octopuses eat mainly crustaceans polychaete worms and other molluscs such as whelks and clams open ocean octopuses eat mainly prawns fish and other cephalopods 86 Major items in the diet of the giant Pacific octopus include bivalve molluscs such as the cockle Clinocardium nuttallii clams and scallops and crustaceans such as crabs and spider crabs Prey that it is likely to reject include moon snails because they are too large and limpets rock scallops chitons and abalone because they are too securely fixed to the rock 84 A benthic bottom dwelling octopus typically moves among the rocks and feels through the crevices The creature may make a jet propelled pounce on prey and pull it toward the mouth with its arms the suckers restraining it Small prey may be completely trapped by the webbed structure Octopuses usually inject crustaceans like crabs with a paralysing saliva then dismember them with their beaks 86 87 Octopuses feed on shelled molluscs either by forcing the valves apart or by drilling a hole in the shell to inject a nerve toxin 88 87 It used to be thought that the hole was drilled by the radula but it has now been shown that minute teeth at the tip of the salivary papilla are involved and an enzyme in the toxic saliva is used to dissolve the calcium carbonate of the shell It takes about three hours for O vulgaris to create a 0 6 mm 0 024 in hole Once the shell is penetrated the prey dies almost instantaneously its muscles relax and the soft tissues are easy for the octopus to remove Crabs may also be treated in this way tough shelled species are more likely to be drilled and soft shelled crabs are torn apart 89 Some species have other modes of feeding Grimpoteuthis has a reduced or non existent radula and swallows prey whole 37 In the deep sea genus Stauroteuthis some of the muscle cells that control the suckers in most species have been replaced with photophores which are believed to fool prey by directing them to the mouth making them one of the few bioluminescent octopuses 90 Locomotion Octopuses swim with their arms trailing behind Octopuses mainly move about by relatively slow crawling with some swimming in a head first position Jet propulsion or backward swimming is their fastest means of locomotion followed by swimming and crawling 91 When in no hurry they usually crawl on either solid or soft surfaces Several arms are extended forward some of the suckers adhere to the substrate and the animal hauls itself forward with its powerful arm muscles while other arms may push rather than pull As progress is made other arms move ahead to repeat these actions and the original suckers detach During crawling the heart rate nearly doubles and the animal requires ten or fifteen minutes to recover from relatively minor exercise 32 Most octopuses swim by expelling a jet of water from the mantle through the siphon into the sea The physical principle behind this is that the force required to accelerate the water through the orifice produces a reaction that propels the octopus in the opposite direction 92 The direction of travel depends on the orientation of the siphon When swimming the head is at the front and the siphon is pointed backward but when jetting the visceral hump leads the siphon points at the head and the arms trail behind with the animal presenting a fusiform appearance In an alternative method of swimming some species flatten themselves dorso ventrally and swim with the arms held out sideways and this may provide lift and be faster than normal swimming Jetting is used to escape from danger but is physiologically inefficient requiring a mantle pressure so high as to stop the heart from beating resulting in a progressive oxygen deficit 91 Movements of the finned species Cirroteuthis muelleri Cirrate octopuses cannot produce jet propulsion and rely on their fins for swimming They have neutral buoyancy and drift through the water with the fins extended They can also contract their arms and surrounding web to make sudden moves known as take offs Another form of locomotion is pumping which involves symmetrical contractions of muscles in their webs producing peristaltic waves This moves the body slowly 37 In 2005 Adopus aculeatus and veined octopus Amphioctopus marginatus were found to walk on two arms while at the same time mimicking plant matter 93 This form of locomotion allows these octopuses to move quickly away from a potential predator without being recognised 91 Some species of octopus can crawl out of the water briefly which they may do between tide pools 94 95 Stilt walking is used by the veined octopus when carrying stacked coconut shells The octopus carries the shells underneath it with two arms and progresses with an ungainly gait supported by its remaining arms held rigid 96 Intelligence Main article Cephalopod intelligence Octopus opening a container by unscrewing its cap Octopuses are highly intelligent 97 Maze and problem solving experiments have shown evidence of a memory system that can store both short and long term memory 98 Young octopuses learn nothing from their parents as adults provide no parental care beyond tending to their eggs until the young octopuses hatch 68 75 In laboratory experiments octopuses can readily be trained to distinguish between different shapes and patterns They have been reported to practise observational learning 99 although the validity of these findings is contested 97 Octopuses have also been observed in what has been described as play repeatedly releasing bottles or toys into a circular current in their aquariums and then catching them 100 Octopuses often break out of their aquariums and sometimes into others in search of food 94 101 102 The veined octopus collects discarded coconut shells then uses them to build a shelter an example of tool use 96 Camouflage and colour change source source source source source source source source source source source source Video of Octopus cyanea moving and changing its colour shape and texture Octopuses use camouflage when hunting and to avoid predators To do this they use specialised skin cells which change the appearance of the skin by adjusting its colour opacity or reflectivity Chromatophores contain yellow orange red brown or black pigments most species have three of these colours while some have two or four Other colour changing cells are reflective iridophores and white leucophores 103 This colour changing ability is also used to communicate with or warn other octopuses 104 Octopuses can create distracting patterns with waves of dark coloration across the body a display known as the passing cloud Muscles in the skin change the texture of the mantle to achieve greater camouflage In some species the mantle can take on the spiky appearance of algae in others skin anatomy is limited to relatively uniform shades of one colour with limited skin texture Octopuses that are diurnal and live in shallow water have evolved more complex skin than their nocturnal and deep sea counterparts 104 A moving rock trick involves the octopus mimicking a rock and then inching across the open space with a speed matching that of the surrounding water 105 Defence Warning display of greater blue ringed octopus Hapalochlaena lunulata Aside from humans octopuses may be preyed on by fishes seabirds sea otters pinnipeds cetaceans and other cephalopods 106 Octopuses typically hide or disguise themselves by camouflage and mimicry some have conspicuous warning coloration aposematism or deimatic behaviour 104 An octopus may spend 40 of its time hidden away in its den When the octopus is approached it may extend an arm to investigate 66 of Enteroctopus dofleini in one study had scars with 50 having amputated arms 106 The blue rings of the highly venomous blue ringed octopus are hidden in muscular skin folds which contract when the animal is threatened exposing the iridescent warning 107 The Atlantic white spotted octopus Callistoctopus macropus turns bright brownish red with oval white spots all over in a high contrast display 108 Displays are often reinforced by stretching out the animal s arms fins or web to make it look as big and threatening as possible 109 Once they have been seen by a predator they commonly try to escape but can also use distraction with an ink cloud ejected from the ink sac The ink is thought to reduce the efficiency of olfactory organs which would aid evasion from predators that employ smell for hunting such as sharks Ink clouds of some species might act as pseudomorphs or decoys that the predator attacks instead 110 When under attack some octopuses can perform arm autotomy in a manner similar to the way skinks and other lizards detach their tails The crawling arm may distract would be predators Such severed arms remain sensitive to stimuli and move away from unpleasant sensations 111 Octopuses can replace lost limbs 112 Some octopuses such as the mimic octopus can combine their highly flexible bodies with their colour changing ability to mimic other more dangerous animals such as lionfish sea snakes and eels 113 114 Pathogens and parasites The diseases and parasites that affect octopuses have been little studied but cephalopods are known to be the intermediate or final hosts of various parasitic cestodes nematodes and copepods 150 species of protistan and metazoan parasites have been recognised 115 The Dicyemidae are a family of tiny worms that are found in the renal appendages of many species 116 it is unclear whether they are parasitic or endosymbionts Coccidians in the genus Aggregata living in the gut cause severe disease to the host Octopuses have an innate immune system their haemocytes respond to infection by phagocytosis encapsulation infiltration or cytotoxic activities to destroy or isolate the pathogens The haemocytes play an important role in the recognition and elimination of foreign bodies and wound repair Captive animals are more susceptible to pathogens than wild ones 117 A gram negative bacterium Vibrio lentus can cause skin lesions exposure of muscle and sometimes death 118 EvolutionFurther information Evolution of cephalopods The scientific name Octopoda was first coined and given as the order of octopuses in 1818 by English biologist William Elford Leach 119 who classified them as Octopoida the previous year 2 The Octopoda consists of around 300 known species 120 and were historically divided into two suborders the Incirrina and the Cirrina 38 More recent evidence suggests Cirrina is merely the most basal species not a unique clade 121 The incirrate octopuses the majority of species lack the cirri and paired swimming fins of the cirrates 38 In addition the internal shell of incirrates is either present as a pair of stylets or absent altogether 122 Fossil history and phylogeny The octopuses evolved from the Muensterelloidea fossil pictured in the Jurassic period 123 The Cephalopoda evolved from a mollusc resembling the Monoplacophora in the Cambrian some 530 million years ago The Coleoidea diverged from the nautiloids in the Devonian some 416 million years ago In turn the coleoids including the squids and octopods brought their shells inside the body and some 276 million years ago during the Permian split into the Vampyropoda and the Decabrachia 124 The octopuses arose from the Muensterelloidea within the Vampyropoda in the Jurassic The earliest octopus likely lived near the sea floor benthic to demersal in shallow marine environments 124 125 123 Octopuses consist mostly of soft tissue and so fossils are relatively rare As soft bodied cephalopods they lack the external shell of most molluscs including other cephalopods like the nautiloids and the extinct Ammonoidea 126 They have eight limbs like other Coleoidea but lack the extra specialised feeding appendages known as tentacles which are longer and thinner with suckers only at their club like ends 127 The vampire squid Vampyroteuthis also lacks tentacles but has sensory filaments 128 The cladograms are based on Sanchez et al 2018 who created a molecular phylogeny based on mitochondrial and nuclear DNA marker sequences 121 The position of the Eledonidae is from Ibanez et al 2020 with a similar methodology 129 Dates of divergence are from Kroger et al 2011 and Fuchs et al 2019 124 123 Cephalopods Nautiloids Nautilus Coleoids Decabrachia Squids and cuttlefish Vampyropoda Vampyromorphida Octopods 155 mya276 mya416 mya530 myaThe molecular analysis of the octopods shows that the suborder Cirrina Cirromorphida and the superfamily Argonautoidea are paraphyletic and are broken up these names are shown in quotation marks and italics on the cladogram Octopoda Cirromorphida part Cirroteuthidae Stauroteuthidae Cirromorphida part Opisthoteuthidae Cirroctopodidae Octopodida Argonautoidea part Tremoctopodidae Alloposidae Argonautoidea part Argonautidae Ocythoidae Octopodoidea Eledonidae Bathypolypodidae Enteroctopodidae Octopodidae Megaleledonidae Bolitaenidae Amphitretidae Vitreledonellidae RNA editing and the genome Octopuses like other coleoid cephalopods but unlike more basal cephalopods or other molluscs are capable of greater RNA editing changing the nucleic acid sequence of the primary transcript of RNA molecules than any other organisms Editing is concentrated in the nervous system and affects proteins involved in neural excitability and neuronal morphology More than 60 of RNA transcripts for coleoid brains are recoded by editing compared to less than 1 for a human or fruit fly Coleoids rely mostly on ADAR enzymes for RNA editing which requires large double stranded RNA structures to flank the editing sites Both the structures and editing sites are conserved in the coleoid genome and the mutation rates for the sites are severely hampered Hence greater transcriptome plasticity has come at the cost of slower genome evolution 130 131 The octopus genome is unremarkably bilaterian except for large developments of two gene families protocadherins which regulate the development of neurons and the C2H2 zinc finger transcription factors Many genes specific to cephalopods are expressed in the animals skin suckers and nervous system 48 Relationship to humans Minoan clay vase with octopus decoration c 1500 BC In culture Ancient seafaring people were aware of the octopus as evidenced by artworks and designs For example a stone carving found in the archaeological recovery from Bronze Age Minoan Crete at Knossos 1900 1100 BC depicts a fisherman carrying an octopus 132 The terrifyingly powerful Gorgon of Greek mythology may have been inspired by the octopus or squid the octopus itself representing the severed head of Medusa the beak as the protruding tongue and fangs and its tentacles as the snakes 133 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 octopuses attacking ships Linnaeus included it in the first edition of his 1735 Systema Naturae 134 135 One translation of the Hawaiian creation myth the Kumulipo suggests that the octopus is the lone survivor of a previous age 136 137 138 The Akkorokamui is a gigantic octopus like monster from Ainu folklore worshipped in Shinto 139 A battle with an octopus plays a significant role in Victor Hugo s 1866 book Travailleurs de la mer Toilers of the Sea 140 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 141 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 142 143 The print is a forerunner of tentacle erotica 144 The biologist P Z Myers noted in his science blog Pharyngula that octopuses appear in extraordinary graphic illustrations involving women tentacles and bare breasts 145 146 Since it has numerous arms emanating from a common centre the octopus is often used as a symbol for a powerful and manipulative organisation company or country 147 Danger Pen and wash drawing of an imagined colossal octopus attacking a ship by the malacologist Pierre de Montfort 1801 Octopuses generally avoid humans but incidents have been verified For example a 2 4 metre 8 ft Pacific octopus said to be nearly perfectly camouflaged lunged at a diver and wrangled over his camera before it let go Another diver recorded the encounter on video 148 All species are venomous but only blue ringed octopuses have venom that is lethal to humans 149 Bites are reported each year across the animals range from Australia to the eastern Indo Pacific Ocean They bite only when provoked or accidentally stepped upon bites are small and usually painless The venom appears to be able to penetrate the skin without a puncture given prolonged contact It contains tetrodotoxin which causes paralysis by blocking the transmission of nerve impulses to the muscles This causes death by respiratory failure leading to cerebral anoxia No antidote is known but if breathing can be kept going artificially patients recover within 24 hours 150 151 Bites have been recorded from captive octopuses of other species they leave swellings which disappear in a day or two 152 Fisheries Main article Octopus as food Octopus fisheries exist around the world with total catches varying between 245 320 and 322 999 metric tons from 1986 to 1995 153 The world catch peaked in 2007 at 380 000 tons and had fallen by a tenth by 2012 154 Methods to capture octopuses include pots traps trawls snares drift fishing spearing hooking and hand collection 153 Octopus is eaten in many cultures such as on the Mediterranean and Asian coasts 155 The arms and sometimes other body parts are prepared in various ways often varying by species or geography Live octopuses are eaten in several countries around the world including the US 156 157 Animal welfare groups have objected to this practice on the basis that octopuses can experience pain 158 Octopuses have a food conversion efficiency greater than that of chickens making octopus aquaculture a possibility 159 Octopuses compete with human fisheries targeting other species and even rob traps and nets for their catch they may themselves be caught as bycatch if they cannot get away 160 In science and technology In classical Greece Aristotle 384 322 BC commented on the colour changing abilities of the octopus both for camouflage and for signalling in his Historia animalium The octopus seeks its prey by so changing its colour as to render it like the colour of the stones adjacent to it it does so also when alarmed 161 Aristotle noted that the octopus had a hectocotyl arm and suggested it might be used in sexual reproduction This claim was widely disbelieved until the 19th century It was described in 1829 by the French zoologist Georges Cuvier who supposed it to be a parasitic worm naming it as a new species Hectocotylus octopodis 162 163 Other zoologists thought it a spermatophore the German zoologist Heinrich Muller believed it was designed to detach during copulation In 1856 the Danish zoologist Japetus Steenstrup demonstrated that it is used to transfer sperm and only rarely detaches 164 Flexible biomimetic Octopus robotics arm The BioRobotics Institute Scuola Superiore Sant Anna Pisa 2011 165 Octopuses offer many possibilities in biological research including their ability to regenerate limbs change the colour of their skin behave intelligently with a distributed nervous system and make use of 168 kinds of protocadherins humans have 58 the proteins that guide the connections neurons make with each other The California two spot octopus has had its genome sequenced allowing exploration of its molecular adaptations 48 Having independently evolved mammal like intelligence octopuses have been compared by the philosopher Peter Godfrey Smith who has studied the nature of intelligence 166 to hypothetical intelligent extraterrestrials 167 Their problem solving skills along with their mobility and lack of rigid structure enable them to escape from supposedly secure tanks in laboratories and public aquariums 168 Due to their intelligence octopuses are listed in some countries as experimental animals on which surgery may not be performed without anesthesia a protection usually extended only to vertebrates In the UK from 1993 to 2012 the common octopus Octopus vulgaris was the only invertebrate protected under the Animals Scientific Procedures Act 1986 169 In 2012 this legislation was extended to include all cephalopods 170 in accordance with a general EU directive 171 Some robotics research is exploring biomimicry of octopus features Octopus arms can move and sense largely autonomously without intervention from the animal s central nervous system In 2015 a team in Italy built soft bodied robots able to crawl and swim requiring only minimal computation 172 173 In 2017 a German company made an arm with a soft pneumatically controlled silicone gripper fitted with two rows of suckers It is able to grasp objects such as a metal tube a magazine or a ball and to fill a glass by pouring water from a bottle 174 See alsoMy Octopus Teacher 2020 documentary film by Pippa Ehrlich and James ReedNotes Tentacle is a common umbrella term for cephalopod limbs In teuthological context octopuses have arms with suckers along their entire length while tentacle is reserved for appendages with suckers only near the end of the limb which octopuses lack 4 References ITIS Report Octopoda Leach 1818 Itis gov 10 April 2013 Retrieved 4 February 2014 a b Coleoidea Recent cephalopods Mikko s Phylogeny Archive Octopoda Merriam Webster Dictionary Retrieved 12 July 2021 Scully Caitlin 11 October 2018 Get to Know th Four Types of Cephalopod U CSan Diego Harper Douglas octopus Online Etymology Dictionary Octopus Dictionary reference com Retrieved 4 February 2014 ὀktapoys ὀktwpoys Liddell Henry George Scott Robert A Greek English Lexicon at the Perseus Project Michel Jean Baptiste Shen Yuan Aiden Aviva Veres Adrian Gray Matthew Pickett Joseph Hoiberg Dale Clancy Dan Norvig Peter Orwant Jon Pinker Steven Nowak Martin 2011 Quantitative Analysis of Culture Using Millions of Digitized Books Science 331 6014 176 182 Bibcode 2011Sci 331 176M doi 10 1126 science 1199644 PMC 3279742 PMID 21163965 Relevant data at Google Ngram Viewer Octopus Oxforddictionaries com 2014 Archived from the original on 30 October 2012 Retrieved 4 February 2014 Peters Pam 2004 The Cambridge Guide to English Usage Cambridge Cambridge University Press ISBN 0 521 62181 X p 388 Fowler Henry Watson 1994 A Dictionary of Modern English Usage p 316 ISBN 9781853263187 In Latin plurals there are some traps for non Latinists the termination of the singular is no sure guide to that of the plural Most Latin words in us have plural in i but not all amp so zeal not according to knowledge issues in such oddities as octopi as caution the following list may be useful octopus podes Tuckey James Hingston Smith Christen 1818 Narrative of an Expedition to Explore the River Zaire Kirk amp Mercein The Many Plurals of Octopus www merriam webster com Butterfield Jeremy 2015 Fowler s Dictionary of Modern English Usage Oxford University Press ISBN 9780191744532 The only correct plural in English is octopuses The Greek original is ὀktwpoys pod which would lead to a pedantic English pl form octopodes The pl form octopi which is occasionally heard mostly in jocular use though based on modL octopus is misconceived Chambers 21st Century Dictionary Archived 24 November 2007 at the Wayback Machine retrieved 19 October 2007 Stamper Kory Ask the editor octopus Merriam Webster Archived from the original on 30 April 2013 Retrieved 26 June 2013 octopus Oxford English Dictionary Online ed Oxford University Press Subscription or participating institution membership required Stevenson Angus Lindberg Christine A eds 2010 New Oxford American Dictionary 3rd ed Oxford University Press ISBN 978 0 19 539288 3 Smithsonian National Zoological Park Giant Pacific Octopus Nationalzoo si edu Archived from the original on 23 February 2014 Retrieved 4 February 2014 Cosgrove J A 1987 Aspects of the Natural History of Octopus dofleini the Giant Pacific Octopus MSc Thesis Department of Biology University of Victoria Canada 101 pp Norman M 2000 Cephalopods A World Guide ConchBooks Hackenheim p 214 High William L 1976 The giant Pacific octopus PDF Marine Fisheries Review 38 9 17 22 O Shea S 2004 The giant octopus Haliphron atlanticus Mollusca Octopoda in New Zealand waters New Zealand Journal of Zoology 31 1 7 13 doi 10 1080 03014223 2004 9518353 S2CID 84954869 O Shea S 2002 Haliphron atlanticus a giant gelatinous octopus PDF Biodiversity Update 5 1 Bradford Alina 21 July 2016 Octopus Facts Live Science Retrieved 26 April 2017 a b c d e f g h i j k l m Ruppert Edward E Fox Richard S Barnes Robert D 2008 Invertebrate Zoology Cengage Learning pp 363 364 ISBN 978 81 315 0104 7 Wells 1978 pp 11 12 Ruth A Byrne Kuba Michael J Meisel Daniela V Griebel Ulrike Mather Jennifer A August 2006 Does Octopus vulgaris have preferred arms Journal of Comparative Psychology 120 3 198 204 doi 10 1037 0735 7036 120 3 198 PMID 16893257 a b Mather Anderson amp Wood 2010 pp 13 15 a b c d Courage 2013 pp 40 41 Semmens 2004 Understanding octopus growth patterns variability and physiology Marine and Freshwater Research 55 4 367 doi 10 1071 MF03155 S2CID 84208773 a b Carefoot Thomas Octopuses and Relatives Locomotion Crawling A Snail s Odyssey Archived from the original on 22 May 2013 Retrieved 19 April 2017 Zelman I Titon M Yekutieli Y Hanassy S Hochner B Flash T 2013 Kinematic decomposition and classification of octopus arm movements Frontiers in Computational Neuroscience 7 60 doi 10 3389 fncom 2013 00060 PMC 3662989 PMID 23745113 Tramacere F Beccai L Kuba M Gozzi A Bifone A Mazzolai B 2013 The morphology and adhesion mechanism of Octopus vulgaris suckers PLOS ONE 8 6 e65074 Bibcode 2013PLoSO 865074T doi 10 1371 journal pone 0065074 PMC 3672162 PMID 23750233 Kier W M Smith A M 2002 The structure and adhesive mechanism of octopus suckers Integrative and Comparative Biology 42 6 1146 1153 CiteSeerX 10 1 1 512 2605 doi 10 1093 icb 42 6 1146 PMID 21680399 S2CID 15997762 Katz Itamar Shomrat Tal Nesher Nir 1 January 2021 Feel the light sight independent negative phototactic response in octopus arms Journal of Experimental Biology 224 5 doi 10 1242 jeb 237529 ISSN 0022 0949 PMID 33536305 a b c d Finned Deep sea Octopuses Grimpoteuthis spp MarineBio 18 May 2017 Retrieved 14 May 2021 a b c d Marshall Cavendish Corporation 2004 Encyclopedia of the Aquatic World Marshall Cavendish p 764 ISBN 978 0 7614 7424 1 a b c Wells 1978 pp 31 35 a b c Courage 2013 pp 42 43 a b Schmidt Nielsen Knut 1997 Animal Physiology Adaptation and Environment Cambridge University Press p 117 ISBN 978 0 521 57098 5 Carefoot Thomas Octopuses and Relatives Locomotion jet propulsion A Snail s Odyssey Archived from the original on 28 April 2017 Retrieved 26 April 2017 a b Wells 1978 pp 24 26 Wells M J Wells J 1995 The control of ventilatory and cardiac responses to changes in ambient oxygen tension and oxygen demand in Octopus The Journal of Experimental Biology 198 Pt 8 1717 1727 doi 10 1242 jeb 198 8 1717 PMID 9319626 Wells J 1996 Cutaneous respiration in Octopus vulgaris The Journal of Experimental Biology 199 Pt 11 2477 2483 doi 10 1242 jeb 199 11 2477 PMID 9320405 a b Wells 1978 pp 73 79 Wells 1978 pp 54 56 a b c d Albertin Caroline B Simakov Oleg Mitros Therese Wang Z Yan Pungor Judit R Edsinger Gonzales Eric Brenner Sydney Ragsdale Clifton W Rokhsar Daniel S 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 Pilleri Georg 1984 Investigations on Cetacea Vol 16 17 Hirnanatomisches Institut der Universitat p 161 Retrieved 30 July 2018 Petrosino Giuseppe Ponte Giovanna Volpe Massimiliano et al 18 May 2022 Identification of LINE retrotransposons and long non coding RNAs expressed in the octopus brain BMC Biology 20 1 doi 10 1186 s12915 022 01303 5 Hochner B 2012 An Embodied View of Octopus Neurobiology Current Biology 22 20 R887 R892 doi 10 1016 j cub 2012 09 001 PMID 23098601 Yekutieli Y Sagiv Zohar R Aharonov R Engel Y Hochner B Flash T 2005 Dynamic model of the octopus arm I Biomechanics of the octopus reaching movement Journal of Neurophysiology 94 2 1443 1458 doi 10 1152 jn 00684 2004 PMID 15829594 S2CID 14711055 Zullo L Sumbre G Agnisola C Flash T Hochner B 2009 Nonsomatotopic organization of the higher motor centers in Octopus Current Biology 19 19 1632 1636 doi 10 1016 j cub 2009 07 067 PMID 19765993 S2CID 15852956 Kawamura G et al 2001 Color Discrimination Conditioning in Two Octopus Octopus aegina and O vulgaris Nippon Suisan Gakkaishi 67 1 35 39 doi 10 2331 suisan 67 35 Kingston Alexandra C N Kuzirian Alan M Hanlon Roger T Cronin Thomas W 2015 Visual phototransduction components in cephalopod chromatophores suggest dermal photoreception Journal of Experimental Biology 218 10 1596 1602 doi 10 1242 jeb 117945 ISSN 1477 9145 PMID 25994635 Ramirez M Desmond Oakley Todd H 2015 Eye independent light activated chromatophore expansion LACE and expression of phototransduction genes in the skin of Octopus bimaculoides Journal of Experimental Biology 218 10 1513 1520 doi 10 1242 jeb 110908 ISSN 1477 9145 PMC 4448664 PMID 25994633 Stubbs Alexander L Stubbs Christopher W 2016 Spectral discrimination in color blind animals via chromatic aberration and pupil shape Proceedings of the National Academy of Sciences 113 29 8206 8211 Bibcode 2016PNAS 113 8206S doi 10 1073 pnas 1524578113 ISSN 0027 8424 PMC 4961147 PMID 27382180 Hu Marian Y Yan Hong Young Chung Wen Sung Shiao Jen Chieh Hwang Pung Pung 2009 Acoustically evoked potentials in two cephalopods inferred using the auditory brainstem response ABR approach Comparative Biochemistry and Physiology Part A Molecular amp Integrative Physiology 153 3 278 283 doi 10 1016 j cbpa 2009 02 040 ISSN 1095 6433 PMID 19275944 Nesher Nir Levy Guy Grasso Frank W Hochner Binyamin 2014 Self Recognition Mechanism between Skin and Suckers Prevents Octopus Arms from Interfering with Each Other Current Biology 24 11 1271 1275 doi 10 1016 j cub 2014 04 024 ISSN 0960 9822 PMID 24835454 S2CID 16140159 Gutnick Tamar Byrne Ruth A Hochner Binyamin Kuba Michael 2011 Octopus vulgaris Uses Visual Information to Determine the Location of Its Arm Current Biology 21 6 460 462 doi 10 1016 j cub 2011 01 052 PMID 21396818 S2CID 10152089 Kennedy E B Lane Buresch Kendra C Boinapally Preethi Hanlon Roger T 2020 Octopus arms exhibit exceptional flexibility Scientific Reports 10 1 20872 doi 10 1038 s41598 020 77873 7 PMC 7704652 PMID 33257824 Mather Anderson amp Wood 2010 p 107 Derby C D 2014 Cephalopod Ink Production Chemistry Functions and Applications Marine Drugs 12 5 2700 2730 doi 10 3390 md12052700 PMC 4052311 PMID 24824020 a b Mather Anderson amp Wood 2010 p 147 Wells Martin J Wells J 1972 Optic glands and the state of the testis in Octopus Marine Behaviour and Physiology 1 1 4 71 83 doi 10 1080 10236247209386890 Young R E Vecchione M Mangold K M 1999 Cephalopoda Glossary Tree of Life web project a b Carefoot Thomas Octopuses and Relatives Reproduction A Snail s Odyssey Archived from the original on 22 April 2017 Retrieved 11 April 2017 a b c Giant Pacific Octopus Enteroctopus dofleini Care Manual PDF AZA Association of Zoos and Aquariums Aquatic Invertebrate Taxonomic Advisory Group in association with AZA Animal Welfare Committee 9 September 2014 Retrieved 31 May 2016 Scheel David Giant Octopus Fact Sheet Alaska Pacific University Archived from the original on 15 November 2012 Retrieved 9 April 2017 Forsythe J W Hanlon R T 1980 A closed marine culture system for rearing Octopus joubini and other large egged benthic octopods Laboratory Animals 14 2 137 142 doi 10 1258 002367780780942737 PMID 7431823 S2CID 19492476 Simon Matt 16 January 2015 Absurd Creature of the Week The Beautiful Octopus Whose Sex Is All About Dismemberment Wired Science Retrieved 20 May 2017 a b Hooper Rowan 21 December 2019 Octopuses were thought to be solitary until a social species turned up New Scientist Anderson Roland C Wood James B Byrne Ruth A 2002 Octopus Senescence The Beginning of the End Journal of Applied Animal Welfare Science 5 4 275 283 CiteSeerX 10 1 1 567 3108 doi 10 1207 S15327604JAWS0504 02 PMID 16221078 S2CID 28355735 Anderson Roland C Wood James B Byrne Ruth A 2002 Octopus Senescence The Beginning of the End Journal of Applied Animal Welfare Science 5 4 275 283 CiteSeerX 10 1 1 567 3108 doi 10 1207 S15327604JAWS0504 02 PMID 16221078 S2CID 28355735 Wodinsky Jerome 1977 Hormonal Inhibition of Feeding and Death in Octopus Control by Optic Gland Secretion Science 198 4320 948 951 Bibcode 1977Sci 198 948W doi 10 1126 science 198 4320 948 PMID 17787564 S2CID 22649186 Jamieson A J Vecchione M 2020 First in situ observation of Cephalopoda at hadal depths Octopoda Opisthoteuthidae Grimpoteuthis sp Marine Biology 167 82 doi 10 1007 s00227 020 03701 1 Norman Mark 16 January 2013 Ask an expert Are there any freshwater cephalopods ABC Science Retrieved 26 April 2017 Edmonds Patricia April 2016 What s Odd About That Octopus It s Mating Beak to Beak National Geographic Scheel D et al 2017 A second site occupied by Octopus tetricus at high densities with notes on their ecology and behavior Marine and Freshwater Behaviour and Physiology 50 4 285 291 doi 10 1080 10236244 2017 1369851 S2CID 89738642 Rodaniche Arcadio F 1991 Notes on the behavior of the Larger Pacific Striped Octopus an undescribed species of the genus Octopus Bulletin of Marine Science 49 667 Caldwell Roy L Ross Richard Rodaniche Arcadio Huffard Christine L 2015 Behavior and Body Patterns of the Larger Pacific Striped Octopus PLOS ONE 10 8 e0134152 Bibcode 2015PLoSO 1034152C doi 10 1371 journal pone 0134152 ISSN 1932 6203 PMC 4534201 PMID 26266543 Goldman Jason G 24 May 2012 How do octopuses navigate Scientific American 168 4 491 497 doi 10 1007 BF00199609 S2CID 41369931 Retrieved 8 June 2017 Courage 2013 pp 45 46 a b Carefoot Thomas Octopuses and Relatives Feeding diets and growth A Snail s Odyssey Archived from the original on 8 May 2017 Retrieved 13 April 2017 Sampaio Eduardo Seco Martim Costa Rosa Rui Gingins Simon 18 December 2020 Octopuses punch fishes during collaborative interspecific hunting events Ecology Ecological Society of America Wiley Publishing 102 3 e03266 doi 10 1002 ecy 3266 ISSN 0012 9658 PMID 33338268 a b Wassilieff Maggy O Shea Steve 2 March 2009 Octopus and squid Feeding and predation Te Ara the Encyclopedia of New Zealand a b Wells 1978 pp 74 75 Wodinsky Jerome 1969 Penetration of the Shell and Feeding on Gastropods by Octopus PDF American Zoologist 9 3 997 1010 doi 10 1093 icb 9 3 997 Carefoot Thomas Octopuses and Relatives Prey handling and drilling A Snail s Odyssey Archived from the original on 6 June 2017 Retrieved 21 April 2017 Johnsen S Balser E J Fisher E C Widder E A 1999 Bioluminescence in the deep sea cirrate octopod Stauroteuthis syrtensis Verrill Mollusca Cephalopoda PDF The Biological Bulletin 197 1 26 39 doi 10 2307 1542994 JSTOR 1542994 PMID 28296499 Archived from the original PDF on 5 March 2011 a b c Huffard Christine L 2006 Locomotion by Abdopus aculeatus Cephalopoda Octopodidae walking the line between primary and secondary defenses Journal of Experimental Biology 209 Pt 19 3697 3707 doi 10 1242 jeb 02435 PMID 16985187 Kassim I Phee L Ng W S Gong F Dario P Mosse C A 2006 Locomotion techniques for robotic colonoscopy IEEE Engineering in Medicine and Biology Magazine 25 3 40 56 doi 10 1109 MEMB 2006 1636351 PMID 16764431 S2CID 9124611 Huffard C L Boneka F Full R J 2005 Underwater Bipedal Locomotion by Octopuses in Disguise Science 307 5717 1927 doi 10 1126 science 1109616 PMID 15790846 S2CID 21030132 a b Wood J B Anderson R C 2004 Interspecific Evaluation of Octopus Escape Behavior PDF Journal of Applied Animal Welfare Science 7 2 95 106 CiteSeerX 10 1 1 552 5888 doi 10 1207 s15327604jaws0702 2 PMID 15234886 S2CID 16639444 Retrieved 11 September 2015 Mather Anderson amp Wood 2010 p 183 a b Finn J K Tregenza T Norman M D 2009 Defensive tool use in a coconut carrying octopus Current Biology 19 23 R1069 70 doi 10 1016 j cub 2009 10 052 PMID 20064403 S2CID 26835945 a b Stewart Doug 1997 Armed but not dangerous Is the octopus really the invertebrate intellect of the sea National Wildlife 35 2 Zarrella Ilaria Ponte Giovanna Baldascino Elena Fiorito Graziano 2015 Learning and memory in Octopus vulgaris a case of biological plasticity Current Opinion in Neurobiology 35 74 79 doi 10 1016 j conb 2015 06 012 ISSN 0959 4388 PMID 26186237 S2CID 31682363 Octopus intelligence Jar opening BBC News 25 February 2003 Retrieved 4 February 2014 Mather J A Anderson R C 1998 Wood J B ed What behavior can we expect of octopuses The Cephalopod Page Lee Henry 1875 V The octopus out of water Aquarium Notes The Octopus or the devil fish of fiction and of fact London Chapman and Hall pp 38 39 OCLC 1544491 Retrieved 11 September 2015 The marauding rascal had occasionally issued from the water in his tank and clambered up the rocks and over the wall into the next one there he had helped himself to a young lump fish and having devoured it returned demurely to his own quarters by the same route with well filled stomach and contented mind Ainge Roy Eleanor 14 April 2016 The great escape Inky the octopus legs it to freedom from aquarium The Guardian Australia Meyers Nadia Tales from the Cryptic The Common Atlantic Octopus Southeastern Regional Taxonomic Centre Retrieved 27 July 2006 a b c Mather Anderson amp Wood 2010 pp 90 97 Hanlon R T Messenger J B 2018 Cephalopod Behaviour 2nd ed Cambridge University Press pp 110 111 ISBN 978 0521723701 a b Carefoot Thomas Octopuses and Relatives Predators and Defenses A Snail s Odyssey Archived from the original on 21 April 2017 Retrieved 13 April 2017 Mathger L M Bell G R Kuzirian A M Allen J J Hanlon R T 2012 How does the blue ringed octopus Hapalochlaena lunulata flash its blue rings Journal of Experimental Biology 215 21 3752 3757 doi 10 1242 jeb 076869 PMID 23053367 Wigton Rachel Wood James B Grass octopus Octopus macropus Marine Invertebrates of Bermuda Bermuda Institute of Ocean Sciences Archived from the original on 19 January 2016 Retrieved 10 August 2018 Hanlon R T Messenger J B 1998 Cephalopod Behaviour 1st ed Cambridge University Press pp 80 81 111 ISBN 978 0 521 64583 6 Caldwell R L 2005 An Observation of Inking Behavior Protecting Adult Octopus bocki from Predation by Green Turtle Chelonia mydas Hatchlings PDF Pacific Science 59 1 69 72 doi 10 1353 psc 2005 0004 hdl 10125 24161 S2CID 54223984 Harmon Katherine 27 August 2013 Even Severed Octopus Arms Have Smart Moves Octopus Chronicles Scientific American Mather Anderson amp Wood 2010 p 85 Norman M D Finn J Tregenza T 2001 Dynamic mimicry in an Indo Malayan octopus PDF Proceedings of the Royal Society 268 1478 1755 8 doi 10 1098 rspb 2001 1708 PMC 1088805 PMID 11522192 Archived from the original PDF on 10 February 2012 Retrieved 1 October 2008 Norman M D 2005 The Mimic Octopus Thaumoctopus mimicus n gen et sp a new octopus from the tropical Indo West Pacific Cephalopoda Octopodidae Molluscan Research 25 2 57 70 Pascal Santiago Gestal Camino Estevez J Arias Christian Andres 1996 Parasites in commercially exploited cephalopods Mollusca Cephalopoda in Spain An updated perspective Aquaculture 142 1 2 1 10 doi 10 1016 0044 8486 96 01254 9 Furuya Hidetaka Tsuneki Kazuhiko 2003 Biology of Dicyemid Mesozoans Zoological Science 20 5 519 532 doi 10 2108 zsj 20 519 PMID 12777824 S2CID 29839345 Castellanos Martinez Sheila Gestal Camino 2013 Pathogens and immune response of cephalopods Journal of Experimental Marine Biology and Ecology 447 14 22 doi 10 1016 j jembe 2013 02 007 Farto R Armada S P Montes M Guisande J A Perez M J Nieto T P 2003 Vibrio lentus associated with diseased wild octopus Octopus vulgaris Journal of Invertebrate Pathology 83 2 149 156 doi 10 1016 S0022 2011 03 00067 3 PMID 12788284 Gofas S 2009 Octopoda WoRMS World Register of Marine Species Retrieved 5 May 2017 Mather Anderson amp Wood 2010 p 145 a b Sanchez Gustavo Setiamarga Davin H E Tuanapaya Surangkana Tongtherm Kittichai Winkelmann Inger E Schmidbaur Hannah Umino Tetsuya Albertin Caroline Allcock Louise Perales Raya Catalina Gleadall Ian Strugnell Jan M Simakov Oleg Nabhitabhata Jaruwat 2018 Genus level phylogeny of cephalopods using molecular markers current status and problematic areas PeerJ 6 e4331 doi 10 7717 peerj 4331 PMC 5813590 PMID 29456885 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 a b c Fuchs Dirk Iba Yasuhiro Heyng Alexander Iijima Masaya Klug Christian Larson Neal L Schweigert Gunter Brayard Arnaud 2019 The Muensterelloidea phylogeny and character evolution of Mesozoic stem octopods Papers in Palaeontology 6 1 31 92 doi 10 1002 spp2 1254 ISSN 2056 2802 S2CID 198256507 a b c Kroger Bjorn Vinther Jakob Fuchs Dirk 2011 Cephalopod origin and evolution A congruent picture emerging from fossils development and molecules BioEssays 33 8 602 613 doi 10 1002 bies 201100001 ISSN 0265 9247 PMID 21681989 S2CID 2767810 Fuchs Dirk Schweigert Gunter 2018 First Middle Late Jurassic gladius vestiges provide new evidence on the detailed origin of incirrate and cirrate octopuses Coleoidea PalZ 92 2 203 217 doi 10 1007 s12542 017 0399 8 ISSN 0031 0220 S2CID 135245479 A Broad Brush History of the Cephalopoda The Cephalopod Group Retrieved 27 March 2017 Young R E Vecchione M Mangold K M 1999 Cephalopoda Glossary Tree of Life web project Retrieved 30 May 2017 Seibel B Vampyroteuthis infernalis Deep sea Vampire squid The Cephalopod Page Retrieved 31 May 2017 Ibanez Christian M Fenwick Mark Ritchie Peter A Carrasco Sergio A Pardo Gandarillas M Cecilia 2020 Systematics and Phylogenetic Relationships of New Zealand Benthic Octopuses Cephalopoda Octopodoidea Frontiers in Marine Science 7 doi 10 3389 fmars 2020 00182 ISSN 2296 7745 Courage 2013 pp 46 49 Liscovitch Brauer N Alon S Porath H T Elstein B Unger R Ziv T Admon A Levanon E Y Rosenthal J J C Eisenberg E 2017 Trade off between transcriptome plasticity and genome evolution in cephalopods Cell 169 2 191 202 doi 10 1016 j cell 2017 03 025 PMC 5499236 PMID 28388405 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 Linnaeus Carl 1735 Systema Naturae Laurentius Salvius 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 Bastian Adolf 1881 Die heilige Sage der Polynesier Kosmogonie und Theogonie Oxford University Leipzig F A Brockhaus pp 107 108 Beckwith Martha Warren 1981 The Kumulipo A Hawaiian Creation Chant University of Hawaii Press pp 52 53 ISBN 978 0824807719 Srinivasan A 2017 The Sucker the Sucker Review PDF London Review of Books 39 17 23 25 Review The Toilers of the Sea by Victor Hugo amp Translated by James Hogarth Kirkus Reviews 2002 Retrieved 14 May 2021 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 Winkel Margarita Tinios Ellis Newland Amy Reigle 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 Paul Zachary 17 May 2017 Extraordinary Octopus Illustrations Pharyngula Retrieved 18 March 2017 Myers Paul Zachary 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 Ross Philip 18 February 2014 8 Foot Octopus Wrestles Diver Off California Coast Rare Encounter Caught on Camera International Business Times Fry B G Roelants K Norman J A 2009 Tentacles of Venom Toxic Protein Convergence in the Kingdom Animalia Journal of Molecular Evolution 68 4 311 321 Bibcode 2009JMolE 68 311F doi 10 1007 s00239 009 9223 8 ISSN 0022 2844 PMID 19294452 S2CID 13354905 Blue ringed Octopuses Hapalochlaena maculosa The MarineBio Conservation Society Archived from the original on 16 February 2017 Retrieved 12 April 2017 Caldwell Roy What makes blue rings so deadly Blue ringed octopus have tetrodotoxin The Cephalopod Page Retrieved 12 April 2017 Wells 1978 pp 68 a b Gillespie G E Parker G Morrison J 1998 A Review of Octopus Fisheries Biology and British Columbia Octopus Fisheries PDF Canadian Stock Assessment Secretariat Rocliffe S Harris A 2016 The status of octopus fisheries in the Western Indian Ocean Retrieved 18 June 2017 Giant Pacific octopus Monterey Bay Aquarium 2017 Archived from the original on 4 July 2018 Retrieved 1 August 2015 Eriksen L 10 November 2010 Live and let dine The Guardian Retrieved 15 April 2015 Killingsworth Silvia 3 October 2014 Why not eat octopus The New Yorker Retrieved 15 April 2016 Ferrier M 30 May 2010 Macho foodies in New York develop a taste for notoriety The Guardian Retrieved 15 April 2015 Wells Martin 1983 Cephalopods do it differently New Scientist Vol 100 no 1382 pp 333 334 ISSN 0262 4079 Sauer Warwick H H Gleadall Ian G et al 6 December 2019 World Octopus Fisheries Reviews in Fisheries Science amp Aquaculture Taylor amp Francis 29 3 279 429 doi 10 1080 23308249 2019 1680603 hdl 10261 227068 ISSN 2330 8249 S2CID 210266167 Aristotle c 350 BC Historia animalium IX 622a 2 10 Cited in Borrelli Luciana Gherardi Francesca Fiorito Graziano 2006 A catalogue of body patterning in Cephalopoda Firenze University Press ISBN 978 88 8453 377 7 Abstract Leroi Armand Marie 2014 The Lagoon How Aristotle Invented Science Bloomsbury pp 71 72 ISBN 978 1 4088 3622 4 The Cephalopoda University of California Museum of Paleontology Retrieved 27 March 2017 Mann T 2012 Spermatophores Development Structure Biochemical Attributes and Role in the Transfer of Spermatozoa Springer p 28 ISBN 978 3 642 82308 4 Laschi Cecilia Cianchetti Matteo Mazzolai Barbara Margheri Laura Follador Maurizio Dario Paolo 2012 Soft Robot Arm Inspired by the Octopus Advanced Robotics 26 7 709 727 doi 10 1163 156855312X626343 ISSN 0169 1864 S2CID 6104200 Godfrey Smith Peter 2018 Other Minds The Octopus the Sea and the Deep Origins of Consciousness William Collins pp 77 105 137 157 ISBN 978 0 00 822629 9 Baer Drake 20 December 2016 Octopuses Are the Closest We Will Come to Meeting an Intelligent Alien Science of Us Retrieved 26 April 2017 Brulliard Karin 13 April 2016 Octopus slips out of aquarium tank crawls across floor escapes down pipe to ocean The Washington Post Retrieved 20 February 2017 The Animals Scientific Procedures Act Amendment Order 1993 The National Archives Retrieved 18 February 2015 The Animals Scientific Procedures Act 1986 Amendment Regulations 2012 The National Archives Retrieved 18 February 2015 Directive 2010 63 EU of the European Parliament and of the Council Official Journal of the European Union Article 1 3 b see page 276 39 Retrieved 18 February 2015 PoseiDRONE The BioRobotics Institute Scuola Superiore Sant Anna Retrieved 14 May 2021 Laschi Cecilia 2015 Soft Robotics Research Challenges and Innovation Potential Through Showcases Soft Robotics 255 264 doi 10 1007 978 3 662 44506 8 21 ISBN 978 3 662 44505 1 Burgess Matt 27 March 2017 This robotic octopus tentacle isn t creepy at all Wired Bibliography Courage K H 2013 Octopus The Most Mysterious Creature in the Sea Penguin Group ISBN 978 0 698 13767 7 Mather J A Anderson R C Wood J B 2010 Octopus The Ocean s Intelligent Invertebrate Timber Press ISBN 978 1 60469 067 5 Wells M J 1978 Octopus Physiology and Behaviour of an Advanced Invertebrate Springer Science Business Media ISBN 978 94 017 2470 8 Further reading Studying the creativity and intelligence of the octopus CBS News 30 August 2020 Untangling the Mysteries of the Octopus Video 7 10 CBS News 12 January 2020 External links The Wikibook Dichotomous Key has a page on the topic of Octopoda Wikimedia Commons has media related to Octopoda Octopuses Overview at the Encyclopedia of Life Octopoda at the Tree of Life Web Project Retrieved from https en wikipedia org w index php title Octopus amp oldid 1127763972, wikipedia, wiki, book, books, library,

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