Spirula spirula is a species of deep-water squid-like cephalopodmollusk. It is the only extant member of the genusSpirula, the familySpirulidae, and the orderSpirulida. Because of the shape of its internal shell, it is commonly known as the ram's horn squid[3] or the little post horn squid. Because the live animal has a light-emitting organ, it is also sometimes known as the tail-light squid.
Live specimens of this cephalopod are very rarely seen because it is a deep-ocean dweller. The small internal shell of the species is, however, quite a familiar object to many beachcombers. The shell of Spirula is extremely light in weight, very buoyant, and surprisingly durable; it very commonly floats ashore onto tropical beaches (and sometimes even temperate beaches) all over the world. This seashell is known to shell collectors as the ram's horn shell or simply as Spirula.
S. spirula has a squid-like body between 35 mm and 45 mm long. It is a decapod, with eight arms and two longer tentacles, all with suckers. The arms and tentacles can all be withdrawn completely into the mantle.
The species lacks a radula[4]: 110 [5]: 26 (or, at most, has a vestigial radula).[6]
Female with dissected mantle cavity
Immature specimens at various stages of development
Immature specimen
Shell
The most distinctive feature of this species is its buoyancy organ, an internal, chambered, endogastrically coiled shell in the shape of an open planispiral (a flat spiral wherein the coils do not touch each other), and consisting of two prismatic layers. The shell functions to osmotically control buoyancy.[6] Another trait is that it is mineralized, a feature only seen in cuttlefish and the nautilus amongst extant species.[7]
The siphuncle is marginal, on the inner surface of the spiral.[8]
Illustration showing the position of the shell inside the mantle
End of mantle showing the photophore
Behaviour
Dated illustration of a live animal, but shown upside down; the photophore on a live animal points downward.[9]
S. spirula is capable of emitting a green light from a photophore located at the tip of its mantle, between the ear-shaped fins.[6] Evidently this seems as a counter-illumination strategy, as in situ observations have captured footage of animals in a vertical stance, with photophore pointing downward and head up.[9]
Habitat and distribution
Oral view of the left tentacular club
By day, Spirula lives in the deep oceans, reaching depths of 1,000 m. At night, it rises to 100–300 m.[10] Its preferred temperature is around 10 °C, and it tends to live around oceanic islands, near the continental shelf.[6]
Most sources cite this species as tropical and they are observed to be plentiful in the subtropical seas around the Canary Islands. Shells are regularly found along the western coasts of South Africa. In 2022, records of the species have also been confirmed in the Arabian Sea.[11] However, significant quantities of shells from dead spirula are washed ashore even in temperate regions, such as coasts of New Zealand. Because of the great buoyancy of the shells, these may possibly have been carried long distances by ocean currents.
Much of the organism's life history has not been observed; for instance, they are thought to spawn in winter in deeper water, yet no spawnlings have been directly seen. They must occasionally venture into the upper 10 m of the sea, for they are sometimes found in albatross guts.[12]
Spirula is likely the closest living relative of the extinct belemnites and aulacocerids. These three groups as a unit are closely related to the cuttlefish, as well as to the true squids.
^Hayward, B.W. (1977). "Spirula (Sepioidea: Cephalopoda) from the Lower Miocene of Kaipara Harbour, New Zealand (note)" (PDF). New Zealand Journal of Geology and Geophysics. 19: 145–147. doi:10.1080/00288306.1976.10423557.
^Barratt, I. & Allcock, L. (2012). Spirula spirula. The IUCN Red List of Threatened Species. Version 2014.2.
^Norman, M. 2000. Cephalopods: A World Guide. Hackenheim, ConchBooks.
^ Nixon, M. (1985), "The buccal mass of fossil and recent Cephalopoda", in Wilbur, Karl M. (ed.), The Mollusca, New York: Academic Press, ISBN0-12-728702-7
^ Landman, Neil H.; Tanabe, Kazushige; Davis, Richard Arnold (1996). Ammonoid Paleobiology. ISBN978-0-306-45222-2.
^ abcd Warnke, K.; Keupp, H. (2005). "Spirula – a window to the embryonic development of ammonoids? Morphological and molecular indications for a palaeontological hypothesis" (PDF). Facies. 51 (1–4): 60. doi:10.1007/s10347-005-0054-9. S2CID 85026080.
^ Lemanis, R.; Korn, D.; Zachow, S; Rybacki, E.; Hoffmann, R. (2016). "The evolution and development of cephalopod chambers and their shape". PLOS ONE. 11 (3): e0151404. Bibcode:2016PLoSO..1151404L. doi:10.1371/journal.pone.0151404. PMC4786199. PMID 26963712.
^ abc Lindsay, Dhugal; Hunt, James; McNeil, Mardi; Beaman, Robin; Vecchione, Michael (27 November 2020). "The first in situ observation of the Ram's Horn squid Spirula spirula turns "common knowledge" upside down". Diversity. 12 (449): 449. doi:10.3390/d12120449.
^ Clarke, M.R. (2009). "Cephalopoda collected on the SOND Cruise". Journal of the Marine Biological Association of the United Kingdom. 49 (4): 961–976. doi:10.1017/S0025315400038042. S2CID 86329056.
^Sajikumar, K.K; Rajeeshkumar, M.P; Vellathi, Venkatesan (June 2022). "Rediscovery of Ram's horn squid, Spirula spirula (Cephalopoda: Spirulidae), from the Arabian Sea".
^ Price, G.D.; Twitchett, R.J.; Smale, C.; Marks, V. (2009). "Isotopic analysis of the life history of the enigmatic squid Spirula spirula, with implications for studies of fossil Cephalopods". PALAIOS. 24 (5): 273–279. Bibcode:2009Palai..24..273P. doi:10.2110/palo.2008.p08-067r. S2CID 131523262.
^ Fox, Alex (3 November 2020). "See strange squid filmed in the wild for the first time". Smithsonian Magazine. Retrieved 2021-04-25.
External links
"Spirula Spirula". Tree of Life web project.
. TONMO.com. Archived from the original on 2006-03-16 – via Internet Archive (archive.org).
May 11, 2023
spirula, spirula, species, deep, water, squid, like, cephalopod, mollusk, only, extant, member, genus, family, spirulidae, order, spirulida, because, shape, internal, shell, commonly, known, horn, squid, little, post, horn, squid, because, live, animal, light,. Spirula spirula is a species of deep water squid like cephalopod mollusk It is the only extant member of the genus Spirula the family Spirulidae and the order Spirulida Because of the shape of its internal shell it is commonly known as the ram s horn squid 3 or the little post horn squid Because the live animal has a light emitting organ it is also sometimes known as the tail light squid SpirulaTemporal range Miocene Recent 1 PreꞒ Ꞓ O S D C P T J K Pg NDorsal view of femaleVentral view of female chromatophores of mantle missing Conservation statusLeast Concern IUCN 3 1 2 Scientific classificationKingdom AnimaliaPhylum MolluscaClass CephalopodaOrder SpirulidaFamily SpirulidaeOwen 1836Genus SpirulaLamarck 1799Species S spirulaBinomial nameSpirula spirula Linnaeus 1758 SynonymsNautilus spirula Linnaeus 1758Live specimens of this cephalopod are very rarely seen because it is a deep ocean dweller The small internal shell of the species is however quite a familiar object to many beachcombers The shell of Spirula is extremely light in weight very buoyant and surprisingly durable it very commonly floats ashore onto tropical beaches and sometimes even temperate beaches all over the world This seashell is known to shell collectors as the ram s horn shell or simply as Spirula Side view of a Spirula shell Ventral view the siphuncle and the last septum of the phragmocone are visible Contents 1 Description 1 1 Shell 2 Behaviour 3 Habitat and distribution 4 Evolutionary relationships 5 See also 6 References 7 External linksDescription EditS spirula has a squid like body between 35 mm and 45 mm long It is a decapod with eight arms and two longer tentacles all with suckers The arms and tentacles can all be withdrawn completely into the mantle The species lacks a radula 4 110 5 26 or at most has a vestigial radula 6 Female with dissected mantle cavity Immature specimens at various stages of development Immature specimen Shell Edit The most distinctive feature of this species is its buoyancy organ an internal chambered endogastrically coiled shell in the shape of an open planispiral a flat spiral wherein the coils do not touch each other and consisting of two prismatic layers The shell functions to osmotically control buoyancy 6 Another trait is that it is mineralized a feature only seen in cuttlefish and the nautilus amongst extant species 7 The siphuncle is marginal on the inner surface of the spiral 8 Illustration showing the position of the shell inside the mantle End of mantle showing the photophoreBehaviour Edit Dated illustration of a live animal but shown upside down the photophore on a live animal points downward 9 S spirula is capable of emitting a green light from a photophore located at the tip of its mantle between the ear shaped fins 6 Evidently this seems as a counter illumination strategy as in situ observations have captured footage of animals in a vertical stance with photophore pointing downward and head up 9 Habitat and distribution Edit Oral view of the left tentacular club By day Spirula lives in the deep oceans reaching depths of 1 000 m At night it rises to 100 300 m 10 Its preferred temperature is around 10 C and it tends to live around oceanic islands near the continental shelf 6 Most sources cite this species as tropical and they are observed to be plentiful in the subtropical seas around the Canary Islands Shells are regularly found along the western coasts of South Africa In 2022 records of the species have also been confirmed in the Arabian Sea 11 However significant quantities of shells from dead spirula are washed ashore even in temperate regions such as coasts of New Zealand Because of the great buoyancy of the shells these may possibly have been carried long distances by ocean currents Much of the organism s life history has not been observed for instance they are thought to spawn in winter in deeper water yet no spawnlings have been directly seen They must occasionally venture into the upper 10 m of the sea for they are sometimes found in albatross guts 12 The species was observed for the first time in its natural habitat in 2020 when an ROV of the Schmidt Ocean Institute recorded it in the depths near the northern Great Barrier Reef 9 13 Evolutionary relationships EditThe order Spirulida also contains two extinct suborders Groenlandibelina including extinct families Groenlandibelidae and Adygeyidae and Belopterina including extinct families Belemnoseidae and Belopteridae Spirula is likely the closest living relative of the extinct belemnites and aulacocerids These three groups as a unit are closely related to the cuttlefish as well as to the true squids See also EditJellyellaReferences Edit Hayward B W 1977 Spirula Sepioidea Cephalopoda from the Lower Miocene of Kaipara Harbour New Zealand note PDF New Zealand Journal of Geology and Geophysics 19 145 147 doi 10 1080 00288306 1976 10423557 Barratt I amp Allcock L 2012 Spirula spirula The IUCN Red List of Threatened Species Version 2014 2 Norman M 2000 Cephalopods A World Guide Hackenheim ConchBooks Nixon M 1985 The buccal mass of fossil and recent Cephalopoda in Wilbur Karl M ed The Mollusca New York Academic Press ISBN 0 12 728702 7 Landman Neil H Tanabe Kazushige Davis Richard Arnold 1996 Ammonoid Paleobiology ISBN 978 0 306 45222 2 a b c d Warnke K Keupp H 2005 Spirula a window to the embryonic development of ammonoids Morphological and molecular indications for a palaeontological hypothesis PDF Facies 51 1 4 60 doi 10 1007 s10347 005 0054 9 S2CID 85026080 Lemanis R Korn D Zachow S Rybacki E Hoffmann R 2016 The evolution and development of cephalopod chambers and their shape PLOS ONE 11 3 e0151404 Bibcode 2016PLoSO 1151404L doi 10 1371 journal pone 0151404 PMC 4786199 PMID 26963712 Spirula spirula Tree of Life tolweb org a b c Lindsay Dhugal Hunt James McNeil Mardi Beaman Robin Vecchione Michael 27 November 2020 The first in situ observation of the Ram s Horn squid Spirula spirula turns common knowledge upside down Diversity 12 449 449 doi 10 3390 d12120449 Clarke M R 2009 Cephalopoda collected on the SOND Cruise Journal of the Marine Biological Association of the United Kingdom 49 4 961 976 doi 10 1017 S0025315400038042 S2CID 86329056 Sajikumar K K Rajeeshkumar M P Vellathi Venkatesan June 2022 Rediscovery of Ram s horn squid Spirula spirula Cephalopoda Spirulidae from the Arabian Sea Price G D Twitchett R J Smale C Marks V 2009 Isotopic analysis of the life history of the enigmatic squid Spirula spirula with implications for studies of fossil Cephalopods PALAIOS 24 5 273 279 Bibcode 2009Palai 24 273P doi 10 2110 palo 2008 p08 067r S2CID 131523262 Fox Alex 3 November 2020 See strange squid filmed in the wild for the first time Smithsonian Magazine Retrieved 2021 04 25 External links Edit Spirula Spirula Tree of Life web project Spirulidae forum TONMO com Archived from the original on 2006 03 16 via Internet Archive archive org Retrieved from https en wikipedia org w index php title Spirula amp oldid 1141600704, wikipedia, wiki, book, books, library,
