Colossal Squid

Taxobox
name = Colossal Squid

---

image_caption =A drawing of a Colossal Squid.
regnum = Animalia
phylum = Mollusca
classis = Cephalopoda
ordo = Teuthida
familia = Cranchiidae
subfamilia = Taoniinae
genus = "Mesonychoteuthis"
genus_authority = Robson, 1925
species = "M. hamiltoni"
binomial = "Mesonychoteuthis hamiltoni"
binomial_authority = Robson, 1925

The Colossal Squid ("Mesonychoteuthis hamiltoni", from Greek "mesos" (middle), "onychos" (claw), and "teuthis" (squid)), sometimes called the Antarctic or Giant Cranch Squid, is believed to be the largest squid species. It is the only known member of the genus "Mesonychoteuthis". Though it is known from only a few specimens, current estimates put its maximum size at 12–14 metres (39–46 feet) long, based on analysis of smaller and immature specimens, making it the largest known invertebrate.

Anatomy and morphology

Unlike the giant squid, whose arm and tentacles only have suckers lined with small teeth, the Colossal Squid's arms and tentacles are also equipped with sharp hooks: some swiveling, others three-pointed. [http://blog.tepapa.govt.nz/2008/04/30/hooks-and-suckers/ Te Papa: Hooks and Suckers] ] Its body is wider and stouter, and therefore heavier, than that of the giant squid. Colossal Squids are believed to have a longer mantle than giant squids, although their tentacles are shorter.

The squid exhibits deep-sea gigantism. The beak of "Mesonychoteuthis hamiltoni" is the largest known of any squid, exceeding that of "Architeuthis" (giant squid) in size and robustness. The Colossal Squid has also the largest eyes documented in the animal kingdom.

Distribution

The squid's known range extends thousands of miles northward from Antarctica to southern South America, southern South Africa, and the southern tip of New Zealand, making it primarily an inhabitant of the entire circumantarctic Southern Ocean.

Ecology and life history

While little is known about the life of this creature, it is believed to hunt prey such as chaetognatha, large fish like the Patagonian toothfish and other squid in the deep ocean using bioluminescence. Based on capture depths of a few specimens, as well as beaks found in sperm whale stomachs, the adult squid ranges at least to a depth of 2200 metres, while juveniles can go as deep as 1000 metres. It is believed to be sexually dimorphic, with mature females generally being much larger than mature males, as is common in many species of invertebrates.

The squid's method of reproduction has not been observed, although some data on their reproduction can be inferred from anatomy. Since males lack an organ called a hectocotylus (a tentacle used in other cephalopods to transfer a spermatophore to the female), they probably use a penis instead, which would be used to directly implant sperm into females.

Many sperm whales carry scars on their backs believed to be caused by the hooks of Colossal Squid. Colossal Squid are a major prey item for Antarctic sperm whales feeding in the Southern Ocean; 14% of the squid beaks found in the stomachs of these sperm whales are those of the Colossal Squid, which indicates that Colossal Squid make up 77% of the biomass consumed by these whales. [Clarke, M.R. (1980). "Cephalopoda in the diet of sperm whales of the southern hemisphere and their bearing on sperm whale biology". "Discovery Reports" 37: 1-324.] Many other animals also feed on this squid, including the beaked whales (such as the bottlenose whales), pilot whale, southern elephant seal, Patagonian toothfish, Pacific sleeper shark, and albatross (e.g., the Wandering and Sooty albatrosses). However, beaks from mature adults have only been recovered from those animals large enough to take such prey (i.e., the sperm whale and Pacific sleeper shark), while the remaining predators are limited to eating juveniles or young adults. [Cherel, Y. & G. Duhamel 2004. PDFlink| [http://www.cephbase.utmb.edu/refdb/pdf/8114.pdf Antarctic jaws: cephalopod prey of sharks in Kerguelen waters.] |531 KiB "Deep-Sea Res I" 51: 17-31.]

Timeline

*1925 – Species was first discovered in the form of two tentacles found in the stomach of a sperm whale. [Robson, G.C. 1925. On "Mesonychoteuthis", a new genus of oegopsid, Cephalopoda. "Annals and Magazine of Natural History", Series 9, 16: 272–277.]
*1981 – A Russian trawler in the Ross Sea, off the coast of Antarctica, caught a large squid with a total length of 4 metres (13 ft), which was later identified as an immature female of "Mesonychoteuthis hamiltoni". [Ellis, R. 1998. "The Search for the Giant Squid". The Lyons Press.]
*2003 – A complete specimen of a subadult female (photo at right) was found near the surface with a total length of 6 m (20 ft) and a mantle length of 2.5 m (8 ft). [Kim Griggs [http://news.bbc.co.uk/1/hi/sci/tech/2910849.stm "Super squid surfaces in Antarctic"] . BBC News, April 2, 2003.]
*2005 – A specimen was captured at a depth of 1625 m while taking a toothfish from a longline off South Georgia Island. Although the mantle was not brought aboard, the mantle length was estimated at over 2.5 m, and the tentacles measured 230 cm. The animal is thought to have weighed between 150 and 200 kg. [ [http://www.sgisland.org/pages/main/news23.htm "Very Rare Giant Squid Caught Alive" "South Georgia Newsletter"] ]
*2007 – The largest recorded specimen was captured by a New Zealand fishing boat off Antarctica. It was initially estimated to measure 10 m (33 ft) in length and weigh 450 kg (992 lb). The squid was taken back to New Zealand for scientific study. [ [http://news.bbc.co.uk/1/hi/world/asia-pacific/6385071.stm "NZ fishermen pull monster squid from Antarctic deep"] , BBC] A study on the specimen later showed that its actual weight was 495 kg (1,091 lb), but that it only measured 4.2 m (14 ft) in total length as a result of the tentacles shrinking "post mortem".Atkinson, K. 2008. [http://www.nzherald.co.nz/category/story.cfm?c_id=82&objectid=10507295 Size matters on 'squid row' (+photos, video)] . "The New Zealand Herald", May 1, 2008.]

Largest known specimen

On February 22, 2007, it was announced by authorities in New Zealand that the largest known Colossal Squid had been captured. The specimen weighed 495 kg (1,091 lb) and was initially estimated to measure 10 m (33 ft) in total length. Fishermen on the vessel "San Aspiring", owned by the Sanford seafood company, caught the animal in the freezing Antarctic waters of the Ross Sea. It was brought to the surface as it fed on an Antarctic toothfish that had been caught off a long line. It would not let go of its prey and could not be removed from the line by the fishermen, so they decided to catch it instead. They managed to envelop it in a net, hauled it aboard and froze it. The specimen eclipsed the previous largest find in 2003 by about 195 kilograms (430 lb), [ [http://www.nzherald.co.nz/section/1/story.cfm?c_id=1&objectid=10430435 "NZ's colossal squid to be microwaved" "The New Zealand Herald"] ] [cite web | title=New giant squid predator found | url=http://news.bbc.co.uk/2/hi/science/nature/3370019.stm | accessmonthday=14 February | accessyear=2007 ] although it is still considerably smaller than some estimates have predicted. The specimen was frozen in a cubic metre of water and transported to the Museum of New Zealand Te Papa Tongarewa, New Zealand's national museum. [http://www.iht.com/articles/ap/2007/03/22/asia/AS-ODD-New-Zealand-Colossal-Squid.php "Colossal squid may be headed for the oven in New Zealand"] , Associated Press ("International Herald Tribune"), March 22 2007.] Kim Griggs, [http://news.bbc.co.uk/1/hi/world/asia-pacific/6453997.stm "Colossal squid's headache for science"] , BBC News, March 15 2007.] Scientists at the museum were considering using a giant microwave to defrost the squid because defrosting the squid at room temperatures would take days and it would be likely for the outside to rot while the core remains frozen. [ [http://www.livescience.com/animals/070322_ap_squid_thaw.html Record Giant Squid Put on Ice] ] However, they later opted for the more conventional approach of thawing the specimen in a bath of salt water. [http://www.tepapa.govt.nz/TePapa/English/CollectionsAndResearch/CollectionAreas/NaturalEnvironment/Molluscs/ColossalSquid/TePapaColossalSquid.htm Te Papa's Specimen: The Thawing and Examination] ] [Richard Black [http://news.bbc.co.uk/1/hi/sci/tech/7367774.stm "Colossal squid out of the freezer"] . BBC News, April 26, 2008.] After thawing, the squid measured only 4.2 m (14 ft) in total length, with the tentacles having shrunk significantly. Although initially thought to be a male, dissection of the specimen showed it to be a female.Richard Black [http://news.bbc.co.uk/1/hi/sci/tech/7374297.stm "Colossal squid's big eye revealed"] . BBC News, April 30, 2008.]

Defrosting and dissection, April-May 2008

Thawing and dissection of the specimen took place at the Museum of New Zealand Te Papa Tongarewa under the direction of technician Mark Fenwick, Dutch marine biologist and toxicologist Olaf Blaauw, AUT biologist Dr Steve O'Shea, Dr Tsunemi Kubodera, and AUT biologist Kat Bolstad.

Parts of the specimen have been examined:
*The beak is considerably smaller than some found in the stomachs of sperm whales, [http://www.radionz.co.nz/news/latest/200804301626/21bc986a Thawing colossal squid continues to reveal information] "Radio New Zealand".] [http://www.thestar.co.za/index.php?fArticleId=4379450 Massive squid may be just a babe] "The Star", South Africa.] suggesting there are Colossal Squid much larger than this one.
*The eye is 27 cm (10.63 in) wide, with a lens 12 cm across. This is the largest eye of any known animal. [http://www.radionz.co.nz/news/latest/200804302138/12bd3892 Scientists focus on colossal squid's eyes] "Radio New Zealand".] These measurements are of the partly collapsed specimen: when living the eye was probably 30 to 40 cm (12 to 16 in) across. [ [http://afp.google.com/article/ALeqM5ipR6P2N6xG6MDAYbpLi1FJ7aOVKA World's biggest squid reveals 'beach ball' eyes] "AFP", via Google.]
*Dissection of the specimen revealed ovaries containing thousands of eggs.

Exhibition

The Museum of New Zealand Te Papa Tongarewa will be displaying this specimen in an exhibition due to open on Saturday 13 December 2008. [ [http://blog.tepapa.govt.nz/2008/09/05/squid-countdown/ Te Papa's Blog entry. 5 September 2008] ]

References

Further reading

*ru icon Klumov, S.K. & V.L. Yukhov 1975. "Mesonychoteuthis hamiltoni" Robson, 1925 (Cephalopoda, Oegopsida). "Antarktika Doklady Komission" 14: 159–189. [English translation: TT 81-59176, Al Ahram Center for Scientific Translations]
*McSweeny, E.S. 1970. Description of the juvenile form of the Antarctic squid "Mesonychoteuthis hamiltoni" Robson. "Malacologia" 10: 323–332.
*Rodhouse, P.G. & M.R. Clarke 1985. Growth and distribution of young "Mesonychoteuthis hamiltoni" Robson (Mollusca: Cephalopoda): an Antarctic squid. "Vie Milieu" 35(3–4): 223–230.

External links

* [http://tolweb.org/tree?group=Mesonychoteuthis&contgroup=Cranchiidae Tree of Life web project: "Mesonychoteuthis hamiltoni"]
* [http://www.tepapa.govt.nz/TePapa/English/CollectionsAndResearch/CollectionAreas/NaturalEnvironment/Molluscs/ColossalSquid/ Museum of New Zealand Te Papa Tongarewa (Te Papa) Colossal Squid Specimen Information]
* [http://www.tonmo.com/science/public/giantsquidfacts.php TONMO.com: Giant Squid and Colossal Squid Fact Sheet]
* [http://www.nzherald.co.nz/section/1/story.cfm?c_id=1&objectid=10425355 "New Zealand Herald": Fishermen haul in world's biggest squid]
* [http://news.nationalgeographic.com/news/2007/02/070222-squid-pictures.html?source=G1902&kwid=ContentNetwork|787369405 "National Geographic News": Colossal Squid Caught off Antarctica]
* [http://news.nationalgeographic.com/news/2008/04/photogalleries/colossalsquid-pictures/ "National Geographic News": Colossal Squid Revealed in First In-Depth Look]
* [http://www.usatoday.com/news/science/2003-04-03-squid_x.htm "USA Today": Colossal Squid Caught in Antarctic Waters]
* [http://news.bbc.co.uk/1/hi/sci/tech/2910849.stm BBC: Super squid surfaces in Antarctic]
* [http://marinebio.org/species.asp?id=247 MarineBio: "Mesonychoteuthis hamiltoni"]