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The 'Colossal Squid' (''Mesonychoteuthis hamiltoni''), sometimes called the 'Antarctic' or 'Giant Cranch Squid', is believed to be the largest squid species. It is the only 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.

Contents

Anatomy and morphology

Distribution

Ecology and life history

Timeline

Largest known specimen

References

External links

Anatomy and morphology

Unlike the giant squid, whose tentacles are equipped with suckers lined with small teeth, the suckers at the tips of the Colossal Squid's tentacles have sharp swiveling hooks. 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 beak of ''Mesonychoteuthis hamiltoni'' is the largest known of any squid, exceeding that of ''Architeuthis'' in size and robustness. The Colossal Squid is also believed to have the largest eyes in the animal kingdom (even larger than those of giant squid).

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. A mature female is generally much larger than a mature male, as in many invertebrate species. (See Sexual dimorphism.)
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.^[1] 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.^[2]

Timeline

Main articles: List of Colossal Squid specimens and sightings



★ 1925 – Species was first discovered in the form of two tentacles found in the stomach of a sperm whale.

★ 1981 – A Russian trawler in the Ross Sea, off the coast of Antarctica, caught a large squid (see image at beginning of article) with a total length of 4 metres (13 feet), which was later identified as an immature female of ''Mesonychoteuthis hamiltoni''.

★ 2003 – A complete specimen of a subadult female (photo at right) was found near the surface with a total length of 6 metres (20 feet) and a mantle length of 2.5 metres (8 feet).

★ 2005 – A specimen was captured at a depth of 1625 metres 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 centimetres. The animal is thought to have weighed between 150 and 200 kilograms.^[3]

★ 2007 – The largest ever specimen, measuring 10 m (33 feet) in length, was captured by a New Zealand fishing boat off Antarctica. It was initially estimated to weigh 450 kilograms (992 pounds). The squid was taken back to New Zealand for scientific study.^[4] A study on the specimen later showed that its actual weight was 495 kg (1,091 pounds). Scientists at New Zealand's national museum, Te Papa Tongarewa, are considering using a giant microwave oven to defrost the animal."Colossal squid may be headed for the oven in New Zealand", Associated Press (''International Herald Tribune''), March 22, 2007.

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 measured 10 metres (33 feet) in length and weighed 495 kilograms (1,091 lb). 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. The specimen eclipsed the previous largest find in 2003 by about 195 kilograms (430 lb).^[5][6] The 10 metre squid is still considerably shorter than some estimates have predicted. Although initially thought to be a male, as of 15 March 2007 the gender is not known. Due to its size, it is thought more likely to be a female.Kim Griggs, "Colossal squid's headache for science", BBC News, March 15, 2007. The specimen was frozen in a cubic metre of water and transported to Te Papa Tongarewa, New Zealand's national museum.

References

1. 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.

2. Cherel, Y. & G. Duhamel 2004. ''Deep-Sea Res I'' '51': 17-31.
3. "Very Rare Giant Squid Caught Alive" ''South Georgia Newsletter''
4. "NZ fishermen pull monster squid from Antarctic deep", BBC
5. "NZ's colossal squid to be microwaved" ''The New Zealand Herald''
6. New giant squid predator found

External links

★ Tree of Life web project: ''Mesonychoteuthis hamiltoni''

★ TONMO.com: Giant Squid and Colossal Squid Fact Sheet

★ ''New Zealand Herald'': Fishermen haul in world's biggest squid

★ ''National Geographic News'': Colossal Squid Caught off Antarctica

★ ''USA Today'': Colossal Squid Caught in Antarctic Waters

★ BBC: Super squid surfaces in Antarctic

★ MarineBio: ''Mesonychoteuthis hamiltoni''