Colossal Squid

This specimen, an immature female, was caught at 760 m (2500 feet) in the Antarctic off Dronning Maud Land by the Soviet trawler Eureka (Эврика) in 1981. Photograph by Alexander Remeslo.^[1]

Scientific classification

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Teuthida
Family:	Cranchiidae
Subfamily:	Taoniinae
Genus:	Mesonychoteuthis Robson, 1925
Species:	M. hamiltoni

Binomial name

Mesonychoteuthis hamiltoni
Robson, 1925

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.

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.^[2] 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.^[3]

Timeline

Main article: List of Colossal Squid specimens and sightings

Complete specimen caught in 2003.

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.^[4]
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.^[5] 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.^[6]

Largest known specimen

See also: Cephalopod size

The specimen caught in early 2007 is the largest cephalopod ever recorded.

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).^[7]^[8] 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.^[9] The specimen was frozen in a cubic metre of water and transported to Te Papa Tongarewa, New Zealand's national museum.^[6]^[9]

References

^ Ellis, R. 1998. The Search for the Giant Squid. New York: The Lyon's Press, p. 147.
^ 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.
^ Cherel, Y. & G. Duhamel 2004. Antarctic jaws: cephalopod prey of sharks in Kerguelen waters.PDF (531 KiB) Deep-Sea Res I 51: 17-31.
^ "Very Rare Giant Squid Caught Alive" South Georgia Newsletter
^ "NZ fishermen pull monster squid from Antarctic deep", BBC
^ ^a ^b "Colossal squid may be headed for the oven in New Zealand", Associated Press (International Herald Tribune), March 22, 2007.
^ "NZ's colossal squid to be microwaved" The New Zealand Herald
^ New giant squid predator found. Retrieved on February 14, 2007.
^ ^a ^b Kim Griggs, "Colossal squid's headache for science", BBC News, March 15, 2007.

External links

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