Question: What is the biggest species of squid?

Colossal squid





The colossal squid (Mesonychoteuthis hamiltoni, from Greek mesos (middle), onycho (claw, nail), and teuthis (squid)), sometimes called the Antarctic squid or giant cranch squid, is believed to be the largest squid species in terms of mass. It is the only known member of the genus Mesonychoteuthis. It is known from only a few specimens, and current estimates put its maximum size at 12–14m (39–46ft) long and weighing possibly up to 750 kilograms (1,650lb),[3][4] based on analysis of smaller and immature specimens, making it the largest-known invertebrate.
Morphology
Unlike the giant squid, whose arms and tentacles have only suckers lined with small teeth, the colossal squid's limbs are also equipped with sharp hooks: some swivelling, others three-pointed.[5] Its body is wider and stouter, and therefore heavier, than that of the giant squid. Colossal squid are believed to have longer mantles than the giant squid, but shorter tentacles.
The squid exhibits abyssal gigantism. The beak of M.hamiltoni is the largest known of any squid, and more robust than that of the giant squid. The colossal squid also has the largest eyes documented in the animal kingdom; a partly collapsed specimen measured 27cm (11in) in diameter, with a 9cm (3.5in) pupil.[6][7] The eye was estimated to be 30 to 40 centimetres (12 to 16in) when the squid was alive.
Distribution
The squid's known range extends thousands of kilometres north of 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.[8]
Ecology and life history
Little is known about the life of this creature, but it is believed to feed on prey such as chaetognatha, large fish such as the Patagonian toothfish, and smaller squid in the deep ocean using bioluminescence. A recent study by Remeslo, Yakushev and Laptikhovsky revealed that Antarctic toothfish make up a significant part of the colossal squid's diet; of the 8,000 toothfish brought aboard trawlers between 2011 and 2014, seventy-one showed clear signs of attack by colossal squid.[9] The colossal squid is thought to have a very slow metabolic rate, needing only around 30 grams (1.1oz) of prey daily for an adult with a mass of 500 kilograms (1,100lb).[10] Estimates of its energy requirements suggest it is a slow-moving ambush predator, using its large eyes primarily for prey-detection rather than engaging in active hunting.[10][11]
Based on capture depths of a few specimens, and beaks found in sperm whale stomachs, the adult colossal squid ranges at least to a depth of 2.2km (7,200ft), and juveniles can go as deep as 1km (3,300ft). 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 (an arm 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 have scars on their backs, believed to be caused by the hooks of colossal squid. Colossal squid are a major prey item for sperm whales in the Antarctic; 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.[12] Many other animals also feed on colossal squid, including beaked whales (such as the southern bottlenose whale), pilot whales, southern elephant seals, Patagonian toothfish, sleeper sharks (Somniosus antarcticus), and albatrosses (e.g., the wandering and sooty albatrosses).[8] However, beaks from mature adults have only been recovered from large predators (i.e. sperm whales and sleeper sharks), while the other predators only eat juveniles or young adults.[13]
History

The species was first discovered in the form of two tentacles found in the stomach of a sperm whale in 1925.[14] In 1981,  a Russian trawler in the Ross Sea, off the coast of Antarctica, caught a large squid with a total length of over 4m (13ft), which was later identified as an immature female of M. hamiltoni.[15] In 2003 a complete specimen of a subadult female was found near the surface with a total length of 6m (20ft) and a mantle length of 2.5m (8ft 2in).[16] This specimen shows that colossal squids may grow larger than 500kg (1,100lb), possibly up to 750kg (1,650lb).[3]
In 2005 a specimen was captured at a depth of 1,625m (5,331ft) 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 2.5m (8ft 2in), and the tentacles measured 2.3m (7ft 7in). The animal is thought to have weighed between 150 and 200kg (330 and 440lb).[17]
The largest recorded specimen was captured in 2007 by a New Zealand fishing boat off Antarctica. It was initially estimated to measure 4.5m (15ft) in length and weigh 450kg (990lb). The squid was taken back to New Zealand for scientific study.[18] A study on the specimen later showed its actual weight was 495kg (1,091lb), but it only measured 4.2m (14ft) in total length as a result of the tentacles' shrinking post mortem.[19]
Largest known specimen


On February 22, 2007, authorities in New Zealand announced the largest known colossal squid had been captured. The specimen weighed 495 kilograms (1,091lb) and was initially estimated to measure 4.5 metres (15ft) in total length.[20] 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, haul it aboard, and freeze it. The specimen eclipsed the previous largest find in 2003 by about 195 kilograms (430lb),[21][22] although it is still considerably smaller than some estimates for this species 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.[23][24] Media reports suggested scientists at the museum were considering using a giant microwave to defrost the squid because thawing it at room temperature would take several days and it would likely begin to decompose on the outside while the core remained frozen.[23] However, they later opted for the more conventional approach of thawing the specimen in a bath of salt water.[25][26] After thawing, the squid measured only 4.2 metres (14ft) in total length, with the tentacles having shrunk significantly.[19] Although initially thought to be a male, closer inspection of the specimen showed it to be a female.[7]
Defrosting and dissection, April–May 2008
Thawing and dissection of the specimen took place at the Museum of New Zealand Te Papa Tongarewa[25] under the direction of senior biologist Chris Paulin, with technician Mark Fenwick, Dutch marine biologist and toxicologist Olaf Blaauw, AUT biologist Steve O'Shea, 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,[27][28] suggesting other colossal squid are much larger than this one.[27][28]
The eye is 27cm (11in) wide, with a lens 12cm (4.7in) across. This is the largest eye of any known animal.[6] These measurements are of the partly collapsed specimen; alive, the eye was probably 30[7] to 40cm (12 to 16 in) across.[29]
Inspection of the specimen with an endoscope revealed ovaries containing thousands of eggs.[7]
Exhibition

The Museum of New Zealand Te Papa Tongarewa began displaying this specimen in an exhibition that opened on December 13, 2008; however the exhibition was closed in 2018 and slated to return in 2019.[30]
Second specimen
In August 2014, Te Papa received a second colossal squid, captured in early 2014.[31] The specimen was also female, was 3.5 metres (11ft) long and weighed approximately 350kg (770lb).[32]
See also
Gigantic octopus
Kraken


Further reading

(in Russian) 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]