Colossal squid

Colossal squid
Size compared to an average human
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Teuthida
Suborder: Oegopsina
Family: Cranchiidae
Subfamily: Taoniinae
Genus: Mesonychoteuthis
Robson, 1925
Species: M. hamiltoni
Binomial name
Mesonychoteuthis hamiltoni
Robson, 1925
Global range of M. hamiltoni

The colossal squid (Mesonychoteuthis hamiltoni, from Greek mesos (middle), onycho (claw, nail), and teuthis (squid)), sometimes called the Antarctic 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 12–14 m (39–46 ft) long and weighing possibly up to 750 kg (1,650 lb),[1][2] 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.[3] 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 27 cm (11 in) in diameter, with a 9 cm (3.5 in) pupil.[4][5] The eye was estimated to be 30 to 40 cm (12 to 16 in) 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.[6]

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 other 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, 71 showed clear signs of attack by colossal squid.[7] The colossal squid is thought to have a slow metabolic rate, needing only around 30 grams (1.1 oz) of prey daily.[8] Estimates of its energy requirements suggest it is a slow-moving ambush predator, using its large eyes primarily for predator detection rather than active hunting.[8][9]

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 2.2 km (7,200 ft), and juveniles can go as deep as 1 km (3,300 ft). 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.[10] 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)[6]. 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.[11]

History

The species was first discovered in the form of two tentacles found in the stomach of a sperm whale in 1925.[12] In 1981 a Russian trawler in the Ross Sea, off the coast of Antarctica, caught a large squid with a total length of 4 m (13 ft), which was later identified as an immature female of M. hamiltoni.[13] In 2003 a complete specimen of a subadult female was found near the surface with a total length of 6 m (20 ft) and a mantle length of 2.5 m (8.2 ft).[14] This specimen shows that colossal squids may grow larger than 500 kg (1,100 lb), possibly up to 750 kg (1,650 lb).[1]

In 2005 a specimen was captured at a depth of 1,625 m (5,331 ft) 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 (8.2 ft), and the tentacles measured 2.3 m (7.5 ft). The animal is thought to have weighed between 150 and 200 kg (330 and 440 lb).[15]

The largest recorded specimen was captured in 2007 by a New Zealand fishing boat off Antarctica. It was initially estimated to measure 4.5 m (15 ft) in length and weigh 450 kg (990 lb). The squid was taken back to New Zealand for scientific study.[16] A study on the specimen later showed its actual weight was 495 kg (1,091 lb), but it only measured 4.2 m (14 ft) in total length as a result of the tentacles' shrinking post mortem.[17]

Largest known specimen

This specimen, caught in early 2007, is the largest cephalopod ever recorded. Here it is shown in its live state during capture, with the delicate red skin still intact and the mantle characteristically inflated.

On February 22, 2007, authorities in New Zealand announced the largest known colossal squid had been captured. The specimen weighed 495 kg (1,091 lb) and was initially estimated to measure 4.5 m (15 ft) in total length.[18] 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 kg (430 lb),[19][20] 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.[21][22] Media reports suggested scientists at the museum were considering using a giant microwave to defrost the squid because defrosting it at room temperature would take days and it would likely rot on the outside while the core remained frozen.[21] However, they later opted for the more conventional approach of thawing the specimen in a bath of salt water.[23][24] After thawing, the squid measured only 4.2 m (14 ft) in total length, with the tentacles having shrunk significantly.[17] Although initially thought to be a male, closer inspection of the specimen showed it to be a female.[5]

Defrosting and dissection, April–May 2008

Thawing and dissection of the specimen took place at the Museum of New Zealand Te Papa Tongarewa[23] 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:

Exhibition

The specimen on display at the Museum of New Zealand Te Papa Tongarewa

The Museum of New Zealand Te Papa Tongarewa began displaying this specimen in an exhibition that opened on December 13, 2008, and was still running as of March 2017.[28]

Second specimen

In August 2014, Te Papa received a second colossal squid, captured in early 2014.[29] The specimen was also female, was 3.5 metres long and weighed approximately 350 kg.[30]

References

  1. 1 2 http://www.unmuseum.org/colossalsquid.htm
  2. ↑ Anderton, H.J. 2007. Amazing specimen of world's largest squid in NZ. New Zealand Government website.
  3. ↑ Te Papa: Hooks and Suckers. Blog.tepapa.govt.nz (2008-04-30). Retrieved on 2011-09-30.
  4. 1 2 Ballance, Alison; Meduna, Veronika (16 September 2014). "Colossal squid to give up its secrets". Radio New Zealand. Retrieved 2015-08-02.
  5. 1 2 3 4 Richard Black "Colossal squid's big eye revealed". BBC News, April 30, 2008.
  6. 1 2 Rosa, Rui & Lopes, Vanessa M. & Guerreiro, Miguel & Bolstad, Kathrin & Xavier, José C. 2017. Biology and ecology of the world's largest invertebrate, the colossal squid (Mesonychoteuthis hamiltoni): a short review. Polar Biology, published online on March 30, 2017. doi:10.1007/s00300-017-2104-5
  7. ↑ Sarchet, Penny (11 June 2015). "Colossal squid vs huge toothfish – clash of the deep-sea titans". New Scientist. doi:10.1080/00222933.2015.1040477. Retrieved 2015-08-02.
  8. 1 2 Rosa, R. & B.A. Seibel 2010. Slow pace of life of the Antarctic colossal squid. Journal of the Marine Biological Association of the United Kingdom, published online on April 20, 2010. doi:10.1017/S0025315409991494
  9. ↑ Bourton, Jody (2010-05-07). "Huge 'monster squid' not fearsome". BBC News. Retrieved 2015-08-02.
  10. ↑ 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.
  11. ↑ Cherel, Y. & G. Duhamel 2004. "Antarctic jaws: cephalopod prey of sharks in Kerguelen waters." (PDF). (531 KB) Deep-Sea Research Part I 51: 17–31.
  12. ↑ Robson, G.C. 1925. On Mesonychoteuthis, a new genus of oegopsid, Cephalopoda. Annals and Magazine of Natural History, Series 9, 16: 272–277.
  13. ↑ Ellis, R. 1998. The Search for the Giant Squid. The Lyons Press.
  14. ↑ Griggs, Kim (2003-04-02). "Super squid surfaces in Antarctic". BBC News. Wellington. Retrieved 2015-08-02.
  15. ↑ "Very Rare Giant Squid Caught Alive". South Georgia Island. Archived from the original on 2010-06-05. Retrieved 2015-08-02.
  16. ↑ "NZ fishermen land colossal squid". BBC News. 2007-02-22. Retrieved 2015-08-02.
  17. 1 2 Atkinson, Kent (May 1, 2008). "Size matters on 'squid row' (+photos, video)". The New Zealand Herald. Retrieved September 25, 2011.
  18. ↑ onboard scientific observer
  19. ↑ Marks, Kathy (March 23, 2007). "NZ's colossal squid to be microwaved". The New Zealand Herald. Retrieved September 25, 2011.
  20. ↑ Rincon, Paul (8 January 2004). "New giant squid predator found". BBC News. Retrieved 14 February 2007.
  21. 1 2 "Colossal Squid May Be Headed for Oven - washingtonpost.com". www.washingtonpost.com. Associated Press. 22 March 2007. Retrieved 2015-08-02.
  22. ↑ Griggs, Kim (2007-03-15). "Colossal squid's headache for science". BBC News. Retrieved 2015-08-02.
  23. 1 2 Te Papa's Specimen: The Thawing and Examination Archived April 25, 2008, at the Wayback Machine.. Tepapa.govt.nz. Retrieved on 2011-09-30.
  24. ↑ Black, Richard (2008-04-28). "Colossal squid comes out of ice". BBC News. Retrieved 2015-08-02.
  25. 1 2 Ballance, Alison (14 October 2014). "Colossal Squid Revealed". Radio New Zealand. Retrieved 2015-08-02.
  26. 1 2 "Massive squid may be just a babe". South Africa: The Star.
  27. ↑ "World's biggest squid reveals 'beach ball' eyes". www.terradaily.com. Wellington: AFP. 30 April 2008. Retrieved 2015-08-02.
  28. ↑ "The Colossal Squid Exhibition - Exhibition". tepapa.govt.nz. Archived from the original on 2012-03-18. Retrieved 2012-03-15. The colossal squid is due for a check-up in March this year. We'll assess her condition and decide how long she can safely stay on display. She'll be with us until at least August 2012
  29. ↑ Tapaleao, Vaimoana (2014-08-11). "Is it a boy? Te Papa gets new colossal squid". New Zealand Herald. ISSN 1170-0777. Retrieved 2015-08-02.
  30. ↑ "Scientists Found Only The Second Intact Colossal Squid — Here's What It Looks Like". 16 September 2014. Retrieved 26 September 2014.

Further reading

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