Greater Hooked Squid

Greater Hooked Squid
Onykia ingens (~400 mm ML)
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Coleoidea
Order:	Teuthida
Suborder:	Oegopsina
Family:	Onychoteuthidae
Genus:	Onykia
Subgenus:	Moroteuthopsis
Species:	O. ingens
Binomial name
Onykia ingens (Smith, 1881)
Synonyms
Onychoteuthis ingens Smith, 1881 Moroteuthis ingens (Smith, 1881)

The Greater Hooked Squid (Onykia ingens) is a species of squid in the family Onychoteuthidae. It occurs worldwide in subantartic oceans.

Although O. ingens was long attributed to the genus Moroteuthis, several authors have recently agreed that Moroteuthis is a junior synonym of Onykia.^[1]

Size and growth

The size of a fully grown Greater Hooked Squid, inclusive of tentacles, is currently unknown. Many estimates, however, predict that the mantle may reach lengths of up to 94 cm (37 in). Research has found that egg sizes of the squid average 2.1 mm inside mature females, while juveniles average 4.6 mm or larger. Juveniles are presumed to live near the surface, until they reach a mantle length of approximately 200 mm, at which time they relocate to deeper water, and larger prey. Greater Hooked Squid exhibit sexual dimorphism, with females growing linearly twice as fast as males, and reaching a fully mature size of more than five times that of male counterparts.^[2]

Penis elongation has been observed in this species; when erect, the penis may be as long as the mantle, head and arms combined.^[3][4] As such, deep water squid like M. ingens have the greatest known penis length relative to body size of all mobile animals, second in the entire animal kingdom only to certain sessile barnacles.^[3]

Left: A dissected male specimen of Onykia ingens, showing a non-erect penis (the white tubular structure located below most of the other organs)

Right: A specimen of the same species exhibiting elongation of the penis to 67 cm in length

Ecology

It is generally accepted that there are large dietary variations between large and small Greater Hooked Squid. One of the most common findings is that juvenile squid (>200 mm ML) consume a greater percentage of crustaceans and cephalopods compared to their size than mature squid, which consume a large percentage of fish and virtually no crustaceans.^[5] Globally, however, myctophid fish (lantern fish) are seen as common prey.^[6] Larger squid are known to practice cannibalism (accounting for up to 6% of diet).^[7] The Greater Hooked Squid, as with many (if not all) large squid, has a number of predators. These include the patagonian toothfish, king penguin, wandering albatross, pilot whale, bottlenose whale, dwarf sperm whale, sperm whale, and other types of squid.^[8]

• 

  Tentacular club of Moroteuthis ingens

• 

  Piece of ventral mantle skin

• 

  Gladius with cross-sections

References

1. ^ Bolstad, K.S.R. 2010. Systematics of the Onychoteuthidae Gray, 1847 (Cephalopoda: Oegopsida). Zootaxa 2696: 1–186. Preview
2. ^ Bolstad, K. 2003. Spotlight on: Moroteuthis ingens. The Octopus News Magazine Online.
3. ^ ^{a b} Arkhipkin, A.I. & V.V. Laptikhovsky 2010. Observation of penis elongation in Onykia ingens: implications for spermatophore transfer in deep-water squid. Journal Molluscan Studies, published online on June 30, 2010. doi:10.1093/mollus/eyq019
4. ^ Walker, M. 2010. Super squid sex organ discovered. BBC Earth News, July 7, 2010.
5. ^ Phillips, K., P. Nichols & G. Jackson 2003. Size-related dietary changes observed in the squid Moroteuthis ingens at the Falkland Islands: stomach contents and fatty-acid analyses. Polar Biology 26(7): 474-485.
6. ^ Phillips, K., P. Nichols & G. Jackson 2003. Dietary variation of the squid Moroteuthis ingens at four sites in the Southern Ocean: stomach contents, lipid and fatty acid profiles. Journal of the Marine Biological Association of the UK 83: 523-534.
7. ^ Cherel, Y. & G. Duhamel 2003. Diet of the squid Moroteuthis ingens (Teuthoidea: Onychoteuthidae) in the upper slope waters of the Kerguelen Islands. Marine Ecology Progress Series 250: 197–203.
8. ^ CephBase: Predators of Moroteuthis ingens.

External links

• CephBase: Greater Hooked Squid
• Tree of Life web project: Onykia ingens
• First observation of a double tentacle bifurcation in cephalopods

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