''Onykia ingens'', the greater hooked squid, is a species of squid in the family Onychoteuthidae. It occurs worldwide in

subantarctic The sub-Antarctic zone is a region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator. The subantarctic region includes many islands ...

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

Size and growth

The size of a fully grown ''O. ingens'', 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. ''O. ingens'' exhibit

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

, with females growing linearly twice as fast as males, and reaching a fully mature size of more than five times that of male counterparts.

Penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...

elongation has been observed in this species; when erect, the penis may be as long as the mantle, head and arms combined.Arkhipkin, A.I. & V.V. Laptikhovsky 2010. Observation of penis elongation in ''Onykia ingens'': implications for spermatophore transfer in deep-water squid. ''Journal of Molluscan Studies'', published online on June 30, 2010. 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.

Ecology

It is generally accepted that there are large dietary variations between large and small ''O. ingens''. 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. Globally, however, myctophid fish (lantern fish) are seen as common prey. Larger squid are known to practice cannibalism (accounting for up to 6% of diet). ''O. ingens'', as with many (if not all) large squid, has a number of predators. These include the

patagonian toothfish The Patagonian toothfish (''Dissostichus eleginoides'') is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around most ...

king penguin The king penguin (''Aptenodytes patagonicus'') is the second largest species of penguin, smaller, but somewhat similar in appearance to the emperor penguin. There are two subspecies: ''A. p. patagonicus'' and ''A. p. halli''; ''patagonicus'' ...

wandering albatross The wandering albatross, snowy albatross, white-winged albatross or goonie (''Diomedea exulans'') is a large seabird from the family Diomedeidae, which has a circumpolar range in the Southern Ocean. It was the last species of albatross to be desc ...

pilot whale Pilot whales are cetaceans belonging to the genus ''Globicephala''. The two extant species are the long-finned pilot whale (''G. melas'') and the short-finned pilot whale (''G. macrorhynchus''). The two are not readily distinguishable at sea, ...

, bottlenose whale,

dwarf sperm whale The dwarf sperm whale (''Kogia sima'') is a sperm whale that inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It was first described by biologist Richard Owen in 1866, based on illustrations by n ...

, sperm whale, and other types of squid.CephBase: Predators of ''Moroteuthis ingens''
. Image:Morotuthis ingens2.jpg, Tentacular club of ''Onykia ingens'' Image:Moroteuthis ingens3.jpg, Piece of ventral mantle skin Image:Moroteuthis ingens4.jpg,

Gladius ''Gladius'' () is a Latin word meaning "sword" (of any type), but in its narrow sense it refers to the sword of ancient Roman foot soldiers. Early ancient Roman swords were similar to those of the Greeks, called '' xiphe'' (plural; singular ''xi ...

with cross-sections

References

External links

Tree of Life web project: Onykia ingensFirst observation of a double tentacle bifurcation in cephalopods
{{Taxonbar, from=Q1950090 Squid Cephalopods described in 1881 Taxa named by Edgar Albert Smith