Mature female (38.4 cm ML, 1.875 kg weight) from the Chatham Rise
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, with females growing linearly twice as fast as males, and reaching a fully mature size of more than five times that of male counterparts.[4]
Penis elongation has been observed in this species; when erect, the penis may be as long as the mantle, head and arms combined.[5][6] 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.[5]
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
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.[7] Globally, however, myctophid fish (lantern fish) are seen as common prey.[8] Larger squid are known to practice cannibalism (accounting for up to 6% of diet).[9]
^Philippe Bouchet (2018). Bieler R, Bouchet P, Gofas S, Marshall B, Rosenberg G, La Perna R, Neubauer TA, Sartori AF, Schneider S, Vos C, ter Poorten JJ, Taylor J, Dijkstra H, Finn J, Bank R, Neubert E, Moretzsohn F, Faber M, Houart R, Picton B, Garcia-Alvarez O (eds.). "Onykia ingens (E. A. Smith, 1881)". MolluscaBase. World Register of Marine Species. Retrieved 16 March 2018.
^Bolstad, K.S.R. 2010. Systematics of the Onychoteuthidae Gray, 1847 (Cephalopoda: Oegopsida). Zootaxa2696: 1–186. Preview
^ abArkhipkin, 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. doi:10.1093/mollus/eyq019
