Ipnops

Ipnops is a genus of deep-sea fish in the family Ipnopidae, which also includes the better-known tripodfish (Bathypterois grallator). Ipnops are small, slender fish that live close to the ocean floor in the bathyal and abyssal zones. The genus is notable for its unusual eyes.

Ipnops
Ipnops murrayi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Aulopiformes
Family:	Ipnopidae
Genus:	Ipnops Günther, 1878
Synonyms
Ipnoceps Fowler 1943 Lychnoculus Murray 1877

Species

There are currently three recognized species in this genus:

• Ipnops agassizii Garman, 1899 (grideye fish)
• Ipnops meadi J. G. Nielsen, 1966
• Ipnops murrayi Günther, 1878

Distribution

Specimens of I. murrayi and I. agassizi have been caught at depths of 1392–3475 m; I. murrayi occurs in the Atlantic Ocean while I. agassizi occurs in the Indo-Pacific region. I. meadi is also found in the Indo-Pacific, but occurs deeper at 3310–4970 m.

Biology

Ipnops has only recently been observed in the wild, so details of their life history has mostly been inferred from the characteristics of captured specimens. They have large mouths with numerous small teeth for swallowing large prey, as well as well-developed gill rakers for capturing smaller items. Examination of stomach contents show a diet of mostly crustaceans and polychaete worms. Their eyes are extremely modified into flat, cornea-like organs that cover most of the upper surface of the head.

The purpose of these structures is debated—they are light-sensitive and may serve to detect bioluminescent prey; it has also been proposed that the organs themselves may be luminescent and act as lures. Ipnops have a well-developed lateral line, which has been suggested to have a primary sensory function given the degenerate state of their other senses.

Like other bathypteroid fishes, Ipnops is hermaphroditic, with male and female gonads combined into a single organ. External fertilization is likely, possibly with ripe eggs held by the pelvic fins to facilitate fertilization. The capture of multiple specimens in single trawls suggests that these fishes may live in aggregates.

Bibliography

• Ellis, Richard (1996). Deep Atlantic: Life, Death, and Exploration in the Abyss. New York, NY: The Lyons Press. ISBN 1-55821-663-4.
• Nielsen, Jørgen G. (1966). "Synopsis of the Ipnopidae (Pisces, Iniomi) with descriptions of two new abyssal species" (PDF). Galathea Rep. 8: 49–79. Archived from the original (PDF) on 2007-06-10. Retrieved 2008-10-08.