''Ipnops'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

deep-sea fish Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep sea fishes include the flashlig ...

in the family

Ipnopidae The Ipnopidae (deepsea tripod fishes) are a family of fishes in the order Aulopiformes. They are small, slender fishes, with maximum length ranging from about . They are found in temperate and tropical deep waters of the Atlantic, Indian, a ...

, which also includes the better-known tripodfish (''

Bathypterois grallator The tripodfish or tripod spiderfish, ''Bathypterois grallator'', is a deep-sea benthic fish in the family Ipnopidae found at lower latitudes. It is now relatively well known from photographs and submersible observations, and seems to prefer to p ...

''). ''Ipnops'' are small, slender fish that live close to the ocean floor in the bathyal and

abyssal zone The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean a ...

s. The genus is notable for its unusual eyes.

Species

There are currently three recognized species in this genus: * ''

Ipnops agassizii ''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 ...

'' 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 The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

while ''I. agassizi'' occurs in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

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 raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of th ...

s for capturing smaller items. Examination of stomach contents show a diet of mostly

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

s and

polychaete worm Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ma ...

s. Their eyes are extremely modified into flat,

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...

-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 Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...

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 In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have se ...

, with male and female gonads combined into a single organ. External fertilization is likely, possibly with ripe eggs held by the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two e ...

s to facilitate fertilization. The capture of multiple specimens in single trawls suggests that these fishes may live in aggregates.

References

Bibliography

* * {{Taxonbar, from=Q2445798 Ipnopidae Taxa named by Albert Günther