Ipnops is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of deep-sea fish in the family Ipnopidae

Ipnopidae

Ipnopidae is a family of fishes in the order Aulopiformes. They are small slender fishes, with maximum length ranging from about to about . They are found in temperate and tropical deep waters of the Atlantic, Indian and Pacific Oceans.A number of species, especially in the genus Bathypterois...

, which also includes the better-known tripod fish

Tripod fish

Tripod fish, Bathypterois grallator, are a deep-sea benthic fish found at lower latitudes. They are now relatively well known from photographs and submersible observations...

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

Bathyal zone

The bathyal zone or bathypelagic – from Greek βαθύς , deep – is that part of the pelagic zone that extends from a depth of 1000 to 4000 metres below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The average temperature hovers at about 39°F...

 and abyssal zone

Abyssal zone

The abyssal zone is the abyssopelagic layer or pelagic zone that contains the very deep benthic communities near the bottom of oceans. "Abyss" derives from the Greek word ἄβυσσος, meaning bottomless. At depths of 4,000 to 6,000 metres , this zone remains in perpetual darkness and never receives...

s. The genus is notable for its unusual eyes.

Distribution

Specimens of I. murrayi and I. agassizi have been caught at depths of 1392-3475 m; I. murrayi occurs in the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 while I. agassizi occurs in the Indo-Pacific

Indo-Pacific

The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...

 region. I. meadi is also found in the Indo-Pacific, but occurs deeper at 3310-4970 m.

Biology

Ipnops has never been observed in the wild, so details of their life history must be 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 raker

Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch and are involved with filter feeding tiny prey. They are not to be confused with the gill filaments that compose the bony part of the gill. Rakers are usually present in two rows, projecting from both the...

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

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s and polychaete worms. Their eyes are extremely modified into flat, cornea

Cornea

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

-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

Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

 prey; it has also been proposed that the organs themselves may be luminescent and act as lures. Ipnops have a well-developed lateral line

Lateral line

The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

, 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

Hermaphrodite

In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

, 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.