''Ipnops'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 flashlight f ...

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 Ocean, I ...

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

Bathypterois grallator The tripod fish or tripod spiderfish, ''Bathypterois grallator'', is a deep-sea benthic fish in the family Ipnopidae found at lower latitudes. It is now an iconic deep-sea fish, being observed and photographed by submersibles, using elongate ...

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

bathyal The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypelag ...

and

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

s. The genus is notable for its unusual eyes.

Species

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

Garman Garman is a surname or first name. Notable people with the name include: Sports * Ann Garman, All-American Girls Professional Baseball League player * Judi Garman (born 1954), American softball coach * Mike Garman (born 1949), American baseball pla ...

, 1899 (grideye fish) * ''

Ipnops meadi ''Ipnops meadi'', also known as the grideye fish, is a highly specialized species of Placodithyran abyssal fish found in the Clarion-Clipperton Zone of the Indo-Pacific Ocean. The species was named after Giles W. Mead of the Harvard Museum of C ...

'' 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 borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

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 (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

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 transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the 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 Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...

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

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

, 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 A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

, 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 (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

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