The Amblyopsidae are a fish family commonly referred to as cavefish, blindfish, or swampfish. They are small freshwater fish found in the dark environments of caves, springs and swamps in the eastern half of the United States. Like other troglobites, most amblyopsids exhibit adaptations to these dark environments, including the lack of functional eyes and the absence of pigmentation. More than 200 species of cavefishes are known, but only six of these are in the family Amblyopsidae. One of these, Forbesichthys agassizii, spends time both underground and aboveground. A seventh species in this family, Chologaster cornuta, is not a cave-dweller but lives in aboveground swamps.
Barracudinas are any member of the marine mesopelagic fish family Paralepididae: 50 or so extant species are found almost worldwide in deep waters. Several genera are known only from fossils dating back to the Ypresian epoch.
Aulopiformes is a diverse order of marine ray-finned fish consisting of some 15 extant and several prehistoric families with about 45 genera and over 230 species. The common names grinners, lizardfishes and allies, or aulopiforms are sometimes used for this group. The scientific name means "Aulopus-shaped", from Aulopus + the standard fish order suffix "-formes". It ultimately derives from Ancient Greek aulós + Latin forma, the former in reference to the elongated shape of many aulopiforms.
The snailfishes or sea snails are a family of marine ray-finned fishes. These fishes make up the Liparidae, which is classified within the order Scorpaeniformes.
Greeneyes are deep-sea aulopiform marine fishes in the small family Chlorophthalmidae. Thought to have a circumglobal distribution in tropical and temperate waters, the family contains just 18 species in two genera. The family name Chlorophthalmidae derives from the Greek words chloros meaning "green" and ophthalmos meaning "eye".
The marine hatchetfishes or deep-sea hatchetfishes as well as the related bottlelights, pearlsides and constellationfishes are small deep-sea ray-finned fish of the stomiiform family Sternoptychidae. They are not closely related to and should not be confused with the freshwater hatchetfishes, which are teleosts in the characiform family Gasteropelecidae. The Sternoptychidae have 10 genera and about 70 species altogether.
Fangtooths are beryciform fish of the family Anoplogastridae that live in the deep sea. The name is from the Greek anoplo, meaning "unarmed", and γαστήρ, meaning "stomach". With a worldwide distribution in tropical and cold-temperate waters, the family contains only two very similar species in one genus, with no known close relatives.
Sabertooth or sabretooth fish are small, fierce-looking deep-sea aulopiform fish comprising the family Evermannellidae. The family is small, with just eight species in three genera represented; they are distributed throughout tropical to subtropical waters of the Atlantic, Indian, and Pacific Oceans.
The Ipnopidae are a family of fishes in the order Aulopiformes. They are small, slender fishes, with maximum length ranging from about 10 to 40 cm. They are found in temperate and tropical deep waters of the Atlantic, Indian, and Pacific Oceans.
The Australian prowfishes are a small family, the Pataecidae, of ray-finned fishes classified within the order Scorpaeniformes. Australian prowfishes are distinguished by a long dorsal fin that begins far forward on the head, forming a "prow" shape, and extends all the way to the caudal fin. They lack scales and pelvic fins.
The complete anglerfish (Lasiognathus) is a genus of deep-sea anglerfish in the family Thaumatichthyidae, with six species known from the Atlantic and Pacific Oceans. Its lure apparatus appears to consist of a fishing rod, a fishing line, bait, and hooks. It is also distinctive for an enormous upper jaw with premaxillaries that can be folded down to enclose the much shorter lower jaw.
The Aulopidae are a small family of aulopiform fish. They are found in most tropical and subtropical oceans, and are commonly known as flagfins.
The Pacific barreleye fish (Macropinna) is a genus of ray-finned fish belonging to Opisthoproctidae, the barreleye family. It contains one species, M. microstoma. It is recognized for a highly unusual transparent, fluid-filled shield on its head, through which the lenses of its eyes can be seen. It was originally believed that the tubular eyes of this fish were fixed in place and, therefore, only provided a tunnel vision view of what was seen above its head. However, in 2008, scientists discovered that its eyes were able to rotate both up and forward in its transparent shield. M. microstoma has a tiny mouth and most of its body is covered with large scales. The fish normally hangs nearly motionless in the water, at a depth of about 600 metres (2,000 ft) to 800 metres (2,600 ft), using its large fins for stability and with its eyes directed upward. In the low light conditions it is assumed the fish detects prey by its silhouette. MBARI researchers Bruce Robison and Kim Reisenbichler observed that when prey such as small fish and jellyfish are spotted, the eyes rotate like binoculars, facing forward as it turns its body from a horizontal to a vertical position to feed. Robison speculates that M. microstoma steals food from siphonophores.
Vision is an important sensory system for most species of fish. Fish eyes are similar to the eyes of terrestrial vertebrates like birds and mammals, but have a more spherical lens. Birds and mammals normally adjust focus by changing the shape of their lens, but fish normally adjust focus by moving the lens closer to or further from the retina. Fish retinas generally have both rod cells and cone cells, and most species have colour vision. Some fish can see ultraviolet and some are sensitive to polarised light.
Benthalbella is a genus of pearleyes.
The whiskered prowfish is a species of marine ray-finned fish, an Australian prowfish belonging to the family Pataecidae. It is endemic to the coastal waters of southern Australia. This species is the only member of the monotypic genus Neopataecus.
Lagiacrusichthys macropinna, the longfin greeneye, is a species of pearleye and the only species in the genus Lagiacrusichthys. L. macropinna live between 0–840 m depth, usually 500 m. This species occurs in Antarctic waters. This species is the only known member of its genus. The genus is named after the fictional monster Lagiacrus from the Monster Hunter video game series and franchise, as both are "rather ferocious coldwater predators" that inhabit the deep ocean.
Scopelarchus analis, the short fin pearleye, is a species of fish that can be found circumglobal in warm waters. It is a member of the Scoperlarchus, a genus of pearleyes.
Benthalbella linguidens, the longfin pearleye, is a species of fish that can be found in the North Pacific from Japan to California. It is a member of the Benthalbella, a genus of pearleyes.
Scopelarchus guentheri, commonly known as the staring pearleye, is a mesopelagic fish known for its unique visual system consisting of two retinas in each eye as well as a distinctive 'pearl organ' found inside each eye. Like other fish in the genus Scopelarchus, S. guentheri has an opaque colored body.
