Sabertooth fishes | |
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Coccorella atrata | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Aulopiformes |
Family: | Evermannellidae Fowler, 1901 |
Genera | |
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.
These fishes are named for their oversized, recurved palatine teeth, similar to those of saber-toothed cats (and the prehistoric Enchodus ). The family is named Evermannellidae after Barton Warren Evermann, noted ichthyologist, naturalist and director of the California Academy of Sciences.
Sabertooth fishes have moderately elongated and compressed bodies which lack normal scales. The head is large and blunt; the terminal mouth is large and lined with slender palatine teeth, and the front is mostly enlarged and is curved inward slightly. A number of shorter, straighter teeth accompany these fang-like teeth. The tongue is toothless.
The eyes of the Odontostomops normalops typically range in size from small to large with a tubular structure while pointing upwards and directly laterally. The Atlantic sabertooth (Cocorella atlantica) have semi-tubular eyes directed dorso-laterally while the Balbo sabertooth (Evermannella balbo) and Indian sabertooth (Evermannella melanoderma) have tubular eyes but directed dorsally and slightly anteriorly. [1] The tubular nature of these eyes allow the sabertooth fish to extend their vision in specific directions, and also are presumed to aid with depth perception in the dark. [2] [3] Evermannella have an additional adaptation called the optical fold. These optical folds are found on the lateral sides of the eyes and are another adaptation that allow these fish to extend their field of vision. The presumed mechanism of these optical folds is by altering the angle of the light from the lateral and ventral sides to better enter the eye. [3] [4]
Similarly, in O. normalops, the horizontal diameter of the eye is significantly smaller than the width of the orbit, whereas in C. atlantica, the diameter of the eye is approximately equal to the interorbital width. In the case of E. balbo and E. melanoderma, the horizontal diameter of the eye is notably wider than the interorbital width. These observations suggest that there exist significant variations in the proportional dimensions of the eyes and orbits among different species of organisms, which may be indicative of distinct anatomical and functional adaptations. [1]
The anal fin (26–37 rays) is the largest of the fins, and runs along the posterior half of the fish, tapering in height towards the emarginated caudal fin. For O. normalops, anal fin ray counts are lowest in the Atlantic, higher in the Indian Ocean, and highest in the Pacific. [1] Further sampling must be done in order to determine a cause for this trend and if this trend exists in other species as well. A single high dorsal fin (10–13 rays) originates slightly before the thoracic pelvic fins. A small adipose fin is also present. The pectoral fins (11–13 rays) are positioned rather low on the body. All fins are spineless and lightly pigmented in shades of brown. [5]
The different families have 44–54 vertebrae, with three discrete bands of muscle tissue (epaxial, mid-lateral, and hypaxial) present in the caudal region. Sabertooths do not have swim bladders, and the stomach is highly distensible.
Evermannella are aulopiforms that have fusiform body structures, resulting in the fish being more deep anteriorly. This is in contrast to the elongated bodies of most other aulopiforms. [2]
Sabertooth fish are usually a drab, light to dark brown when preserved; however, a brassy green iridescence is seen on the flanks, cheeks, and ocular region of well-preserved specimens. The naked skin is easily torn. The Atlantic sabertooth (Coccorella Atlantica) is the largest species, at up to 18.5 cm standard length.
Almost nothing is known of the biology and ecology of evermannellids. They are active, visual predators and confine themselves to the mesopelagic zone, about 400m - 1000m for adults. [1] [4] However, larvae and small juvenile sabertooth fishes tend to be found at depth ranges between 50m - 100m, descending to deeper water with age. [1] At these depths, extremely little light is available; the view from below is like the sky at twilight. The sabertooth fish use their telescopic, upward-pointing eyes— which are thus adapted for improved terminal vision at the expense of lateral vision— to pick out squid, cuttlefish, and smaller fish silhouetted against the gloom above them.
Their distensible stomachs allow sabertooth fishes to swallow prey larger than themselves; their recurved teeth likely function in a manner similar to a snake's, preventing a captured fish from backing out and helping to guide the fish down the sabertooth's pharynx. Sabertooth fishes are solitary animals; it is not known whether they undergo diel vertical migrations.
Their reproductive habits are poorly studied; they are assumed to be nonguarding, pelagic spawners. True synchronous hermaphroditism with external fertilization is known in Evermannella indica and Odontostomops normalops , and the former species appears to spawn throughout the year. Sabertooth fish larvae are planktonic and have long snouts and oblong eyes before metamorphosis.
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.
Telescopefish are small, deep-sea aulopiform fish comprising the small family Giganturidae. The two known species are within the genus Gigantura. Though rarely captured, they are found in cold, deep tropical to subtropical waters worldwide.
Barreleyes, also known as spook fish, are small deep-sea argentiniform fish comprising the family Opisthoproctidae found in tropical-to-temperate waters of the Atlantic, Pacific, and Indian Oceans.
Enchodus is an extinct genus of aulopiform ray-finned fish related to lancetfish and lizardfish. Species of Enchodus flourished during the Late Cretaceous, and survived the Cretaceous–Paleogene extinction event, persisting into the late Eocene.
The black swallower, Chiasmodon niger, is a species of deep sea fish in the family Chiasmodontidae. It is known for its ability to swallow fish larger than itself.
The Synodontidae or lizardfishes are benthic (bottom-dwelling) marine and estuarine bony fishes that belong to the aulopiform fish order, a diverse group of marine ray-finned fish consisting of some 15 extant and several prehistoric families. They are found in tropical and subtropical marine waters throughout the world.
This glossary of ichthyology is a list of definitions of terms and concepts used in ichthyology, the study of fishes.
The deepsea lizardfish, Bathysaurus ferox, is an aulopiform of the family Bathysauridae, found in tropical and subtropical seas across the world. The deepsea lizardfish should not be confused with the true or "typical" lizardfishes of the related family Synodontidae.
The balbo sabretooth, Evermannella balbo, is a sabertooth of the family Evermannellidae, found circumglobally in tropical and subtropical seas, at depths of between 100 and 1,000 m. Its length is up to 17 cm.
Stratodus is a genus of giant prehistoric aulopiform fish found in Cretaceous-aged marine strata of Kansas, Alabama, Morocco, Israel, and Niger, South Dakota, Jordan. It has also been found in the Tamaguélelt Formation of Mali, dating to the Lower Eocene, indicating that Stratodus survived the Cretaceous-Paleogene extinction event. This sleek fish has an upper jaw filled with multiple rows of tiny teeth and was the largest aulopiform, reaching 5 meters in length.
The pearleyes are a family, Scopelarchidae, of aulopiform fishes, distinguished by their unique visual system, with two retinas in each eye.
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 brownsnout spookfish or brown-snout spookfish is a species of barreleye in the family Opisthoproctidae. It and the glasshead barreleye fish are the only vertebrates known to employ a mirror, in addition to a lens, to focus an image in its eyes. This species probably has a worldwide tropical and temperate distribution; in the Atlantic Ocean it is known from Bermuda, the Bahamas, the Greater Antilles, and the Gulf of Mexico, and in the Pacific Ocean it is known from the California Current region and the South China Sea. It is found in the mesopelagic and bathypelagic zones at a depth of 500–2,400 meters (1,600–7,900 ft), but usually occurs below 1,000 meters. In the Gulf of Mexico it is found shallower, at 310–460 meters (1,020–1,510 ft).
Black seadevils are small, deepsea lophiiform fishes of the family Melanocetidae. The five known species are all within the genus Melanocetus. They are found in tropical to temperate waters of the Atlantic, Indian, and Pacific Oceans, with one species known only from the Ross Sea.
Synodus intermedius, the common sand diver, is a species of fish in the lizardfish family, the Synodontidae, a basal ray-finned fish in the class Actinopterygii. Sand divers inhabit subtropical marine ecosystems, (37-17°N), including sandy- bottom areas on continental shelves, coral reefs, estuaries, bays, and reef structures. They are demersal or benthic fish, which means they live on or close to the sea bed. Distribution ranges from the northern Gulf of Mexico south to the Guianas, and western Atlantic north to North Carolina and Bermuda. They are a common lizardfish in the West Indies. They grow to about 40 cm (16 in) total length, and weigh around 1 kg (2.2 lb).
Cancelloxus burrelli, the Slender platanna-klipfish, is a species of clinid found in subtropical waters of the Atlantic Ocean along the South African coast from the Orange River to Algoa Bay in South Africa. It can be found from the intertidal zone down to about 20 metres (66 ft). This species can reach a maximum length of 12 centimetres (4.7 in) TL.
Opisthoproctus soleatus is a species of fish in the family Opisthoproctidae. It was first described in 1888 by Léon Vaillant. The species lives in most tropical seas, but is more common in the eastern Atlantic, from western Ireland to Mauritania and from Sierra Leone to Angola, and also in the South China Sea. O. soleatus can grow to a standard length of 10.5 centimetres (4.1 in) and usually live from about 500 to 700 metres deep.
Astyanax microschemos is a species of characid fish from Brazil. It belongs to the A. scabripinnis species complex and differs from other species outside it by having a lower number of branched anal fin rays and its shallow body depth being about 26.9-29.7 vs more than 35% of its standard length (SL). Compared to species of its own complex, it can be distinguished by the combination of its shallow body depth, and smaller interorbital width. The species name comes from the Greek mikroschemos, meaning "low stature", which refers to the shallow body depth of the animal.
Coccorella atlantica is a species of sabertooth fish, found in the northeastern part of the Atlantic Ocean. The body composition of C. atlantic differs from other species, as their eyes are semi-tubular and directed dorso-laterally. The eye diameter is about equal to the interorbital width as well.
Evermannella melanoderma, the Indian sabertooth fish, is a species of the Evermannelidae family located in tropical and subtropical waters in the Atlantic Ocean. The body composition of E. melanoderma differs from other species, as their eyes are tubular and directed dorsally and slightly anteriorally. The eye diameter is much broader than the interorbital width as well.