Sabertooth fish
Encyclopedia
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 Ocean
.
These fishes are named for their oversized, recurved palatine
teeth
, similar to those of saber-toothed cat
s. The family is named "Evermannellidae" after Barton Warren Evermann
, noted ichthyologist
, naturalist
and director of the California Academy of Sciences
.
. The head is large and blunt; the terminal mouth is large and lined with slender palatine teeth, the frontmost of which are greatly enlarged and curve inward slightly. A number of shorter, straighter teeth accompany these fang-like teeth. The tongue
is toothless. The eye
s range in size from small to large; they are tubular in structure and point upwards. The lateral line
runs uninterrupted. The different families have 44–54 vertebrae, and there are three discrete bands of muscle
tissue (epaxial, midlateral, and hypaxial) present in the caudal region. Sabertooths do not have swim bladders, and the stomach
is highly distensible.
There is a single high dorsal fin
(with 10–13 rays) originating slightly before the thoracic pelvic fins. 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 emarginate caudal fin. A small adipose fin is also present. The pectoral fins (11–13 rays) are positioned rather low on the body. All fins are spine
less and lightly pigmented in shades of brown.
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 centimetres standard length.
and ecology
of evermannellids. They are active, visual predators and confine themselves to the mesopelagic zone
, c. 200–1,000 metres down; they are most commonly trawled from between 200–400 metres. At these depths there is extremely little or light; 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 that are silhouetted against the gloom above them.
Their distensible stomachs allow sabertooth fish 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 fish are solitary animals; it is not known whether they undergo diel vertical migration
s.
Their reproductive habits are poorly studied; they are assumed to be non-guarding, pelagic spawn
ers. 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 plankton
ic and have long snouts and oblong eyes before metamorphosis. Both larvae and juveniles remain at shallower depths of 50–100 metres, descending to deeper water with age.
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
comprising the family Evermannellidae. The family is small, with just eight species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in three genera
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...
represented; they are distributed throughout tropical to subtropical waters of the Atlantic
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...
, Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, and Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
These fishes are named for their oversized, recurved palatine
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
, similar to those of saber-toothed cat
Saber-toothed cat
Saber-toothed cat or Sabre-toothed cat refers to the extinct subfamilies of Machairodontinae , Barbourofelidae , and Nimravidae as well as two families related to marsupials that were found worldwide from the Eocene Epoch to the end of the Pleistocene Epoch ,...
s. The family is named "Evermannellidae" after Barton Warren Evermann
Barton Warren Evermann
Barton Warren Evermann was an American ichthyologist. He was born in Monroe County, Iowa, and graduated from Indiana University in 1886. For 10 years, he served as teacher and superintendent of schools in Indiana and California. He was professor of biology at the Indiana State University in...
, noted ichthyologist
Ichthyology
Ichthyology is the branch of zoology devoted to the study of fish. This includes skeletal fish , cartilaginous fish , and jawless fish...
, naturalist
Natural history
Natural history is the scientific research of plants or animals, leaning more towards observational rather than experimental methods of study, and encompasses more research published in magazines than in academic journals. Grouped among the natural sciences, natural history is the systematic study...
and director of the California Academy of Sciences
California Academy of Sciences
The California Academy of Sciences is among the largest museums of natural history in the world. The academy began in 1853 as a learned society and still carries out a large amount of original research, with exhibits and education becoming significant endeavors of the museum during the twentieth...
.
Physical description
Sabertooth fishes have moderately elongate and compressed bodies which lack normal scalesScale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
. The head is large and blunt; the terminal mouth is large and lined with slender palatine teeth, the frontmost of which are greatly enlarged and curve inward slightly. A number of shorter, straighter teeth accompany these fang-like teeth. The tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
is toothless. The eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s range in size from small to large; they are tubular in structure and point upwards. The 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...
runs uninterrupted. The different families have 44–54 vertebrae, and there are three discrete bands of muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
tissue (epaxial, midlateral, and hypaxial) present in the caudal region. Sabertooths do not have swim bladders, and the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
is highly distensible.
There is a single high dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
(with 10–13 rays) originating slightly before the thoracic pelvic fins. 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 emarginate caudal fin. A small adipose fin is also present. The pectoral fins (11–13 rays) are positioned rather low on the body. All fins are spine
Spine (zoology)
A spine is a hard, thorny or needle-like structure which occurs on various animals. Animals such as porcupines and sea urchins grow spines as a self-defense mechanism. Spines are often formed of keratin...
less and lightly pigmented in shades of brown.
Sabertooth fish are usually a drab, light to dark brown when preserved; however, a brassy green iridescence
Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...
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 centimetres standard length.
Life history
Almost nothing is known of the biologyBiology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
and ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
of evermannellids. They are active, visual predators and confine themselves to the mesopelagic zone
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
, c. 200–1,000 metres down; they are most commonly trawled from between 200–400 metres. At these depths there is extremely little or light; 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
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
, cuttlefish
Cuttlefish
Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
, and smaller fish that are silhouetted against the gloom above them.
Their distensible stomachs allow sabertooth fish to swallow prey larger than themselves; their recurved teeth likely function in a manner similar to a snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
's, preventing a captured fish from backing out and helping to guide the fish down the sabertooth's pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
. Sabertooth fish are solitary animals; it is not known whether they undergo diel vertical migration
Diel vertical migration
Diel vertical migration, also known as diurnal vertical migration, is a pattern of movement that some organisms living in the ocean and in lakes undertake each day. Usually organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone...
s.
Their reproductive habits are poorly studied; they are assumed to be non-guarding, pelagic spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
ers. 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
Ichthyoplankton
Ichthyoplankton are the eggs and larvae of fish. They are usually found in the sunlit zone of the water column, less than 200 metres deep, which is sometimes called the epipelagic or photic zone...
are plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic and have long snouts and oblong eyes before metamorphosis. Both larvae and juveniles remain at shallower depths of 50–100 metres, descending to deeper water with age.
Species
There are eight species in three genera:- Genus Coccorella
- Atlantic sabretooth, Coccorella atlantica (Borodin, 1931).
- Coccorella atrata (AlcockAlfred William AlcockAlfred William Alcock was a British physician naturalist and carcinologist.Alcock was the son of a sea-captain, John Alcock in Bombay, India who retired to live in Blackheath...
, 1894).
- Genus Evermannella
- Evermannella ahlstromi Johnson & Glodek, 1975.
- Balbo sabretoothBalbo sabretoothThe 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...
, Evermannella balbo (RissoAntoine RissoGiuseppe Antonio Risso , called Antoine Risso, was a Niçard naturalist.Risso was born in Nice, County of Nice, a part of the Duchy of Savoy, and studied under Giovanni Battista Balbis. He published , and . Risso's dolphin was named after him...
, 1820).
- Evermannella indica Brauer, 1906.
- Evermannella megalops Johnson & Glodek, 1975.
- Indian sabertooth, Evermannella melanoderma Parr, 1928.
- Genus Odontostomops
- Undistinguished sabretooth, Odontostomops normalops (Parr, 1928).