Sabertooth fish

Taxobox
name = Sabertooth fishes

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image_width = 240px
image_caption = "Coccorella atrata"
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Aulopiformes
familia = Evermannellidae
subdivision_ranks = Genera
subdivision = "Coccorella" "Evermannella" "Odontostomops" See text for species.

Sabertooth fishes (also spelt sabretooth) 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 appropriately named for their oversized, recurved palatine teeth redolent of the saber-toothed cats. The family name "Evermannellidae" was given in honour of Dr. Barton Warren Evermann, a noted ichthyologist, naturalist and director of the California Academy of Sciences.

Physical description

Sabertooth fishes have moderately elongate and compressed bodies which lack normal scales. The head is large and blunt; the terminal mouth is large, and it is 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 eyes range in size from small to large; they are tubular in structure and point upwards. The lateral line runs uninterrupted. The vertebrae number 44–54 and there are three discrete bands of muscle tissue (epaxial, midlateral, and hypaxial) present in the caudal region. The swim bladder is absent 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 spineless 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.

Life history

Almost nothing is known of the biology 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 to no 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 migrations.

Their reproductive habits are poorly studied; they are assumed to be non-guarding, 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. 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" (Alcock, 1894).
* Genus "Evermannella"
** "Evermannella ahlstromi" Johnson & Glodek, 1975.
** Balbo sabretooth, "Evermannella balbo" (Risso, 1820).
** "Evermannella indica" Brauer, 1906.
** "Evermannella megalops" Johnson & Glodek, 1975.
** Indian sabertooth, "Evermannella melanoderma" Parr, 1928.
* Genus "Odontostomops"
** Undistinguished sabretooth, "Odontostomops normalops" (Parr, 1928).

References

*
* "Fishes: An introduction to ichthyology". Peter B. Moyle and Joseph J. Cech, Jr; p. 336. Printed in 2004. Prentice-Hall, Inc; Upper Saddle River, NJ. ISBN 0-13-100847-1