Tuesday, August 24, 2010
August 24, 2010 : Lancetfish
Lancetfishes are large oceanic predatory fishes in the genus Alepisaurus ("Scaleless lizard"), the only living genus in the family Alepisauridae.
Lancetfishes grow up to 2 metres (6.6 ft) in length. Very little is known about their biology, even though they are widely distributed in all oceans, except the polar seas. Specimens have been recorded as far north as Greenland. They are often caught as by-catch for vessels long-lining for tuna.
The generic name is from Greek a- meaning "without", lepis meaning "scale", and sauros meaning "lizard".
Lancetfishes possess a long and very high dorsal fin, soft-rayed from end to end, with an adipose fin behind it. The dorsal fin has 41 to 44 rays and occupies the greater length of the back. This fin is rounded in outline, about twice as high as the fish is deep, and can be depressed into a groove along the back. The body is slender, flattened from side to side, deepest at the gill covers, and tapers back to a slender caudal peduncle.
The mouth is wide, gaping to the back of the eye, and each jaw has two or three large fang-like teeth, in addition to numerous smaller teeth. The caudal fin is very deeply forked; its upper lobe is prolonged as a long filament, although most lancetfishes seem to lose this when captured. The anal fin originates under the last dorsal ray, and is deeply concave in outline. The ventral fins are about halfway between the anal and the tip of the snout, while the pectoral fins are considerably longer than the body is deep and are situated very low down on the sides. There are no scales, and the fins are exceedingly fragile.