[sawrd-teyl, sohrd-] 
| any of several small, brightly colored, viviparous, freshwater fishes of the genus Xiphophorus, native to Central America, having the lower part of the caudal fin elongated into a swordlike structure: often kept in aquariums. |
| sword·tail (sôrd'tāl') n. A small, brightly colored, live-bearing freshwater fish (Xiphophorus helleri) of Central America, having a long tapering extension of the caudal fin in the male and popular in home aquariums. |
swordtail
(Xiphophorus helleri), popular tropical fish of the live-bearer (q.v.) family Poeciliidae (order Atheriniformes). The swordtail is an elongated fish, growing to about 13 centimetres (5 inches) long and characterized, in the male, by a long, swordlike extension of the lower tail fin lobe. The fish is closely related to the platy (q.v.) and, like its relative, has been used extensively in genetic and medical research. Originally green with a red stripe on each side, the swordtail has been bred in many colour varieties
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