Killifishes and Live-Bearers: Cyprinodontiformes

Physical characteristics: Male green swordtails have a long extension on the bottom of the tail fin that forms a sword. Males grow to 51/2 inches (14 centimeters) in total length, the sword being 1½ to 3 inches (4 to 8 centimeters) long. Females grow to 6 inches (16 centimeters). Both sexes have a grayish green background color. Males have two lines of reddish dots on a squared-off dorsal fin and a line of bright to dark red along the entire body. The sword is shiny yellowish green bordered in black.

Geographic range: The native home of green swordtails is Mexico and northwestern Honduras.

Habitat: Green swordtails live in rivers, streams, warm springs and their runoffs, canals, and ponds with heavy plant life.

The dominant male in a group of green swordtails drives off rivals in a feeding area or an area where females have grouped. (Hans Reinhard/Bruce Coleman, Inc. Reproduced by permission.)

Diet: Green swordtails eat plants and insects.

Behavior and reproduction: The dominant male in a group of green swordtails drives off rivals in a feeding area or an area where females have grouped. These fish are live-bearers. Males insert their sperm into females. The females can store sperm and produce several broods from a single mating.

Green swordtails and people: Green swordtails are used in the aquarium business and are frequently used in medical research.

Conservation status: Green swordtails are not threatened or endangered. ∎