Xiphophorus hellerii Heckel, 1848, Orizaba, Mexico.
OTHER COMMON NAMES
English: Swordtail; Spanish: Cola de espada.
Males grow to 5.5 in (14 cm) in total length, with a sword length of 1.6–3 in (4–8 cm). Females grow to 6.3 in (16 cm). Sexually dimorphic. Males and females have basically the same grayish green background color. Males have a gonopodium, a slender body, a long extension on the bottom of the caudal fin forming a “sword,” two lines of reddish dots on a squared-off dorsal fin, and a pronounced line of color that is bright to dark red to almost brown running longitudinally along the body from the snout through the eye to the base of the caudal fin. Sometimes paralleled on the flanks by one or two fainter reddish lines above and below. The sword is an iridescent yellowish green bordered in black. Females are robust and rounded, with squared-off anal and dorsal fins. Caudal fin is asymmetrically rounded, with a hint of a protrusion from the lower part of the fin. There is a shadow on the area over the vent (gravid spot).
in Rio Nantla, Veracruz, Mexico, to northwestern Honduras. Naturalized in the continental United States (ten states) and Hawaii; Michoacan, Morelos, Nuevo Leon, and Coahuila, Mexico; Transvaal, South Africa; Sri Lanka; New Caledonia, Australia; Fiji; Guam; Rйunion; and Madagascar.
Inhabit rivers, streams, warm springs and their runoffs, canals, and ponds with heavy vegetation.
While they are not territorial, male swordtails form hierarchical groups. A dominant male drives off rivals within a feeding domain or an area where females have congregated. The mating success rate of a dominant male is about 80% within his area of activity. Females form hierarchical groups of several individuals that stay in close proximity to a dominant male.
FEEDING ECOLOGY AND DIET
Plant material and insects form the greatest part of the diet. In aquaria they are voracious, consuming a wide variety of foods, such as fruit flies, frozen or live brine shrimp and chironomid larvae, flake foods, high-protein paste foods, small fish, and algae.
Green swordtails are live-bearers. Males impregnate females by means of a gonopodium. Females can store sperm and may produce, from a single mating, several broods over an eightmonth period. Swordtails undergo lecithotrophic (type 1) gestation and development, with fry being produced approximately every 30 days. Brood sizes are fairly large; 100 or more fry may be produced by a large female.
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
The green swordtail has considerable economic importance in the aquarium trade and frequently is used in genetic and
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