The various Xiphophorus species are native to areas of Belize, Guatemala, Honduras, and especially Mexico. All small fishes, they reach maximum lengths of 2.5–14 cm (1.0–5.5 in).
IUCN lists two Xiphophorus species, the Marbled swordtail (X. meyeri) and the Northern platyfish (X. gordoni), as Endangered, while the Monterrey platyfish (X. couchianus) is listed as Critically Endangered.
Xiphophorus species are regularly used in genetic studies and scientists have developed many interspecific hybrids. The Xiphophorus Genetic stock center, founded by Dr. Myron Gordon in 1939 is an important source of these fish for research.
In addition, several species are commonly kept by aquarium hobbyists, especially X. helleri, X. maculatus and X. variatus. In fact, these are a key category in fishkeeping, a group of extremely hardy livebearing fish, along with the molly and guppy, that adapt to almost any water conditions, from cold to tropical, freshwater to fully marine. Unlike many species, these are available almost completely as captive-raised, because of the ease with which they breed.