Astyanax

Astyanax is a genus of freshwater fish in the family Characidae, order Characiformes. Native to Central and South America, species in this genus occupy rivers, streams, and floodplain habitats from southern Mexico to northern Argentina. The group includes more than 100 described species and has undergone extensive taxonomic revision.

These fish are typically small to medium-sized, with laterally compressed bodies and a coloration that ranges from silvery to golden, often with a dark lateral stripe or dusky fins. They are schooling, omnivorous fish that feed on small invertebrates, plant matter, and detritus. In the wild they inhabit a variety of habitats, including fast and slow-flowing waters, with vegetation and cover.

Astyanax mexicanus, the Mexican tetra, is among the most studied members and is famous for including surface-dwelling populations and cave-dwelling morphs that have lost their eyes and pigmentation. This system is widely used to study evolution, genetics, and development.

Reproduction in Astyanax generally involves group spawning in which adults release eggs and sperm into the water; eggs are often pelagic and lack parental care. Incubation times depend on temperature and species.

In the aquarium trade, several Astyanax species are kept for their hardiness and active schooling behavior. They require a spacious, well-filtered tank and should be kept in groups. Some species can adapt to a wide range of water conditions; however, proper care and compatible tank mates are advised. Conservation status varies by species, with many little-studied and potentially threatened by habitat loss and pollution.