Serrasalmidae

Serrasalmidae is a family of freshwater fishes in the order Characiformes, native to tropical South and Central America. The group includes the well-known piranhas and their herbivorous relatives, commonly referred to as pacus, with a broad size range across species.

Morphology and dentition vary across the family. Serrasalmids are typically laterally compressed, with a strong jaw apparatus. Teeth are highly specialized: piranhas (genera such as Serrasalmus and Pygocentrus) have sharp, triangular teeth adapted for cutting flesh, while many pacus (including Colossoma, Piaractus, Mylossoma, and Myleus) possess flatter, molariform teeth for crushing seeds and fruit.

Ecology and behavior are diverse within the family. They inhabit rivers, floodplains, and flooded forests and often form schools. Diets range from omnivory and frugivory in pacus to carnivory in some piranhas, with opportunistic feeding in many species. Reproduction is mainly egg-based, with most species releasing eggs into the water during seasonal floods; some species exhibit timing linked to rainfall and river dynamics.

Taxonomy and representatives. Genera commonly associated with the piranha lineage include Serrasalmus and Pygocentrus. Pacus are represented by Colossoma, Piaractus, Mylossoma, and Myleus, among others. The group is of considerable ecological importance in Neotropical freshwater systems and has substantial economic value for local fisheries and, in some cases, the aquarium trade.

Conservation and human interactions. Serrasalmids face pressures from overfishing, habitat loss, and water management changes. Some species are important food resources, while others are kept in aquaculture or kept as ornamental fish in captivity; non-native introductions have affected local ecosystems in certain regions.