Goodeidae

Goodeidae is a family of freshwater fishes in the order Cyprinodontiformes, commonly known as goodeids or splitfins. They are native to the Americas, with most species restricted to Mexico and parts of Central America; a few species historically occurred in the southwestern United States. The group shows a high degree of endemism and occupies a range of freshwater habitats, from springs and streams to small rivers with clear water and vegetation.

Biology and reproduction: Goodeids are generally livebearers, with internal fertilization. Females give birth to relatively developed, free-swimming juveniles after gestation that varies among species. In many goodeids embryos receive nutrients through placenta-like tissues in the female, a form of matrotrophy that is characteristic of the family. Males typically have a modified anal fin used in courtship, and coloration and fin shape can differ markedly between species.

Ecology: Across habitats they feed on small invertebrates, algae, and plant matter. They often show territorial or selective feeding behaviors, and some species exhibit pronounced sexual dimorphism in coloration or fin morphology, which is often driven by mate choice.

Conservation and human use: Many goodeid species are threatened by habitat loss, water extraction, pollution, and the introduction of non-native fishes. Some species are extinct in the wild but persist in captive populations, and several are the focus of conservation programs. The aquarium trade includes several goodeids, and captive breeding has been important for maintaining endangered species such as Ameca splendens and Zoogoneticus tequila.

Taxonomy: Goodeidae comprises two subfamilies, Goodeinae and Empetrichthyinae, and includes genera such as Ameca, Zoogoneticus, Xenotoca, and Goodea.