Nothobranchius

Nothobranchius, known as nothobranchs or simply nothos, is a genus of small, freshwater killifish, classified in the family Nothobranchiidae in the order Cyprinodontiformes. There are about a hundred species in the genus, many with very small distributions. They are primarily native to East Africa from Sudan to northern South Africa, whereas a dozen species are found in the upper Congo River Basin, with the greatest species richness being in Tanzania.

Nothobranchius typically inhabit ephemeral pools that are filled only during the monsoon season, and show extreme life-history adaptations to survive the dry season. When their habitats dry up, the adult fish die and the eggs survive encased in the clay during the dry season. The embryos survive the dry season by entering diapause, facilitated by their specialized eggs that have a very hard chorion and are resistant to desiccation and hypoxia. These species reach maturity very quickly once diapause is broken and have a very short life span; one species, Nothobranchius furzeri, reaches maturity in 17 days and seldom lives beyond 6 months.