Nothobranchius is a genus of African annual killifish in the family Nothobranchiidae, found across the seasonal floodplains and rain-fed pools of eastern and southeastern Africa — the atlas's countries span Tanzania, Kenya, Mozambique, Zambia, Ethiopia, the Democratic Republic of the Congo, Malawi and Sudan. The 66 species covered are small, 1–4 in, and share the defining trait of the genus: they live in temporary pools that dry up completely each year. Adults die when the water disappears, but their eggs survive buried in the drying mud through diapause, a suspended state of development that can last months, hatching again when the rains refill the pool. This annual life cycle makes Nothobranchius grow, mature and reproduce unusually fast for a fish, a trait that has made species like the turquoise killifish (N. furzeri) important model organisms in vertebrate aging research.
In the hobby, Nothobranchius are prized by killifish specialists for the intense, often shockingly vivid colour of the males, and for the challenge of the annual-species husbandry cycle itself — eggs are collected from a peat spawning medium, stored in a barely damp state to mimic the dry season, then rewetted to trigger a synchronized hatch. Because their habitat is tied to pools that can vanish under agricultural conversion or altered rainfall patterns, the genus carries real conservation weight: the atlas tally shows 24 Vulnerable and 10 Endangered species against 3 Critically Endangered, and Nothobranchius supplies 20 of the species the atlas flags under its CARES conservation program, reflecting how much of the genus's long-term survival now depends on hobbyist breeding programs alongside habitat protection.