Aphanius is a genus of small, hardy toothcarps in the pupfish family Cyprinodontidae, distributed from the Mediterranean basin through the Middle East and Anatolia to Iran, with the atlas's records spanning Greece, Turkey, Albania, Croatia, France, Algeria, Egypt, and Iran. These are compact, deep-bodied fish, most only a few centimeters long, adapted to marginal and often extreme habitats — coastal lagoons, brackish marshes, spring-fed pools, and isolated desert oases — where salinity and temperature can swing widely over a season. Many species are true habitat specialists, confined to a single spring system or short stretch of river.
The genus draws a narrow but devoted following among killifish and brackish-water specialists rather than the mainstream aquarium trade. The Mediterranean toothcarp (Aphanius fasciatus) is the most familiar, prized for its tolerance of salinities from fresh water to full seawater; the Persian killifish (A. farsicus), Mesopotamian killifish (A. mesopotamicus), and Sirhan killifish (A. sirhani) are narrower-range species better known to conservation-minded keepers. Aphanius is also one of freshwater fish's clearer conservation warning signs: because so many species depend on a single spring or wetland, habitat loss, water extraction, and competition from introduced species can eliminate an entire population at once. The atlas lists 6 of its 10 Aphanius species under CARES, and one carries a Critically Endangered rating, underscoring how precarious some of these range-restricted populations have become.