Fundulus

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Fundulus is a group of small ray-finned fishes in the family Fundulidae. They are the main representative genus of Fundulidae and belong to the order Cyprinodontiformes (the toothcarps). Most Fundulus fish lay eggs, not live births. They are typically under 4 inches (10 cm) long, but a few species are larger, such as the giant killifish (F. grandissimus) and the northern studfish (F. catenatus), which can reach about twice the average size.

There are about 39 recognized Fundulus species. Many of them are commonly called killifish or topminnows; the term “studfish” is used for some other Fundulus species and isn’t usually used for the whole genus.

Fundulus species live in a wide range of habitats, including marine, brackish estuaries, and freshwater. This makes them a good model for studying how animals adapt to different aquatic environments.

Scientists have sequenced long-read reference genomes for several Fundulus species (including F. xenicus, F. catenatus, F. nottii, and F. olivaceus) to aid research. Fossil Fundulus species are known as well. The Cuban killifish (Cubanichthys cubensis, a pupfish) used to be placed in Fundulus.