Bahamian “blue holes” are vertical caves that filled with water during the last 15,000 years. During this time, a few species of fish colonized them. Some blue holes support only the endemic Bahamas Mosquitofish; some contain mosquitofish and a larger predatory fish, the Bigmouth Sleeper.
Dr. Brian Langerhans studies mosquitofish evolution in these habitats. Without predators, their populations are dense, and they’ve evolved a sleek, streamlined body shape, an energy-efficient form for foraging.
However, in habitats with predators, mosquitofish evolved a robust body shape which enables them to quickly flit away from the sleeper.