'Blind' Mexican Cavefish
Credit: Richard Borowsky

Although their appearance varies wildly, the freshwater Mexican cavefish (Astyanax mexicanus) is the same species as the surface-dwelling Mexican tetra.

So-called "Blind" Mexican cavefish are an example of convergent evolution, a new study shows. This type of evolution is characterized by several populations repeatedly, and independently, losing their sight and pigmentation as they adapt to their dwellings.