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'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. [Read related article: Cavefish Not Blind to Attractions of Surface-Dwelling Cousins]
Click on for more images of the ghostly cavefish and how it compares to its surface-dwelling cousin.