Various animals have colonized caves, and in the course of evolution, many have lost their eyes. We still do not fully understand how the loss of an entire organ unfolds as organisms adapt to dark caves. In this study, Ph.D. student Kerry McGowan and colleagues examined a small fish, the cave molly, that colonized caves relatively recently and exhibits functional eyes that are reduced in size. Using gene expression analyses, McGowan et al. showed that several eye-related genes are expressed less in cave mollies compared to their surface ancestors. Evolution has modified many of these genes in other completely blind cavefishes, suggesting that cave adaptation may occur in similar fashions.
McGowan KL*, Passow CN, Arias-Rodriguez L, Tobler M, Kelley JL. 2019. Expression analyses of cave mollies (Poecilia mexicana) reveal key genes involved in the early evolution of eye regression. Biol Lett. 15(10):1-7.
A cavefish from the Cueva del Azufre system in southern Mexico.
Note the small eye. PC: Michael Tobler.