Why are cave-dwelling eels growing skin over their left eyes? It may be evolution in action.

Two moray eels present in caves on Christmas Island, Australia, had pores and skin protecting their left eye.  (Picture credit score: Wen-Chien Huang)

Moray eels that lurk in gloomy, underwater caves seem like adjusting to the darkness by rising pores and skin over their eyes.

The newly described bean-eyed snake moray (Uropterygius cyamommatus) is the primary moray eel species identified to inhabit anchialine caves — caves carved into volcanic or limestone rock which are related to the ocean and whose water ranges fluctuate with the tides. Throughout expeditions to Christmas Island, Australia, and Panglao Island within the Philippines, scientists discovered two specimens that had no seen left eyes, suggesting that the eels could also be adapting to their gloomy surroundings by going blind, one eye at a time.