Fig. 3.

Sleep and circadian phenotypes in different cavefish species. (A) Cartoon diagram of A. mexicanus, with eyed surface populations (fish on top) found throughout Mexico and Southern Texas, and eyeless cave populations (fish on bottom) in various caves throughout North East Mexico (red box on map). Both a loss of sleep and loss of circadian rhythms have been described for these fish. (B) The Somalian cavefish, Phreatichthys andruzzii, are blind albino fish that inhabit caves in Somalia (map). A loss of light-entrainable rhythms and a gain of food-entrainable rhythms have been described for these fish. (C) Hillstream loaches, Balitoridae, are found throughout Southeast Asia (map). There are eyed, surface-dwelling species (top cartoon) and various populations of fish that have evolved in caves of Thailand and Laos (red asterisks on map). Cave Balitoridae species are either fully or partially eyeless. For all species of fish listed, average sizes are 5–10 cm in length.