Sensory Adaptations of Fishes to Subterranean Environments

Caves and other subterranean habitats represent one of the most challenging environments on the planet. Other than salamanders, bony fishes are the only vertebrate group that has successfully colonized and are completely restricted to those habitats. Despite being known to science for over 150 years, only recently have cavefishes become model systems for evolutionary studies. Several cavefishes, such as the Mexican characid Astyanax mexicanus, have provided valuable insights into how fishes have evolved to cope with life in perpetual darkness and often-limited food resources. Much less is known about the biology of other cavefishes and their sensory modalities. Here, we summarize the current understanding of nonvisual sensory modalities in cavefishes. Enhancement of mechanosensation appears to be the most common adaptive strategy, but little is known of other sensory modalities in these fishes. Only comparative studies nested within well-resolved phylogenies will clarify the sensory adaptation of fishes to subterranean habitats.