Hearing and Acoustic Communication in Cavefishes

The constant darkness of caves and other subterranean habitats imposes sensory constraints that offer a unique opportunity to examine how sensory modalities evolve. Adaptations to the underground environment represent replicate natural evolutionary experiments to a similar extreme environment, as many species have evolved similar morphological, physiological, and behavioral adaptations to survive in perpetual darkness and limited resource. Although fish hearing has been studied for over a century and all fish up to date have been shown to be able to hear sounds, hearing in cavefishes has not been well explored. Moreover, despite the diversity of sound-generating mechanisms that have evolved across the Teleostei, acoustic communication was not demonstrated in any cavefish species. Here we review the evidence for hearing in fishes, and particularly in cavefishes. We also discuss our own results in the group Amblyopsids. We chose to study the Amblyopsids because they are a small phylogenetic group with a large portion of its diversity comprised by cavefish, and its phylogeny well understood.