Adaptations to Subterranean Life

The loss of characters, especially eyes and pigment, in subterranean animals has attracted the attention of biologists since their first discovery centuries ago. Adaptationist ideas with regard to subterranean organisms were originally developed, not in connection with loss of eyes and pigment, but rather in connection with constructive changes such as appendage elongation and elaboration of extra-optic sensory structures. Three studies of adaptation epitomize adaptation as it applies to subterranean species. In Poulson’s study of life history and metabolic and neurological changes in cave fish, his basic approach was comparative, using related surface-dwelling species. Using quantitative genetics, Culver and colleagues studied the amphipod G. minus, focusing on the adaptation to the darkness of caves. Jeffery and colleagues focused on the causes of eye and pigment degeneration in the Mexican cavefish A. mexicanus. Using an array of techniques, they demonstrated the critical role pleiotropic selection plays.