How the cavefish lost its eyes—again and again

The article discusses the evolutionary history of the Mexican tetra, a species of cavefish that has lost its eyes multiple times. Researchers have found that the cavefish, which live in pitch-black cave environments, have lost their eyes through a process of regressive evolution. The article explains that the energetic cost of maintaining eyes is not worth the benefit for these fish, as they have no use for vision in their dark habitats. Over time, the eyes have become smaller and more rudimentary, until they eventually disappear entirely. This process has occurred independently in different populations of Mexican tetras, suggesting that the loss of eyes is a common adaptation to life in dark cave environments. The article highlights the fascinating insights that the Mexican tetra's evolution can provide into the mechanisms of regressive evolution and the adaptation of species to extreme environments. The research underscores the importance of understanding the evolutionary history of organisms and how they respond to the selective pressures of their environment.