Why animals sleep has long puzzled scientists, although many studies suggest benefits to brain function, memory and learning. But linkurl:research;http://www.cell.com/current-biology/abstract/S0960-9822(11)00292-2 published online today in Current Biology reports that three distinct populations of cavefish sleep dramatically less than their open-water relatives, suggesting that sleep is not a cognitive necessity but an ecological adaptation to the specific environment of a population.
A cave variety in front of two open water varieties of the Mexican tetra, Astyanax mexicanus
Image: Courtesy of Richard Borowsky
"This study is the first to show that cavefish may have dramatic reductions in sleep," wrote linkurl:William Jeffery,;http://www.life.umd.edu/labs/jeffery/ an evolutionary and developmental biologist at the University of Maryland who was not involved in the research. The findings suggest that sleeplessness has "significance for survival in the cave environment."The Mexican tetra is a freshwater fish known mostly for its blind cave variety, although populations also exist in open water. The blind...
E.R. Duboué et al., "Evolutionary Convergence on Sleep Loss in Cavefish Populations," Current Biology, 21:8, 2011.

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