Scientists Demonstrate Adaptation of Animal Vision in Extreme Cold Environments; Rhodopsin Evolves to Increase Reaction Rates

Cell biologists at the University of Toronto (U of T) have discovered animals can adapt their ability to see even with extreme changes in temperature. The researchers looked deeply into the eyes of catfish living in cold-water streams at altitudes of up to nearly three kilometers (1.6 miles) in the Andes Mountains to find out how. Their findings were published online on June 19, 2017 in PNAS. The article is titled “Evolution of Non-Spectral Rhodopsin Function at High Altitudes.” Vision is initiated when several chemical proteins in the retina are activated. It is a key sensory system that enables organisms to adapt to their environment, as how killer whales did to improve their ability to see underwater in predominantly blue-tinted light. Examining the impact of cold temperatures on the habitats of Andean catfishes, the team of researchers led by U of T evolutionary biologist Belinda Chang, PhD, studied the role of a protein known as rhodopsin that enables vision in dim light. The scientists found that rhodopsin serves another function as well: it accelerates the speed at which vision occurs among the fish living at the highest - and therefore coldest - elevations. "When we think about adaptations to the visual system, light and color are usually the first variables that come to mind," said Dr. Chang, Professor in the Departments of Ecology & Evolutionary Biology and Cell & Systems Biology at U of T. "These results add a new dimension to the question of how complex biological processes can adapt to extreme environments."
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