Mutation behind night blindness in humans helps whale sharks see in the dark

Even a fisher’s yarn would sell a whale shark short. These fish—the biggest on the planet—stretch up to 18 meters long and weigh as much as two elephants. The superlatives don’t end there: Whale sharks also have one of the longest vertical ranges of any sea creature, filter feeding from the surface of the ocean to nearly 2000 meters down into the inky abyss. Swimming between bright surface waters and the pitch black deep sea should strain the shark’s eyes, making their lifestyle impossible. But researchers have now uncovered the genetic wiring that prevents this from happening. The study, published this week in the Proceedings of the National Academy of Sciences , pinpoints a genetic mutation that makes a visual pigment in the whale shark’s retina more sensitive to temperature changes. As a result, the pigments—which sense blue light in dark environments— are activated in the chilly deep sea and deactivated when the sharks return to the balmy surface to feed , allowing them to prioritize different parts of their vision at different depths . Ironically, the genetic alteration is surprisingly similar to one that degrades pigments in human retinas, causing night blindness. It remains unclear why whale sharks dive so deep. Because prey is scarce at these depths, the behavior may be linked to mating. But whatever they do, the sharks rely on a light-sensing pigment in their retinas called rhodopsin to navigate the dark w...
Source: Science of Aging Knowledge Environment - Category: Geriatrics Source Type: research