Sharks see everything in black and white as they’re colour-blind-India News and Travel Times Provides India-centric and other News and Features

Sharks are colour-blind with the toothy predators likely forever seeing the world in black and white, according to a study which is the first to investigate the genetic basis and spectral tuning of the shark visual system. The ramifications could be huge, helping to save both sharks and people. “The work will have a major influence on human interactions with sharks,” Discovery News quoted Nathan Hart, a research associate professor at the University of Western Australia’s School of Animal Biology and The Oceans Institute, as saying. “Firstly, this knowledge may enable us to design fishing gear that is more specific for target fish species and thus reduces unnecessary bycatch of sharks. “Secondly, it may help us to design equipment that is less attractive to sharks (wetsuits and surfboards, for example) that may help to reduce attacks on humans,” Hart said. Taking a study from last year as their base, Hart and his colleagues isolated and sequenced genes encoding shark photopigments involved in vision. Photopigments are light-sensitive molecules. Through a biochemical process, they signal this detection of light to the rest of the visual system. Photopigments are found in two places - rods and cones. The former type is more sensitive and is generally used under very dim light. The latter type is smaller and less sensitive, but is faster responding, applying more to righter-light conditions. The researchers determined that the studied sharks, in this case two wobbegong species, are cone monochromats. This means that the sharks only had one type of cone and one type of rod gene, supporting that they are colour-blind. The findings strengthen earlier speculation about not only wobbegongs, but other shark species. Sharks belong to a cartilaginous fish group that also includes skates and rays. Prior research indicates that skates have “no colour vision at all”, Hart noted. “Rays have more than one photopigment and so they have the retinal ‘machinery’ for colour vision,” Hart said. “Recent behavioural tests in my lab have also demonstrated that they have functional colour vision,” he said. Sharks are probably not the only large water dwellers that are colour-blind as other research has indicated that marine mammals like whales, dolphins and seals, cannot detect colours either. “It may be that colour is not useful to them, or that they have lost the pigments for another reason,” Hart said. “It is likely that the ancestors of modern sharks could see in colour,” he added. The study has been published in Royal Society Biology Letters.

Sharks see everything in black and white as they’re colour-blind, finds study