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Sharks are colour-blind: Scientists

Last Updated: Wednesday, September 19, 2012 - 22:16

Washington: Scientists have discovered that sharks are colour blind, a find which can impact human interactions with the predator.
Australian researchers have investigated the genetic basis and spectral tuning of the shark visual system for the first time.

"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," co-author Nathan Hart, a research associate professor at the University of Western Australia`s School of Animal Biology and The Oceans Institute, told Discovery News.

"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.

Building on a study from last year, 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 brighter-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 color-blind.

The findings strengthen earlier speculation about not only wobbegongs, but other shark species.

Sharks are not the only large water dwellers that are colour-blind. Other research indicates that marine mammals, such as 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 added.

The study was published in the journal Royal Society Biology Letters.


First Published: Wednesday, September 19, 2012 - 22:16
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