Melbourne: Scientists have claimed that sharks are colourblind after they found that the animal's eyes contain only one type of cone photoreceptor, a finding which could someday help to prevent attacks on humans.
For its research, a team from the University of Western Australia and the University of Queensland looked at the potential for colour vision in a number of Australian shark species.
The scientists, led by Nathan Hart, measured the light-sensitive cells in the sharks' eyes using a specialised instrument called a microspectrophotometer and concluded that they have only one type of cone photoreceptor in the retina.
"Humans have three cone types that are sensitive to blue, green and red light, respectively, and by comparing signals from the different cone types we get the sensation of colour vision.
"However, we found that sharks have only a single cone type and by conventional reckoning this means that they don't have colour vision. It has long been assumed that sharks have some sort of colour vision and indeed have a preference for certain colours.
"Our study shows that contrast against the background,rather than colour per se, may be more important for object detection by sharks, and this may help us to design long-line fishing lures that are less attractive to sharks, whilst still effective for the target fish species, and thus help to reduce
the massive by-catch of sharks in this industry," he said
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