A paper in Naturwissenschaften by researchers from the Universities of Western Australia and Queensland claims that sharks may be colour blind. Whereas people have 3 cone types capable of receiving red, green or blue light, it seems that sharks may only have one. This implies that contrast against a background might be more important than actual colour. Given that the wavelengths of sunlight are absorbed the deeper you go, starting with reds and yellows, perhaps this shouldn’t be surprising.
The researchers looked at the retinal cells from 17 species of shark caught in Queensland and Western Australia. They are suggesting that their findings might help to design long-line fishing lures that are less attractive to sharks, thereby reducing the chances of them being caught by accident. It might also make it possible to design swimsuits and surf boards that are less “attractive” to sharks.
Apparently many marine mammals such as whales, dolphins and seals, also have only one single, green-sensitive cone type in their eyes. So it sounds as though two different groups of marine creatures have evolved a similar visual design separately. Perhaps in the marine environment, colour is just a distraction and confers no evolutionary advantages. Perhaps the extra information being sent to the brain, is more of a hindrance than a help underwater.