Wobbegongs spend most of their time on the sea floor and hunt mostly at night using an unusual sit-and-wait ambush strategy
The PhD study bt Dr. Susan Theiss showed that the wobbegong visual system contains only a single class of cone photoreceptor. Cone photoreceptors are the retinal cells that are used for vision under bright light conditions, whereas as rod photoreceptors are used in dim light.
These previous studies looked at opsins, which are light-sensitive proteins found in the photoreceptor cells of the retina. Rod opsins are used in low light and produce a black and white image, while cone opsins are used in bright light, and often to see colours.
Two or more different types of cone opsins are needed for colour vision.
In the latest study: Cone monochromacy and visual pigment spectral tuning in wobbegong sharks, published in The Royal Society's Biology Letters, the researchers isolated the genes that encode the cone visual pigment proteins and found that only one cone pigment gene was present.
Their findings confirm that wobbegongs possess only one cone opsin, meaning they see the world in shades of grey.
Sharks are highly visual animals, but the world they see lacks colour and will appear as shades of grey like we see when we watch a black and white movie. It may be possible to use this knowledge to change the way a shark reacts to certain objects.
—Assistant Professor Nathan Hart from the UWA Oceans Institute and School of Animal Biology