Ubaid KhalidUnlike chimaeras and rays, sharks are unable to see colors and so they are color blind. There are essentially two kinds of specialized cells in the retina of an eye that can pick out light. These cells are called photoreceptors and the two main cell types in vertebrates are rods and cones. The rod cells are extremely sensitive to light and so they work in dim light. They give a black-and-white image of the objects. However, the rods do not have the ability to distinguish colors. Cones are not very much sensitive to low light but they can pick out different light wavelengths.
In case of sharks, they possess rods and cones but in order to see colors, the animal requires different types of cones and not just one type. Actually, the visible light contains different colors with each having its own wavelength. Now to detect the wavelength of each color, the animal must have different types of cone cells that in turn may recognize colors of different wavelengths.
When 17 species of sharks were studied, it was observed that they did not possess different types of cones. They had only one cone type and in some cases, there were only rods and no cones at all. For that reason, if the sharks (and also skates) possess only rods and no cones, it means they can only see the contrast and brightness of the image rather than its colors. On the contrary, the chimaeras and rays possess three different types of cone cells in the retina. Thus, they can easily distinguish colors of different wavelengths.
Sources:
Schmidt, Jennifer V. “Do Sharks See Color?” The Shark Research Institute.
Tripp, Emily. “Do Sharks Have Color Vision?” Marine Science Today
