How do deep-sea sharks see in the dark?
There is some light in the deep sea, where many animals are bioluminescent. But most deep-sea sharks don’t see well and probably rely heavily on their other senses: smell, vibration and electroreception. The exception is the deep-sea catshark. Catsharks are well adapted for seeing in dim light. They have big, well-developed eyes with large numbers of light-gathering cells. In addition, in the back of their eyes, catsharks have a reflective surface, called a tapetum lucidum, which helps concentrate dim light. Catsharks, unlike other sharks, can also adjust the size of their pupil. Catsharks get their name from the similarities between their eyes and the eyes of cats, which hunt in the dark on land.
