Ecology: Concepts and Applications 4th Edition by Manual Molles

Exercise 3

Below about 600 to 1,000 m in the oceans there is no sunlight. However, many of the fish and invertebrates at these depths have eyes. In contrast, fish living in caves are often blind. What selective forces could maintain eyes in populations of deep-sea fish? (Hint: Many species of deep-sea invertebrates are bioluminescent.)