EYES Shark eyes are similar to those of humans in that the eyeball is a rigid structure, containing a cornea, iris, pupil, lens and retina. Some species have an eyelid-like structure called a nictitating membrane, which protects the eye from being injured by thrashing prey while the shark is feeding. Eye size and position vary with species. The eyes of deep-water sharks are often emerald green and adapted to perceive the luminescence of other animals that also dwell where little sunlight reaches. As water passes over the gills, oxygen is absorbed by blood in the gills.
Some sharks have small openings called spiracles behind the eyes at the top of the head.
Spiracles are rudimentary first gill slits and are reduced or absent in most active, fast-swimming sharks. 6 prior hits today.