Parietal Eyes

Lizards, frogs, lampreys, and some fish species possess a unique organ known as a third, or parietal, eye. Though referred to as an "eye," this photoreceptive organ does not "see" in the same way that a standard eye does. Instead, it uses a different biochemical method of detecting light than normal eyes and helps regulate circadian rhythms and hormone production for thermoregulation. The parietal eye is associated with what gland that humans, too, possess? More...