Leatherback Turtle's Third Eye
A pink spot on the Leatherback's head turns out to be a window on a light-sensitive part of the brain.Leatherback turtles have a prominent pink or white spot on the top of their heads, and, according to Dr. John Davenport, Emeritus professor of Zoology at University College Cork in Ireland, it really is a window on their brains. He's found that the thin, pale skin overlays a section of thin bone, which, in turn, covers the pineal gland in the brain. This structure actually has light-sensitive neurons. Dr. Davenport hypothesizes that this cranial "sun-roof" allows the turtle to sense and time solar radiation and determine the "equilux," that day in the fall and spring when day and night are the same length, and which signals the approach of winter. His data suggests that the turtles use this cue to time their migration to warmer waters.