The Parietal Eye of the Iguana - Discover How the Iguana"s Third Eye Works and Its Intended Purpose

There is something about iguana anatomy that many people do not know.
The iguana not only has two eyes on either side of his head, but also a "third" eye, referred to as the parietal eye.
The name parietal comes from the fact that the eye is positioned between the raised areas of the parietal bones of the iguana's skull.
The third eye is positioned on the very center top of the iguana's head.
It is not a cyclops type of an eye, staring up at you and blinking.
It basically appears as a small round scale on most iguanas.
On a bearded dragon, the third eye usually blends in so well with its coloring you can barely see it.
This third eye does contain a lens, but the lens interprets light and darkness, as in shadows and highlights.
The parietal eye lens does not "process" shapes, images, or colors.
Actually it is not an eye at all, but a light and energy monitor to indicate environmental changes from overhead.
The eye serves as the iguana radar motion detector, in a sense.
Most all of us have heard the phrase "sleeping with one eye open.
" That is pretty much what an iguana does.
In the wild, when an iguana basks in the sun, the third eye easily detects changes in the highlights and shadows of the environment.
These changes in light can indicate danger, a predator, or simply that it is time for the iguana to move from sun to shade.
The eye serves as the iguana's thermoregulator, or thermostat, aiding him in determining when to change locations to regulate his body temperature from warmer to cooler or vice versa.
It is amazing that an iguana can detect a plane or bird overhead in the sky that we may not even notice.
The third eye is that keen.
Iguanas will dodge or duck at highway overpasses, bridges, and railroad trestles when riding with you in the car.
Owners should also bear in mind not to suddenly reach from above into the iguana enclosure to pick up your pet because the third eye will alert him to react.
For this reason, some people associate the third eye with aggressive behavior.
However, it is not the third eye causing this aggression.
The iguana just instinctively feels threatened or launched into a higher awareness that something is afoot because of the light and shadow changes and the sudden detection of movement.
It is also believed that the third eye has some effect on the breeding behavior of iguanas.
It is known to be associated with triggering hormone production.
There are still some questions as to all of the purposes and functions of the iguana parietal eye.
As more research and study is performed, hopefully more facts will be revealed.