Iguana 3 Eyes (FAQ)

This organ, which is a variation of a brain structure that regulates an animal’s body clock, is usually covered with skin and sits on the head, as shown by the photograph below. It aids in finding low-level illumination in animals that rely on it, and thus aids navigation by moonlight or starlight.

However, vertebrates have four eyes, which is unusual in the extreme. The lampreys are the only ones known to be so endowed. Both these eyes and two parietals are divided, one of which is derived from the parapineal and the other from the pineal. However, lampreys’ exceptionalism in this respect has just been challenged.

Arturo de Frias Marques (Own work) via Wikimedia Commons. CC BY Surgical experiments on lizards have also shown that removing the pineal eye from their body temperature controls their body temperature, a process called thermoregulation.

It appears that it is a pale scale and can’t distinguish shapes or colors, but it does have a tendency to see light and movement, aiding iguanas in identifying predatory birds from above.

If caught, they can also detach their tails and will grow another without permanent damage.

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The third and fourth eyes refer to pineal and parapineal organs, eye-like photosensory structures on the top of the head that play key roles in orientation and in circadian and annual cycles. The new findings help to clarify the evolutionary history of vertebrates’ vertebrates.

The photosensitive pineal organ is present in a variety of lower vertebrates, such as fishes and frogs, according to the researchers. It’s often described as the “third eye” in primitive vertebrates, and it was widespread in primitive vertebrates.

“On the one hand, there was this belief that the third eye was simply reduced in several vertebrate groups, including mammals and birds, and was retained only in lizards in fully land-dwelling vertebrates,” Krister Smith of the Senckenberg Research Institute in Germany. “On the other hand, there is the suggestion that the lizard third eye originated from a different organ, the parapineal, which is especially present in lampreys.” These two ideas didn’t really cohere.