A parietal eye, also known as a parietal organ or third-eye is a part of the epithalamus present in some animal species. The eye may be photoreceptive and is usually associated with the pineal gland, regulating hormone production for thermoregulation.

The tuatara is a well known species with a parietal eye, and it is also found in lizards, frogs and lampreys, as well as some species of fish, such as tuna and pelagic sharks, where it is visible as a light-sensitive spot on top of their head. A poorly developed version, often called the parapineal gland, occurs in salamanders. In birds and mammals the parietal organ (but not the pineal gland) is absent.

External link

• Melissa Kaplan's Herp Care Collection

Lizards | Endocrine system

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