Many species of lizards possess a mediam eye on the dorsal surface of the head. The functions of this organ (the parietal or third eye) are imperfectly understood. It is known to secrete the indoleamine hormone melatonin, and is undoubtedly part of a hierarchically-arranged control system for seasonal physiological and activity patterns which includes also the pineal, the retinas of the lateral eyes, and many areas of the brain. Ultimate control of the system (sometimes referred to as the master clock) may lie in the suprachiasmatic nucleus of the hypothalamus.

The parietal eye also has a thermoregulatory function (which is related to the functions described above, since thermo-regulation in lizards has rhythmical components). Experiments involving occlusion or removal of the parietal eye show that two thermoregulatory elements can be distinguished, a relatively log-term effect which may be mediated by melatonin, and an acute response, which is almost certainly not..

The proposed research will involve both laboratory and field studies. The experimental animal will be the lizard Psamodromus algirus, which is abundant in many parts of the Iberian peninsula. The laboratory programme has already commenced and includes background studies of the behaviour of the species. There is now a requeriment for field studies to complement the laboratory work, and to provide a check that behaviour observed in the laboratory is natural and not related to the conditions of captivity