Melatonin content of the pineal, parietal eye and blood plasma of the lizard, Trachydosaurus rugosus: effect of constant and fluctuating temperature.

Lizards acclimated to a light cycle accompanied by a thermocycle of 30 degrees C/15 degrees C had a more robust rhythm in pineal and plasma melatonin levels than those acclimated to constant 30 degrees C. At constant 15 degrees C, the melatonin rhythm was abolished entirely. A similar thermosensitivity in melatonin content was found in the parietal eye, indicating that this photoreceptive structure may also be capable of synthesising methoxyindoles.