[Circadian and circannuel fluctuations of pineal metatonin content in Testudo hermanni G. (Reptilia-Chelonia) under natural conditions of photoperiod and temperature (author's transl)].

Pineal content of melatonin is measured by RIA. The tortoise, Testudo hermanni, in natural lighting, shows peak night-time melatonin levels during summer (may to september) at the period of greatest activity. During hibernation, melatonin levels are very low and no circadian variation can be detected.