PINEAL-GLAND AND CIRCADIAN LOCOMOTOR-ACTIVITY RHYTHM IN THE LACERTID GALLOTIA-GALLOTI EISENTRAUTI - PINEALECTOMY INDUCES ARRHYTHMICITY

In order to contribute to a comparative view on lacertids, the effect of pinealectomy on the freerunning activity displayed under constant d arkness and temperature (27.5 degrees C +/- 0.5) has been studied in t he lizard Gallotia galloti eisentrauti. Animals showed an entrained mo tor activity rhythm under an initial light-dark (12:12 hours) routine and freerunning circadian periods ranging between 24.1 and 25.5 h duri ng constant darkness (periodograms obtained by Sokolove & Bushell's me thod). After pinealectomy, most animals showed no significant circadia n rhythm, their locomotor activity becoming diffuse throughout the who le 24 h period. Thus, the pineal gland seems to play an important role as a main pacemaker regulating the endogenous activity rhythm under c onstant conditions. This result contrasts with that found in Podarcis sicula where after pinealectomy only changes in length of the freerunn ing period were found.