EFFECT OF PHOTOPERIOD ACCLIMATION ON THERMOREGULATION OF LIZARD, SCELOPORUS UNDULATUS

Preferred temperatures of Sceloporus undulatus, which were acclimated to 20°C under 12 hour and 6 hour photoperiods, were determined in a thigmothermal gradient. The longer photoperiod (12 hours light) increased the preferred temperature in lizards collected in May while the shorter photoperiod (6 hours light) decreased the preferred temperature in lizards collected in July. Response in the preferred temperature to photoperiod is suggested to be a physiological adaptation which facilitates the use of the mechanism of acclimation of the thermal tolerance to seasonal changes in environmental temperatures. Photoperiod differences did not alter the criitcal maximum or lethal maximum temperatures. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company