Environmental control of annual testicular cycles in the lizard Anolis carolinensis. I. Interaction of light and temperature in the initiation of testicular recrudescence

Publisher Website
Google Scholar
Abstract
Adult male Anolis carolinensis were placed under several combinations of light and temperature starting in midSeptember to elucidate the environmental factors regulating the initiation of testicular recrudescence (TR). TR normally starts in the fall, proceeds gradually throughout the winter, and is completed in early spring. This pattern appears to be very similar from year to year. TR was greatly accelerated by 14 hours of light daily when body temperatures were kept constant at 32°C; or when body temperatures were fluctuated to emulate a normal thermal cycle (day 32°, night 20°). A pronounced testicular cycle occurred under the latter conditions. If the daily heating (32°) was given at night (with 20°C during the daytime) there was virtually no response to long day‐lengths. A photoperiod consisting of 12 or 6 hours of light daily, with body temperature kept constant at 32°C caused a delay in TR as compared to animals in nature or to those kept at a constant low body temperature (20°C). However, once TR began, it was accelerated by the high temperature.Photoperiods of 0 to 14 hours of light daily had no influence on the initiation or rate of TR at 20°C. Testes developed at approximately the same rate as in nature. After 150 days, the testes were unusually enlarged but spermatogenic activity was still low.These data suggest that even though a distinct photoperiodism is evident in Anolis, day‐length probably acts only in a permissive way to facilitate the temperature response which is the more direct modifier of TR. Different aspects of TR may have different thermal requirements. TR may be spontaneously initiated by an “endogenous trigger” and then modified by the thermal relations of the animal.