Changes in dermal reflectance and vascularity and their effects on thermoregulation inAmphibolurus nuchalis (reptilia: Agamidae)

Abstract

1. The contributions made by changes in dermal reflectance and dermal vascularity to temperature regulation have been studied in the agamid lizardAmphibolurus nuchalis with the use of85Kr and133Xe. 2. Skin reflectivity varied directly with the body temperature, increasing at elevated body temperatures which decreased the rate of absorption of radiant energy. Decreases in body temperature below the preferred are accompanied by decreases in reflectance which increase the rate of absorption of radiant energy. 3. Subcutaneous blood flow varied directly with the body temperature when measured under conditions of thermal stability. This temperature-dependent increase in dermal blood flow is interpreted as a machanism facilitating the transfer of heat between the core and the periphery of the animal. 4. Peripheral blood vessels demonstrate the capacity to autoregulate and may dilate during basking as a result of local heating, facilitating the increase in dermal blood flow. 5. Dead α-MSH-injected animals heated at a faster rate than dead hypophysectomised animals, suggesting that local heating of the skin due to low reflectance is a major factor responsible for increased subcutaneous blood flow during heating.