Importance of the limbs in the physiological control of heat exchange in Iguana iguana and Sceloporus undulatus

摘要

Lizards use physiological mechanisms to control warming and cooling. Theoretical studies have predicted that the limbs are a major site for the physiological control of heat exchange via changes in blood flow during warming and cooling. To test this we measured thermal time constants in Iguana iguana (1 kg) and Sceloporus undulatus (10 g) warming and cooling in a wind tunnel. We isolated the limbs from the environment by wrapping them in cotton gauze and aluminum foil to test for the importance of the limbs as sites of heat exchange control. We used a physiologically based heat transfer model that included the contribution of blood flow to estimate the thermal time constants. In response to long warming and cc( ling, the thermal time constants for warming and cooling differed consistently only in I. iguana. Insulating the limbs wila cotton gauze abolished the difference between warming and cooling in I iguana. In S. undulatus, animals with both it sulated and uninsulated limbs had warming and cooling thermal time constants that were not significantly different. As predicted, the limbs were a major site for physiological control of heat exchange in 1 kg Iguanas. However, the small lizard was unable to physiologically control warming and cooling and is expected to rely heavily on behavioral thermoregulation.