Variation and repeatability of cutaneous water loss and skin resistance in relation to temperature and diel variation in the lizard Sceloporus consobrinus.

Abstract

Variation in rates of water loss has been proposed to be an important mechanism in the survival of terrestrial organisms, as high rates of water loss in desiccating environments may lead to hydric stress and death. Vapor density deficit, the driving force for evaporative water loss, increases exponentially as temperature increases. Acute temperature changes may be the result of daily behavioral thermoregulation of ectotherms, which may influence the among individual variation rates of water loss. The goals of this study were to determine (1) how rates of cutaneous water loss (CWL) and skin resistance (Rs) are affected by acute temperature acclimation, (2) how rates of CWL and Rs vary throughout the day allowing behavioral thermoregulation and (3) the repeatability of CWL and Rs within and among sampling periods. We measured CWL and calculated skin resistance (Rs) of 30 male Sceloporus consobrinus lizards across three summers. We measured CWL on the dorsal and ventral surface of each lizard at 23°C followed by measurements at 35°C, and three separate times throughout the day. We found a significant increase in Rs and decrease in CWL at increased acclimation temperatures (35°C), a significant difference in CWL and Rs throughout the day allowing behavioral thermoregulation, and support for the repeatability of CWL and Rs. Our results demonstrate variability in CWL and Rs in relation to temperature acclimation and thermoregulation, but mixed evidence for repeatability across treatments. Our results suggest other factors, such as peripheral blood flow, may be influencing the inter-individual variation in CWL and Rs.