Functional trade-offs between thermoregulation and water balance in a South American Lizard

Abstract

The maintenance of ideal amounts of water and body temperature close to optimal values results in a functional conflict between thermoregulation and water balance, typically with the last being prioritized. Besides presenting high cutaneous resistance for water loss, non-avian reptiles can trigger cooling responses through respiratory evaporative water loss, such as panting and gaping, therefore avoiding brain overheating (selective brain cooling). These responses can be inhibited by dehydration, as observed in few studies restricted to lizards from arid zones. Thus, studies aimed to understand physiological capacities and tolerances associated with these functional conflicts are relevant in specific environmental contexts. Spatial and temporal variations in environmental temperature and precipitation represent key-factors to understanding these process related to thermoregulation, hydric balance, and organismal performance. This becomes urgent especially considering ectothermic vertebrates in the context of anthropogenic climate change in tropical zones, as in South America, in which predictions for the next decades already set increases in environmental temperatures and extensions of dry season duration. In this context, this proposal aims to evaluate the occurrence, threshold, and intensity of gaping and/or panting in both sexes of a South-American lizard species (Tropidurus catalanensis) from Cerrado, in different temperatures and hydration status over two seasons (dry vs rainy), also evaluating the effects on their locomotor performance. The occurrence of selective brain cooling and how it is affected by dehydration will also be investigated. (AU)