Thermal physiology and water balance in anurans along an altitudinal gradient in the Atlantic Rainforest

Abstract

Anurans can be regarded as model organisms for the study of thermal physiology and water balance due to their highly permeable skin (which makes them particularly sensitive to water availability in the environment) and ectothermy (which makes them dependent of external heat sources for body temperature regulation). Thus, temperature and water availability are known to exert a strong influence on the ecology, physiology, morphology, and behavior of anuran amphibians and can vary substantially along an ecological gradient. The present study aim to test whether intraspecific variations in physiological and/or molecular parameters can be associated to an altitudinal gradient in the Atlantic Rainforest. First, we will evaluate basic parameters related to thermal biology (critical thermal minimum and maximum) and water balance (evaporative water loss, skin resistance to evaporation, rates of rehydration from free water) of selected species found at low and high areas. Concurrently, for the same species and localities, we will study the levels of aquaporins (AQP) and heat shock proteins (HSP) expression. AQPs are proteins that form channels at the cell membrane, altering cell permeability several folds. HSPs are chaperones functioning during conformational changes of other proteins, under situations of thermal stress. Therefore, the core goal of the present study is trying to understand whether variation in physical (climate) characteristics along an altitudinal gradient are reflected in organismal physiological responses and/or at the molecular level. These two approaches are, however, independent and relevant in their own merit. Nonetheless, the verification of a possible congruency, or not, between these two levels of biological organization can disclose some of the factors possibly involved in an ecologically based variation. (AU)