The Effects of Water Imbalance on Body Temperature Dynamics During Critical Physiological Processes in an Ectothermic Squamate Reptile, Antaresia childreni

Ectotherms rely on external heat to attain target body temperatures which can vary based on the animal’s current physiological activity. Many ectotherms become thermophilic (“heat-loving”) during crucial physiological processes like digestion and reproduction, behaviorally thermoregulating to increase body temperature higher than what they otherwise prefer. However, there is a positive relationship between body temperature and water loss that dictates increasing body temperature typically elicits an increase in water loss. Animals that inhabit areas where water is at least seasonally limited (e.g., deserts, wet-dry forests) may face a tradeoff between prioritizing behavioral thermophily to optimize physiological processes versus prioritizing water balance and potentially sacrificing some aspect of total performance capability.It is thus far unknown how reduced water availability and subsequent dehydration may influence thermophily in ectotherms. I hypothesized that behaviorally thermoregulating ectotherms exhibit thermophily during critical physiological events, and the extent to which thermophily is expressed is influenced by the animal’s hydric state. Using Children’s pythons (Antaresia childreni), I investigated the effects of dehydration on behavioral thermophily during digestion and reproduction. I found that dehydration caused a suppression in digestion-associated thermophily, where dehydrated snakes returned to pre-feeding body temperature sooner than they did when they were hydrated. In contrast, water deprivation at different reproductive stages had no effect on thermophily despite leading to a significant increase in the female’s plasma osmolality. ii Additionally, the timing of water deprivation during reproduction had differing effects on plasma osmolality and circulating triglyceride, total protein, and corticosterone concentrations. My research provides evidence of the sensitive and complex dynamic between body temperature, water balance, and physiological processes. At a time when many dry ecosystems are becoming hotter and drier, my investigation of dehydration and its influence on thermal dynamics and physiological metrics provides insight into cryptic effects on the vital processes of digestion and reproduction.