Thermal plasticity in the metabolic performance curve of Diplolaemus leopardinus, an endemic lizard of the Andes Mountains, Argentina

IBARGÜENGOYTÍA, N; BACIGALUPE, L; VICENZI, N; SASSI, P

Simposio; 8th Symposium on the environmental physiology of ectotherms and plants; 2019

In ectotherms, environmental temperature exerts a strong influence on multiple phenotypic aspects such as locomotion, metabolic rate/ energy balance, reproduction and growth. In particular, thermal sensitivity of metabolism is especially interesting due to its ecological relevance and direct effects on fitness. The aim of this work was to evaluate the thermal plasticity in the metabolic performance curve of Diplolaemus leopardinus, an Andean lizard of the North of Mendoza, Argentina. Seventeen lizards were captured, transported to the laboratory, and exposed during two weeks to two acclimation treatments (20°C and 30°C). We used a split cross design: the 17 individuals were assigned randomly to one of the two treatments, and after measuring their thermal traits, they were exposed to the alternative temperature. Metabolic rate was estimated for each individual at five temperatures (20 °C, 24 °C, 28 °C, 32 °C and 34 °C), by quantifying indirectly as carbon dioxide production using an open circuit respirometry system (FMS, Sable Systems, Anderson, NV). We used a Peltier-effect cabin to achieve constant ambient temperatures (PELT-5, Sable System, Anderson, NV). We calculated the thermal performance curve for each individual in both treatments, and obtained the maximum performance and optimal temperature for each curve. Our results reveal that maximum performance was higher in the coldest treatment, but optimal temperature did not show effect of the acclimation temperature. Lizards showed physiological compensatory adjustments to cold temperatures, increasing their metabolic rate. The capacity for thermal acclimation may evolve in response to seasonal variation in climate typical of temperate arid highlands. The increase in metabolism under cold exposure may improve organisms performance, whereas a decrease in metabolism under warm exposure would allow the conservation of energy stores.