Effects of temperature and thermal acclimation on frog metabolic performance

The threat of global climate change makes it critical to understand how changing patterns of temperature variability influence ecological processes such as population growth rates and predator-prey interactions. According to the metabolic theory of ecology (MTE), rates of ecological processes are fundamentally limited by organism metabolic rates. Metabolism has in turn been found to scale predictably with temperature according to the Boltzmann-Arrhenius (BA) equation for enzyme kinetics, which can be adapted to account for enzyme deactivation at high temperatures (e.g., Sharpe-Schoolfield model). An important outstanding question is how key metabolic parameters, such as the activation energy for metabolism, are influenced by organismal responses including thermal acclimation. In this study, I investigated how thermal acclimation influences key MTE model parameters for adult spring peeper frogs (Pseudacris crucifer), by using the rate of their observable respiratory movements as a proxy for metabolic rate. After holding frogs at one of three “acclimation temperatures” for two weeks, they were transferred to one of eight “performance temperatures.” I then recorded frog respiratory rates at several time points following the transfer. Statistical model fitting was used to estimate key MTE model parameters and to determine whether and how thermal acclimation influenced spring peeper thermal performance. I found that the Sharpe-Schoolfield model provided a better description of the thermal performance curve for spring peeper metabolism than the BA equation, and that thermal acclimation did not significantly alter metabolic responses to temperature so long as mass scaling effects were accounted for in the model.