Meeting Abstract
Within-season temperature variability is expected to increase as the climate continues to change, making it increasingly important to understand organism responses to sudden temperature shifts. According to the Metabolic Theory of Ecology (MTE), whole-body metabolic responses to temperature can provide useful insights into the potential effects of temperature on physiological performance and ecological processes (e.g., population growth rates). In this study, we assessed how changing temperatures influenced whole-body respiratory rates in the Mexican axolotl, Ambystoma mexicanum. Axolotls were acclimated to one of three acclimation temperatures (7, 16, and 25 C) for 3 weeks before measuring oxygen consumption across a range of performance temperatures (7, 10, 13, 16, 19, 22, 25, 28 C), such that all combinations of acclimation and performance temperatures were tested. Axolotl respiratory rates were then measured at the new performance temperatures at 2, 4, and 6 days following the temperature shift. Respirometry data were then used to parameterize thermal performance curves based on the Sharpe-Schoolfield model. Immediately following the temperature shift, cold-acclimated axolotls out-performed warm-acclimated axolotls across the full range of temperatures. However, the cold-acclimated axolotls experienced reduced metabolic performance within a few days of exposure to the warmer performance temperatures, followed by a gradual convergence of performance curves for all acclimation temperatures. These results are consistent with the “colder-is-better” hypothesis of thermal biology, possibly driven by responses to thermal stress (e.g., greater energy expenditure) at higher acclimation temperatures.
