Meeting Abstract
Vertebrate animals respond to environmental stressors by secreting glucocorticoid hormones which help mobilize energy to support physiological processes and behaviors important for immediate survival. Ectotherms rely on environmental temperatures to regulate body temperature (Tb), and many escape extreme temperatures by moving to different microhabitats or constructing refuges. Therefore, ectotherms exposed to extreme temperatures may respond by secreting glucocorticoids in order to support thermoregulatory behaviors and changes in metabolic demands. As it can take time to move and construct safer refuges, it may be beneficial for glucocorticoids to increase in response to extreme temperatures even before Tb rises. In this study, we wanted to test whether exposure to extreme temperatures alone can initiate the glucocorticoid response. Ornate box turtles (Terrapene ornata ornata) with Tbs at 21°C were exposed for 1 hour to 21°C (control), 4°C (cold), or 38°C (hot). While this exposure time allowed for a change in Tb, this was not enough time for Tbs to reach experimental temperatures. We found that glucocorticoid concentrations were significantly higher in the cold exposed group compared to the hot exposed group. Also, we found that glucocorticoid concentration significantly increased as Tb departed from a preferred Tb (~28°C). These results indicate that glucocorticoid secretion may be dependent upon how far Tb departs from a preferred Tb rather than just exposure. However, as Tbs only rose slightly above preferred in our hot treatment, it is unclear whether this response also occurs at extreme hot temperatures. This presentation will conclude with a subsequent study testing the hypothesis that glucocorticoid concentration is correlated with how far Tb differs from preferred Tb at hot temperatures.
