Meeting Abstract
Glucocorticoids (GCs) are hormones involved in metabolism that are also released in response to stressors, where they induce numerous behavioral and physiological responses to help the organism cope with the stressor. In many vertebrates, both baseline and stress-induced GCs change on a seasonal basis. It is hypothesized that seasonal variation in GCs is related to seasonal changes in energy balance, reproduction, and immune function. To better understand seasonal patterns of GCs, we measured baseline and stress-induced corticosterone (CORT) in field-caught male and female Allegheny Mountain Dusky salamanders across three seasons (spring, summer, and fall). In this species, mating occurs in the spring. Baseline plasma CORT was highest in the spring and declined over the course of the summer. Additionally, the CORT response to capture and handling was less in the spring compared to summer and fall. Both the seasonality of baseline CORT and the magnitude of stress-induced GCs were greater in females relative to males. In addition, plasma CORT was negatively correlated with relative fat body condition, but had no interaction with white blood cell differentials. We are currently measuring gonadal masses to determine whether reproductive investment contributes to seasonal CORT patterns. Overall, this study showed that plasma CORT does vary seasonally, and the variation is influenced by sex and fat body condition, suggesting that reproductive investment and energy balance play a role in seasonal patterns of GCs.
