Plasma corticosterone mediates metabolic rate in Cottonmouth snakes
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Abstract
The use of glucocorticoid hormones has become a powerful technique to assess the physiological and behavioral responses to stressful environmental changes. Glucocorticoids are metabolic hormones secreted by the hypothalamus–pituitary–adrenal axis that trigger an increase in glucose metabolism and available energy to cope with a stressor. Stressors originate from environmental, physiological, and behavioral pressures and produce immediate and delayed hormone responses that influence an individual’s metabolic response. The objective of this study was to test the relationship between metabolism and corticosterone (CORT; primary glucocorticoid in reptiles) by comparing baseline and stress-induced changes in CORT with standard metabolic rates in Cottonmouth snakes. I assessed the relationship between stress and metabolism by relating mass-adjusted metabolic rates and residuals from a linear model relating CORT to environmental variables that could potentially influence the stress response. Covariates influencing CORT varied between the baseline and elevated models, with the baseline model having more environmental factors influencing the level of plasma CORT (Julian date, sex, shedding status, and time of day) than stress-induced (body temperature). Both baseline and elevated CORT levels showed a positive relationship with individual metabolic rate. Accounting for factors that influence individual variation in the stress response can provide more information into the potential for natural selection to shape hormonal response resulting from different metabolic phenotypes.