Meeting Abstract
As global climate patterns change, quantifying thermal reaction norms for metabolic and hormonal function is increasingly important. In particular, characterizing the physiological response to both heat stress and prolonged cold exposure in ectotherms is essential for understanding the maintenance of long-term energy balance. Glucocorticoids, such as corticosterone, are often assayed to evaluate the physiological response to stress by the hypothalamic-pituitary-interrenal (HPI) axis in reptiles. However, other biomarkers, such as circulating levels of blood glucose and insulin, provide more specific information on energy balance by which we can quantify organismal responses to potentially stressful conditions, including thermal extremes. Under homeostatic conditions, insulin generally modulates glucose uptake into tissues. However, in mammals, there is evidence that under high temperature conditions the typical insulin-glucose relationship is decoupled and insulin responds independently to thermal stress. Few studies have measured insulin in reptiles, especially in response to temperature extremes. Here we use garter snakes (Thamnophis spp.) to quantify the thermal response curve of insulin in reptiles under simulated heat stress and hibernation (cold stress) conditions. Our studies integrate and compare traditional measures (corticosterone) and metabolism with insulin providing evidence that, similar to mammals, the insulin response in reptiles acts independently of its role in glucose regulation under temperature extremes.
