Collaborative Research: IPY: Extremes of Hibernation Physiology: Patterns of Expression, Regulation and Limits

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Because of their high latitude distribution, arctic ground squirrels are naturally exposed to the most extreme seasonal changes in day length and temperature of any hibernator. Arctic ground squirrels have unique adaptations that allow them to thrive under arctic conditions. The proposed work will resolve important questions in hibernation physiology using integrated approaches including respirometry for measuring rates of metabolism and respiratory exchange, stable isotope analysis for assessing changes in metabolic fuel use and body composition, and genomic approaches for a molecular understanding of hibernation in extreme conditions. This project seeks to 1) elucidate which metabolic fuels (fat, carbohydrate, protein) arctic ground squirrels draw from during arctic hibernation, 2) quantify the expression of genes for enzymes involved in metabolic fuel selection, 3) identify lower thermal limits to hibernation at sub-zero body temperatures, and 4) continue monitoring body and hibernacula temperatures in a natural population on the North Slope of Alaska. These field measures will be related to changes in body condition over winter, annual timing of hibernation and other life history events, and effects on reproduction and persistence of this population in the context of climate change. It is anticipated that arctic ground squirrels will hibernate in ambient temperatures as low as -40 degrees C, and that they will increase reliance on protein to fuel metabolism with decreasing ambient temperatures. At low temperatures, regulation of metabolic fuel selection by arctic ground squirrels will be accomplished via increased expression of genes that promote protein metabolism and gluconeogenesis (synthesis of sugar). Because hibernators have been used as models for cerebral ischemia (reduced blood flow to the brain), traumatic head injury, and hypothermia, investigations of the physiology and genomics of hibernation have biomedical implications. Moreover, this research will help us better understand organismal responses to a changing climate in the sensitive arctic ecosystem. This project is interdisciplinary and will provide training, in both field and lab settings, to 1 post-doc, 2 PhD students and undergraduates in molecular, isotopic, physiological and ecological techniques. It is international with a collaborating scientist from the Shanghai Institutes of Biology in China. Results of this research will be disseminated through publications and presentations at regional, national and international meetings and local interpretive displays.