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Title: | CIRCULATORY AND METABOLIC ADAPTATIONS TO HIGH ALTITUDE IN DEER MICE (PEROMYSCUS MANICULATUS) |
Authors: | Wearing, Oliver H. |
Advisor: | Scott, Graham R. |
Department: | Biology |
Publication Date: | 2022 |
Abstract: | High-altitude deer mice (Peromyscus maniculatus) have evolved to thrive in a persistently cold, low-O2 (i.e., hypoxic) environment that many low-altitude natives find inhospitable. As a result of strong directional selection on the aerobic capacity for heat generation (i.e., thermogenesis), these small endotherms have evolved an enhanced aerobic capacity in hypoxia. However, the physiological modifications regulating tissue O2 supply that might underlie this evolved change in aerobic capacity remain unresolved. Furthermore, very little attention has been paid to mechanisms that possibly reduce routine metabolic demands as a means of coping with cold hypoxia. The overarching goals of my Ph.D. thesis were: A) to understand the integration and mechanistic underpinnings of changes in circulatory physiology that underlie evolved increases in aerobic capacity in high-altitude deer mice; B) to elucidate the effects of chronic exposure to hypoxia or cold hypoxia on cardiovascular physiology, and C) to uncover potential strategies for reducing metabolic demands in high-altitude deer mice. I showed that (i) evolved increases in haemoglobin-O2 affinity and tissue O2 diffusing capacity likely interact to enhance aerobic capacity in hypoxia, and (ii) that evolved changes in adrenergic control of the heart likely contribute to increase cardiac output and thus help enhance aerobic capacity. I also showed that hypoxia alone has relatively modest but sex specific effects on routine metabolism, body temperature, and cardiovascular function in mice. However, cold hypoxia leads to energy-saving reductions in body temperature setpoint that curb the metabolic costs of endothermy, and high-altitude deer mice have evolved a lower body temperature than their low-altitude counterparts. My thesis shows that both environmentally-induced plasticity and evolutionary adaptations in circulatory physiology and metabolism help improve O2 supply and reduce O2 demands in high-altitude deer mice, to help them cope with the unremitting cold and hypoxic conditions at high altitude. |
URI: | http://hdl.handle.net/11375/27682 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Wearing_Oliver_H_2022June_PhD.pdf | 3.73 MB | Adobe PDF | View/Open |
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