Mechanisms and Evolution of Hypoxia Tolerance

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For most air-breathing vertebrates, decreases in environmental oxygen (termed hypoxia) are a rare occurrence, but when they do occur they can have devastating metabolic consequences resulting in death within minutes. In the aquatic environment however, periods of hypoxia are a common, naturally occurring phenomenon. In light of this, it is perhaps not surprising that among all vertebrates, fish boast the largest number of hypoxia tolerant species. Hypoxia has clearly played an important role in shaping the evolution of traits that enhance their survival during hypoxia exposure. Despite several decades of study, we still do not have a complete understanding of the factors that explain why there is variation in hypoxia tolerance among fish and the biochemical mechanisms that explain why some fish are more tolerant of hypoxia than others. To address this knowledge gap, my research program uses the natural variation in hypoxia tolerance seen among a group of closely related fish species called sculpins, which inhabit the marine near shore environment, from tidepools to deep waters. Some species live only within tidepools, which are environments that are heavily influenced by the daily tidal cycle, resulting in large, daily fluctuations in oxygen, temperature, salinity, pH, etc, while other species are confined to subtidal environments and deeper waters that do not experience fluctuations in these parameters. My research program uses these sculpins along with a combination of common garden experiments and hypoxia exposures, in adults, parents, and developing embryos, to determine whether variation in hypoxia tolerance is due to genetically based natural selection and adaptation or due to previous hypoxia exposure during the organism's lifetime. In addition, we investigate the molecular, biochemical, and physiological mechanisms that explain variation in hypoxia tolerance in these sculpins. Research of this nature is important because the prevalence of aquatic hypoxia is on the rise due to human-related activities, thus fishes and other aquatic organisms are now experiencing unprecedented fluctuations in their environment that are testing their tolerance limits. Understanding the factors that set species' tolerance limits to hypoxia is an essential first step in predicting which animals will be most at risk due to a changing environment. This grant will allow me to train 5 graduate (3PhD & 2MSc) and 2 undergraduate (1 BSc Honors & 1 NSERC-USRA) students per year in the most advanced analytical and conceptual approaches for understanding how animals interact with their environment. **