Environmental, hormonal and cellular correlates of thermal biology and adaptation in fish.

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This NSERC discovery research program will investigate the function of thyroid hormones and stress proteins (heat shock proteins, HSPs) to understand how fish respond to changing environments and environmental (temperature) extremes. Irrespective of the cause (human versus natural), the world’s climate has been changing over the past 50-100 years and has been more variable. Freshwater fish are ectotherms (unable to use internal processes to regulate body temperature) and restricted in their ability to physically escape inhospitable temperatures, thus they may be particularly sensitive to the effects of climate changes. This program will study lake whitefish, a cold water, thermally sensitive fish that develops at 2-4°C and lives in deep lakes with year round deep water temperatures of 10-13°C. As the most commercially fished, freshwater fish in North America and a fish of great importance to our First Nations People, whitefish are very valuable both economically and culturally. This fact, coupled with their sensitivity to warm temperatures and ease of handling and rearing in the laboratory, make lake whitefish an ideal species to study adaptation to thermal stress and changing environments. Thyroid hormones are key metabolic hormones in all vertebrates (animals with a backbone) and are fundamental in regulating body temperature in mammals and other endotherms. Despite this fact, the role of thyroid hormones in regulating metabolism as it relates to thermal biology and stress remains to be investigated in fish and other ectotherms. This research program specifically seeks to understand the function of thyroid hormones in thermal stress and adaptation to changing temperatures and the precise cellular and physiological (internal) mechanisms involved. The function of thyroid hormones in mitochondrial bioenergetics and biosynthesis under different thermal regimes will be investigated. These studies will lead to a better understanding of thermal biology in ectotherms and may offer insight into the evolution of the role of thyroid hormones in endothermy. One key aspect of this research is my ability to study wild populations of lake whitefish in Saskatchewan that are living in very shallow lakes which in the summer months routinely reach the lethal temperature limit (23-25°C) for lake whitefish. These populations of lake whitefish have adapted to living outside the temperature limits in which the species is normally found. By using a proteomic approach to make a direct comparison of the total protein profiles between fish in shallow lakes and those living in deep lakes in Saskatchewan, my research team will identify the key systems involved in thermal adaption at the cellular level. Over the course of this NSERC discovery program my research team (3 graduate and 8 undergraduate students) and I will make significant advances in our understanding of how fish adapt to changing environments. Ultimately, this work will provide some of the necessary information to help us understand how thermally sensitive fish may adapt and survive a changing climate.