Integrative cardiorespiratory physiology

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The circulatory system is an essential life support system for all vertebrates. The heart powers this life support system. Consequently, cardiac design and function can determine how animals compensate for, tolerate and adapt to their environment. My vision is to address a central question: What cardiovascular features permit life in a particular environment? Mechanisms are sought that permit fish survival in extremely diverse and changing environments, with a special emphasis on excessive warming and oxygen deprivation. Consideration is given to Arctic, temperate and tropical fishes, as well as unusual fishes that tolerant prolonged hypoxia/anoxia. The experimental approaches range from in vivo studies with whole animals through to cellular studies of electrophysiological mechanisms. Specific experiments will examine the hypoxia-intolerant trout heart, which can be pre-conditioned improve hypoxia tolerance, and the primitive hagfish heart, which survives anoxia for days by suppressing activity via unknown mechanisms. These studies of hypoxic survival will focus on the role that hydrogen sulphide potentially plays as an endogenous metabolic regulator of the heart. In addition, the remarkable and unique ability of the crucian carp and goldfish hearts to beat normally for months during anoxia will be explored. Most fish hearts, however, are hypoxia-intolerant. Thus, a current hypothesis for the upper thermal limit of salmon is that oxygen insufficiency for the working heart triggers cardiac collapse. Studies will examine whether or not this is the case, what sets maximum heart rate and the role of the coronary circulation in fishes that breathe air during hypoxia. Discoveries from this basic research program have the potential to find applications with ecologists who wish to known how aquatic animal distributions are limited by their environment, fisheries managers who seek better tools to conserve wild fish, and those who are interested in the impacts of global warming on the earth's aquatic habitats.