Mechanisms of environmental acclimation and adaptation in fish

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The long-term goal of my research program is to understand the mechanisms that fish use to cope with environmental change, and how these mechanisms vary among individuals and populations. In the next six years, we will focus on mechanisms related to the regulation of aerobic metabolism because aerobic metabolism is a fundamentally important process that is known to shape the distribution and abundance of animals and that may even play a role in the generation of new species. We will examine the mechanisms underlying plasticity and intraspecific variation in aerobic metabolism in Atlantic killifish, Fundulus heteroclitus. This is an ideal species in which to pursue our research objectives because we have previously shown that killifish exhibit substantial plasticity in aerobic metabolism in response to changes in temperature and oxygen levels: two environmental factors are extremely important for fish. In addition, we have shown that northern populations of killifish have higher aerobic metabolic rate and development rate than do southern populations, but they have poorer ability to tolerate low oxygen levels. In contrast, northern populations of killifish are able to increase the amount of mitochondria, the organelle responsible for aerobic metabolism, in response to cold temperatures, while killifish from southern populations cannot mount this compensatory response. Our proposed research takes advantage of this variation in multiple aspects of aerobic metabolism as a window into the mechanisms that underlie the responses of aerobic metabolism environmental change. Our proposed research is divided across three interrelated themes in which we will examine: 1) plasticity and intraspecific variation in aerobic metabolism, 2) the role of variation in aerobic metabolism during early development, and 3) the relationship between variation in aerobic metabolism and the ability to tolerate low environmental oxygen. We will examine responses that occur at various time scales, including responses due to phenotypic plasticity that occur on a time-scale of days to months, and responses that vary between populations as a result of changes due to adaptive evolution that occur over many years. We propose to use cutting-edge genomic methods combined with detailed biochemical and physiological analyses, with a particular emphasis on mitochondrial function. Together this research will provide novel insights into the genetic, physiological and molecular mechanisms underlying the responses of aerobic metabolism to changes in temperature and oxygen levels on both short and long time scales and reveal the mechanisms that fish use to cope with environmental change. This fundamental work is particularly important because this mechanistic knowledge can be used to help predict the likely responses of fishes to the effects of global climate change and environmental degradation due to human activities.