Cellular mechanisms and ecophysiological consequences of selenium toxicity in fish

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Selenium (Se) is currently recognized as a priority aquatic pollutant in many areas of the world, including Canada. Selenium is efficiently incorporated into aquatic food webs and can act as a developmental toxicant (teratogen) causing deformities in larval fish. However the biochemical/cellular mechanisms that cause deformities, and the long-term physiological and ecological consequences of deformities, are not well understood. The overall objective of this proposed research is to investigate mechanisms of developmental toxicities caused by Se and their physiological and ecological relevance to fish. We will test the hypothesis that oxidative stress resulting from Se exposure plays a key role in causing deformities using the following approaches: (1) incubating embryos in the presence of antioxidants and inhibitors of antioxidants, (2) blocking expression of key mediators of antioxidant status, (3) staining whole fish to identify production of reactive oxygen species and cell death, (4) determining the extent of oxidative cell membrane damage, and (5) determining differences among body tissues in the concentration and speciation (molecular form) of Se. In separate experiments, embryos exposed to Se will be raised to the juvenile and adult stages. In these experiments, we will test the hypothesis that Se-induced deformities cause irreversible physiological consequences that negatively affect fitness of individual fish. These experiments will include (1) swim performance, (2) energy storage/mobilization capacity, (3) physiological stress response challenges, and (4) reproductive capacity. These integrated experiments will address several major data gaps in our knowledge of the aquatic ecotoxicology of Se, namely (1) the role of oxidative stress in Se-induced larval deformities, (2) the physiological consequences of sublethal Se exposure, (3) species and life stage differences in responses to Se exposure, and (4) Se distribution and speciation in fish tissues. The objectives of this research proposal fit closely with my long term research goal, which is to investigate mechanisms of developmental and reproductive toxicities in fish exposed to priority aquatic pollutants.