Understanding endocrine disruptor effects in fish at various levels of biological organization

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Industrial and municipal discharges, such as pulp and paper mill effluents and sewage, contain compounds known as "endocrine disruptors". These compounds have chemical structures which make them able to mimic fish hormones, such as estrogen and testosterone. When fish are exposed to the endocrine disruptors, their normal hormone systems are altered. This can result in effects such as smaller ovaries and testes, "intersex" (in which both ovary and testis tissue are in one gonad), lower blood levels of reproductive hormones and changes in the numbers of offspring that can be produced. Research in my lab is focused on understanding how pollutants which are endocrine disruptors work to interfere with normal functioning of fish reproductive systems. We are concerned with the effect that endocrine disrupting contaminants can have in coastal systems. We therefore do our studies using a common east coast saltwater minnow, the mummichog (Fundulus heteroclitus). Working in the lab, we expose different life stages of the fish to estrogens and androgens, as well as estrogen and androgen antagonists (block rather than mimic the natural hormones). We then determine at what life stages (e.g., developing embryos/larvae, juveniles, reproductive adults) the effects occur. When we understand what life stages are being affected, we then investigate the biochemical mechanisms by which the contaminants have their effects. We are primarily interested in the effect that the endocrine disruptors have on normal functioning of the ovary and testis in developing fish and in reproductive adults. By determining the mechanisms by which endocrine disruptors work, we hope to be able to develop fish bioassays which will be able to assess the potential of industrial and municipal effluents to cause reproductive effects in fish. The long-term goal is to understand mechanisms of endocrine disruptor effects in wild fish, and therefore to find ways to protect our coastal environments.