Multifactorial regulation of reproduction and gonadal function in fish

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The NSERC discovery grant has been the cornerstone of my entire research program, with a long-term objective to investigate the hormonal control of reproduction and growth in fish. Gonadotropic and somatotropic processes are highly integrated and involve the hormones of the brain-pituitary-peripheral axis. Changes in metabolism are essential during and after the transition from reproductive to growth phase, especially in oviparous species like fish with high energy demands during gametogenesis. Our findings indicate that thyroid hormones, the hypothalamic gonadotropin inhibiting hormone (GnIH), and gonadotropin-releasing hormone (GnRH), are critical players in the control of pituitary gonadotropin (LH &FSH) and growth hormone (GH) production in goldfish. The same peptides (GnIH and GnRH), produced in the ovary and testis, are also involved in the paracrine control of gametogenesis in fish. General hypothesis: thyroid hormones (THs) work in concert with the pituitary gonadotropins (LH and FSH), growth hormone (GH), and gonadal hormones (steroids & peptides) to regulate reproduction, metabolism, and gametogenesis in fish. To test this hypothesis, we will investigate the control of pituitary hormone production during somatotropic and gonadotropic phases and study changes in metabolic pathways required to sustain reproduction and growth energetically. Furthermore, we will build on our past work to investigate the role of thyroid hormones as a component of a complex multifactorial system that regulates testicular development and gametogenesis through interaction with gonadal hormones. My proposed research will focus on two primary research areas which are directly related and conducted simultaneously to investigate: A)The role of THs in the seasonally related multifactorial regulation of pituitary hormone production & related metabolic energy allocation during reproductive and growth phases in fish B)The role of thyroid hormones working in concert with the brain, pituitary, and gonadal hormones to regulate testicular function and spermatogenesis. The proposed research will be used as a vehicle for HQP training in the broad areas of comparative endocrinology and will involve graduate and undergraduate students and visiting scientists. I am committed to promoting EDI in the training environment and will make every effort to provide a safe working environment free from harassment, bullying, and discrimination. The findings will enhance our understanding of the integrated control of reproduction and growth and associated changes in fish metabolism and provide crucial information on the integrated regulation of testicular development and gametogenesis in fish with relevance to other vertebrate species. The proposed studies will have translational potential in environmental toxicology by improving our ability to assess adverse impacts of environmental contaminants with hormone-like activities in the aquatic ecosystem.