Neuroendocrine and environmental control of puberty in fish

Early sexual maturation leads to a significant loss of body weight during the spawning season, and farmed Atlantic cod (Gadus morhua) of both sexes currently reach puberty as early as two years of age, before reaching commercial size. Photoperiod treatmen t has been the most efficient strategy to delay puberty in cod, and also to manipulate broodstock to spawn out of season. However, further development of effective treatments to delay puberty and control spawning is hampered by the lack of basic knowledge on the regulatory mechanisms controlling pubertal development in cod, most notably the neuroendocrine control where no information is available. The main objective with this project is to elucidate how different forms of GnRH affect gonadotropes in the p ituitary of Atlantic cod during puberty. This will be done by cloning and sequencing of the different GnRH forms and their receptors, monitoring the distribution and expression profiles of GnRH and their receptors in the brain and pituitary throughout pub ertal development, and by investigating how the GnRH and GnRH receptors are regulated by photoperiod manipulation.