Aspectos morfofisiológicos da maturação sexual do salmão do Atlântico (Salmo Salar)

Abstract

The life cycle of salmon is complex and endowed with different life strategies and this complexity is applied to the reproductive life of these fish. In aquaculture, early puberty is still the main problem in commercial farming of Atlantic salmon due to the considerable negative effects of this condition on growth and welfare. The present study aimed to providemorphophysiological evidences regarding the effects of exogenous factors (photoperiod and salinity) and endogenous (treatment with sex steroids) on the neuroendocrine axes that control the growth and sexual maturation of Atlantic salmon. Using the model of maturation in postsmolt salmon we observed that different environmental factors modulated different aspects of spermatogenesis, resulting in a differential activation of the pituitary gland and testis; with salinity stimulating the onset and the shorter photoperiod the completion of spermatogenesis. Studying the effects of sex steroids in early sexual maturation we concluded that high and constant plasma levels of androgens directly stimulated spermatogonial differentiation at theexpense of undifferentiated spermatogonia and that regulatory mechanisms can operate in vivo to avoid that circulating androgen levels are maintained high, in particular regarding to testosterone. Also, the increased number of differentiated spermatogonia was associated with consistent changes in testicular transcript levels for anti-Müllerian hormone (amh) and Insulin-like growth factor-3 (igf3).