Correlations between pituitary and testis in sexually maturing male rainbow trout, Oncorhynchus mykiss, during spermatogenesis

Histological changes in the pituitary of sexually maturing male rainbow trout, Oncorhynchus mykiss, were correlated with spermatogenesis in the testes. Granular basophils in the pituitary appeared simultaneously with the development of spermatogonial cysts in the testis. There was no histological evidence that basophils released their granules during spermatogonial cyst formation. A coefficient of correlation was calculated to test the interaction between the numbers of granular basophils and cysts of spermatogonia. The correlation was not significant. These findings suggest that granules from pituitary basophils do not play a significant role in the development of spermatogonial cysts. Histological sections revealed that basophils degranulated rapidly with the appearance of cysts of spermatocytes. A significant correlation (r = −96) between basophils and cysts of spermatocytes occurred when the interaction between these two variables was tested. The negative correlation indicated that pituitary basophils decreased in number as cysts of spermatocytes in the testes increased. These findings provide support for the hypothesis that basophils may play a significant role in the development of spermatocyte cysts in rainbow trout testes. A second nongranular basophil observed in the pituitaries of fish in this study had no apparent correlation with any of the stages of spermatogenesis. While previous investigators have reported the appearance of granular basophils in the pituitary concurrent with the process of spermatogenesis, this marks the first study that compares histological changes in the testis directly with those in the pituitary in sexually maturing rainbow trout. In addition, it reports for the first time a significant correlation between basophils and a specific stage in the cycle of spermatogenesis.