Histological studies on the testes of pond specimens of Tilapia nigra (Gunther) (Pisces: Cichlidae) and their implications of the pituitary-testis relationship
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T. nigra pond specimens were studied histologically and histochemically to investigate the relative development of the spermatogenetic and the interstitial tissue elements. The earliest phases showed active spermatogenesis but poor development of interstitial tissue. Maximal development of apparently active interstitial tissue occurred about the period of spermiation and shortly afterwards, when spermatogenetic activity is low. It is suggested that two pituitary hormones (an FSH-like and an LH-like hormone) would best explain this situation, the FSH-like principle probably being active largely in the early phases of the testicular growth while the LH-like principle probably reaches maximal effect at about the spermiation period. It is also suggested that in the early phases of testicular growth, the interstitial tissue probably does not mediate pituitary stimulation of spermatogenesis. Pond conditions seem to stimulate testicular growth and maturity as judged from the more advanced sexual stages of the gonads and the sexual colouration of pond specimens over lacustrine samples.