Effects of exogenous hormones on the pituitary gonadotrophic activity in tilapia previously treated with a dithiocarbamoylhydrazine derivative (i.c.i. 33,828)
1973
Dadzie, S., Department of Biology, University of Stirling, Stirling, Scotland
Administration of pituitary extracts and commercially prepared hormones into Methallibure- treated Tilapia has revealed that the chorionic gonadotrophins (HCG and PMS) have stimulatory effects on the regressed gonads and on the appearance of the secondary sexual characters and spawning behaviour. On the other hand, the gonadotrophic hormones (FSH and LH), when used singly, were less effective. However, the gonads, the secondary sexual characters, and spawning behaviour, were all stimulated when the two hormones were administered in combination. Evidence is presented on the regulation of maturation directly by the pituitary. The possibility of the elaboration of one gonadotrophic hormone with LH and FSH-like properties, in the pituitary gland of Tilapia, is discussed. Extracts of carp pituitary suppressed gametogenesis and gonadal weights in Methallibure-treated fish. In the testis, the treatment led to an abnormal development. Testosterone propionate also suppressed gametogenesis and gonadal weights, but restored the secondary sexual characters and spawning behaviour. Evidence is presented on th.: control of the secondary sexual characters and spawning behaviour by the gonads (androgens) and its mediation through the pituitary.
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