The effect of cadmium chloride on the pituitary ACTH cells, gonadotropin- and thyrotropin-secreting cells, thyroid gland and gonads of the catfish, Clarias batrachus was investigated. Exposure to cadmium chloride caused a significant increase in the ACTH cell nuclear indices at day 7, 14 and 28, whereas the thyrotropin- and gonadotropin-secreting cells showed inactivation and accumulation of secretary products. The epithelial height of the thyroid follicles was also significantly reduced (P < 0.001) as compared to that of the untreated control fish. In experimental female fish, the gonosomatic index had undergone a significant reduction at all intervals studied (day 7, 14 and 28). However, in the male catfish a significant reduction in the gonosomatic index was observed only after exposure for 28 days. Ovarian maturation seems to have become arrested at perinucleolar stage and spermatogenesis at spermatocyte stage. The possible involvement of the hypothalamo-hypophyseal system in gonadal regression was discussed.

Department of Zoology Nagpur University India