Histological effects of 17 alpha-methyltestosterone on the gonadal sex differentiation of Oreochromis niloticus L. fry
2001
Paller, V.G.V. (Philippines Univ. Los Banos, College, Laguna (Philippines). Inst. of Biological Sciences) Guerrero, R.D. III
The effects of 17 alpha-methyl testosterone (MT) on the gonadal sex differentiation of Nile tilapia (Oreochromis niloticus) were studied. Sexually undifferentiated fry at 7 days post hatching, 9-11 mm total length, were treated with the synthetic androgen at a dose of 0, 15, 30, and 60 mg/kg diet for 25 days. The control and treated fry were histologically processed and examined for light and electron microscopy to observed the effects of the synthetic hormone on gonadal sex differentiation. Gonadal development in the treated fry was similar to the control from 7 until 14 days posthatching (7-14 mm total length). Differences in the histology of the gonads of control and treated fry were noted at 21-30 days posthatching, except in the fry treated with MT-15. Intersexes were observed in gonads treated with MT-30. MT-60 fry showed gonadal masculinization in presumptive female gonads. Gonads of presumptive males developed into structurally defined testes like those of the control. The ultrastructure of germ cells in MT60-treated gonads of presumptive females had very few endoplasmic reticula and mitochondria with undefined cristae. This study showed the degeneration of oocytes in the presumptive female gonads as an effect of synthetic male hormone treatment administered to sexually undifferentiated O. niloticus. This study also confirmed that oogonia develop ahead of the spermatogonia in the species
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