Sex hormone induction of sex reversal in the teleostClarias lazera and evidence for female homogamety and male heterogamety

The fry of Clarias lazera were administered orally with 17-α-methyltestosterone (MT) at a dose of 100 μg/g of diet for 60 days and 17-β-estradiol (ED) at a concentration of 100 μg/g of diet for 90 days, respectively. Of three MT-treated males which were individually mated with normal females, one produced all female offspring, supporting the belief that the female of C. lazera is homogametic. This MT-treated male possessed two testes, which consisted of many lobules with numerous sperm and a few primary ova situated on the sperm duct of only one testis, showing direct evidence that this MT-treated male was a sex reversal with female genotype. Of three ED-treated females which were individually mated with normal males, one produced offspring in a 3♂:1♀ ratio, providing evidence that the male of C. lazera is heterogametic. This ED-treated female possessed two ovaries, in which there were many mature and primary ova and a few cyst-like testes situated on the surface of only one ovary, indicating direct evidence that this ED-treated female was a sex reversal with male genotype.