Sex hormone induction of sex reversal in the goldfish and evidence for male heterogamity

Methyltestosterone and estrone were administered orally to fry of the goldfish, Carassius auratus, daily for two months; thereafter, they were raised on a normal diet. All but one of the methyltestosterone‐treated fish developed into males, while all estrone‐treated fish developed into females. Of seven methyltestosterone‐treated males mated with normal females, six produced progeny in a 1 ♀:1 ♂ ratio and the remaining one produced only females. Of eleven estrone‐treated females mated with normal males, seven produced progeny in a 1 ♀:1 ♂ ratio and four yielded offspring in a ratio of 1 ♀ : 3 ♂. Induction of sex reversal in both directions by heterologous sex hormones was successfully accomplished. The sex ratios of the progeny of hormone‐treated goldfish provide evidence that the male is heterogametic (XY).