Sex Reversal of Gynogenetic Grass Carp by Implantation of Methyltestosterone

Abstract
Fifty-five-day-old gynogenetic grass carp C. idella, all females, were administered methyltestosterone through release from silicone elastomer (silastic) i.p. implants during 460-656-day treatments in earthen ponds. Gonads of 27 implanted fish were examined; 5 had testes, 9 had bisexual gonads, 8 had gonads with no germ cells and 5 had underdeveloped ovaries. No male germ cells were detected in the gonads of untreated gynogenetic fish. The successful sex reversal of gynogenetic grass crap will permit testing of the hypothesis that breeding a functionally sex-reversed male with normal females will produce only female offspring.