Sex Reversal of Gynogenetic Grass Carp by Implantation of Methyltestosterone

Abstract

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