Hormonal induction of sex reversal in fish

Abstract

Hormonal induction of sex reversal is possible in 47 species (15 families) of gonochores (34 species, nine families) and hermaphrodites using one of the 31 (16 androgens, 15 estrogens) steroids. Intensity of endocrine treatment for sex reversal increases among the taxonomic groups in the following order: Cichlidae < Cyprinodondidae < Anabantidae < Poecilidae < Salmonidae < Cyprinidae. 17 α-methyltestosterone and estradiol-17β are the most preferred hormones for induction of masculinization and feminization, respectively. Dietary treatment and immersion are the most acceptable methods for administering steroids. The labile period is not always restricted to a specific life stage at least among poecilids, anabantids, cyprinodontids, cichlids and cyprinids. Androgen treatment of (castrated) sterile fish may restore masculinity but estrogen may fail to restore femininity. Hormonal induction of sex reversal may result in higher mortality among fish bearing homogamous (XX or ZZ) genotypes. However the sex reversed fish especially the cichlids and cyprinids may grow up to two to three times faster, when treated at optimal dose for sex reversal. Hormonally sex reversed fish may also suffer from poor reproductive performance.