THE EFFECTS OF PREGNENINOLONE AND RELATED STEROIDS ON SEXUAL DEVELOPMENT IN FISH (Lebistes reticulatus)

Abstract

70 fish were fed pregneninolone tablets, 21 were injected with testosterone propionate, 36 were injected with progesterone, 32 with desoxycorticosterone acetate, 13 with adrenal cortical extract, and 8 with pregnanediol. 83 animals served as controls, 42 of which were segregated at birth and injected with the steroid solvent, sesame oil. The effects of preneninolone were purely androgenic and this compound fulfilled the expected actions of an androgen in this species, better than testosterone propionate. Pregneninolone fed to immature guppies from birth completely prevented the development of any [female] secondary sex characters and caused the precocious assumption of [male] secondary sex characters. Pregneninolone induced a marked initial precocious maturation of existing germinal elements in sexually immature [male] fish; prolonged treatment resulted in an exhaustion of testes to such an extent that only gonad remnants remained. Testosterone propionate and pregneninolone had no sex-reversing effect on the ovary but caused an inhibition of yolk deposition. Testosterone had effects like those of pregneninolone on secondary sex characters except for an estrogen-like inhibition of [male] red colors. Testosterone-treated [male][male] contained testes which, except for smaller size, were similar to mature testes treated with pregneninolone. Progesterone, desoxycorticosterone acetate, adrenal cortical extract, and pregnanediol had no effects on sexual development in Lebistes.