The effect of sex steroids on primary and secondary sex differentiation inthe sexually dichromatic reedfrog (Hyperolius argus : Hyperolidae) from the Arabuko Sokoke forest of Kenya

The current study examined the role of steroids in primary and secondary se x differentiation in the African reedfrog (Hyperolius argus: Hyperolidae). This species is sexually dimorphic: males have a solid green dorsum and fem ales are reddish-brown with large white spots. This study is the first to r eport the effects of sex steroids on the development of a sexually dichroma tic species and the first to examine the role of sex steroids on developmen t of the vocal sac. Both males and females metamorphosed solid green withou t spots. Approximately 2 months after metamorphosis, control females transf ormed to the female-typical color pattern. Control males never developed th is color pattern (remained green), but developed vocal sacs. To examine the role of sex steroid hormones on primary (gonadal differentiation) and seco ndary (vocal sac development and dorsal coloration) sex differentiation, te stosterone (T) or estradiol-17 beta (E-2) were administered throughout larv al development. At metamorphosis, 53% of the controls were males, based on gross gonadal morphology and histology of a subsample. Both doses of T prod uced 100% males. All E-2-treated animals had ovarian cavities and/or follic les when examined histologically (at both doses) but 50% had testicular tis sue in addition to these ovarian characteristics. Both doses of T induced v ocal sac development and both doses of E-2 induced female coloration. Thus, both T and E-2 induced secondary sex characteristics (vocal sac developmen t and dorsal color change, respectively) but E-2 produced hermaphroditic go nads, whereas T induced complete sex reversal, (C) 1999 Academic Press.