GONADAL DEVELOPMENT IN JAPANESE MEDAKA (ORYZIAS-LATIPES) EXPOSED TO 17-BETA-ESTRADIOL

The purpose of this research was to evaluate the Japanese medaka (Oryz ias latipes) as an ecotoxicological model for the rapid evaluation of environmental estrogens, A novel short-term (48-h) exposure to 17 beta -estradiol is proposed in development of a positive control for disrup tion of gonadal development. Recently hatched medaka fry (30 fry per d ose group) with undifferentiated gonads were exposed to 4.0, 29.4, and 115.6 mu g/liter of 17 beta-estradiol (acetone carrier) for 48 h in a water bath at 25 degrees C. The fry were then grown-out in spring wat er for 2 weeks, killed, and processed for histological evaluation. Hig h lethality was encountered during the grow-out period in the 115.6 mu g/liter dose group. Fry lit the spring water and acetone (carrier) co ntrol groups developed into females or males. Fry exposed to 17 B-Estr adiol developed primarily into females or had testis-ova. (C) 1998 Els evier Science Ltd. All rights reserved.