Reproductive and developmental effects of bioactive constituents of pulp mill effluent on female mosquitofish, Gambusia affinis

Although most studies of environmental endocrine disruptors have focused on those with estrogenic or anti-androgenic activity, the masculinization of female mosquitofish represents the earliest example of environmental androgens. Female mosquitofish, Gambusia affinis, were utilized to assess the androgenicity of specific bioactive constituents identified in pulp and paper mill effluent. Male mosquitofish possess an elongated anal fin, gonopodium, used as an intromittent organ in copulation. Gonopodial development can be induced in females through exposure to androgens or chemicals with androgenic capacity. This study first established the use of the mosquitofish anal fin as a bioindicator of androgen exposure. Anal fin ray elongation in female mosquitofish exhibited a dose-dependent response to oral administration of 17alpha-methyltestosterone. Similar responses were observed in vitellogenin expression, gonadosomatic index, and the frequency and number of late-stage vitellogenic follicles. These data established the use of mosquitofish as an appropriate model for endocrine disruption studies. The Fenholloway River (Taylor County, FL, USA) receives effluent from a pulp mill. Female mosquitofish were exposed to androstenedione, which is an androgenic constituent identified in Fenholloway River water and sediment. Oral administration of androstenedione failed to induce gonopodial development at any concentration utilized whereas treatment via the water by the static renewal method induced gonopodial development at concentrations one log dose above and higher than those detected in water from the Fenholloway River. There was also a significant negative association between fish growth and androst enedione concentration. No other significant effects were observed. Female mosquitofish were then exposed via the water by the static renewal method to androstadienedione, which is another androgenic constituent identified in Fenholloway River sediment. Gonopodial development was induced in females following exposure to the two highest concentrations. A significant negative association between overall growth and concentration was observed in androstadienedione exposed females as well as a significant negative association in the number of developing embryos per fish. No other significant effects following exposure to androstadienedione were observed. The results of this study indicate that mosquitofish are a suitable species for use as a model in determining androgenic potential of effluent constituents.