Use of the Australian crimson-spotted rainbowfish (Melanotaenia fluviatilis) as a model test species for investigating the effects of endocrine disruptors.

Few studies have investigated the potential reproductive effects of toxicants on Australian freshwater fish species. The present study uses the Australian rainbowfish (Melanotaenia fluviatilis) as a model for testing the potential effects of 17beta-estradiol. Groups of reproductively active rainbowfish were exposed to waterborne 17beta-estradiol (control, carrier control, and 30, 100, 300, and 1,000 ng/L) for 3- and 14-d periods. Biomarkers of both low ecological relevance (plasma estradiol and testosterone, phosphoprotein, gamma-glutamyltranspeptidase [GTP]) and high ecological relevance (egg counts, hatchability, larval lengths, histopathology) were measured and the relationships between these examined. Relative to the controls, exposed female rainbowfish had a decline in plasma estradiol. An increase in phosphoprotein (vitellogenin) also was observed after exposure to 1,000 ng/L after 3 d, and histological examination of the gonads showed an increase in oocyte atresia at 1,000 ng/L on days 3 and 14. Changes in egg production were observed at 300 and 1,000 ng/L. No changes were detected to egg hatchability and larval lengths of offspring. Although there were no changes in male rainbowfish plasma testosterone or the histological organization of testes, levels of phosphoprotein increased and GTP activities were increased after 3 d of exposure at all test concentrations, but these declined at day 14. The present study demonstrated that, though measurements at the biochemical level were responsive to 17beta-estradiol exposure, fewer changes were observed in markers of higher ecological relevance at the exposures concentrations and durations tested.