Development of a reproductive performance test for endocrine disrupting chemicals using pair-breeding fathead minnows (Pimephales promelas)

Existing in vivo tests (with the exception of the full lifecycle test) are not adequate for assessing the reproductive effects of endocrine disrupting chemicals (EDCs) on fish, and hence the need for partial life-cycle tests has been recognized internationally. In this paper we describe the developm ent of a short-term (6 week) reproductive performance test for EDCs using p air-breeding fathead minnows (Pimephales promelas). In the test, reproducti ve performance in paired fish is assessed over two 3 week periods, one with exposure to the test chemical and one without. The test is highly integrat ive and measures effects of exposure to chemicals on fecundity, gonadosomat ic index (GSI), vitellogenin (VTG) induction, and secondary sexual characte ristics (fat pad and tubercles in males). In this test, exposure to butyl b enzyl phthalate (BBP) at a nominal concentration of 100 mu g/L (measured co ncentration between 69 mu g/L and 82 mu g/L) had no discernible effects on reproductive performance. In contrast, all reproductive parameters measured were affected by exposure to 4-NP, albeit some (e.g. VTG induction and red uction in the prominence of secondary sexual characteristics - lowest effec tive dose between 0.65 mu g/L and 8.1 +/- 1 mu g/L [measured]) were more se nsitive than others (e.g. number of eggs and spawnings, where the lowest ef fective dose was between 8.1+/- 1 mu g/L and 57.7 +/- 3 mu g/L [measured]). Concentrations of 4-NP at or above 48 mu g/L [measured] inhibited reproduc tion completely.