Abstract
Nonylphenol ethoxylates (NPEOs) were evaluated in the laboratory for potential effects on the reproductive physiology and fecundity of fathead minnows (Pimephales promelas). Groups of three adult male and three female fathead minnows were exposed in a continuous flow‐through system to 0, 0.21, 0.65, 2.1, or 7.9 μg NPEO/L for 42 d. Rabbit anti‐goldfish vitellogenin (VTG) antiserum was prepared and a competitive enzyme‐linked immunosorbent assay (ELISA) was adapted for measurement of plasma VTG in fish following exposure. Plasma 17β‐estradiol (E2) and testosterone (T) were also quantified by ELISA at the end of the exposure. Neither survival nor fecundity of fathead minnows exhibited a concentration‐dependent response to NPEOs. No significant differences were observed in plasma VTG concentrations among treatments for males or females. Mean plasma VTG concentrations in females ranged from 291.7 to 895.1 μ VTG/ml among treatments and did not overlap with mean concentrations measured in the plasma of males, which ranged from less than the method detection limit (0.27 μg VTG/ml) to 3.2 μg VTG/ml. Plasma E2 concentrations exhibited a significant difference between males and females within all NPEO treatments, but no differences were observed among treatments. Similarly, plasma T concentrations did not exhibit a concentration‐dependent response to NPEOs.