Effects on reproductive potential and endocrine status in the mummichog ( Fundulus heteroclitus) after exposure to 17α-ethynylestradiol in a short-term reproductive bioassay

Abstract

A short-term reproductive bioassay with the mummichog ( Fundulus heteroclitus) was developed to link changes in endocrine status to reproductive potential subsequent to endocrine disrupting substance (EDS) exposure. Sexually mature mummichog were separated by sex and exposed to the synthetic estrogen 17α-ethynylestradiol (EE 2) at nominal concentrations of 0–100 ng/L for 21 days using a static daily renewal protocol. Half of the fish were sampled on Day 21. At 100 ng/L, male fish had induction of vitellogenin (VTG), increased gonadosomatic index (GSI), decreased testosterone production and decreased circulating 11-ketotestosterone (11-KT). Female fish had decreased circulating estradiol (E 2) and testosterone (T) at 100 ng/L. There were some impacts at lower concentrations of EE 2 in both sexes, though the results were not consistent. On Day 21, the remaining male and female fish were combined at each treatment and exposed for an additional 7 days during which spawning and fertilization success were also assessed. Males exposed to 100 ng/L EE 2 exhibited VTG induction, increased GSI, and decreased T production on Day 28. Female fish had increased E 2 and T production at 1 and/or 10 ng/L and circulating E 2 levels remained depressed above 10 ng/L. Female fish exposed to 100 ng/L spawned fewer eggs; fertilization was also impaired. In a parallel exposure, measured EE 2 water concentrations were approximately 10–20% of nominal for the 100 ng/L EE 2 treatment over a 24-h static exposure; levels in the other treatments were below detectable levels. Fish exposed to nominal concentrations of EE 2 below environmentally relevant levels (i.e., <10 ng/L) showed minimal effects while both the endocrine system and reproductive potential were affected at 100 ng/L EE 2 (nominal).