M4 AM Endocrine Disruption in Fish
Monday, 14 November 2005: 8:00 AM - 11:40 AM in Ballroom 4

(MAC-1117-981604) Devlopment of partial and full lifecycle reproductive bioassays in the estuarine mummichog, Fundulus heteroclitus .

MacLatchy, D¹, Dube, M², Peters, R¹, Shaughnessy, K¹, ¹ University of New Brunswick, Saint John, NB, Canada² University of Saskatchewan, Saskatoon, SK, Canada

ABSTRACT- We have developed, in a northern, western Atlantic saltwater minnow, the mummichog (Fundulus heteroclitus), a short-term (7-day) exposure bioassay for reproductive endocrine responses and a lifecycle (adult, embryo, larval, juvenile, adult) exposure to assess population-level effects. The bioassays have been validated by exposures to 17-ethynyl estradiol (EE₂), an environmentally-relevant estrogenic EDS (endocrine disrupting substance) in fish. We have optimized whole organism (plasma steroid and vitellogenin) and tissue (gonadal steroid production) assays for this species and have developed spawning and grow-out procedures for the full lifecycle protocol. In the short-term bioassay, at high (>250 ng/L) EE₂ exposures, the effect on males was depression of androgen steroidogenesis and plasma steroid levels. In females, high EE₂ depressed gonadal production and circulating E₂ levels; however, EE₂ concentrations <100 ng/L caused increased gonadal production and plasma E₂. Male and female plasma vitellogenin responded in a concentration-dependent fashion to EE₂. Endocrine perturbations resulted in changes in reproductive status and progeny development using rhe full lifecycle bioassay. EE₂ causes delays in time to hatch and cumulative hatch in progeny from exposed adults and larvae. At 100ng/L, survival of juvenile fish was higher, some gonadal male fish displayed female secondary sex characteristics, and sex ratios were skewed toward females. In addition, post-hatch males had decreased gonad sizes and females showed increased hepatic vitellogenin. The protocols used are specifically designed to provide mechanistic information linked back to endocrine-mediated effects. Cost-effective short-term bioassays occur in a timeframe suitable to identifying key endocrine responses, while longer-term bioassays link impairments in endocrine homeostasis to effects on reproduction and development. Research in the lab is currently focusing on further standardization of the bioassay as well as approaches to compare effects of EDSs on freshwater and marine/estuarine fish.

Key words: mummichog, ethynylestradiol, fish, EDS