MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(PET-1117-829478) In vitro steroidogenesis in Golden Shiner (Notemigonus crysoleucas) collected from a Lake Ontario tributary surrounded by pesticide usage.

Peters, L^{1, 2}, Park, B², Struger, J³, Palace, V², ¹ University of New Brunswick, Saint John, NB, Canada² Fisheries and Oceans Canada, Winnipeg, MB, Canada³ Environment Canada, Burlington, ON, Canada

ABSTRACT- Reductions in circulating levels of sex steroids can indicate exposure to compounds impacting the reproductive system of fish. Effects correlated with such reductions include delayed maturation, reduced gonad size and fecundity, and the inhibited expression of secondary sex characteristics. Assessing plasma sex steroid levels in small-bodied species is problematic due to insufficient plasma volumes and potential confounding effects of acute capture stress. Therefore, the use of an in vitro incubation technique to assess the biosynthetic capacity of fish gonadal tissue to produce sex steroids has become a reliable alternative. This in vitro technique was used to examine potential reproductive effects of pesticide exposure in golden shiner (Notemigonus crysoleucas), a small bodied forage fish species, collected from four locations on Twenty Mile Creek, ON. This creek is a tributary of Lake Ontario, and is surrounded by moderate to heavy pesticide usage. Previous laboratory studies have shown significantly lower gonado-somatic indices in female fathead minnows exposed to Twenty Mile Creek water, and an overall delay in maturation. Clopyralid, dicamba, MCPA, 2,4-D, simazine, atrazine, metribuzin and metalochlor residues have routinely been detected in surface waters in Twenty Mile Creek. Results of this field study indicate that the in vitro technique is suitable for evaluating steroidogenic capacity in golden shiners. Correlations with other reproductive parameters that are used to investigate potential impacts of pesticides at different sites will be made.

Key words: steroidogenesis, Notemigonus crysoleucas, reproduction, pesticides