Burrowing in the Freshwater Mussel Elliptio complanata is Sexually Dimorphic and Feminized by Low Levels of Atrazine

Abstract

The widely used herbicide atrazine (ATR) may have endocrine-associated adverse effects, including on behavior. In this study, 120 adult freshwater mussels, Elliptio complanata, were exposed to ATR at the environmentally relevant concentrations of 1.5, 15, or 150 μg/L. Burrowing depth was evaluated hourly for 6 h and at sacrifice animals were sexed by gonad smear. Female controls burrowed overall approximately 30% less than males, the first report of sexual dimorphism in this behavior. Atrazine at 15 μg/L feminized burrowing in both sexes, in that exposed animals burrowed 20% less than their same-sex controls. Males treated with 1.5 μg /L ATR displayed approximately 20-fold higher vitellogenin (VTG) levels than same-sex controls. Higher concentrations of ATR were not associated with increasing effects. A scatterplot showed a weak binomial curve associating low burrowing with high VTG levels. Taken together, these data suggest a nonlinear dose response in behavioral and physiological feminization produced by ATR and support the need to reconsider the widespread use of this compound.

Acknowledgments

This study was supported by an Adelphi University Faculty Research Grant to KF. The funders had no role in the details of the study design; data collection analysis and interpretation; writing of the report; or decision to publish. A special thank you to Peter R. Warny of WildMetro, Inc., in New York for showing us where mussels live and teaching us to collect them and to Matt Sherman and Christopher Powers for maintaining the mussels in the laboratory.