Burrowing in the freshwater mussel Elliptio complanata is sexually dimorphic and feminized by low levels of atrazine

This study examined the potential feminizing effects of the widely-used herbicide atrazine on the freshwater mussel Elliptio complanata. While the majority of E. complanata are dioecious, the gonads in any given individual have the potential to express anywhere between fully male and fully female. The researchers had unpublished data indicating that female E. complanata burrow less than males, thus potential endocrine-disrupting effects of atrazine were studied through this endpoint, as well as through analyzing vitellogenin (an egg yolk protein precursor) levels in gonadal tissue.

Mussels exposed to atrazine burrowed approximately 20-30% less than same-sex controls, with mid-level doses (15 µg/L) causing the largest difference in burrowing. Vitellogenin levels were significantly higher in male E. complanata exposed to atrazine, as opposed to those not exposed. Overall, this study indicated that atrazine has a feminizing effect on E. complanata.