2,4-dichlorophenoxyacetic acid alters intracellular pH and ion transport in the outer mantle epithelium of the bivalve Anodonta cygnea

This study examined effects of the widely-used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on physiological processes related to shell growth of the freshwater mussel Anodonta cygnea. Both in vivo and ex vivo exposure to 2,4-D caused an increased transepithelial short-circuit current across the outer mantle epithelium. 2,4-D exposure also caused an increased pH in some cells of the outer mantle epithelium of the mussels. These molecular-level observations indicate that 2,4-D enhances the activity of V-ATPases on the outer mantle epithelium of A. cygnea due to stimulated hydrogen ion transporters. This physiological imbalance can cause shell formation processes to move out of equilibrium, and ultimately affect the process of shell deposition in this freshwater mussel.