Toxic effects of atrazine on freshwater mussels (Elliptio complanata)

Atrazine (ATR) is a commonly found herbicide contaminant in water bodies across the United States. In this study, native freshwater mussels (Elliptio complanata) were investigated to determine histopathological effects and bioaccumulation of ATR under laboratory conditions. Mussels were collected from the Rice Creek Field Station, Oswego, NY, and were exposed to two different concentrations of ATR (15 and 150 μg/L) for 4 weeks. Histopathological phenotypes induced by ATR include reduced or no ciliary epithelium, ciliary cells merged or completely absent, skeletal rods and connective tissue reduced, causing malformed gill filaments; inhibition of condensation of spermatogenic cells and induced necrosis in spermatocytes in testis; disintegration of acini, oocytes, follicles, and epithelium of the duct, disintegration of the yolk and stalk connecting acini to the follicular wall in ovaries. There were no apparent ATR-mediated histopathological effects in the mantle tissue. Liquid chromatography-mass spectrometry was used to quantify the levels of bioaccumulation of ATR in the tissues where the teratogenic effects are observed from the histological analysis. Bioaccumulation of ATR was observed in gills (0.11 µg/g in the ATR 15 µg/L group and 0.51 µg/g in the ATR 150 µg/L group) and visceral tissues (0.11 µg/g in the ATR 15 µg/L group and 0.63 µg/g in the ATR 150 µg/L), correlating with the histopathological phenotypes. ATR's action mechanism is identified as induced apoptosis in the cells. Further investigation is warranted to elucidate the biochemical response and determine the derivates of ATR in this species.