Fluoxetine alters adult freshwater mussel behavior and larval metamorphosis

We used acute and partial-lifecycle tests to examine the effects of the pharmaceutical fluoxetine on freshwater mussels (Unionida). In acute tests lasting 24–48 h, we determined median effective concentrations (EC50s) for fluoxetine with larval (glochidia viability) and juvenile (survival) life-stages of fatmucket (Lampsilis siliquoidea) and black sandshell (Ligumia recta). In a 28-d behavioral test we exposed brooding adult female wavy-rayed lampmussels (Lampsilis fasciola) to 0.37 and 29.3 μg/L fluoxetine to determine effects on adult behavior (foot protrusion, mantle lure display and glochidia parturition). We also assessed the effects of 24-h exposure of 1 and 100 μg/L fluoxetine on glochidia viability duration and metamorphosis success for the wavy-rayed lampmussel. Fluoxetine EC50s ranged from 62 μg/L for juveniles (96 h) to 293 μg/L for glochidia (24 h). In adults, statistically significant increases were observed in foot protrusion at 0.37 and 29.3 μg/L fluoxetine and lure display rates at 29.3 μg/L; glochidia parturition was not significantly affected at any test concentration. Twenty-four hour exposure of glochidia to fluoxetine did not affect viability duration, but likelihood of metamorphosis to the juvenile stage significantly increased with 1 and 100 μg/L treatments. Our results demonstrated effects of fluoxetine to unionid mussels at concentrations less than previously reported and approaching concentrations measured in surface waters.

► Novel approach combines standardized toxicity assay with sublethal endpoints for FW mussels
► Lowest published LOEC for fluoxetine in FW mussels (adult behavior)
► Exposure of glochidia to < 1 μg/L fluoxetine increased metamorphosis success
► Proposes potential mechanistic pathway for metamorphosis in FW mussels
► Early lifestages of FW mussels among most sensitive animals to acute exposures of fluoxetine