Methyl- and Propyl-Paraben Differential Toxic Potential on the Bacterium Aliivibrio fischeri and Marine Bivalve Mollusks: First Evidence for Their Adverse Effects on Mussel Mytilus galloprovincialis

This study investigated methyl- (MeP) and propyl- (PrP) adverse effects on the bacterium Aliivibrio fischeri (using the Bioluminescence Inhibition/Microtox® bioassay) and the marine bivalve mollusk Mytilus galloprovincialis (in terms of mussel mortality, cellular, oxidative and genotoxic stress indices). Specifically, although the assessment of MeP and PrP behavior into aquatic media (artificial sea water/ASW and 2% NaCl), primarily performed by UHPLC-UV-MS analysis, showed only a slight hydrolysis of PrP to 4-HBA in ASW, both species exposure to different concentrations of each paraben revealed differences among MeP and PrP toxic potential. Interestingly, the Microtox® bioassay showed that PrP mediated toxicity in Aliivibrio fischeri were more pronounced than MeP in all periods tested (5 and 15 min). Similar findings were also observed in hemocytes of mussels exposed for 4 days to 0.3 and 2 μg L-1 of each compound, as revealed by the disturbance of mussel hemocytes’ lysosomal membrane integrity, the enhanced levels of superoxides, nitric oxides, and lipid peroxidation byproducts, as well as the formation of micronuclei. These findings are of great interest, since MeP and PrP differential toxic potential, as well their ability to induce pre-pathological alterations in marine species, like mussels give new evidence for their risk to aquatic biota.