DO MICROPLASTICS MODIFY THE MORPHOPHYSIOL- OGY OF GILLS AND GONADS IN THE MUSSEL MYTILUS GALLOPROVINCIALIS?

Plastic contamination is a contemporary pollution problem; this historical moment is called The plastic Era1. Plastic undergoes fragmentation to form microplastics (MPs), that accumulate at dif- ferent trophic levels. Aquatic organisms ingest MPs, that, binding other pollutants, facilitate their uptake into living organisms, in what is called the Trojan horse effect. This study investigated the effects of polystyrene MPs in the gills and gonads of Mytilus gal- loprovincialis, a good bioindicator of the marine environment and widely exploited as food. Animals were exposed for 48 and 72h to 2 concentrations of 5μm MPs (0.5 and 1μg/mL), alone or conjutaminant. The analyses showed alteration of gills and gonads in all treated animals, regardless of MPs concentration, conjugation with BPA and exposure time. In the gills, alterations in septum and lamellae, presence of granules and infiltration of hemolymphatic cells were found; increased levels of HSP70 and p63 and increased positive cells for the PCNA immunological signal were observed. PCNA is involved in cell cycle regulation, DNA synthesis and repair, HSP70 in protein folding and inflammation, p63 in tissue growth and development; their increase is indicative of cell stress. In the gonads, alterations in the germinal epithelium were demonstrated, with the detachment of cells from each other in males, and degeneration of oocytes in females. The alteration of chromatin profile in spermatozoa was evident. Mucus cells increased in num- ber in both the gills and gonads of treated animals, particularly at the higher MPs concentration. In all organs examined, the analysis of the functionality of the antioxidant machinery showed the occurrence of cellular stress conditions, indifferent to BPA conjugation, but greater with the highest MPs concentration tested. In conclusion, the results clearly demonstrate the stressogenic effect of MPs. The Trojan horse effect for BPA does not seem to occur; further morpho-functional and molecular investigations are need- ed to resolve any doubts.