COMPARATIVE CYTOTOXIC EFFECTS OF MICRO AND NANOPLASTICS ON THE REPRODUCTIVE PROCESS OF MYTILUS GALLOPROVINCIALIS

Micro and nanoplastics are emerging contaminants of global con- cern due to their persistence in marine environments and the potential to interfere with biological processes in aquatic organ- isms. Their small size facilitates cellular uptake, raising concerns about their impact on reproductive health, particularly in filter- feeding invertebrates. In this study, we compare the cytotoxic effects of polystyrene microplastics (MPs) and nanoplastics (NPs) on the ovaries of Mytilus galloprovincialis after exposure to envi- ronmentally relevant concentrations for 1, 3, and 11 days. Histological and immunohistochemical analyses revealed diffuse follicular atresia in exposed mussels. Hemocyte infiltration implied altered immune activation. No significant structural changes were found in collagen organisation and PCNA expres- sion. MPs, but not NPs, disrupt glycosylation patterns in ovarian cells of M. galloprovincialis. Analyses on cortex alterations in oocytes are currently ongoing. Referring to the possible mecha- nisms leading to the observed tissular alterations, MNPs exposure also disturbed the physiological ovarian redox homeostasis by tar- geting mitochondria. In particular, we found an increase in reac- tive oxygen species production and lipid peroxidation, accompa- nied by a reduction in the mitochondrial superoxide dismutase 2 protein levels as a key enzyme involved in intracellular antioxi- dant defence. The distinct immune and cytological responses between MPs and NPs suggest size-dependent mechanisms of tox- icity. These findings highlight potential reproductive risks posed by micro- and nanoplastics in marine invertebrates and underscore the need for further investigation.