MORPHOLOGICAL CONDITIONS OF MUSSEL GONADS AFTER EXPOSURE TO POLYSTYRENE MICROPLAS- TICS ALONE AND CONJUGATED WITH BISPHENOL A OR CADMIUM

In the marine environment, plastic contamination is one of the major contemporary pollution problems. Physical and chemical factors such as temperature wave and photo-oxidation cause the fragmentation process and the formation of microplastics (MPs). The small particle sizes and their increased bioavailability1 led to the accumulation of MPs in a wide variety of environments at dif- ferent trophic levels.2 In addition to their intrinsic toxicity, MPs, due to their high surface area/volume ratio and hydrophobicity, can interact with and absorb other molecules/particles present in the environment, acting as vectors and releasing them at new sites, as well as in living organisms. This effect, called Trojan Horse, is based on MPs features (composition, size, shape, color, functional groups). Our research is aimed to verify the cytotoxic effects of polystyrene (PS) microplastics alone and conjugated with bisphe- nol A (BPA) on the gonads of Mytilus galloprovincialis, a good bioindicator of the marine environment.3 In the preliminary study presented here, mussels were exposed to PS (5 μm) alone and con- jugated with BPA for 48 and 72 h at two different concentrations (0.5 μg/mL, 1 μg/mL). Histological analysis showed that treat- ment with PS alone and conjugated caused structural alterations in ovarian follicles and sperm cysts, in a dose-dependent manner; no differences were observed between the different particles. At the highest concentration, the ovary is characterized by mostly degen- erated oocytes; the testis shows the disorganization of germ cells within the cysts. We also recorded the presence of immune cell infiltrates in the connective tissue of all the treated specimens. These preliminary data suggest that MPs alone and conjugated may have a toxic effect on mussels reproduction. Furthermore, biochemical and molecular analyses will be needed to verify whether the conjugated MPs can act as a Trojan Horse in this organism.