One of the most widespread aquatic organisms in the rivers and estuarine ecosystems, in the world, is Asian clam Corbiculafluminea. This clam, that can adapt to environmental changes, is an invasive species in several areas and it was adopted as a model for toxicity tests. This study evaluated the effects of the exposure to cadmium (Cd), to microplastics (MPs) and their mixtures on C. fluminea. The oxidative stress responses, lipid peroxidation (LPO), changes in the activity of energy-related enzymes and neurotoxicity were assessed on the gill, digestive gland and gonad. The results show that Cd, MPs and their mixtures cause oxidative stress, damage and neurotoxicity. The enzymes superoxide dismutase (SOD), glutathione S-transferase (GST), acetylcholinesterase (AChE) and the LPO levels could be chosen as biomarkers of Cd pollution. Exposure to MPs induced an increase in reduced/oxidized glutathione (GSH/GSSG) ratio and increased AChE activity. The combined exposure to Cd and MPs caused a synergetic effect in gill and gonad, while an antagonism response was recorded in the digestive gland. The results provide new insights for unveiling the biologic effects of heavy metal, microplastics and their mixtures on C. fluminea. Besides, we demonstrated that the Asian clam is a good bioindicator of microplastic pollution that can occur in aquatic environments.

Microplastics (MPs) are a worldwide contaminant of significant environmental concern due to their persistence, widespread distribution, and toxic potential. These plastic particles are taken up by invertebrates such as bivalves. Previous studies have indicated that MPs can serve as carriers for other contaminants, such as heavy metals, thereby increasing their bioavailability to organisms, with unpredictable ecological consequences. Therefore, the main aim of this study was to evaluate the effects of exposure to MPs, cadmium (Cd), and their mixtures (Mix) in the gills, digestive gland, and gonad of the Asian clam, Corbicula fluminea, assessing the oxidative stress responses, LDH activity, and neurotoxicity over 7, 14, 21, and 30 days. The results show that exposure to MPs and their mixtures with the lowest Cd concentration led to the activation of the first line of antioxidant defenses, especially SOD and CAT, in the gills, digestive gland, and gonads. An increase in GST activity was also observed in the gonads. However, the response of GST activity in the gills and digestive gland was opposite that observed in the gonads. Furthermore, LDH activity exhibited contrasting responses, increasing in the digestive gland and decreasing in the gills and gonads. Exposure to MPs induced AChE activity, which contradicts previous findings. The results provide novel insights into the biological responses occurring in different target organs and shed light on the effects of MPs and their mixtures on C. fluminea.