Evaluation of physiological changes in Mytilus galloprovincialis exposed to an isothiazolinone-based compound: A multi-marker approach

The present study aims to assess, through a multi-marker analysis, the changes in physiological parameters in the Mediterranean mussel, Mytilus galloprovincialis, due to exposure to methylchloroisothiazolinone (CMIT). The CMIT is an isothiazolinone-based compound widely employed in the formulations of several commercial products as a biocidal agent. The increasing use of isothiazolinones, especially during the COVID-19 pandemic, has increased concerns about the health of the ecosystem. Therefore, in the present study, specimens of M. galloprovincialis were exposed to environmentally relevant sub-lethal concentrations of CMIT (0.01 and 0.1 mg L^-¹) for 14 days. Responses in target tissues such as haemolymph (H), digestive gland (DG), and gills (G) were assessed. Cytotoxicity and phagocytosis ability were analysed in haemocytes. Also, cytotoxicity was measured in DG cells along with cell ability to respond to osmotic shock via the Regulatory Volume Decrease (RVD) assay. In G, oxidative stress indexes (protein carbonylation, TBARS, and superoxide dismutase) were measured. Findings indicated alterations in cell physiological functionality and osmoregulatory response as well as high vulnerability of biochemical responses. These results demonstrate the potential toxicity of CMIT on key physiological and biochemical parameters. This basic research exploits potency and lays the groundwork for future studies that will fully elucidate the effects of isothiazolinones on model organisms and the wider ecosystem, and indirectly on human health.