Exploring the impacts of mercury chloride exposure on fatty acids profile, oxidative stress response and histomorphological aspect of Cerastoderma edule detoxifying organs

•Risks associated to mercury chloride toxicity were evaluated in the detoxifying organs of Cerastoderma edule.•Increasing exposure concentrations altered the redox status of Cerastoderma edule gills and digestive gland.•Fatty acids modification could be a useful indicator of mercury chloride contamination.•Cerastoderma edule tissues contaminated with mercury chloride exhibited several histomorphological anomalies.•Damages were more pronounced in the gills than the digestive gland. Mercury chloride (HgCl2) is a highly toxic compound which provokes a wide range of complicated disorders. The present work aimed to investigate the potential effects of HgCl2 toxicity on the redox state, fatty acids composition and histomorphological aspect of Cerastoderma edule (C. edule) gills and digestive gland. To this end, C. edule were exposed to HgCl2 graded concentrations (1, 10 and 100 µg.L−1) for 6 days. Results showed that HgCl2 exposure caused a significant increase in the levels of hydrogen peroxidase (H2O2) and malondialdehyde (MDA). Fatty acids (FA) analysis in the treated gills and digestive glands indicated an increase in saturated and monounsaturated fatty acids and a decrease in polyunsaturated fatty acids, mainly eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. However, the levels of arachidonic (ARA) and linoleic (C18:2n-6) acids were enhanced especially at the sharpest concentration (100 µg/L). In our investigation, we noticed a significant alteration in the estimated desaturases and elongases’ activities in the treated gills as compared to the digestive glands. A concentration-dependent increase in the enzymatic (superoxide dismutase, glutathione peroxidase and catalase) and non-enzymatic (metallothionein, reduced glutathione and vitamin C) antioxidants was also observed in all treated C. edule. The histopathological changes detected in HgCl2-treated gills and digestive glands varied in a concentration-dependent manner. Overall, this work presented novel evidences about the mechanisms of HgCl2-induced toxicity in bivalves.