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Lead (Pb) is one of the most toxic heavy metals that affect the physiological status of aquatic organisms. The present investigation evaluated the possible toxic effect of lead chloride (PbCl2) on biomarkers responses, DNA damage and histological alterations in Venus verrucosa gills and digestive gland. Three concentrations of PbCl2 (D1:1µgL−1, D2: 10µgL−1 and D3: 100µgL−1) were chosen for V. verrucosa exposure during six days. At the end of the trial, it was found that Pb tended to accumulate in both gills and digestive gland in a dose-dependent manner. However, gill tissues exhibited the highest metal burden. Our results showed an increase of malondialdehyde, protein carbonyls and advanced oxidation protein product levels in both organs following PbCl2exposure. The induction of both non-enzymatic and enzymatic antioxidant systems; as well as the decrease of the acetylcholinesterase activity and degradation of DNA structure was recorded in the gills and digestive gland. The histopathological alterations observed in gills (disruption of lamellas and cilia filaments ...) and digestive gland (lumens occlusion, necrosis and fibrosis) confirmed the aforementioned results. Our data highlighted the short-term toxicity effects of PbCl2 on V. verrucosa and pointed out a high sensitivity of gills towards this metal. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (chromium (VI)), a highly toxic heavy metal, is a common pollutant of aquatic ecosystems. The present study aimed to elucidate the potential toxic effects of chromium (VI) on oxidative stress biomarkers and fatty acids profile in the gills and digestive gland of Venus verrucosa , an ecologically and economically important bivalve species. Three doses of chromium (VI) (1, 10 and 100 μg.L−1) were chosen for V. verrucosa exposure during 7 days under controlled conditions. A significant increase in the levels of malondialdehyde, lipid hydroperoxides and hydrogen peroxide was observed in the gills and digestive gland of chromium (VI)-exposed V. verrucosa as compared to the control group. Furthermore, an induction of enzymatic antioxidant activities (superoxide dismutase, glutathione peroxidase and glutathione S-transferase) and an enhancement of non-enzymatic antioxidant levels (non-protein thiols, glutathione and vitamin C) were marked. An alteration of fatty acids composition was also noted following chromium (VI) exposure. The obtained results highlighted the importance of assessing oxidative damage biomarkers and fatty acids profile in the study of chromium (VI)-induced toxicity in V. verrucosa. • Venus verrucosa was exposed to chromium (VI) at three doses: 1, 10 and 100 μg.L−1. • Chromium (VI) induced oxidative stress in V. verrucosa gills and digestive gland. • Chromium (VI) altered the fatty acids profile in V. verrucosa soft tissues. • V. verrucosa is a good bioindicator of aquatic ecosystems pollution with chromium. [ABSTRACT FROM AUTHOR]

• 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 (HgCl 2) is a highly toxic compound which provokes a wide range of complicated disorders. The present work aimed to investigate the potential effects of HgCl 2 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 HgCl 2 graded concentrations (1, 10 and 100 µg.L−1) for 6 days. Results showed that HgCl 2 exposure caused a significant increase in the levels of hydrogen peroxidase (H 2 O 2) 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 HgCl 2 -treated gills and digestive glands varied in a concentration-dependent manner. Overall, this work presented novel evidences about the mechanisms of HgCl 2 -induced toxicity in bivalves. [ABSTRACT FROM AUTHOR]