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The present study aimed to investigate the effects of lead chloride (PbCl2) exposure at graded concentrations on the gills of Venus verrucosa. Clams were randomly divided into four groups: group 1 severed as control and groups D1, D2, and D3 were exposed to 1, 10, and 100 µg/L of PbCl2, respectively, during 7 days. The exposure to PbCl2 increased malondialdehyde, lipid hydroperoxide, and hydrogen peroxide levels in a concentration-dependent manner. Results showed also decreases in the contents of total lipids, saturated, monounsaturated, and polyunsaturated fatty acids. Furthermore, a decrease in the amount of omega (ω-3), docosahexaenoic, and eicosapentaenoic acids was noted. However, an increase of omega (ω-6) as well as arachidonic acid and its precursors' (linoleic and eicosadienoic acids) was observed. This change was supported by a significant inhibition in the desaturase and elongase activities of treated gills. In conclusion, our investigation revealed that lipids and fatty acids alteration could be useful as bio-indicator of PbCl2 toxicity. Article Highlights: The content of lead was determined in dose-dependent manner. The fatty acid profile was assessed as bio-indicator of lead chloride gradual exposure. Desaturase and elongase activities were evaluated. [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]