Early and efficient induction of antioxidant defense system in Mytilus galloprovincialis embryos exposed to metals and heat stress.

The present study aims to elucidate the stress response of early life stages of Mytilus galloprovincialis to the combine effects of selected metals and elevated temperature. For this purpose, we investigated the response of a large panel of oxidative stress markers such as catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) activities and lipid peroxidation (thiobarbituric acid reactive substrates (TBARS) concentration) and metallothionein accumulation (MT) as well as selected gene transcription level and metal accumulation in mussels larvae exposed to a sub-lethal concentration of Cu (9.54µg/L), Ag (2.55µg/L) and mixture of the two metals (Cu (6.67µg/L)+Ag (1.47µg/L)) along with a temperature gradient (18, 20 and 22°C) for 48h. Cu and Ag applied as single or mixture were differentially accumulated in mussel larvae according to the exposure temperature. Sod, cat, gst and mt-10 gene transcription levels showed an important increase in larvae exposed to Cu, Ag or to the mix compared to the control condition at 18°C. The same pattern but with higher induction levels was recorded in larvae co-exposed to metals at 20°C. At 22°C, a significant decrease in mRNA abundance of cat, gst and sod and a significant up-regulation of mts targets (mt10 and mt20) were observed.

RESULTS: suggest that co-exposure to metals and moderate elevated temperature (20 and 22°C) significantly increased the antioxidant enzyme activities of catalase (CAT), and glutathione-S-transferase (GST) and caused an increase of metal and metallothionein concentrations. In contrast, no significant change in lipid peroxidation products measured as TBARS content was observed indicating a protective response of anti-oxidative system. This study provides first evidences of the early and efficient protective response of antioxidant defense mechanisms in mussel's early life stages facing in multi stressors situations.