Temperature-dependent stress response in oyster, Crassostrea virginica: Pollution reduces temperature tolerance in oyster

Combined effects of temperature and a toxic metal, cadmium (Cd), on energy metabolism were studied in a model marine bivalve, the easternoyster Crassostrea virginica, acclimated at 20, 24 and 28 ◦C and exposed to 50 g l−1 of Cd. Both increasing temperature and Cd exposureled to a rise in standard metabolic rates, and combined stressors appeared to override the capability for aerobic energy production resultingin impaired stress tolerance. Oysters exposed to elevated temperature but not Cd showed no significant change in condition, survival rate andlipid peroxidation, whereas those exposed to both Cd and temperature stress suffered high mortality accompanied by low condition index andelevated lipid peroxidation. Furthermore, RNA/DNA ratios indicative of protein synthesis rate, and levels of glutathione, which is involved inmetal detoxification, increased in Cd-exposed oysters at 20 ◦C but not at 28 ◦C. Implications of the synergism between elevated temperatures andcadmium stress on energy metabolism of oysters are discussed in the light of the potential effects of climate change on oyster populations inpolluted areas

Biomarkers in Ruditapes decussatus: a potential bioindicator species

The clam Ruditapes decussatus is distributed worldwide and due to its ecological and economical interest has been proposed as a bioindicator in areas where mussels are not available. The accumulation of several anthropogenic compounds in their tissues suggests that they possess mechanisms that allow them to cope with the toxic effects of these contaminants. Besides pollutant uptake, the use of biomarkers is pointed out in this paper since it is a promising approach to monitor the effect of these contaminants in the marine environment. Biomarkers complement the information of the direct chemical characterization of different types of contaminants. Therefore, the aim of this paper is to review the role of several biomarkers: (metallothioneins (MT), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) (total and selenium-dependent), lipid peroxidation (measured as MDA, one of the final products of lipid peroxidation), glutathione S-transferase (GST) and acetylcholinesterase (AChE), measured in different tissues of the clam R. decussatus, in laboratory conditions and under various environmental stresses, in two ecosystems (Ria Formosa lagoon- Portugal) and Bizerta lagoon (Tunisia) in a perspective of a multibiomarker approach to assess environmental changes. Experiment and field studies are in good agreement since MT levels, especially in the gills, the first target tissue of these contaminants, can be used as biomarker of exposure to Cd. GPx and MDA may also be determined in this respect. AChE activity is inhibited by pesticide and, to a less extent, by metal exposure in the gills and whole soft body of clams. However, the induction of GST isoforms experimentally demonstrated is not observed in the field because only global GST activity was determined. The whole set of results opens new research perspectives for the use of this species to assess the effect of mixtures of pollutants in the aquatic environment.PAUILF (Programme d’Action Universitaire Integreée Luso-Françaiseinfo:eu-repo/semantics/publishedVersio

Honeybee biomarkers as promising tools to monitor environmental quality

International audienceThe aim of this study was to distinguish the impacts of two different anthropogenic conditions using the honeybee Apis mellifera as a bioindicator associatedwith a battery of biomarkers previously validated in the laboratory. Both the urban (RAV, Ravine des Cabris) and semi-natural (CIL, Cilaos) sites in La Reunion Islandwere compared in order to assess the impacts of two types of local pollution using the discriminating potential of biomarkers. Hives were placed at the CIL and RAV sites and honeybees were collected from each hive every three months over one year. Honeybee responses were evaluated with respect to several biochemical biomarkers: glutathione-S-transferase (GST), acetylcholinesterase (AChE), alkaline phosphatase (ALP) and metallothioneins (MT). The results showed a significant difference between the localities in terms of GST, AChE and ALP activities, as regarding midgut MT tissue levels. Compared to the CIL site, ALP and MT tissue levels were higher at the RAV site, although AChE activity was lower. GST displayed more contrasted effects. These results strongly suggest that the honeybees based in the more anthropized area were subjected to sublethal stress involving both oxidative stress and detoxification processes with the occurrence of neurotoxic pollutants, amongst which metals were good candidates. A classification tree enabled defining a decision procedure to distinguish the sampling locations and enabled excellent classification accuracy (89%) for the data set. This field study constitutes a strong support in favour of the in situ assessment of environmental quality using honeybee biomarkers and validates the possibility of performing further ecotoxicological studies using honeybee biomarkers. (Résumé d'auteur