Impact of heat stress on Mytilus edulis: contaminants affect survival and HSP 70 proteoform expression

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Motility of adherent hemocytes as a potential marker of immunocompetence and immunotoxic effects in bivalves

International audienc

Bioturbation and soil resistance to wind erosion in Southern Tunisia

International audienceWind erosion is a major threat to the sustainability of arid and semi-arid ecosystems. In these environments, biological soil crusts positively impact soil resistance to erosion. Less is known, however, on the impact of soil bioturbation by animals. In Southern Tunisia, bioturbation is mainly carried out by termites, ants and rodents which deposit mineral and organic components on the soil surface in the form of soil sheetings for termites or as soil heaps for ants and rodents. We here question the properties of these soils and measure their resistance to wind erosion. We showed that soil sheetings are made of sand grains linked together by bridges of organic matter, clay particles and other small size minerals such as carbonates and gypsum. The stability of these aggregates is comparable to that of biological soil crusts, despite their very different organizations. Conversely, the soil excavated by ants and rodents mainly consists in individual sand grains, which are impoverished in organic carbon and prone to wind erosion. In conclusion, this study highlights the importance of termites, as key soil bioturbator, on the dynamics of soil aggregates in Southern Tunisia. It also shows that they have an opposite effect than that of ants and rodents on the resistance of soil to erosion

Response of the Pacific oyster Crassostrea gigas to hypoxia exposure under experimental conditions.

International audienceThe molecular response to hypoxia stress in aquatic invertebrates remains relatively unknown. In this study, we investigated the response of the Pacific oyster Crassostrea gigas to hypoxia under experimental conditions and focused on the analysis of the differential expression patterns of specific genes associated with hypoxia response. A suppression subtractive hybridization method was used to identify specific hypoxia up- and downregulated genes, in gills, mantle and digestive gland, after 7-10 days and 24 days of exposure. This method revealed 616 different sequences corresponding to 12 major physiological functions. The expression of eight potentially regulated genes was analysed by RT-PCR in different tissues at different sampling times over the time course of hypoxia. These genes are implicated in different physiological pathways such as respiration (carbonic anhydrase), carbohydrate metabolism (glycogen phosphorylase), lipid metabolism (delta-9 desaturase), oxidative metabolism and the immune system (glutathione peroxidase), protein regulation (BTF3, transcription factor), nucleic acid regulation (myc homologue), metal sequestration (putative metallothionein) and stress response (heat shock protein 70). Stress proteins (metallothioneins and heat shock proteins) were also quantified. This study contributes to the characterization of many potential genetic markers that could be used in future environmental monitoring, and could lead to explore new mechanisms of stress tolerance in marine mollusc species