Le pathobiome dans les maladies des moules marines du genre Mytilus

National audienc

Impact of epizootics on mussel farms: Insights into microbiota composition of Mytilus species

International audienceOutbreaks of marine mussel mortality on French farms could have different aetiologies. One of them implies Vibrio splendidus strains. Beyond the involvement of this pathogen, there is considerable evidence that diseases often result from interactions between several microbes and the host. In this study, we explored the bacterial communities associated with mussel species and the surrounding water collected from a mussel farm affected by mortalities. The microbiota of Mytilus edulis, Mytilus galloprovincialis and their hybrids displayed an abnormal abundance of Proteobacteria, in particular the genera Vibrio, Cobetia and Arcobacter. Despite the dysbiosis, the Mediterranean mussel showed a different microbiota profile with a higher richness and presence of the phylum Bacteroidetes. Bipartite network analyses at the level of bacteria families confirmed this finding and showed that the microbiomes of M. edulis and the hybrids tended to cluster together. In addition, injection of mussels with the virulent V. splendidus induced less mortality rate in M. galloprovincialis compared to the other Mytilus sp. suggesting a better resistance of the Mediterranean mussel to infection. Our findings point to a probable aetiology of pathobiome-mediated disease in mussels. To fully understand this phenomenon, more knowledge is needed on the roles of pathobiotic systems and their development during disease establishment

Does cryptic diversity within the Eurytemora affinis complex show differential sensitivity to lithium exposure?

International audienceA cryptic species complex encompasses morphologically indistinguishable species that are genetically divergent. Some of the most frequently used species in ecotoxicological assessment show evidence of cryptic diversity that may affect the results of a given test. Linking cryptic diversity to sensitivity of chemicals has rarely been investigated. Lithium (Li) is an alkali metal considered as one of the most important emerging pollutants under concern due to high demand for this compound essentially to produce rechargeable batteries. Li environmental concentrations are expected to increase in the next years and its effects on marine and coastal organisms remain relatively unrecognized. Here, we focused on two of six cryptic species of the estuarine copepod complex Eurytemora affinis, exposing natural populations on two continents. Our main objective was to characterize the differential sensitivity of these two-field collected E. affinis cryptic species (the European and the North-Atlantic clade) to Li using a larval bioassay. Ovigerous females of the North-Atlantic clade were sampled in the St. Lawrence estuary (Canada) and for the European clade in the Seine estuary (France) and incubated to recover early-stage larvae (nauplii). We assessed survival and growth of E. affinis nauplii exposed to a gradient of Li concentrations (1, 10, 50 and 100 mg.L-1) for 96 h at 5 PSU and 15°C. LC50 were estimated by using log-logistic model. LC50 for the nauplii from North-Atlantic and European clades of E. affinis were 243.42 (± 3.56) mg.L-1 and 241.41 (± 2.05) mg.L-1 at 24 h exposure and 86.31 (± 1.07) mg.L-1 and 72.78 (± 1.15) mg.L-1 respectively after 96 h. Li inhibit growth rate of nauplii at ≥ 50 mg.L-1 with an EC50 at 96 h of 60.19 (± 1.13) mg.L-1 for the North-Atlantic clade nauplii. The estimated EC/LC50 values were too high to cause extreme effects at environmental concentrations observed in Northern Hemisphere estuaries. No significant differences were observed in Li sensitivity between the two clades. However, further studies should be performed to test other contaminants, to improve knowledge on sensitivity of the cryptic species E. affinis complex to assure routine ecotoxicological tests are appropriate

Insights into the microbiota of farmed and wild Mytilus SP: is there a link between bacteria communities and host susceptibility?

International audienc

Insights into the microbiota of farmed and wild Mytilus SP: is there a link between bacteria communities and host susceptibility?

International audienc

Susceptibility of the Non-Targeted Crustacean Eurytemora affinis to the Endocrine Disruptor Tebufenozide: A Transcriptomic Approach

Copepods are zooplanktonic crustaceans ubiquitously widespread in aquatic systems. Although they are not the target, copepods are exposed to a wide variety of pollutants such as insect growth regulators (IGRs). The aim of this study was to investigate the molecular response of a non-targeted organism, the copepod Eurytemora affinis, to an IGR. Adult males and females were exposed to two sub-lethal concentrations of tebufenozide (TEB). Our results indicate a sex-specific response with a higher sensitivity in males, potentially due to a differential activation of stress response pathways. In both sexes, exposure to TEB triggered similar pathways to those found in targeted species by modulating the transcription of early and late ecdysone responsive genes. Among them were genes involved in cuticle metabolism, muscle contraction, neurotransmission, and gametogenesis, whose mis-regulation could lead to moult, locomotor, and reproductive impairments. Furthermore, genes involved in epigenetic processes were found in both sexes, which highlights the potential impact of exposure to TEB on future generations. This work allows identification of (i) potential biomarkers of ecdysone agonists and (ii) further assessment of putative physiological responses to characterize the effects of TEB at higher biological levels. The present study reinforces the suitability of using E. affinis as an ecotoxicological model

The copepod Eurytemora affinis as a relevant species to assess estuarine sediment toxicity: Effects on gene expression and swimming behavior

International audienc

Effects of antibiotics and the UV-filter benzophenone-3 (BP-3) on fitness-related behaviors of the European sea bass (Dicentrarchus labrax)

International audienc

Application of a crustacean bioassay to evaluate a multi-contaminated (metal, PAH, PCB) harbor sediment before and after electrokinetic remediation using eco-friendly enhancing agents

International audienceElectrokinetic (EK) remediation can be a suitable technology for treating contaminated dredged harbor sediment, stored on terrestrial disposal sites. Citric acid (CA) and biosurfactants (rhamnolipids and saponin) were chosen as enhancing agents for simultaneous metal (Cd, Cr, Cu, Pb, Zn) and PAH/PCB removal by EK because of their potential low toxicity with a view to site restoration. Three EK runs were performed using a periodic voltage (1 V cm− 1) and various concentrations of agents. The best combination of CA (0.2 mol L− 1) and saponin (0.85 g L− 1) did not remove high amounts of metals (4.4–15.8%) and provided only slightly better results for PAH and PCB removal (29.2% and 38.2%, respectively). The harbor sediment was highly resistant to metal and organics mobilization and transport because of an aged contamination, a high buffering capacity, a very low hydraulic permeability and a high organic matter content. The efficiency of the EK process was also assessed by measuring the acute toxicity of the EK-treated sediment on E. affinis copepods exposed to sediment elutriates. Fortunately, the use of CA and biosurfactants did not significantly impact on sediment toxicity. Some treated sediment sections, particularly those near the anode compartment, were statistically more toxic than the raw sediment. More particularly, E. affinis copepods were significantly sensitive to low pH values and oxidative conditions, to Cu, and to a lesser extent to Pb amounts. The speciation of these metals probably changed in these pH and redox conditions so that they became more easily leachable and bioavailable. In contrast, toxicity was negatively correlated to PAH and PCB amounts after EK treatment, probably due to the production of oxidized metabolites of PAHs and PCBs