The Role of a marine protected area in safeguarding the genetic diversity of rare species: the case of <i>Patella ferruginea</i> Gmelin, 1791 (Gastrpoda: Patellidae) = Il Ruolo delle aree marine protette per la salvaguardia della diversità genetica di specie rare: il caso di <i>Patella ferruginea</i> Gmelin, 1791 (Gastropoda: Patellidae)

Patella ferruginea (Gastropoda: Patellidae) is an endangered marine gastropod, distributed on the western Mediterranean coasts, whose range has progressively contracted, due to intense human exploitation. Our attention focused on its genetic structure, in order to gather information about levels of genetic variability of P. ferruginea from the Asinara Marine Protected Area and a neighbouring non-protected area

Tissue-Specific Biomarker Responses in the Blue Mussel Mytilus spp. Exposed to a Mixture of Microplastics at Environmentally Relevant Concentrations

The impact of a microplastic (MP) mixture composed of polyethylene (PE) and polypropylene (PP) plastic particles, prepared from commercially available products, was evaluated in blue mussels Mytilus spp. exposed to three environmentally relevant concentrations: 0.008 μg L−1 (low), 10 μg L−1 (medium), and 100 μg L−1 (high). Organisms were exposed for 10 days followed by 10 days of depuration in clean seawater under controlled laboratory conditions. The evaluation of MP effects on mussel clearance rate, tissue structure, antioxidant defenses, immune and digestive parameters, and DNA integrity were investigated while the identification of plastic particles in mussel tissues (gills, digestive gland, and remaining tissues), and biodeposits (feces and pseudofaeces) was performed using infrared microscopy (μFT-IR). Results showed the presence of MPs only in the digestive gland of mussels exposed to the highest tested concentration of MPs with a mean of 0.75 particle/mussel (after the 10 days of exposure). In biodeposits, PE and PP particles were detected following exposure to all tested concentrations confirming the ingestion of MPs by the organisms. A differential response of antioxidant enzyme activities between digestive gland and gills was observed. Significant increases in superoxide dismutase (SOD) and catalase (CAT) activities were measured in the digestive gland of mussels exposed to the low (0.008 μg L−1) and medium (10 μg L−1) concentrations of MPs and in the gills from mussels exposed to the highest concentration (100 μg L−1) of MPs that could be indicative of a change in the redox balance. Moreover, an increase in acid phosphatase activity was measured in hemolymph of mussels exposed to 0.008 and 10 μg L−1 concentrations. No significant difference was observed in the clearance rate, and histopathological parameters between control and exposed mussels. This study brings new insights on the potential sublethal impacts of MPs at environmentally relevant concentrations in marine bivalves

Compréhension de l’hybridation des moules du genre Mytilus en Atlantique et implications pour la bio-surveillance

La présence de différentes espèces du genre Mytilus et leur hybridation est un paramètre mesuré sur une base volontaire par certains pays de la Mer du Nord pour la surveillance des effets biologiques des contaminants chimiques dans le cadre du programme CEMP (Coordinated EnvironMental Monitoring Programme) de la convention des mersrégionales OSPAR. Cette hybridation pouvant potentiellement influencer la réponse physiologique et la capacité de bioaccumulation des individus hybrides, il apparaît pertinent de développer en France la mesure de ce paramètre qui pourrait être étendue auréseau ROCCH et à la DCSMM dans lecadre dudescripteur 8 «contaminants chimiques et effets biologiques». L’objectif de cette étude est i) d’évaluer l’évolution de la distribution sur le littoral français de M. edulis et M. galloprovincialisdepuis 35 ans en utilisant la banque de tissus du ROCCH, ii) de déterminer les différences debioaccumulation et de réponses des biomarqueurs entre M.edulis etM. galloprovincialiset leurshybridesvia du caging(transplantation in situ). L’évolution de la prévalence des deux espèces de M. eduliset M. galloprovincialis sur certains sites du ROCCH a montré que des différences de composition génétique peuvent être observées pour certains sites entre 1981 et 2016. La cause de ces changements et notamment un lien potentiel avec lespratiques mytilicoles reste à éclaircir. Pour les stations où un changement est observé une réinterprétation des données historiquesdu ROCCHprenant en compte le facteur génétique pourra nous éclairer sur l’intérêt d’appliquer ce critère etéventuellementdel’élargir à plus de sites de façon rétrospective. Que ce soit au niveau des paramètres biologiques, des marqueurs écotoxicologiques, ou encorede la bioaccumulation des contaminants chimiques, des différences entre les lots testés in situdes espèces M. eduliset M. galloprovincialiset leurs hybrides sont observées. Une tendance univoque ne peut pas être dégagée concernant la capacitéde l’une ou de l’autre espèce à accumuler plus ou moins de contaminantschimiques, les différences observées entre espèces étant contaminant-spécifiques. De plus, l’étude in situdont sont issusces résultats a pu êtreconduitesur un site expérimental seulement.Des différences entre sites pourraient ainsi complexifier davantage les résultats déjàobtenus. Les conséquences sur l’interprétation des données de surveillance issues d’analyses sur les moules sont difficiles à prédire, mais il est certain, d’après les résultatsobtenus ici, que préciser l’espèce ou la présence d’individus hybrides(ou del’introgression)dans les bases de données serait judicieux. Une étude plus vaste sur plusieurs sites, à l’échelle nationale et/ou internationale (incluant également les zones d’hybridation entre M. eduliset M. trossulus, troisième espèce potentiellementprésente en Atlantique Nord-Est) pourrait être une perspective pertinente de ces travaux

Copper induces expression and methylation changes of early development genes in Crassostrea gigas embryos

International audienceCopper contamination is widespread along coastal areas and exerts adverse effects on marine organisms such as mollusks. In the Pacific oyster, copper induces severe developmental abnormalities during early life stages; however, the underlying molecular mechanisms are largely unknown. This study aims to better understand whether the embryotoxic effects of copper in Crassostrea gigas could be mediated by alterations in gene expression, and the putative role of DNA methylation, which is known to contribute to gene regulation in early embryo development.For that purpose, oyster embryos were exposed to 4 nominal copper concentrations (0.1, 1, 10 and 20 μg L−1 Cu2+) during early development assays. Embryotoxicity was monitored through the oyster embryo-larval bioassay at the D-larva stage 24 h post fertilization (hpf) and genotoxicity at gastrulation 7 hpf. In parallel, the relative expression of 15 genes encoding putative homeotic, biomineralization and DNA methylation proteins was measured at three developmental stages (3 hpf morula stage, 7 hpf gastrula stage, 24 hpf D-larvae stage) using RT-qPCR. Global DNA content in methylcytosine and hydroxymethylcytosine were measured by HPLC and gene-specific DNA methylation levels were monitored using MeDIP-qPCR.A significant increase in larval abnormalities was observed from copper concentrations of 10 μg L−1, while significant genotoxic effects were detected at 1 μg L−1 and above. All the selected genes presented a stage-dependent expression pattern, which was impaired for some homeobox and DNA methylation genes (Notochord, HOXA1, HOX2, Lox5, DNMT3b and CXXC-1) after copper exposure. While global DNA methylation (5-methylcytosine) at gastrula stage didn’t show significant changes between experimental conditions, 5-hydroxymethylcytosine, its degradation product, decreased upon copper treatment. The DNA methylation of exons and the transcript levels were correlated in control samples for HOXA1 but such a correlation was diminished following copper exposure. The methylation level of some specific gene regions (HoxA1, Hox2, Engrailed2 and Notochord) displayed changes upon copper exposure. Such changes were gene and exon-specific and no obvious global trends could be identified. Our study suggests that the embryotoxic effects of copper in oysters could involve homeotic gene expression impairment possibly by changing DNA methylation levels

Transcriptomic response of the Pacific oyster Crassostrea gigas to hypoxia

International audienceMarine intertidal organisms commonly face hypoxic stress during low tide emersion; moreover, eutrophic conditions and sediment nearness could lead to hypoxic phenomena; it is indeed important to understand the molecular processes involved in the response to hypoxia. In this study the molecular response of the Pacific oyster Crassostrea gigas to prolonged hypoxia (2 mg O2 L− 1 for 20 d) was investigated under experimental conditions. A transcriptomic approach was employed using a cDNA microarray of 9058 C. gigas clones to highlight the genetic expression patterns of the Pacific oyster under hypoxic conditions. Lines of oysters resistant (R) and susceptible (S) to summer mortality were used in this study. ANOVA analysis was used to identify the genes involved in the response to hypoxia in comparison to normoxic conditions. The hypoxic response was maximal at day 20. The principal biological processes up-regulated by hypoxic stress were antioxidant defense and the respiratory chain compartment, suggesting oxidative stress caused by hypoxia or an anticipatory response for normoxic recovery. This is the first study employing microarrays to characterize the genetic markers and metabolic pathways responding to hypoxic stress in C. gigas

Rapid mitochondrial adjustments in response to short-term hypoxia and re-oxygenation in the Pacific oyster, Crassostrea gigas.

International audienceAs oxygen concentrations in marine coastal habitats can fluctuate rapidly and drastically, sessile marine organisms such as the oyster Crassostrea gigas can experience marked and rapid oxygen variations. In this study, we investigated the responses of oyster gill mitochondria to short-term hypoxia (3 and 12 h, at 1.7 mg O2 l(-1)) and subsequent re-oxygenation. Mitochondrial respiratory rates (states 3 and 4 stimulated by glutamate) and phosphorylation efficiency [respiratory control ratio (RCR) and the relationship between ADP and oxygen consumption (ADP/O)] were measured. Cytochrome c oxidase (CCO) activity and cytochrome concentrations (a, b, c1 and c) were measured to investigate the rearrangements of respiratory chain subunits. The potential implication of an alternative oxidase (AOX) was investigated using an inhibitor of the respiratory chain (antimycin A) and through gene expression analysis in gills and digestive gland. Results indicate a downregulation of mitochondrial capacity, with 60% inhibition of respiratory rates after 12 h of hypoxia. RCR remained stable, while ADP/O increased after 12 h of hypoxia and 1 h of re-oxygenation, suggesting increased phosphorylation efficiency. CCO showed a fast and remarkable increase of its catalytic activity only after 3 h of hypoxia. AOX mRNA levels showed similar patterns in gills and digestive gland, and were upregulated after 12 and 24 h of hypoxia and during re-oxygenation. Results suggest a set of controls regulating mitochondrial functions in response to oxygen fluctuations, and demonstrate the fast and extreme plasticity of oyster mitochondria in response to oxygen variations

Conformation and structural features of diuron and irgarol: insights from quantum chemistry calculations

The structure and the conformations of diuron and irgarol have been investigated from crystal structure analyses and Density Functional Theory (DFT) calculations. Significant changes in terms of conformer distribution are found according to the surroundings (gas phase or water). Irgarol appears expectedly as flexible from a conformational point of view, nine or eight conformers being identified in the isolated state and water, respectively. Natural Bond Orbital (NBO) analyses have been realised on the energetic minima to rationalise the conformational preferences. Molecular electrostatic potential calculations have been carried out to bring to light and rank the potential intermolecular interaction sites of the two biocides. The interaction potential of irgarol, essentially represented by the triazine nitrogen atoms and the NH groups, is found to be much more sensitive to the conformational preferences that the one of diuron, the N3 triazine being preferred as HB acceptor, in agreement with the crystallographic data available

Molecular and cellular response to short-term oxygen variations in the Pacific oyster Crassostrea gigas

International audienceIntertidal organisms have to face daily high oxygen variations from hypoxic to hyperoxic conditions. To cope with such constraints, these organisms must have well developed compensatory mechanisms involving antioxidant and energetic adjustments. The oyster Crassostrea gigas is regularly exposed to high oxygen fluctuations and is a good model to understand these physiological regulations. This study aimed to explore the mechanisms involved in response to short-term oxygen variations in the digestive gland and hemocytes of C. gigas. The effects of returning into water after an emersion period were tested for 24 h at two different oxygen concentrations (normoxic 8.8 mg O2 L−1 and hypoxic 2.6 mg O2 L−1). Gene expression on several antioxidant enzymes was performed. In addition, a marker of oxidative damage, the malondialdehyde (MDA) was quantified. Hemocyte parameters measured were viability, concentration of different cellular sub-populations and oxidative activity. Changes in energetic metabolism were investigated measuring mRNA levels of pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK). Moreover, mRNA levels of the transcription factor HIFα were analyzed. Higher levels of the alternative oxidase (AOX) mRNA in normoxic conditions corroborate the hypothesis of the AOX having a role in the redox balance. MDA levels did not show any condition effect, suggesting that hypoxic conditions did not cause oxidative stress. mRNA levels of antioxidant enzymes and hemocyte oxidative activity increased during the 24 h of immersion. This suggests that the disruption of tidal cycles by maintaining oysters immersed resulted in an increase of oxygen-dependent activities. No clear hypoxic responses were detected neither in a switch of PEPCK and PK toward anaerobic metabolism, nor in HIFα regulation. PK mRNA levels were significantly higher in nomoxic conditions, suggesting that more elevated oxygen concentrations would lead to higher energetic metabolism. Hemocyte concentrations were higher in hypoxic conditions suggesting an increased hematopoiesis. This study brings new insights in understanding how oysters, and more in general intertidal molluscs, cope with short-term oxygen variations