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

Presence of vascular endothelial growth factor during the first half of IVM improves the meiotic and developmental competence of porcine oocytes from small follicles

The aim of the present study was to investigate the effect of vascular endothelial growth factor (VEGF) on the meiotic and developmental competence of porcine oocytes from small follicles (SF; 0.5-3mm diameter). When cumulus-oocyte complexes (COCs) from medium-sized follicles (MF; 3-6mm diameter) and SF were cultured for IVM, the maturation rates were significantly higher for oocytes from MF than SF. Concentrations of VEGF in the medium were significantly higher for COCs cultured from MF than SF. When COCs from SF were exposed to 200ngmL-1 VEGF during the first 20h of IVM, the maturation rate improved significantly and was similar to that of oocytes derived from MF. The fertilisability of oocytes was also significantly higher than that of VEGF-free SF controls. Following parthenogenetic activation, the blastocyst formation rate improved significantly when SF COC culture was supplemented with 200ngmL-1 VEGF, with the rate similar to that of oocytes from MF. The results of the present study indicate that VEGF markedly improves the meiotic and developmental competence of oocytes derived from SF, especially at a concentration of 200ngmL-1 during the first 20h of IVM

External fertilization and excapsular development in

Strategies for biomass control are actively sought in response to proliferation of the introduced, suspension-feeding gastropod Crepidula fornicata along European coasts. Among these, dredging, crushing and on-site rejection may only be envisaged if the risk of further dissemination through the release of gametes and of excapsulated embryos/larvae is found to be nil or extremely low. This study evaluates such risk using three approaches: (1) determination of the periods of brood presence/absence, (2) external fertilizations of gametes obtained by gonad stripping, (3) cultures of mechanically-excapsulated embryos and larvae. A period of near- or total brood absence was observed between September 2006 and January 2007. The few zygotes (1.5% to 7.5%) obtained from external fertilizations did not proceed beyond the 4-cell stage. Excapsulated young embryos and mid-stages died in less than 4 days of culture. Despite their ability to swim, grow and feed, excapsulated veligers all died before metamorphosis. No juveniles were obtained from external fertilizations and excapsulated cultures, indicating that the release of crushed catches directly at sea could not present a dissemination risk from the standpoint of gamete or prematurely-excapsulated larval dispersal. Furthermore, by carrying out the crushing operations during the period of brood absence, the dissemination risk becomes nil. Negative ecological impact of such operations could be offset by attraction of motile predators, as yet unaccustomed to this introduced species, and their subsequent generalization to live slipper limpets and invasive feral Crassostrea gigas. At the very least, this biomass reduction approach would concentrate bottom habitat unavailability to restricted zones, freeing up the rest of the subtidal for other, formerly displaced species, as well as reducing the pressure on the trophic carrying capacity of affected habitats

Optimisation de la métamorphose de Paracentrotus lividus par l’utilisation de macroalgues alternatives à Corallina sp.

International audienceMetamorphosis induction cues (by chemical mediation or direct contact) were tested in Paracentrotus lividus using three different macroalgae treatments: Corallina sp., Palmaria palmata, and Laminaria digitata. Higher percentages of metamorphosis were reached in Paracentrotus lividus larvae by direct contact with a Palmaria palmata substrate

Utilisation of intertidal mudflats by the Dunlin Calidris alpina in relation to microphytobenthic biofilms

International audienceThe small-scale spatial distribution of Dunlin Calidris alpina staging and wintering in Bourgneuf Bay (France) was investigated on two different mudflats colonized by either epipsammic- or epipelic-dominated microphytobenthos assemblages. Shorebird counts were conducted monthly at ebb tide from October 2011 to May 2012 and from November 2012 to May 2013. Multiple linear regressions followed by hierarchical partitioning of variance showed that microphytobenthos biomass was not a significant factor to explain Dunlin densities. However, on epipelic-dominated mudflats, Dunlins did not show their typical ‘‘tide follower’’ behaviour and instead significantly selected the highest microphytobenthos biomass zones. The biomass of a gastropod predator of an important local Dunlin prey, Retusa obtusa, was negatively correlated with Dunlin densities. This paper provides new suggestions in the ways that biofilms on mudflats affect small shorebird foraging

Optimisation des régimes alimentaires pour l'élevage larvaire de Paracentrotus lividus dans le but de promouvoir la diversification de l'aquaculture

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Modélisation de l'affinage de l'huître

L'affinage traditionnel des huîtres creuses, pratiqué dans les claires ostréicoles de la façade Atlantique française, est soumis aux fluctuations des facteurs environnementaux. Un procédé d'affinage contrôlé en terme de matières organique et inorganique particulaires (MOP et MIP) et de température a été développé afin de réduire la variabilité de croissance de la chair des huîtres. Cet élevage intensif repose sur la production de la diatomée Skeletonema costatum, distribuée aux huîtres avec une concentration moyenne de 4–5 mg de MOP·L–1. Un modèle écophysiologique de l'huître Crassostrea gigas, simulant les croissances du soma et des réserves–gonades, a été appliqué aux conditions d'affinage contrôlé dans le but d'analyser les réponses du bivalve. Son élaboration a nécessité un retour à l'expérimentation. Deux fonctions d'alimentation ont été étudiées au laboratoire : la filtration et la production de pseudofèces, intervenant dans la régulation de l'ingestion. Les résultats, pour une température de 14 °C, et pour une gamme de MOP et de MIP variant respectivement de 4 à 18 mg·L–1 et de 15 à 55 mg·L–1, montrent que l'ingestion est régulée par la production de pseudofèces, la filtration ne présentant pas de variation significative (moyenne de 2,09 ± 0,11 L·h–1·g–1, avec un taux d'activité de 59%). Cette production de pseudofèces, qui engendre une augmentation de la fraction organique ingérée par le mécanisme de sélection pré-ingestive, permet de compenser la variabilité des concentrations en MIP. Des simulations ont permis d’analyser les effets négatifs de ce facteur environnemental sur la croissance du bivalve. Il apparaît alors que la ration utilisée en affinage contrôlé (4–5 mg de MOP.L–1) permet une croissance en chair sèche malgré des concentrations simulées atteignant 50 mg·L–1 de MIP. Lors de l'élaboration du modèle pour les conditions spécifiques à l'affinage contrôlé, la gamétogenèse est apparue comme un processus déterminant pour la répartition de l'énergie chez le bivalve

Growth and biochemical composition of a microphytobenthic diatom (Entomoneis paludosa) exposed to shorebird (Calidris alpina) droppings

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Remote sensing of wild oyster reefs (crassostrea gigas) in a shellfish ecosystem

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