Pseudo-nitzschia Peragallo (Bacillariophyceae) diversity and domoic acid accumulation in tuberculate cockles and sweet clams in M’diq Bay, Morocco

The diversity of Pseudo-nitzschia (Bacillariophyceae) and accumulation of the neurotoxin domoic acid (DA) in two types of shellfish; tuberculate cockles (Acanthocardia tuberculata) and sweet clams (Challista chione) was explored in M’diq Bay,Morocco during 2007. The highest abundances of Pseudo-nitzschia were found during the period from March to October, with peaks occurring in May and September. Toxin analysis showed an accumulation of domoic acid in shellfish sampled during spring and autumn. The maximum toxin concentration was 4.9 mg DAg–1 of the whole tissue recorded in sweet clam during spring. Using transmission electron microscopy, thirteen Pseudo-nitzschia species were identified, eight of which are known as producers of domoic acid: P. multistriata, P. cuspidata, P. galaxiae, P. multiseries, P. pseudodelicatissima, P. pungens var. aveirensis, P. calliantha and P. fraudulenta. The five non- toxic species observed were P. subpacifica, P. arenysensis, P. dolorosa, P. subfraudulenta, and P. cf. caciantha

Effects of temperature on photosynthetic parameters and TEP production in eight species of marine microalgae

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Adult-mediated connectivity affects inferences on population dynamics and stock assessment of nursery-dependent fish populations

We explore how alternative hypotheses on the degree of mixing among local subpopulations affect statistical inferences on the dynamics and stock assessment of a harvested flatfish population, namely, the common sole population in the Eastern Channel (ICES area VIId). The current paradigm considers a single, well-mixed, spatially homogeneous population with juveniles from all coastal nursery grounds along the French and UK coasts that contribute to a single adult population and one pool of eggs. Based on the available data and ecological knowledge, we developed a spatial Bayesian integrated life-cycle model that consists of three subpopulations (one near the UK coast and two near the French coast, denoted UK, West FR and East FR, respectively) supported by their respective local nurseries, with the connectivity among the three components limited to low exchanges during larval drift. Considering the population dynamics among three subpopulations (instead of a single homogeneous one) drastically changes our inferences on the productivity of nursery sectors and their relative contribution to total recruitment. Estimates of the East FR subpopulation’s contribution to total recruitment increase (29% in the single population model; 48% in the three subpopulation model), balanced by a decrease in the UK subpopulation’s contribution (53%; 34%). Whereas an assessment based on the hypothesis of a single spatially homogeneous population in the EC indicates exploitation far above MSY (current F/FMSY = 1.8), an assessment that considers a metapopulation with three loosely connected subpopulations revealed a different status, with the UK and East FR subpopulations being exploited above MSY (current F/FMSY = 1.9 and 2, respectively) and the West FR subpopulation approaching full exploitation (current F/FMSY = 1.05). This approach contributes to the quantitative assessment of spatial fishery and coastal habitat management plans

Dynamics of soluble extracellular polymeric substances and transparent exopolymer particle pools in coastal ecosystems.

International audienceTime series of soluble extracellular polymeric substance (S-EPS) and transparent exopolymer particle (TEP) fractions, as well as biological, physical and chemical parameters, were studied in natural phytoplankton assemblages at 2 macrotidal sites located in the English Channel for 3 yr. The first site, the Bay des Veys (BDV), is sheltered from prevailing winds and influenced by a high river discharge, whereas the second, Lingreville-sur Mer (LGV), is exposed to the open ocean and to dominant winds. At both sites, the highest TEP concentrations were measured in spring and summer (1735 and 3604 μg equiv X l-1 at BDV and LGV, respectively) and were correlated with phytoplankton biomass and nitrogen concentrations. During the autumn and winter, TEP dynamics were not related to phytoplankton dynamics but appeared controlled by hydrodynamics. In contrast to TEP concentrations, S-EPS did not present any seasonal dynamics and was not correlated with TEP variations. The highest amount of S-EPS was recorded in spring at LGV (25.8 mg equiv. glucose l-1) and in summer at BDV (26.4 mg equiv. glucose l-1). The S-EPS pool was separated in 2 fractions according to the molecular weight: low (LW) and high (HW). The LW fraction was produced in higher quantity than the HW fraction, and with larger temporal fluctuations. Therefore, both S-EPS fractions seem controlled by different environmental parameters depending on the season and on the studied ecosystem. The different dynamics observed for TEP and S-EPS confirm the complexity of carbon excretion processes in phytoplankton, and the results reveal different metabolic pathways and different origins for these carbon excretions

The mechanism of phosphorylation of anti-HIV D4T by nucleoside diphosphate kinase

International audienceThe last step in the intracellular activation of antiviral nucleoside analogs is the addition of the third phosphate by nucleoside diphosphate (NDP) kinase resulting in the synthesis of the viral reverse transcriptase substrates. We have previously shown that dideoxynucleotide analogs and 3'-deoxy-3'-azidothymidine (AZT) as di- or triphosphate are poor substrates for NDP kinase. By use of protein fluorescence, we monitor the phosphotransfer between the enzyme and the nucleotide analog. Here, we have studied the reactivity of D4T (2',3'-dideoxy-2',3'-didehydrothymidine; stavudine) as di- (DP) or triphosphate (TP) at the pre-steady state. The catalytic efficiency of D4T-DP or -TP is increased by a factor of 10 compared with AZT-DP or -TP, respectively. We use an inactive mutant of NDP kinase to monitor the binding of a TP derivative, and show that the affinity for D4T-TP is in the same range as for the natural substrate deoxythymidine triphosphate, but is 30 times higher than for AZT-TP. Our results indicate that D4T should be efficiently phosphorylated after intracellular maturation of a prodrug into D4T-monophosphate

Integrative Taxonomy of the Pavlovophyceae (Haptophyta): A Reassessment

International audienceThe Pavlovophyceae (Haptophyta) contains four genera (Pavlova, Diacronema, Exanthemachrysis and Rebecca) and only thirteen characterised species, several of which are important in ecological and economic contexts. We have constructed molecular phylogenies inferred from sequencing of ribosomal gene markers with comprehensive coverage of the described diversity, using type strains when available, together with additional cultured strains. The morphology and ultrastructure of 12 of the described species was also re-examined and the pigment signatures of many culture strains were determined. The molecular analysis revealed that sequences of all described species differed, although those of Pavlova gyrans and P. pinguis were nearly identical, these potentially forming a single cryptic species complex. Four well-delineated genetic clades were identified, one of which included species of both Pavlova and Diacronema. Unique combinations of morphological/ultrastructural characters were identified for each of these clades. The ancestral pigment signature of the Pavlovophyceae consisted of a basic set of pigments plus MV chl cPAV, the latter being entirely absent in the Pavlova + Diacronema clade and supplemented by DV chl cPAV in part of the Exanthemachrysis clade. Based on this combination of characters, we propose a taxonomic revision of the class, with transfer of several Pavlova species to an emended Diacronema genus. The evolution of the class is discussed in the context of the phylogenetic reconstruction presented. (C) 2011 Elsevier GmbH. All rights reserved

Pseudo-nitzschia Peragallo (Bacillariophyceae) diversity and domoic acid accumulation in tuberculate cockles and sweet clams in M'diq Bay, Morocco

International audienceThe diversity of Pseudo-nitzschia (Bacillariophyceae) and accumulation of the neurotoxin domoic acid (DA) in two types of shellfish; tuberculate cockles (Acanthocardia tuberculata) and sweet clams (Challista chione) was explored in M'diq Bay, Morocco during 2007. The highest abundances of Pseudo-nitzschia were found during the period from March to October, with peaks occurring in May and September. Toxin analysis showed an accumulation of domoic acid in shellfish sampled during spring and autumn. The maximum toxin concentration was 4.9 mg DA g-1 of the whole tissue recorded in sweet clam during spring. Using transmission electron microscopy, thirteen Pseudo-nitzschia species were identified, eight of which are known as producers of domoic acid: P. multistriata, P. cuspidata, P. galaxiae, P. multiseries, P. pseudodelicatissima, P. pungens var. aveirensis, P. calliantha and P. fraudulenta. The five non-toxic species observed were P. subpacifica, P. arenysensis, P. dolorosa, P. subfraudulenta, and P. cf. caciantha

Parental and direct feeding effects of dietary selenium in rainbow trout (Oncorhynchus mykiss) fry

Session Nutrition: Physiology and RequirementsParental and direct feeding effects of dietary selenium in rainbow trout (Oncorhynchus mykiss) fry. Aquaculture Europe 201

Integrating mark-recapture data within a Bayesian life-cycle model to evaluate spatial structure and population dynamics of sole. A coastal and nursery dependent flatfish : Eastern Channel Sole

The common sole -Solea solea- is one of the most harvested flatfish population in the Eastern English Channel -EEC; ICES area VIId-. In the EEC, this population is currently assessed and managed as a homogeneous single stock. However, some ecological clues indicate that a metapopulation structure formed by a set of three loosely connected subpopulations associated with local coastal nurseries areas cannot be ruled out. Results show that key estimates of population dynamics parameters, stock assessment and management reference points are highly sensitive to the hypotheses made on the spatial structure. A Bayesian integrated life-cycle model was developed to explore the sensitivity of population dynamics and stock assessment to the level of connectivity in the metapopulation structure, by considering a gradient of connectivity between: -i the current ICES hypothesis where all coastal nurseries contribute to one single homogeneous well mixed population and -ii a metapopulation structure with three loosely connected subpopulations and their associated coastal nurseries. While assessment obtained when hypothesizing a single spatially homogeneous population indicates catches near MSY, considering a metapopulation structure with three subpopulations revealed contrasted status, with two subpopulations being exploited above MSY and one below MSY. A preliminary analysis of existing mark-recapture data supports the idea of a low connectivity within the EEC. We analyzed an extensive mark-recapture dataset of more than 40,000 fish tagged by CEFAS in the English Channel and the North Sea  between 1955 and 2007 to evaluate the connectivity induced by the movement of adults fish between the three potential subpopulations in the EEC, and with nearby areas. Results revealed very low connectivity between subpopulations in the EEC, and low movement of fish between the EEC and the North Sea. Ongoing development within the SMAC project include additional tag-recapture experiments and the development of a tag-integrated life cycle model designed to simultaneously estimate fish connectivity, populations dynamics and stock assessment. Preliminary results on simulated data reveal that a moderate number of recaptured fish should provide enough information, in both quality and quantity, to reliably estimate metapopulation dynamics, and assess the consequence of the metapopulation structure on stock assessment

Antimicrobial and antifouling activities achieved by extracts of seaweeds from Gulf of California, Mexico

Se analizaron seis especies de macroalgas comunes del Golfo de California: Dictyota flabellata,Padina concrescens, Laurencia johnstonii, Gymnogongrus martinensis, Ulva lactuca y Codium fragile para determinar su potencial aplicación industrial a través de la evaluación de la actividad antibacteriana frente a bacterias patógenas (5 cepas) y el potencial anti-incrustante como inhibidores de crecimiento de especies colonizadoras en ambientes marinos (7 bacterias, 5 hongos y 11 microalgas). Los extractos orgánicos de L. johnstonii, U. lactuca y D. flabellata presentaron antibiosis bacteriana. Los extractos etéreos fueron más activos en comparación con los extractos de butanol frente a la cepa bacteriana Staphylococcus aureus. Los mejores resultados de actividad anti-incrustante se obtuvieron con U. lactuca y L. johnstonii (0.1-1µg ml-1) frente a todas las cepas probadas. C. fragile mostró una significativa actividad anti-incrustante presentado una concentración mínima inhibitoria (MIC) entre 1-10 µg ml-1 frente a las microalgas marinas Rhodosorus magnei, Neorhodella cyanea y Prymnesium calathiferum