Reproduction of the invasive slipper limpet, Crepidula fornicata , in the Bay of Brest, France

The reproduction of Crepidula fornicata was studied in the Bay of Brest in order to characterise the first step of the reproductive cycle of this invasive species. The survey was carried out from 2000 to 2003 and different parameters were measured, namely, the percentage of the different sexual stages, the straight length of the shell and the percentage of brooding females using a survey of the embryonic development and the fecundity. The juvenile frequency increases generally from mid-June or mid-August, depending on the year. In 2001 and 2003, a first peak was observed as early as May, but it was followed by a rapid disappearance of the individuals. The sex-ratio female/male increased from 0.22 to 0.46 between 2001 and 2003. The sex change between intermediates and females took place mainly in summer and was well marked in 2001 and 2003. The survey of the embryonic development in the egg capsules brooded by the females provided an annual phenology of the laying and hatching processes. The laying period extends from February to September with three to four major periods of egg-laying per year and corresponding hatching periods about 1 month later. Each female lays two to four times per year on average. The first egg-laying concerned fewer females than subsequent ones, except in 2003, and exhibited a higher fecundity. The annual mean of the number of eggs for each stage was not significantly different, thus indicating no significant mortality rate during embryonic development. For the C. fornicata population in the Bay of Brest, several reproductive characteristics tend to highlight its invasive capacity: (1) a long reproductive period, (2) reproduction in a ‘multi-trials' process equivalent to a spreading out of the risks and (3) a relatively high fecundit

Differential δ13C and δ15N signatures among scallop tissues: Implications for ecology and physiology

International audienceThere have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle), of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicators (stable carbon and nitrogen isotopes ratios, biochemical components and seston Chl a) to track nutritive activity and energy allocation in P. maximus from the Bay of Brest (France). In addition to seasonal variation in the isotopic composition of P. maximus tissues, we found strong differences in the mean isotopic signatures of different organs. This has serious implications for interpretation of animal diets and potential use in animal physiology. Furthermore, we present evidence that seasonal variations of metabolism will cause changes in the isotopic composition not related to changes in the diet. Interpretation of isotopic data may require consideration of values from several separate organs. Finally, 15N appears powerful to track metabolite fates in the scallop P. maximus

A multidisciplinary approach to the spatial dimension in ecosystem-based fisheries management

This study considers how to reconcile different spatial scales to find the best common denominator to be used as an ecosystem-based management unit. For this, two fishery production zones differing ecologically, economically, legally and institutionally were investigated. The first case study is located within French territorial waters, in a MPA created in 2007- the Parc Naturel Marin d'Iroise (PNMI). The second case study, the Bay of Biscay, covers both territorial waters and the French exclusive economic zone. The paper adopts a multidisciplinary approach. Relevant questions concern how marine space is shared between exploited species and fishing fleets, especially the spatial mobility strategies they employ. An assessment of the institutional system established for the PNMI contributes to the discussion of changes in coastal space use. It is obvious that the area in need of protection, defined on the basis of essential fish habitats, does not solely concern the fisheries located within the coastal zone. Experiments conducted by scientists and professionals in the Bay of Biscay provide other key points for the discussion in terms of what institutional frameworks to promote

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Compréhension des mécanismes de biominéralisation (quantification spatialisée des fractions minérale et organique et influence de facteurs environnementaux)

Malgré un grand nombre d études relatives à l utilisation des otolithes, les connaissances sur les mécanismes de formation de l otolithe et leur modulation par les facteurs environnementaux et physiologiques restent parcellaires. En particulier, la caractérisation des fractions minérale et organique des structures de I otolithe et l influence de leurs propriétés qualitatives et quantitatives sur l opacité restent peu documentées, Pourtant ces informations sont d importance en vue d une calibration robuste de l archive otolithe . Le premier axe de recherche s est concentré sur l opacité et les effets de la température, la croissance et du métabolisme à partir d expérimentation en milieu contrôlé. L opacité a ainsi été définie comme une fonction de deux contributions énergétiques: l une relative à la croissance somatique et l autre indépendante de la croissance somatique et associée à des mécanismes de maintenance. Le second axe de recherche s est focalisé sur l analyse des propriétés physico-chimiques des structures de l otolithe. Le développement d une approche de micro-spectrométrie Raman, non destructive, nous a permis de discriminer de manière quantitative des signatures organique et minérale à une très haute résolution. La caractérisation de micro et macrostructures a permis la construction d un modèle de prédiction de l opacité en fonction des signatures de ces deux fractions. Si la relation entre facteurs modulant la biominéralisation et caractéristiques physicochimiques des structures reste à établir, les résultats obtenus dans cette thèse ouvrent de pistes prometteuses pour une meilleure compréhension des mécanismes de formation de l otolithe.Despite numerous applications on the use of otoliths at both population and individual levels, knowledge regarding the mechanisms of the otolith and their variations with environmental and physiological factors has to be improved. In particular, the characterization of mineral and organic fractions of the otolith structures and the influence of their qualitative and quantitative composition on the opacity remain poorly documented. Vet this information is of key interest for the calibration of the archive otolith allowing a robust analysis of information. The first issue of this study focused on the analysis of the opacity and the effects of temperature, growth and metabolism through experiments in controlled conditions. Results led to the modelling of opacity as a function of two energetic contributions: one related to somatic growth and the other independent of somatic growth and associated to maintenance mechanisms. The second issue dealt with the physico-chemical characterization of otolith structures. The development of an approach based on micro-spectrometry Raman, non-destructive, has allowed to quantitatively discriminating organic and mineral signatures at very high resolution. It has led to the characterization of microstructures (L and D zones) and macrostructures (translucent and opaque zones) led to the development of a predictive model of opacity from the signatures of these two fractions. The relationship between the environmental and metabolic factors and the chemical composition of structural features has still to be established but our results promising perspectives for a better understanding of the mechanisms of otolith biomineralisation.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Variations of the stable isotope ratios of carbon and oxygen of the Patella vulgata (Linnæus, 1758) shells according to the vertical zonation of collect

Isotopic investigations performed on carbonated shells from anthropogenic middens provide information about past environments and cultural practices of the human populations who left these vestiges. Patella vulgata, an intertidal gastropod that inhabits northwest Atlantic rocky shores, is commonly occurring as shells in European shell middens, constituting therefore a good candidate for isotopic studies. However, high tidal ranges characterize most of European Atlantic coastlines, and species largely distributed upper to lower foreshore, as Patella sp., may encounter pronounced variations in immersion time depending on their elevation in the intertidal zone, which could affect their shell stable isotopic ratios. In this study, we compared carbon and oxygen stable isotopes of Patella vulgata shells collected in the same station at three different cotidal levels. Isotopic measurements are analyzed in terms of individual growth and aim to characterize the cotidal origin of the specimens. Our results demonstrate the absence of a significant link between the cotidal level on the shore and the growth and δ18O profiles of the shell, as high shore and low shore shells show the highest similitude while medium shore shells had a reduced growth with a higher heterogeneity. Consequently, the SST reconstructions were not significantly different. Thus, the use of the δ18O of archaeological shells as an SST proxy appears unaffected by the cotidal origin of the specimens. In contrast, the δ13C scales from the high shore (lower δ13C values) to the low shore (higher δ13C), constituting a promising new proxy for determining the precise elevation in the intertidal zone where the shells were collected

Characterising Inter-Individual Growth Variability of Patella vulgata Shell Through Calcein Marking Experiments: Consequences for Palaeo-Environmental Studies

International audienceSclerochronological data from archaeological shell middens provides crucial information about past environments and subsistence practices of coastal human populations. These studies rely on a strong knowledge of species-specific growth patterns, as it is the main driver of the quantity and quality of information recorded in biogenic carbonates. The limpet Patella vulgata is highly represented in eastern Atlantic shell middens. In this study, the micro-increment formation of its shell was investigated through in situ marking experiments, using calcein fluorochrome (150 mg.L−1) coupled with cohort study and local SST recording. Calcein-stained growth structures confirmed the efficacy of the fluorochrome, and our results shows a disturbed tidal increment formation, with on average more than one increment per day, but less than one increment per tide. Growth is not mainly influenced by environmental factors, but could be forced by competition among limpets and endogenous factor (age and sex), resulting in a highly heterogenous population in terms of growth rates. Growth interruption could not be detected solely by micro-increment observation, causing a major issue for cross-calibration with recorded temperatures, sclerochronological estimation of growth and isotopic profiles. For palaeo-environmental application, we recommend to consider that there is no general population pattern, even at a micro-habitat scale

Effect of photoperiod on conditioning of the great scallop

International audienceA 45 days experiment was conducted by exposing adult scallops with empty gonads to three different photoperiod regimes under constant food and temperature conditions: Simulated natural/decreasing photoperiod (N), constant photoperiod (C) and increasing photoperiod (I). At the end of the experiment the I and C groups had significantly higher gonad indexes and larger oocyte diameters compared to the N group. No significant changes were found in the N group during the experiment. The adductor muscles and digestive glands did not change significantly during the experiment and no differences were found between the groups. These results suggest that photoperiod affects early rebuilding of gonads in scallops from Western Norway