Does the invasive plant Elymus athericus modify fish diet in tidal salt marshes?

The invasion of Mont-Saint-Michel Bay salt marshes (France) by a grass species (Elymus athericus) has led to important changes in vegetation cover, which is likely to modify the habitat for many invertebrates. Some of them constitute the main food items for several fish species, such as young sea bass (Dicentrarchus labrax) and sand goby (Pomatoschistus minutus), that feed in salt marsh creeks during high tides. As a result, fish nursery functions of salt marshes could be modified by the E. athericus invasion. In order to test this hypothesis, gut contents of the two most abundant fish species (sea bass and sand goby) were compared before and after E. athericus invasion in the same salt marsh creek and using the same methodology. The accessibility and availability of the main food item, the semi-terrestrial amphipod Orchestia gammarella, were estimated and compared between invaded (dominated by E. athericus) and original areas (dominated by Atriplex portulacoides). Gut content analysis showed a significantly greater percentage of fish leaving with empty guts from E. athericus areas than from A. portulacoides areas. The sea bass diet composition study showed a major shift in the relative importance of the main food items: before E. athericus invasion, diets were dominated by the semi-terrestrial species O. gammarella, whereas after the E. athericus invasion they were dominated by a marine mysid Neomysis integer. The same trend was found for sand gobies, with a shift of the main food item from O. gammarella before invasion to the polychaete Hediste diversicolor after invasion. These trophic changes may be explained by the lower accessibility and availability of O. gammarella in invaded communities than in natural ones. The E. athericus invasion, observed throughout northern Europe, is thus likely to disturb trophic function of natural salt marshes for fish. This preliminary study of the E. athericus invasion is also an illustration that invasive species are an urgent problem in conservation biology

Approche quantitative de la fonction de nourricerie des systèmes estuaires-vasières (cas du bar européen (Dicentrarchus labrax, L. 1758 ; a.k.a. Morone labrax) dans cinq nourriceries du Ponant)

Les populations de poissons côtiers colonisent de manière plus ou moins fréquente et à diverses écophases les écosystèmes estuariens. Les marais salés constituent un des nombreux éléments de ces mosaïques d'écosystèmes. La première partie de ce travail consiste en une approche descriptive de la composition des assemblages piscicoles au travers de l'analyse des guildes écologiques, et débouche sur la définition et la validation de guildes colonisatrices. Elles sont définies puis critiquées au travers de l'étude des populations de poissons présentes dans quatre systèmes estuariens de la façade ouest de la France : Baie du Mont Saint-Michel, Baie de Saint-Brieuc, Estuaire de la Loire et Baie de l'Aiguillon. Le second niveau s'intéresse à la caractérisation de la fonction de nourricerie de ces écosystèmes chez les juvéniles de bars européens (Dicentrarchus labrax) au travers de la définition proposée par Beck et al. (2001). Une approche combinée, basée sur des études de contenus stomacaux et sur l'analyse des rapports isotopiques des muscles de juvéniles capturés dans les marais salés, montre que les poissons s'alimentent activement dans ces systèmes et que les proies consommées in situ contribuent de manière significative à la première année de croissance. Une étude des microstructures des otolithes par M.E.B. révèle la présence de marques spéciales qui peuvent être attribuées au passage dans les marais salés. L'analyse micro structurale montre que le recrutement des jeunes bars est étalé dans le temps avec des migrations marines plus ou moins longues (de 33 à 126 jours). Une fois installés dans les systèmes estuariens, la croissance s'accélère. Une analyse micro chimique des otolithes par ICPMS révèle des compositions caractéristiques de chacune des nourriceries estuariennes. Ceci suggère que les compositions en éléments traces peuvent être utilisées comme signature chimique discriminante chez les poissons. Enfin, après un bilan de cette approche combinée, une réflexion est engagée concernant l'efficacité de ces analyses dans le conseil aux gestionnaires. Une réflexion similaire est menée concernant la pérennité et la reproductibilité de telles études qui mélangent de forts investissements de terrain et de l'écologie théorique (guildes, traits d'histoire de vie).Coastal fish populations settle more or less frequently, at different stages, estuarine systems. Tidal marshes are one of the components of these mosaics of habitats. The first part of this work describes fish assemblages through the utilisation of these systems by fishes analysed in order to propose revised functional classification of ecological guilds. This new classification is used to compare four fish communities of estuarine system of the western coast of France : the Mont Saint-Michel Bay, the Saint-Brieuc Bay, the Loire estuary and the Aiguillon Bay. The second part aims at characterizing the nursery function as defined by Beck et al. (2001). A combinative approach based on gut content analysis, and stable isotope analysis shows that YoY sea bass (Dicentrarchus labrax) that are caught in tidal marshes feed actively in situ and that the salt marsh's preys contribute significantly to the first year's food resources. An examination of the microstructure of the YoY sea bass otoliths using SEM shows characteristic marks, which are interpreted as fingerprints of the passage in the salt marsh. The microstructural analysis showed that sea bass recruit in estuarine areas after variable length of time (33 days to 126 days) spent in marine waters during migration from spawning areas to estuaries. After entry into estuarine complexes, growth rate increases. Microchemical analysis of the whole otolith using ICPMS technology revealed characteristic signatures of each of the studied estuarine systems. This suggests that the chemical composition of trace elements in the otolith can be used as chemical tag of the fish. After a synthesis of this combinative approach, a reflection is committed concerning the effectively of these approach in order to advise managers. The same though is engaged to evaluate the sustainability of these studies that mix strong field investments and theoretical ecology (guilds, life history traits...).LA ROCHELLE-BU (173002101) / SudocPARIS-Museum-Bib. d'ichtyologie (751052306) / SudocSudocFranceF

Encyclopédie des historiographies : Afriques, Amériques, Asies

Quels rapports les sociétés humaines entretiennent-elles avec leur passé et quels récits font-elles du temps révolu ? Pour ce premier volume de l’Encyclopédie des historiographies. Afriques, Amériques, Asies, 157 spécialistes représentant 88 institutions académiques en France et dans le monde explorent l’univers des productions humaines qui constituent des sources pour l’historien et déchiffrent les nombreuses modalités (« scientifiques », littéraires, artistiques, monumentales…) de l’écriture du passé. Évoquant tour à tour l’Afrique, l’Amérique latine, l’Asie, l’Océanie, les 216 notices de l’ouvrage présentent des matériaux historiques de toute nature, issus de toutes les époques, souvent méconnus, ainsi que l’histoire de leurs usages. L’entreprise collective qu’est l’Encyclopédie se veut novatrice : il s’agit de susciter une réflexion historiographique résolument non-occidentalo-centrée qui complète utilement les démarches épistémologiques traditionnelles. Nouvel outil de connaissance historique forgé à l’heure de la mondialisation, l’Encyclopédie des historiographies est aussi une véritable invitation au voyage.What are the different types of relations that non-Western societies upkeep with their past and how are narratives about the past produced by them? In this first volume of the Encyclopaedia of Historiography: Africa, America, Asia, 157 specialists from 88 international academic institutions explore the wealth of evidence that constitutes source material for historians. They also examine the immensely diverse modes or genres of narrated history: “scientific”, literary, artistic, architectural, etc. 216 entries dealing with Africa, Latin America, Oceania, and Asia, cover a large variety of sources, including many which are unfamiliar to the Western or non-Western reader, along with the history of how they have been exploited. By bringing together for the first time such an abundance of material the reader is offered the possibility of exploring continents and building meaningful connections across space and time. In addition to being a new tool for historical enquiry in an era of globalization, this encyclopaedia is also an invitation to travel the world

High Risk of Anal and Rectal Cancer in Patients With Anal and/or Perianal Crohn’s Disease

International audienceBackground & AimsLittle is known about the magnitude of the risk of anal and rectal cancer in patients with anal and/or perineal Crohn’s disease. We aimed to assess the risk of anal and rectal cancer in patients with Crohn’s perianal disease followed up in the Cancers Et Surrisque Associé aux Maladies Inflammatoires Intestinales En France (CESAME) cohort.MethodsWe collected data from 19,486 patients with inflammatory bowel disease (IBD) enrolled in the observational CESAME study in France, from May 2004 through June 2005; 14.9% of participants had past or current anal and/or perianal Crohn’s disease. Subjects were followed up for a median time of 35 months (interquartile range, 29–40 mo). To identify risk factors for anal cancer in the total CESAME population, we performed a case-control study in which participants were matched for age and sex.ResultsAmong the total IBD population, 8 patients developed anal cancer and 14 patients developed rectal cancer. In the subgroup of 2911 patients with past or current anal and/or perianal Crohn’s lesions at cohort entry, 2 developed anal squamous-cell carcinoma, 3 developed perianal fistula–related adenocarcinoma, and 6 developed rectal cancer. The corresponding incidence rates were 0.26 per 1000 patient-years for anal squamous-cell carcinoma, 0.38 per 1000 patient-years for perianal fistula–related adenocarcinoma, and 0.77 per 1000 patient-years for rectal cancer. Among the 16,575 patients with ulcerative colitis or Crohn’s disease without anal or perianal lesions, the incidence rate of anal cancer was 0.08 per 1000 patient-years and of rectal cancer was 0.21 per 1000 patient-years. Among factors tested by univariate conditional regression (IBD subtype, disease duration, exposure to immune-suppressive therapy, presence of past or current anal and/or perianal lesions), the presence of past or current anal and/or perianal lesions at cohort entry was the only factor significantly associated with development of anal cancer (odds ratio, 11.2; 95% CI, 1.18-551.51; P = .03).ConclusionsIn an analysis of data from the CESAME cohort in France, patients with anal and/or perianal Crohn’s disease have a high risk of anal cancer, including perianal fistula–related cancer, and a high risk of rectal cancer