Introduction pratique à la systématique des organismes des eaux continentales françaises.- 8 : Rotifères

The authors propose a key for the families, a key for the principal planktonic genera and a key for the planktonic species of the most common genera in the french or european continental waters. These keys are found on morphological, anatomical and ecological characters easy to observe, even for unspecialized people. Their reading is made easier by the presence of connecting figures and a short but enough presentation of the group. The preference given to the planktonic genera and species insolve the forsaking of others which existence must not be forgotten by the reader !Outre une clé des familles, les auteurs proposent dans cet opuscule une clé des principaux genres planctoniques et une clé des espèces planctoniques des genres les plus communs dans les eaux continentales françaises ou européennes. Ces clés s'appuient sur des caractères morphologiques, anatomiques et écologiques aisés à observer, même pour des non spécialistes. Leur lecture est facilitée par la présence de figures correspondantes et une présentation sommaire mais suffisante du groupe. Le choix délibéré de privilégier les espèces planctoniques, dont les limites sont nécessairement plus ou moins subjectives, implique l'abandon d'espèces ne répondant pas aux critères définis mais dont le lecteur ne devra pas oublier l'existence.Pourriot Roger, Francez André-Jean. Introduction pratique à la systématique des organismes des eaux continentales françaises.- 8 : Rotifères. In: Bulletin mensuel de la Société linnéenne de Lyon, 55ᵉ année, n°5, mai 1986. pp. 148-176

Impact des changements globaux sur le fonctionnement des tourbières (couplage C-N-S et interactions biotiques)

Dans un contexte de changements globaux, la fonction de "puits" de carbone (C) des tourbières est susceptible de basculer vers une fonction "source", en libérant dans l'atmosphère de grandes quantités de C initialement stockées dans la tourbe. Cette thèse vise à caractériser et quantifier, à différents niveaux d'organisation, i) l'impact d'un réchauffement climatique sur le fonctionnement biogéochimique (C-N-S) d'une tourbière à Sphaignes et ii) l'impact de la restauration d'une tourbière abandonnée après exploitation sur les interactions entre les plantes recolonisatrices (Eriophorum angustifolium), la macrofaune (Lumbricus rubellus) et les microorganismes potentiellement impliqués dans la régénération du processus de tourbification. Le fonctionnement de la tourbière et les interactions biotiques ont été étudiées par couplage des cycles C-N-S et traçage isotopique 13C-15N-34S. Une augmentation modérée de + 1C simulée par "Open Top Chambers" (OTCs) diminue significativement les flux de C à l'échelle de l'écosystème, la production primaire des Sphaignes et le compartiment microbien étant les plus affectés. A l'échelle des communautés, l'activité des bactéries anaérobies, des champignons et des protozoaires (estimée par SIP 13C-PLFAs) est significativement ralentie. Nous avons montré qu'un organisme ingénieur comme le ver de terre L. rubellus jouait un rôle positif dans le recyclage de la matière organique en fournissant indirectement des éléments (C > N > S) à la plante. Ces transferts seraient dépendants des traits fonctionnels de l'organisme. A l'échelle de l'individu, nous avons caractérisé par approche NanoSIMS, les transferts "anticorrélés" N-S ver de terre -> tourbe.In a context of global change, peatlands "sink" function of carbon (C) is likely to switch to a "source" function, releasing into the atmosphere large quantities of C initially stored in the peat. This thesis aims to characterize and quantify at different levels of organization: i) the impact of global warming on Sphagnum-peatland biogeochemical functioning (CNS) and ii) the impact of restoration of peatland abandoned after harvesting of peat on the interactions between recolonizing plants (Eriophorum angustifolium), macrofauna (Lumbricus rubellus) and the microorganisms potentially involved in the regeneration process of peat forming. The peatland functioning and biotic interactions have been studied by coupling C-N-S and isotope tracing 13C-15N-34S. A moderate increase of + 1C simulated by "Open Top Chambers" (OTCs) significantly reduces C fluxes at the ecosystem level, the primary production of Sphagnum and the microbes are most affected. At the community level, the activity of anaerobic bacteria, fungi and protozoa (estimated by SIP 13C-PLFAs) was significantly slowed. We showed that a soil engineer as the earthworm L. rubellus played a positive role in recycling organic matter indirectly by providing elements (C > N > S) to the plant. Transfers depend on the functional traits of the organism. At the individual level, we have characterized using NanoSIMS, "anticorrelated" NS transfers from earthworms to peat.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Rôle régulateur de la macrofaune lombricienne dans la dynamique de l'herbicide atrazine en sol cultivé tempéré

RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Population dynamics and food preferences of the testate amoeba Nebela tincta major-bohemica-collaris complex (Protozoa) in a Sphagnum peatland

International audiencePopulation dynamics and food preferences of the testate amoeba species complex Nebela tincta major-bohemica-collaris (“Nebela collaris sensu lato”) were described from a Sphagnum peatland over one growing season. The average abundance of Nebela collaris sensu lato was 29582 ind. l-1 active, and 2263 ind. l-1 encysted forms. On average, 17.4% of Nebela collaris sensu lato specimens were observed associated with prey, 71% of which could not be identified because of their poor preservation state. Among the identified prey, those most frequently ingested were micro-algae (45% of the total predator-prey associations, especially diatoms: 33%), and spores and mycelia of fungi (36%). Large ciliates, rotifers and small testate amoebae were also ingested, but mainly in summer. The seasonal variations in the proportions of prey categories in the ecosystem and the percentage of identifiable prey lead us to hypothesise that (1) Nebela collaris sensu lato ingest mainly immobile, senescent or dead organisms, and (2) that the more mobile micro-organisms such as ciliates and micro-Metazoa become more accessible, in relatively dry conditions, when the water film is thi

Diversity and comparative genomics of chimeric viruses in Sphagnum-dominated peatlands

A correction has been published:Virus Evolution, Volume 2, Issue 2, 1 July 2016, vew030, https://doi.org/10.1093/ve/vew030International audienceA new group of viruses carrying naturally chimeric single-stranded (ss) DNA genomes that encompass genes derived from eukaryotic ssRNA and ssDNA viruses has been recently identified by metagenomic studies. The host range, genomic diversity, and abundance of these chimeric viruses, referred to as cruciviruses, remain largely unknown. In this article, we assembled and analyzed thirty-seven new crucivirus genomes from twelve peat viromes, representing twenty-four distinct genome organizations, and nearly tripling the number of available genomes for this group. All genomes possess the two characteristic genes encoding for the conserved capsid protein (CP) and a replication protein. Additional ORFs were conserved only in nearly identical genomes with no detectable similarity to known genes. Two cruciviruses possess putative introns in their replication-associated genes. Sequence and phylogenetic analyses of the replication proteins revealed intra-gene chimerism in at least eight chimeric genomes. This highlights the large extent of horizontal gene transfer and recombination events in the evolution of ssDNA viruses, as previously suggested. Read mapping analysis revealed that members of the 'Cruciviridae' group are particularly prevalent in peat viromes. Sequences matching the CP ranged from 0.6 up to 10.9 percent in the twelve peat viromes. In contrast, from sixty-nine available viromes derived from other environments, only twenty-four contained cruciviruses, which on average accounted for merely 0.2 percent of sequences. Overall, this study provides new genome information and insights into the diversity of chimeric viruses, a necessary first step in progressing toward an accurate quantification and host range identification of these new viruses

Short-term changes in the structure of microbial communities following bare peat recolonization by Agrostis stolonifera and Eriophorum angustifolium.

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