Éditeur(s) : EDP Sciences
Résumé : Bonamiosis is a parasitic disease (causative agent: Bonamia ostreae) affecting the European flat oyster Ostrea edulis, responsible for a drastic decline in its aquaculture production. Selective breeding programs for resistance to bonamiosis have been undertaken to counter this disease. In the present study, a 6-month cohabitation challenge experiment was performed in order to transmit the disease from wild oysters injected with the parasite to two tested families of oysters (20 and 8-month old at the beginning of the experiment, with different genetic backgrounds) originating from a selective breeding program developed by IFREMER in France. Mortalities were checked daily and ventricular heart smears were performed on dying or moribund oysters to detect the level of infection by B. ostreae. Mortality started after 4 months of cohabitation in the tested oysters. The cumulative mortalities after 6 months were 58% for the wild oysters, 9% for Family 1 (20-month old) and 20% for Family 2 (8-month old). In the dying oysters, the parasite could be detected in 67% of the wild oysters, 68% of Family 1 and 89% of Family 2. It was detected in only 11% of the surviving oysters of Family 2. The mortality and the level of infection by the parasite were significantly higher in Family 2 than in Family 1. Our results demonstrate that prespawning oysters as young as 1 year-old can become infected with the parasite and, most importantly, can die from bonamiosis. This result is inconsistent with the commonly accepted critical age of 2 years-old for the disease development. Additionally, no clear relationship between shell length and level of infection was observed. We also review the different methods for infection of the European flat oyster O. edulis with B. ostreae under experimental conditions and their main results.
La bonamiose est une maladie parasitaire (agent causal : Bonamia ostreae) affectant l'huître plate européenne Ostrea edulis, responsable d'un déclin drastique de sa production aquacole. Des programmes de sélection pour la résistance à la bonamiose ont été entrepris pour contrer cette maladie. Dans cette étude, une expérience de 6 mois d'infection par cohabitation a été réalisée de manière à transmettre la maladie à partir d'huîtres sauvages injectées avec le parasite vers deux familles testées d'huîtres (âgées de 20 et 8 mois en début d'expérience, avec des origines génétiques différentes) issues du programme de sélection développé par IFREMER en France. Les mortalités ont été vérifiées quotidiennement et des frottis de coeur ventriculaire réalisés sur les huîtres mortes ou moribondes pour détecter le niveau d'infection par B. ostreae. La mortalité a commencé chez les huîtres testées après 4 mois de cohabitation. Les mortalités cumulées après 6 mois étaient de 58 % chez les huîtres sauvages, 9 % chez la Famille 1 (âgées de 20 mois) et 20 % chez la Famille 2 (âgées de 8 mois). Chez les huîtres mourantes, le parasite a pu être détecté chez 67 % des huîtres sauvages, 68 % de la Famille 1 et 89 % de la Famille 2. Il n'a pu être détecté que chez 11 % des huîtres survivantes de la Famille 2. La mortalité et le niveau d'infection par le parasite étaient significativement plus élevés chez la Famille 2 que chez la Famille 1. Nos résultats démontrent que des huîtres âgées de un an peuvent devenir infectées par le parasite et surtout, peuvent mourir de bonamiose. Ce résultat contraste avec l'âge critique de développement de la maladie communément accepté de 2 ans. De plus, aucune relation claire entre la longueur de la coquille et le niveau d'infection n'a été observée. Nous faisons également la revue des différentes méthodes d'infection de l'huître plate européenne O. edulis avec B. ostreae en conditions expérimentales et leurs principaux résultats.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2008-12 , Vol. 21 , P. 423-439

Droits : EDP Sciences, IFREMER, IRD 2008
http://archimer.ifremer.fr/doc/2008/publication-4783.pdf
DOI:10.1051/alr:2008053
http://archimer.ifremer.fr/doc/00000/4783/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Geographical distribution of parasite species can provide insights into the evolution and diversity of parasiticcommunities. Biogeography of marine parasites is poorly known, especially because it requires anunderstanding of host-parasite interactions, information that is rare, especially over large spatial scales.Here, we have studied the biogeographical patterns of dactylogyrid parasites of chaetodontids, one of themost well-studied fish families, in the tropical Indo-west Pacific region. Dactylogyrid parasites were collectedfrom gills of 34 butterflyfish species (n = 560) at nine localities within an approximate area of62 million km2. Thirteen dactylogyrid species were identified, with richness ranging from 6 to 12 speciesat individual localities. Most dactylogyrid communities were dominated by Haliotrema angelopterum orHaliotrema aurigae, for which relative abundance was negatively correlated (q = !0.59). Parasite richnessand diversity were highest in French Polynesia and the Great Barrier Reef (Australia) and lowest in Palau.Three biogeographic regions were identified based on dactylogyrid dissimilarities: French Polynesia,characterised by the dominance of H. angelopterum, the western Pacific region dominated by H. aurigae,and Ningaloo Reef (Australia), dominated by Euryhaliotrema berenguelae. Structure of host assemblageswas the main factor explaining the dissimilarity (turnover and nestedness components of the Bray-Curtis dissimilarity and overall Bray-Curtis dissimilarity) of parasite communities between localities,while environment was only significant in the turnover of parasite communities and overall dissimilarity.Spatial structure of localities explained only 10% of the turnover of parasite communities. The interactionof the three factors (host assemblages, environment and spatial structure), however, explained the highestamounts of variance of the dactylogyrid communities, indicating a strong colinearity between the factors.Our findings show that spatial arrangement of chaetodontid dactylogyrids in the tropical Indo-westPacific is primarily characterised by the turnover of the main Haliotrema spp., which is mainly explainedby the structure of host assemblages.
ISSN: 0020-7519

hal-01562156
https://hal-univ-perp.archives-ouvertes.fr/hal-01562156
DOI : 10.1016/j.ijpara.2017.01.006

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
We studied the monogenean communities of 34 species of butterflyfish from the tropical Indo-West Pacific, identifying 13 dactylogyrid species (including two species that are presently undescribed). Monogenean assemblages differed significantly between host species in terms of taxonomic structure, intensity and prevalence. Parasite richness ranged from 0 (Chaetodon lunulatus) to 11 (C. auriga, C. citrinellus and C. lunula). Host specificity varied between the dactylogyrids species, being found on 2-29 of the 34 chaetodontid species examined. Sympatric butterflyfish species were typically parasitized by different combinations of dactylogyrid species, suggesting the existence of complex host-parasite interactions. We identified six clusters of butterflyfish species based on the similarities of their dactylogyrid communities. Dactylogyrid richness and diversity were not related to host size, diet specialization, depth range or phylogeny of butterflyfish species. However, there was a weak positive correlation between monogenean richness and diversity and host geographical range. Most communities of dactylogyrids were dominated by Haliotrema aurigae and H. angelopterum, indicating the importance of the genus Haliotrema in shaping monogenean communities of butterflyfishes. This study casts light on the structure of the monogenean communities of butterflyfishes, suggesting that the diversity and complexity of community structures arises from a combination of host species-specific parameters.
ISSN: 0031-1820

hal-01380679
https://hal-univ-perp.archives-ouvertes.fr/hal-01380679
DOI : 10.1017/S0031182016001463

Éditeur(s) : HAL CCSD Frontiers Media
Résumé : International audience
The Anopheles midgut hosts diverse bacterial communities and represents a complex ecosystem. Several evidences indicate that mosquito midgut microbiota interferes with malaria parasite transmission. However, the bacterial composition of salivary glands and ovaries, two other biologically important tissues, has not been described so far. In this study, we investigated the dynamics of the bacterial communities in the mosquito tissues from emerging mosquitoes until 8 days after a blood meal containing Plasmodium falciparum gametocytes and described the temporal colonization of the mosquito epithelia. Bacterial communities were identified in the midgut, ovaries, and salivary glands of individual mosquitoes using pyrosequencing of the 16S rRNA gene. We found that the mosquito epithelia share a core microbiota, but some bacteria taxa were more associated with one or another tissue at a particular time point. The bacterial composition in the tissues of emerging mosquitoes varied according to the breeding site, indicating that some bacteria are acquired from the environment. Our results revealed temporal variations in the bacterial community structure, possibly as a result of the mosquito physiological changes. The abundance of Serratia significantly correlated with P. falciparum infection both in the midgut and salivary glands of malaria challenged mosquitoes, which suggests that interactions occur between microbes and parasites. These bacteria may represent promising targets for vector control strategies. Overall, this study points out the importance of characterizing bacterial communities in malaria mosquito vectors.
ISSN: 1664-302X

hal-01546162
https://hal.archives-ouvertes.fr/hal-01546162
DOI : 10.3389/fmicb.2015.01500

Éditeur(s) : Université des Sciences et Techniques du Languedoc, Montpellier
Résumé : On étudie les parasitoses à Marteilia refringens et à Haplosporidium armoricanum de l’huître plate européenne Ostrea edulis. L’étude de M. refringens précise certains aspects de la biologie de l’agent infectieux. Elle montre que les modalités du cycle de développement du parasite et l‘ultrastructure des stades les plus évolués de la sporogenèse peuvent être modifiées selon les conditions hydrobiologiques du milieu dans lequel est cultivé l’hôte. Elle établi que l’action du parasite conduit à la destruction des épithéliums digestifs de l’huître et s’exerce en interférant avec le métabolisme protéique d’O. edulis. Elle précise l‘ultrastructure des cellules impliquées dans des proliférations hémocytaires atypiques associées à la parasitose et établit la nature néoplasique du phénomène. L’étiologie de l’hémocytose n’est toutefois pas déterminée. Enfin elle met en évidence un cas d‘hyperparasitisme de M. refringens par une Microsporidie. L’étude ultrastructurale de la sporogenèse et des effets pathogènes du Protozoaire vis à vis de l’hôte nous conduit à identifier l’hyperparasite comme Nosema ormieresi et montre que certains stade de M. refringens peuvent être fortement altérés par l’infestation microsporidienne. L’étude d’une Haplosporidie observée chez O. edulis du bassin d’Arcachon (France) nous amène à comparer la sporagenèse du parasite avec celle d’autres Haplosporidies d’invertébrés marins. Les caractéristiques de la spore nous incitent à inclure le parasite dans le genre Haplosporidium et le rapprochement du Protozoaire avec Minchinia armoricana conduit à l’identifier comme Haplosporidium armoricanum. L’étude de la pathogenèse des infections à M. refringens et à H. armoricanum permet de préciser les relations entre les parasites étudiés et leur hôte commun l’huître plate et les interactions hôte-parasite-milieu pouvant intervenir dans le caractère des deux maladies.

Droits : The Author, Univ. Montpellier, ISTPM
http://archimer.ifremer.fr/doc/00083/19411/17022.pdf
http://archimer.ifremer.fr/doc/00083/19411/

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : 5 pages
International audience
This study investigates the recent evolution of a rich parasite community associated with one of the world's most invasive species, the cichlid fish Oreochromis mossambicus. Populations from the species' native range (Mozambique) are compared to a population from New Caledonia (Wester Pacific), an island where the species was introduced in 1954. The results support the complete local extinction of the gill parasite community in the course of the invasion process. Up to six gill parasite species per locality were documented in the O. mossambicus native range, and previous surveys consistently reported at least one parasite species introduced along African cichlid species established out of Africa. The absence of parasites in New Caledonia is therefore exceptional. This can be attributed to local factors, such as a strong initial population bottleneck, the likely absence of multiple host introductions, and the frequent occurrence of brackish watersheds that might enhance the probability for natural deparasitation.
ISSN: 0932-0113

hal-01356378
https://hal.archives-ouvertes.fr/hal-01356378
PUBMED : 27334451
DOI : 10.1007/s00436-016-5168-1

Éditeur(s) : HAL CCSD Cushman Foundation for Foraminiferal Research
Résumé : International audience
Benthic foraminifera are heterotrophic protists that utilize different trophic mechanisms and nutritional resources. They exhibit a wide range of trophic behaviours: selective (grazing) and indiscriminate herbivory, symbiosis, carnivory, parasitism, uptake of dissolved organic matter, passive suspension feeding and, most commonly, deposit feeding. The benthic foraminifera Ammonia tepida, previously known as an herbivore, fed as a carnivore in laboratory experiments where mobile metazoans were provided. We observed predation on the three types of metazoans provided: nematodes, copepods, and a larval gastropod. This foraminifera used its pseudopodial network to entrap the invertebrates, which were then stripped of their soft internal tissues within 24 hours. Our experiments are the first to demonstrate that Ammonia tepida, despite its limited motility, is able to utilize larger mobile animals as a food source. The great abundance of small metazoans in most marine environments suggests that they are a food source for foraminifera. Further study of foraminiferal feeding strategies will enhance our understanding of their role in marine communities.
ISSN: 0096-1191

hal-01248040
https://hal.archives-ouvertes.fr/hal-01248040
https://hal.archives-ouvertes.fr/hal-01248040/document
https://hal.archives-ouvertes.fr/hal-01248040/file/dupuy%20et%20al%202010.pdf

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Based on their small size and genomic properties, ultrasmall prokaryotic groups like the Candidate Phyla Radiation have been proposed as possible symbionts dependent on other bacteria or archaea. In this study, we use a bipartite graph analysis to examine patterns of sequence similarity between draft and complete genomes from ultrasmall bacteria and other complete prokaryotic genomes, assessing whether the former group might engage in significant gene transfer (or even endosymbioses) with other community members. Our results provide preliminary evidence for many lateral gene transfers with other prokaryotes, including members of the archaea, and report the presence of divergent, membrane-associated proteins among these ultrasmall taxa. In particular, these divergent genes were found in TM6 relatives of the intracellular parasite Babela massiliensis.
ISSN: 1462-2912

Droits : http://creativecommons.org/licenses/by/
hal-01480348
http://hal.upmc.fr/hal-01480348
http://hal.upmc.fr/hal-01480348/document
http://hal.upmc.fr/hal-01480348/file/emi13477.pdf
DOI : 10.1111/1462-2920.13477

Éditeur(s) : HAL CCSD Kasetsart University
Résumé : http://www.ceropath.org/references/rodent_protocols_book
Technical book
"Protocols for field and laboratory rodent studies" present the best practices for the studies of rodents and rodent-borne pathogens and parasites from the field to the laboratory. It aims at covering the different steps of rodent studies: 1) Trapping, 2) Dissection and preparation of tissue samples for pathogens screening, 3) Identification of species, 4) Isolation of helminths, 5) Preparing rodent specimens for collections. This book gathers accurate recommendations and techniques, based on those generally accepted in the literature and adapted from the experience of the different authors during rodent surveys and laboratory work. Its presentation is designed to work in the fields with a clear and colorful organization of each chapter, with: inserts providing definitions and recommendations, protocols detailed step by step, and an emphasis on illustrations with several photographs. This book is a publication generated by the CERoPath project (Community Ecology of Rodents and their Pathogens in a changing environment, www.ceropath.org) funded by the French Ministry of Research from 2008 to 2011.
http://hal.ird.fr/ird-00714514

ird-00714514
http://hal.ird.fr/ird-00714514
http://hal.ird.fr/ird-00714514/document
IRD : fdi:010056183

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: Increasingly, similarity networks are being used for evolutionary analyses of molecular datasets. These networks are very useful, in particular for the analysis of gene sharing, lateral gene transfer and for the detection of distant homologs. Currently, such analyses require some computer programming skills due to the limited availability of user-friendly freely distributed software. Consequently, although appealing, the construction and analyses of these networks remain less familiar to biologists than do phylogenetic approaches. Results: In order to ease the use of similarity networks in the community of evolutionary biologists, we introduce a software program, EGN, that runs under Linux or MacOSX. EGN automates the reconstruction of gene and genome networks from nucleic and proteic sequences. EGN also implements statistics describing genetic diversity in these samples, for various user-defined thresholds of similarities. In the interest of studying the complexity of evolutionary processes affecting microbial evolution, we applied EGN to a dataset of 571,044 proteic sequences from the three domains of life and from mobile elements. We observed that, in Borrelia, plasmids play a different role than in most other eubacteria. Rather than being genetic couriers involved in lateral gene transfer, Borrelia's plasmids and their genes act as private genetic goods, that contribute to the creation of genetic diversity within their parasitic hosts. Conclusion: EGN can be used for constructing, analyzing, and mining molecular datasets in evolutionary studies. The program can help increase our knowledge of the processes through which genes from distinct sources and/or from multiple genomes co-evolve in lineages of cellular organisms.
ISSN: 1471-2148

hal-01544799
https://hal.archives-ouvertes.fr/hal-01544799
DOI : 10.1186/1471-2148-13-146

Éditeur(s) : Elsevier Sci Ltd
Résumé : Time-series studies have reported trophic cascades in land, freshwater and marine environments in many geographic areas. However, the spatial extent of habitats, a key metric of ecosystem structure, has not been mapped in these studies. Marine reserves can provide experimental, before-after and inside-outside (control-impacted), situations for assessing the impact of fishing on ecosystems. We mapped seabed habitats and their associated communities (biotopes) in New Zealand's oldest marine reserve for comparison with pre-reserve maps created about 30 years previously. Areas grazed bare by sea urchins were entirely replaced in the centre of the reserve by kelp, or alga turf, an intermediate biotope between heavily grazed encrusting algae and lightly grazed kelp. Urchins declined following increased abundance and body size of spiny (rock) lobsters and fish (especially snapper) in the reserve but maintained bare rock outside. While this gradient in habitat change matched the gradient of predator abundance, it also matched the extent of reef habitat area. Thus the trophic cascade may be influenced by the effect of habitat on the abundance and behavioural interactions of urchins and their predators. Further ecosystem changes may arise should the abundance of mega-predators, such as seals, cetaceans and large sharks, increase in the region; if parasites become pathogenic; and/or when invasive species reach the reserve. No-take marine reserves provide real-world experiments that show the importance of species in food webs, and the consequences of fishing for ecosystems. Because these changes in ecosystem structure may continue, and will vary with environment, climate and species distributions, reserves need to be permanent and replicated geographically. Habitat maps should be produced for all reserves to enable ecological changes in the ecosystem to be spatially quantified. (C) 2012 Elsevier Ltd. All rights reserved.
Biological Conservation (0006-3207) (Elsevier Sci Ltd), 2012-10 , Vol. 155 , P. 193-201

Droits : 2012 Elsevier Ltd. All rights reserved
http://archimer.ifremer.fr/doc/00107/21842/20067.pdf
DOI:10.1016/j.biocon.2012.05.009
http://archimer.ifremer.fr/doc/00107/21842/