Can the intake of antiparasitic secondary metabolites explain the low prevalence of hemoparasites among wild Psittaciformes?

Background: Parasites can exert selection pressure on their hosts through effects on survival, on reproductive success, on sexually selected ornament, with important ecological and evolutionary consequences, such as changes in population viability. Consequently, hemoparasites have become the focus of recent avian studies. Infection varies significantly among taxa. Various factors might explain the differences in infection among taxa, including habitat, climate, host density, the presence of vectors, life history and immune defence. Feeding behaviour can also be relevant both through increased exposure to vectors and consumption of secondary metabolites with preventative or therapeutic effects that can reduce parasite load. However, the latter has been little investigated. Psittaciformes (parrots and cockatoos) are a good model to investigate these topics, as they are known to use biological control against ectoparasites and to feed on toxic food. We investigated the presence of avian malaria parasites (Plasmodium), intracellular haemosporidians (Haemoproteus, Leucocytozoon), unicellular flagellate protozoans (Trypanosoma) and microfilariae in 19 Psittaciformes species from a range of habitats in the Indo-Malayan, Australasian and Neotropical regions. We gathered additional data on hemoparasites in wild Psittaciformes from the literature. We considered factors that may control the presence of hemoparasites in the Psittaciformes, compiling information on diet, habitat, and climate. Furthermore, we investigated the role of diet in providing antiparasitic secondary metabolites that could be used as self-medication to reduce parasite load. Results: We found hemoparasites in only two of 19 species sampled. Among them, all species that consume at least one food item known for its secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, were free from hemoparasites. In contrast, the infected parrots do not consume food items with antimalarial or even general antiparasitic properties. We found that the two infected species in this study consumed omnivorous diets. When we combined our data with data from studies previously investigating blood parasites in wild parrots, the positive relationship between omnivorous diets and hemoparasite infestation was confirmed. Individuals from open habitats were less infected than those from forests. Conclusions: The consumption of food items known for their secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, as well as the higher proportion of infected species among omnivorous parrots, could explain the low prevalence of hemoparasites reported in many vertebrates

Suivi de la dynamique du parasite Marteilia refringens dans trois populations d'huîtres plates, Ostrea edulis

Marteilia refringens est un Protozoaire parasite de la glande digestive de l'huître plate, Ostrea edulis, à l'origine de mortalités bloquant l'élevage de cette espèce depuis 1968. Appartenant au phylum Paramyxea, il est caractérisé par un développement endogène complexe sous formes de clivages internes successifs dans une cellule primaire aboutissant à une structure de cellules emboîtées. Le seul moyen de contrôle de la marteiliose est une gestion du risque de contamination. Dans ce cadre, la connaissance du cycle parasitaire de M. refringens est primordiale. Notre étude a consisté à placer dans un biotope où fonctionne le cycle de Marteila refringens, une claire ostréicole, des huîtres plates infectées depuis un an et deux ans avec des jeunes huîtres saines qui ont été infectées au cours de l'étude, et à comparer la dynamique du parasite dans chacune des populations. Plusieurs paramètres ont été étudiés : la prévalence, l'intensité parasitaire (en différenciant plusieurs stades de maturité) et une étude  des stades de développement du parasite. Ce suivi a 'été réalisé en histologie et complété en hybridation in situ dans certains cas. Cette étude a permis de décri're la cinétique de l'infection des huîtres saines et de montrer qu'elle intervenait deux mois après la libération des premières spores par les huîtres infectées. De plus, si une multiplication interne a été démontrée, des phases du cycle décrites par certains auteurs n'ont pas été observées. Enfin, des formes de M. refringens ont été mises en évidence dans l'espèce Cereus pedunculatus, sans que cet hôte apparaisse fonctionnel toutefois. Ce modèle d'infection semi-expérimental a montré qu'il constituait un système de reproduction quasiment contrôlé de la marteiliose et représente un atout majeur pour l'étude du cycle biologique de M. refringens

ETUDE DE LA DYNAMIQUE DU PARASITE MARTEILIA REFRINGENS CHEZ SON HOTE OSTREA EDULIS

NANTES-Ecole Nat.Vétérinaire (441092302) / SudocSudocFranceF

Certified and peasant seeds: which network for millet seed supply?

International audienceIn West Africa, alliance built between researchers, policy makers and fondation aspire to enhance agricultural productivity, food security and rural well-being of 33 million smallholder farming households. In order to, they bred and released quality-improved certified seed through a network of agro-dealers and regulatory frameworks. Supported at the expense of peasant seed used and shared for ages by farmers, this process is likely to impact agroecosystem’s resilience and crop diversity. For now, certified and peasant seed coexist within farmer’s field. However, coexistence modalities between certified and peasant seeds in farmer seed network are still un- appreciated. By combining quantitative and qualitative analysis, we present a study of millet seed circulation according to their certified or peasant origin. The aim is to identify the coexis- tence modalities in seed exchange between farmers. From surveys of 79 people in the Koungheul region of Senegal, we identified several levels of coexistence, both in the perceptions of varieties by farmers and in networks mobilized for seed supply. Based on our comparative analysis, our results suggest that origin of seed shapes farmer seed networks. The acquisition of certified seeds from agro-dealer also modifies the context and modalities of exchange by inducing their social isolation and limiting self-production. Nonetheless, after the harvest, certified and peasant seed are commingled and embedded into an open and complex social network involving multiples ac- tors. Our results provide a better understanding of seed exchange networks between farmers, by characterizing the structure, the scope and modalities of exchange of certified seed. This study highlights a gap between agricultural policies and local seed management by farmers, results that could feed into the reflections on the governance of plant genetic resources

Infection dynamics of <I>Marteilia refringens</I> in flat oyster <I>Ostrea edulis</I> and copepod <I>Paracartia grani</I> in a claire pond of Marennes-Oléron Bay

International audienceThe protozoan parasite Marteilia refringens has been partly responsible for the severe decrease in the production of the European flat oyster Ostrea edulis Linnaeus in France since the 1970s. The calanoid copepod Paracartia grani Sars was recently found to be a host for M. refringens in French shallow-water oyster ponds (Œclaires¹). This study reconsidered M. refringens transmission dynamics in the light of this finding, taking into account not only oyster infection dynamics and environmental factors but also data concerning the copepod host. P. grani population dynamics in the claire under study revealed that this species is the dominant planktonic copepod in this confined ecosystem. During winter, M. refringens overwintered in O. edulis, with P. grani existing only as resting eggs in the sediment. The increase in temperature in spring controlled and synchronized both the release of M. refringens sporangia in the oyster feces, and the hatching of the benthic resting eggs of the copepod. Infection of oysters by M. refringens was limited to June, July and August, coinciding with (1) the highest temperature recorded in the claire, and (2) the highest abundance of P. grani. PCR detection of M. refringens in P. grani during the summer period was linked to the release of parasite sporangia by the oyster. Our results are supported by previous results on the effective transmission of this parasite from the oyster to the copepod

Ecosystem services related to small forests in temperate rural landscapes

Many temperate rural landscapes are composed of cropland, pastures and a diversity of tree-based landcovers including small patches of forests. As these small forests are relatively persistent in time, they can be considered as ecological infrastructures that influence ecological processes, including those who contribute to the provision of ecosystem services (ES). In this presentation, we review ES provided by small forests. Based on several long-term studies in French rural landscapes, we analyse the main factors influencing the production of these ES, the role of remote sensing data in ES mapping, and the role of ES in management decisions made by diverse stakeholders. Our analysis shows that small forests provide many ES to farmers, but also to other stakeholders, such as hunters or tourists. ES production is primarily influenced by the internal structure and composition of forests, as well as by the spatial configuration of forests and adjacent land covers, factors which do not only depend on local practices but also on other factors that are more difficult to influence. Remotely sensed data can be used to map ES that are related to the structure and composition of forests over large spatial scale. This may help to identify hotspots of ES production and to propose specific management actions to consolidate the provision of ES at the landscape or regional levels

Ecosystem services related to small forests in temperate rural landscapes

International audienceMany temperate rural landscapes are composed of cropland, pastures and a diversity of tree-based landcovers including small patches of forests. As these small forests are relatively persistent in time, they can be considered as ecological infrastructures that influence ecological processes, including those who contribute to the provision of ecosystem services (ES). In this presentation, we review ES provided by small forests. Based on several long-term studies in French rural landscapes, we analyse the main factors influencing the production of these ES, the role of remote sensing data in ES mapping, and the role of ES in management decisions made by diverse stakeholders. Our analysis shows that small forests provide many ES to farmers, but also to other stakeholders, such as hunters or tourists. ES production is primarily influenced by the internal structure and composition of forests, as well as by the spatial configuration of forests and adjacent land covers, factors which do not only depend on local practices but also on other factors that are more difficult to influence. Remotely sensed data can be used to map ES that are related to the structure and composition of forests over large spatial scale. This may help to identify hotspots of ES production and to propose specific management actions to consolidate the provision of ES at the landscape or regional levels

Claire ponds as an experimental model for <I>Marteilia refringens</I> life-cycle studies: new perspectives

International audienceSince its first description, the paramyxean parasite Marteilia refringens (Grizel et al.) has been recognised as a significant pathogen of the European flat oyster Ostrea edulis L. The existence of a complex life-cycle involving several hosts was postulated early on by many authors, although it remains unsolved. Recent developments in the DNA-based diagnosis of M. refringens provides new prospects for the detection of the parasite in potential hosts. However, this screening remains impeded by the number of species living in the vicinity of oyster beds. We report here on the use of semi-closed oyster ponds (so called ‘claire’ in Marennes-Oléron Bay) as a study model for the life-cycle of M. refringens. Claires are located in an endemic area for M. refringens and transmission of the disease to healthy oysters has been shown to be effective during the course of this study. The environmental characteristics of the claires strongly limit the number of species compared with intertidal areas and oyster beds. Consequently, extensive sampling of a limited number of species cohabiting with oysters was possible. These were preserved for future screening of M. refringens. The experimental model should bring new insights to the life-cycle of M. refringens, as it enables us to propose new conceptual schemes of M. refringens transmission. The role of species as potential hosts is discussed regarding their biology and geographical distribution

Needle in a haystack: involvement of the copepod <I>Paracartia grani</I> in the life-cycle of the oyster pathogen <I>Marteilia refringens</I>

International audienceMarteilia refringens is a major pathogen of the European flat oyster, Ostrea edulis Linnaeus. Since its description, the life-cycle of this protozoan parasite has eluded discovery. Attempts to infect oysters experimentally have been unsuccessful and led to the hypothesis of a complex life-cycle involving several hosts. Knowledge of this life-cycle is of central importance in order to manage oyster disease. However, the exploration of M. refringens life-cycle has been previously limited by the detection tools available and the tremendous number of species to be screened in enzootic areas. In this study, these two restrictions were circumvented by the use of both molecular detection tools and a mesocosm with low biodiversity. Screening of the entire fauna of the pond for M. refringens DNA was systematically undertaken using PCR. Here, we show that the copepod Paracartia(Acartia) grani is a host of M. refringens. Not only was DNA of M. refringens consistently detected in P. grani but also the presence of the parasite in the ovarian tissues was demonstrated using in situ hybridization. Finally, successful experimental transmissions provided evidence that P. grani can be infected from infected flat oysters