Dialogue : altérité, interaction, énaction

International audienc

A geometric analysis of the macronutrient needs of Drosophila suzukii larvae

International audienceThe nutritional needs of animals largely depend on their ecology and habitat. Phenotypes and general performance often depend on the synergistic influence of multiple nutrients. These effects are currently studied within the geometric framework of nutrition. Contrary to its close relative Drosophila melanogaster, the invasive Spotted-Wing Drosophila, Drosophila suzukii, attacks fresh, undamaged fruit devoid of microbial growth. Different oviposition habits suggest different nutritional needs by the two species. We investigated the combined influence of carbohydrate and protein concentrations on the larval performance of a D. suzukii population. Proportions of individuals that survived until the adult stage were maximal at intermediate protein and low sugar concentrations. Larval development was shortest under high protein diets. Observations on this population are congruent with what is known of D. suzukii larval ecology, as ripening, undamaged fruit is generally poor in sugars and proteins in comparison to ripe, yeast-colonized fruit. We discuss the limitations of fly nutrition experiments based on laboratory food, such as ours, where the natural dynamics of microbial growth is neglected

A high-throughput spectrophotometric assay of adult size in Drosophila that facilitates microbial and biochemical content analysis

International audienceLarge-scale laboratory experiments often necessitate the processing of numerous samples in little time, their long-time storage and the joint analysis of morphological, biochemical, and microbiological features. Combining different types of assays is often not compatible with classical methods to estimate size in adult Drosophila flies. We therefore designed a new spectrophotometric assay for the high-throughput estimation of adult size in Drosophila that facilitates microbial and biochemical content analysis. The new method uses optical density at 202 nm of single fly homogeneates as size proxy. We tested the method in a variety of Drosophila populations -including wild caught flies- and compared its explanatory power with two classical size estimates: wet-weight and wing-length. It was also used to control for size when comparing the fat content of different fly populations. Results show fly homogenate optical density is an powerful size proxy that may be used for both male and female flies

Comparaison de la qualité alimentaire des baies de différents cépages sur les chenilles d'un papillon deprédateur de raisin

National audienc

Microbiota acquisition and transmission in Drosophila flies

Summary: Understanding the ecological and evolutionary dynamics of host-microbiota associations notably involves exploring how members of the microbiota assemble and whether they are transmitted along host generations. Here, we investigate the larval acquisition of facultative bacterial and yeast symbionts of Drosophila melanogaster and Drosophila suzukii in ecologically realistic setups. Fly mothers and fruit were major sources of symbionts. Microorganisms associated with adult males also contributed to larval microbiota, mostly in D. melanogaster. Yeasts acquired at the larval stage maintained through metamorphosis, adult life, and were transmitted to offspring. All these observations varied widely among microbial strains, suggesting they have different transmission strategies among fruits and insects. Our approach shows microbiota members of insects can be acquired from a diversity of sources and highlights the compound nature of microbiotas. Such microbial transmission events along generations should favor the evolution of mutualistic interactions and enable microbiota-mediated local adaptation of the insect host

Influence of bacteria on the maintenance of a yeast during Drosophila melanogaster metamorphosis

International audienceInteractions between microorganisms associated with metazoan hosts are emerging as key features of symbiotic systems. Little is known about the role of such interactions on the maintenance of host-microorganism association throughout the host’s life cycle. We studied the influence of extracellular bacteria on the maintenance of a wild isolate of the yeast Saccharomyces cerevisiae through metamorphosis of the fly Drosophila melanogaster reared in fruit. Yeasts maintained through metamorphosis only when larvae were associated with extracellular bacteria isolated from D. melanogaster faeces. One of these isolates, an Enterobacteriaceae, favoured yeast maintenance during metamorphosis. Such bacterial influence on host-yeast association may have consequences for the ecology and evolution of insect-yeast-bacteria symbioses in the wild

The ecology of fly-bacteria-yeast symbiosis: no relevance of laboratory interactions to in-natura processes

National audienc

New set of microsatellite markers for the spotted-wing <em>Drosophila suzukii</em> (Diptera: Drosophilidae): a promising molecular tool for inferring the invasion history of this major insect pest

International audienceHistorical and observational data for invasive species are often sparse and incomplete, so molecular genetic markers are increasingly used and have proved to be efficient tools to make inferences about invasion histories. Here, we report the development of 28 polymorphic microsatellite markers in the invasive spotted-wing drosophila, Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae) designed from recent genomics resources, and their cross-amplification in closely related Drosophila species of the suzukii subgroup. The markers, located on autosomal chromosomes, were characterized in two distinct invasive populations from France and Hawaii (USA), and in four sister species of the suzukii subgroup. They all showed substantial polymorphism as well as revealing strong genetic differentiation between the two genotyped populations. These markers represent a promising molecular tool for population genetic studies on D. suzukii, more especially in order to reconstruct the pathways and demographic processes of the world-wide invasion in this major insect pest

The ecology of fly-bacteria-yeast symbiosis: laboratory interactions and their relevance to in-natura processes

National audienc

Invasive Drosophila suzukii facilitates Drosophila melanogaster infestation and sour rot outbreaks in the vineyards

How do invasive pests affect interactions between members of pre-existing agrosystems? The invasive pest Drosophila suzukii is suspected to be involved in the aetiology of sour rot, a grapevine disease that otherwise develops following Drosophila melanogaster infestation of wounded berries. We combined field observations with laboratory assays to disentangle the relative roles of both Drosophila in disease development. We observed the emergence of numerous D. suzukii, but no D. melanogaster flies, from bunches that started showing mild sour rot symptoms days after field collection. However, bunches that already showed severe rot symptoms in the field mostly contained D. melanogaster. In the laboratory, oviposition by D. suzukii triggered sour rot development. An independent assay showed the disease increased grape attractiveness to ovipositing D. melanogaster females. Our results suggest that in invaded vineyards, D. suzukii facilitates D. melanogaster infestation and, consequently, favours sour rot outbreaks. Rather than competing with close species, the invader subsequently permits their reproduction in otherwise non-accessible resources and may cause more frequent, or more extensive, disease outbreaks