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International audience; Le frelon asiatique, introduit en France en 2004, est rapidement devenu une espèce envahissante en Europe. La cible préférée de ce prédateur, qui chasse en vol, est l'abeille domestique, un maillon essentiel de la biodiversité et principal pollinisateur de nombreuses cultures vivrières. Alors que ce frelon semble participer au syndrome d’effondrement des colonies d’abeilles, son comportement de vol qui fait son succès de prédation est peu étudié et son impact sur les ruchers reste difficilement mesurable. Développer une méthodologie fiable et automatisée permettant de détecter, suivre et compter les frelons, les abeilles butineuses et les événements de prédation à l'entrée des ruches permettrait de quantifier précisément l'impact du frelon sur les ruchers et d'analyser son évolution dans le temps, ainsi que le moment et les conditions favorables à l'intervention ou au piégeage. Un travail exploratoire, soutenu en 2020 par l’i-Site MUSE (Key Initiative Data & Life Sciences), a consisté à chercher à dénombrer automatiquement à partir de données de vidéosurveillance le ratio captures/attaques dont sont victimes les abeilles par tranche horaire. Nous avons évalué l’intérêt des méthodes de deep learning pour traiter des données collectées en environnement non contrôlé, et notamment le couplage du réseau de neurones profond YoloV4 au système de suivi V-OUI. L’étude a exploité 360 heures de films basse résolution pris entre 2016 et 2018. Le réseau de neurones profond a permis de détecter différentes catégories d’insectes avec des taux de prédictions appréciables (variant de 85 à 90% selon les classes d’objet) mais leur suivi s’est avéré plus problématique principalement à cause de la vitesse d’acquisition trop faible des caméras utilisées. Nous discutons des solutions permettant d’améliorer les stratégies d’entrainement et de validation, ainsi que des algorithmes de suivi d’insectes en mouvement au comportement en apparence erratique.

Honey bees are the most economically important crop pollinator worldwide. They depend on a diversity of pollen for reproduction and colony growth. However, the influence of landscape composition on diversity and quantity of pollen collection by honey bees remains largely unexplored, particularly in variegated landscapes. Pollen on honey bees was trapped from 41 hives across ten sites in the Western Cape, South Africa during summer. Sampled hives were near eucalyptus trees surrounded by a high percentage of natural vegetation. Hives could therefore potentially be presented with a diverse range of flowers. To obtain a measure of relative abundance and representation of plant taxa pollen samples were collected at hives, sorted by color, weighed and DNA barcoded. Landscape analysis was performed to estimate the relative availability of the main floral resource-types and how this influenced the composition of pollen collected. Overall, eucalyptus made up the largest portion (∼49%) of pollen loads, the remainder was composed of 31 other taxa (12% native and 39% alien plants). An increase in the area of eucalyptus resulted in an increased as well as the relative amount of eucalyptus and natural pollen collected. Conversely, an increase in the area of eucalyptus resulted in a decrease in alien plant pollen and vice versa. Our results provide important quantitative evidence that shows the amount and diversity of pollen used by honey bees in summer appears to be disproportionately met by human-modified landscapes; whereas, natural vegetation, despite its large extent and diversity, performs a lower-level role during this season.

Dans le cadre de la Mission CNRS pour les Initiatives Transverses et Interdisciplinaires qui a organisé le colloque; Communication phéromonale et la régulation chez l’abeille domestique Apis mellifera . Sociétés d’abeilles Sociétés humaines

An observatory of honeybee colonies (Apis mellifera), consisting of at least 200 colonies, divided into 10 apiaries of 20 colonies, was monitored for three years on sunflower honeyflow (2015-2017). The purpose of this observatory is to understand which factors control colony performance during sunflower honeyflow in south-western France. From the temporal dynamics of weight gain, statistical analysis reveals a hierarchy of factors. First, variability in apiary scale performance is an image of the effect of resource variability. But, in addition to this primordial factor, two other factors contribute very significantly to performance. On the one hand, the amount of capped brood and the number of bees at the time of the installation of the apiary: these two elements testify to the vitality of the colony. The second remarkable factor is the Varroa load, which strongly penalizes performance beyond a certain threshold. The negative effect of the Varroa load on the colony performance is minimized in case of abondant sunflower honey flow., Un observatoire de colonies d'abeilles domestiques (Apis mellifera), constitué d'au moins 200 colonies, réparties en 10 ruchers de 20 colonies, a été suivi pendant trois ans (2015–2017). Le but de cet observatoire est de comprendre quels sont les facteurs qui contrôlent la performance des colonies pendant la miellée de tournesol dans le sud-ouest de la France. À partir de la dynamique temporelle du gain de poids, l'analyse statistique permet de faire apparaître une hiérarchisation des facteurs. En premier lieu, la variabilité de la performance à l'échelle des ruchers est une image de l'effet de la variabilité de la ressource. Mais, en complément de ce facteur primordial, deux autres facteurs contribuent très significativement à la performance. Il s'agit de la vitalité de la colonie représentée par la quantité de couvain operculé et le nombre d'abeilles au moment de l'installation du rucher sur la miellée. Le deuxième facteur remarquable est la charge en Varroa qui pénalise fortement la performance au-delà d'un certain seuil. La pénalisation de la performance due à la charge en Varroa est moindre en cas de miellée de tournesol aboudante.

Les méthodes permettant l’évaluation de la toxicité des pesticides pour les abeilles ont tendance à évoluer ces dernières années et ne se cantonnent plus seulement à la détermination de la DL50 (dose provoquant la mort de la moitié des individus). Les récentes recommandations de l’European Food Safety Authority (EFSA) préconisent notamment de développer des tests à même d’identifier des effets comportementaux dans une gamme d’exposition sublétale. Le présent document décrit une méthode qui permet de mesurer les effets délétères des insecticides sur les capacités locomotrices à des niveaux d’exposition qui ne provoquent pas la mort de l’abeille mais qui peuvent compromettre ses chances de survie ou ses performances au sein de la colonie. A l’instar du « test de vol de retour à la ruche des butineuses expérimentées », ce test pourrait dans le futur donner lieu à l’élaboration d’une méthode réglementaire d’évaluation des effets sublétaux des insecticides, après validation via un test interlaboratoires. Ce test locomoteur de laboratoire s’inspire des méthodes traditionnellement utilisées sur les rongeurs et à ce titre, il est standardisable, et peut en particulier être transposé sur des abeilles d’âge connu, sur tous les stades adultes. Le test est par exemple ici utilisé avec succès sur des abeilles jeunes, âgée de moins de 24h.

Parmi toutes les espèces pollinisatrices, les abeilles domestiques (Apis mellifera) sont connues pour avoir une très bonne capacité de pollinisation. Néanmoins, nous avons observé au cours des dix dernières années un déclin majeur des colonies d'abeilles. De nombreux facteurs biotiques et abiotiques (pesticides, pathogènes etc.) sont impliqués dans ce déclin mais aucun n'est tenu responsable seul. Les expositions multiples peuvent être le moyen de comprendre le syndrome d’effondrement des colonies. Par conséquent, il est étudié ici, les impacts d’une co et tri-exposition aux doses sub-létales de deux pesticides (boscalide et pyriproxyfène) et d'un agent pathogène (Paenibacillus larvae) sur le développement des larves. Ces deux pesticides sont couramment utilisés sur les cultures fruitières pollinisées par les abeilles. La loque américaine est une maladie causée par Paenibacillus larvae et c'est une des principales causes pour expliquer le CCD (Neumann et Carreck 2010). Une partie de l'étude consiste à déterminer la dose sans effet (NOED/DSE) pour chaque facteur. Ensuite, les effets de la co et de la tri-exposition aux trois facteurs sur la mortalité, sur la nymphose, sur l'émergence et sur le poids des larves sont observés. Nous déterminons une DSE pour le pyriproxyfène et le boscalide à 80ppb et 80ppm respectivement sur l'alimentation, et à 2- 3spores par larve pour l’agent infectieux à loque américaine. Par ailleurs, nos résultats montrent un effet de potentialisation des co-expositions (bi ou tri- expositions) pour la mortalité, le poids et l'émergence des larves. Il est prévu d'étudier l'impact de la co-exposition de la pyriproxyfène et de l’agent infectieux de la loque sur les interactions sociales adultes, afin de savoir si l'effet est retrouvé sur les comportements les plus importants des abeilles sociales., Among all pollinating species, domestic bees (Apis mellifera) are known to have very good pollination capacity. Nevertheless, we observed in the last ten years a major decline of bee colonies. Many abiotic and biotic factors are involved in this decline (pesticides, pathogens etc.) but no one is responsible on its own. The multiple expositions may be the way to understand the colony collapse disorder (CCD). Therefore, in the current study we focused on the co-exposition impacts of sub-lethal doses to two pesticides (boscalid, and pyriproxyfen) and one pathogen (Paenibacillus larvae) on larval development. These two pesticides are commonly used on fruit crop pollinated by bees. The American foulbrood is a disease caused by Paenibacillus larvae and it’s one of the main treats to explain the CCD (Neumann & Carreck, 2010) One part of the study consists of the determination of no observed effect dose (NOED) for each factor. The other part is focused on impacts of co and tri-exposition on mortality, on pupation, on emergence and on weight of larvae. We determine an NOED for the pyriproxyfen and the boscalid respectively at 80ppb and 80ppm on alimentation, and at 2-3 spores per larvae for the American foulbrood. Furthermore, our results show a potentiation effect of co-exposition of the three factors for the larvae mortality, weight, and emergence. It is planned to study the impact of the co-exposition of pyriproxyfen and foulbrood on adult social nteractions, to know if the effect act on the most important behaviors of social bees.

Durant les 50 dernières années, l’intensification agricole a profondément modifié la physionomie des paysages en Europe. Pour satisfaire les demandes croissantes des populations humaines, les systèmes de grandes cultures produisent aujourd’hui des céréales, maïs et autres oléagineux sur des surfaces de plus en plus étendues, au détriment de la diversité des variétés culturales locales et des habitats semi-naturels comme les prairies et réseaux bocagers. Comme beaucoup d’autres organismes, les abeilles sont affectées par ces changements environnementaux. Bien que les cultures à floraison massive, telles que le colza ou le tournesol, offrent des ressources florales très abondantes pour les abeilles, leur floraison reste temporaire et limitée dans le temps. En conséquence, les apiculteurs ont désormais recours à des transhumances et au nourrissage artificiel pour faire face aux périodes de disette saisonnière récurrentes dans ces zones de grandes cultures. En outre, la diversité des abeilles sauvages est érodée et l’efficacité des mesures de compensation agro-environnementales destinées à semer des mélanges floraux reste à démontrer. Nous proposons ici une revue des travaux de recherche récents entrepris par l’UMT PrADE pour documenter l’écologie de l’alimentation des abeilles et caractériser leurs interactions avec les surfaces cultivées et naturelles dans un système de grandes cultures., Honeybee and wild bee foraging ecology in open field agroecosystems Over the past 50 years, agricultural intensification has led to drastic changes in land cover structure and composition in Europe. To meet the increasing demands of human populations, modern open field crop systems have increased the amount and size of cereal, maize and oilseed crop fields at the expense of the diversity of local crop varieties and of semi-natural habitats like pastures, hedgerows and forested areas. Like many other organisms, bees are affected by those environmental changes. Although the socalled mass-flowering crops such as oilseed rape and sunflower provide bees with locally abundant and attractive floral resources, their blooming only covers short periods of time. Professional beekeepers now have to cope with recurrent seasonal food shortage periods, and resort to transhumance and artificial feeding to limit honeybee colony losses. In the meantime, non-managed wild bee species are threatened, and many doubts persist about the effectiveness of floral resource enhancements as agroenvironmental schemes to protect their diversity. We provide here a review of the recent research carried out by the UMT PrADE to document the bee foraging ecology and their interactions with cropped and natural areas in an open field agrosystem.

Des méthodes brevetées récemment pourraient contribuer à améliorer les stratégies utilisées classiquement pour l’évaluation de la toxicité des insecticides chez les abeilles et les autres pollinisateurs. La comparaison des effets des pyréthrinoïdes in situ et in ovo suggère que la toxicité pourrait dans le futur être déterminée via des méthodes in vitro plutôt que sur des animaux vivants, a l’instar des principes modernes de pharmacotoxicologie humaine.

En 2012, l’UMT PrADE a publié une étude dans laquelle le vol de retour à la ruche de 650 butineuses marquées d'une micropuce électronique RFID a été enregistré, et dont certaines ont été expérimentalement exposées à une faible dose de thiaméthoxam (la substance active des pesticides Cruiser® et Cruiser OSR®) utilisé en protection des cultures. Cette molécule, même administrée à une faible dose n’entraînant pas d’effet direct sur la survie, provoque la disparition des butineuses. En conditions habituelles de butinage, ce phénomène peut aboutir à un taux de mortalité deux à trois fois supérieur chez les butineuses intoxiquées. Il s’ensuivit des controverses sur l’approche scientifique (réalisme des doses, prédiction des effets sur la colonie par un modèle) et sur l’interprétation des résultats (généricité des effets) qui a motivé la réalisation d’une série de travaux pour tenter de les lever une à une. Cette épopée nous a amené à combler de nombreuses lacunes de connaissances sur la modulation des effets toxiques selon le contexte paysager, climatique ou sanitaire des abeilles. Toujours grâce au dispositif RFID, nous avons confirmé pour la première fois l’impact d’un insecticide néonicotinoïde sur la survie des ouvrières en conditions réelles d’exposition au champ., In 2012, colleagues of UMT PrADE tagged 650 free-ranging honeybees with tiny radio-frequency identification (RFID), microships that were glued to each bee’s thorax. This device allowed the researchers to track the bees as they came and went from their hives after an oral exposure to sublethal dose of the insecticide thiamethoxam (active ingredient of Cruiser® and Cruiser OSR®). Compared to the non-exposed bees, the treated bees were about two to three times more likely to die while away from their nests. This study was related to controversy as regards the scientific methodology (fieldrealistic doses, predictive model for colonial effects) and the generalization of results in real conditions. This controversy was a true motivation for our scientific investigation to address the lack of knowledge on the modulation of insecticide effects according to landscape, weather or sanitary status of bees. Using also the RFID device, we confirmed that field exposure to neonicotinoid accelerated the disappearance of bees.

International audience; In the agricultural environment,honeybees may be exposed to combinations of pesticides. Untilnow, the effects of these combinations on honey bee health have been poorly investigated. In this study,we assessed the impacts of biological and chemical insecticides, combining low dietary concentrations of Bacillus thuringiensis (Bt) spores (100 and 1000 mg/L) with the chemical insecticide fipronil(1 mg/L). In order to assess the possible effects of Crytoxins, the Bt kurstaki strain (Btk) was compared with a Bt strain devoid of toxin-encodingplasmids (BtCry-). The oral exposure to fipronil and Bt spores from both strains for 10 days did not elicit significant effects on the feeding behavior and survival after 25days. Local and systemic physiological effects were investigated by measuring the activities of enzymes involved in the intermediary and detoxication metabolisms at two sampling dates (day10 and day 20). Attention was focused on head and midgut glutathione-S-transferase (GST), midgut alkaline phosphatase (ALP), abdomen glyceraldehyde-3-phosphate dehydrogenase (GAPD) and glucose 6-phosphate dehydrogenase (G6PD). We found that Bt Cry- and Btk spores induced physiological modifications by differentially modulating enzyme activities. Fipronil influenced the enzyme activities differently at days 10 and 20 and, when combined with Bt spores, elicited modulations of some spore-induced physiological responses. These results show that an apparent absence of toxicity may hide physiological disruptions that could be potentially damaging for the bees, especially in the case of combined exposures to other environmental stressors.

International audience; A substantial honeybee decline is being observed worldwide. Agricultural intensification and loss of wild floral resources rank among the main factors contributing to this decline. Landscape enhancement of floral resources has been proposed as an agro-environmental scheme intended to provide honeybees with compensatory food sources in intensive agrosystems. Floral scheme efficiency has rarely been evaluated with respect to landscape context. In this study, we developed and validated a modeling tool to delineate the landscape areas likely to be associated with higher efficiency of floral enhancement schemes. In particular, the proximity of some landscape elements used by honeybees, either as foraging habitat or as visual landmark for orientation, may partly determine floral scheme efficiency. We investigated this issue using resource selection functions (RSFs), i.e. models that aim to predict the occurrence of foraging honeybees at floral patches as a function of the presence of keystone landscape elements in their proximity. However, deciding which landscape elements are effectively in the proximity or not is mostly a matter of subjectivity. The novelty of our approach resides in its use of a distance-weighting function to explicitly account for the spatial location of surrounding landscape elements. In that respect, a distance function should be scaled on movement patterns of foraging organisms. Herein, we inferred movement patterns from the autocorrelative properties of honeybee foraging activity. This modeling approach was developed on Phacelia (Phacelia tanacetifolia) field margin strips, a typical “honeybeefriendly” floral scheme. A foraging survey conducted on 170 Phacelia plots (2 m × 2 m) from 17 Phacelia strips, all positioned within the foraging range of an experimental apiary, revealed that (i) the floral scheme efficiency is positively influenced by the presence of linear landscape elements such as hedgerows and forest edges, but negatively affected by the presence of alternative floral resources, and that (ii) weighting the relative importance of those landscape elements by incorporating a distance function into models considerably improved their predictive power. This modeling tool has the potential to help land managers optimizing their financial investment by avoiding low-efficiency landscape areas, or favoring high-efficiency ones, at the time of planning floral enhancement schemes

Since 2006, disastrous colony losses have been reported in Europe and North America. The causes of the losses were not readily apparent and have been attributed to overwintering mortalities and to a new phenomenon called Colony Collapse Disorder. Most scientists agree that there is no single explanation for the extensive colony losses but that interactions between different stresses are involved. As the presence of Varroa in each colony places an important pressure on bee health, we here address the question of how Varroa contributes to the recent surge in honey bee colony losses, Seit 2006 werden in Europa und Nordamerika katastrophale Völkerverluste gemeldet. Die Ursachen dieser Verluste waren nicht leicht zu erklären, sie wurden als überwinterungsbedingte Mortalitäten bewertet und unter dem Begriff Colony Collapse Disorder (CCD) zusammengefasst. Die meisten Wisenschaftler stimmen dahingehend überein, dass diesen Völkerverlusten keine Einzelursache zugrunde liegt, sondern, dass vermutlich verschiedene Stressfaktoren zusammenwirken. Da der Varroa-Befall einen wichtigen Druck auf die Gesundheit der Bienen in den Völkern darstellt, gingen wir der Frage nach, inwiefern Varroa an den seit kurzem beobachteten Völkerverlusten beteiligt sein kann. Verschiedene physikalische und physiologische Faktoren mit negativer Wirkung der Varroa-Milbe auf die Gesundheit der einzelnen Biene und den Volkszusammenhang sind bereits bekannt. So führt das wiederholte Saugen von Hämolymphe zu Verletzungen der Bienen, zu erniedrigten Werten im Proteingehalt, sowie dem Lebend- und Trockengewicht und zur Behinderungen in der Organentwicklung. Die parasitische Milbe und die von ihr übertragenen Viren führen zu morphologischen Fehlentwicklungen, reduzierter Widerstandskraft und Lebenserwartung und zu negativen Effekten auf die Flugdauer und Heimfindungsfähigkeit der Sammlerinnen. Die Milbe schwächt das Immunsystem der Bienen, indem die Expression von Genen der Immunantwort reduziert wird. Zusammen mit erhöhten DWV-Viren-Titern reduziert sie damit die Lebensfähigkeit der Arbeiterinnen und die Koloniefitness. Die Rolle der Varroa-Milbe als Vektor in der horizontalen und vertikalen Übertragung von Viren ist hingehend bekannt, und Ko-Infektionen von V. destructor mit verschiedenen Viren wurden bereits als wichtige Faktoren im Varroa-bedingten Zusammenbruch von Völkern beschrieben. V. destructor muss deshalb weiterhin als eine ernsthafte Bedrohung der Honibiene gelten, und weiterhin werden Honigbienenpopulationen weltweit durch diese parasitische Milbe dezimiert. Die Hypothese, dass CCD durch eindringende Varroa-Milben und ihre immunsuppressiven Fähigkeiten hervorgerufen wird, ist damit nicht auszuschliessen und wird durch die Befunde von vanEngelsdorp et al. (2009) gestärkt. Die Varroa-Milbe ist seit Jahren in den meisten Ländern vertreten, aus denen auch Völkerverluste gemeldet werden. Obwohl die Milbenpopulationen kontrolliert werden können, kann trotzdem spekulativ postuliert werden, dass die Verluste zumindest teilweise durch einen Varroa-Befall der Völker bedingt sein können. Welche Veränderungen in der Varroa-Biologie können also die jetzigen Verluste im Vergleich zu denen vor 20 Jahren erklären? Wir diskutieren potentielle Ursachen, einschliesslich Veränderungen in der Biologie und Populationsdynamik von Varroa und ihrem Wirt, der Kontrolle von Varroa durch Akarizide, indirekte Effekten der Varroa-Behandlungen, sowie synergistische Effekte multipler Faktoren

The invasion of the Western honey bee, Apis mellifera, by Varroa destructor is attributed to two mitochondrial haplotypes (K and J) that shifted last century from their primary host the Eastern honey bee, A. cerana, in north-east Asia. Here, mitochondrial DNA sequences (cox1, cox3, atp6 and cytb: 2700 base pairs) were obtained from mites infesting both Eastern and Western honeybees (respectively 21 and 11 colonies) from Asia including regions where the shifts first occurred. A total of eighteen haplotypes were uncovered in Asia (11 on A. cerana and 7 on A. mellifera). Two new variants of the K haplotype and two of the J haplotype were found on Western honeybees in what appeared to be well-established infestations. New haplotypes may represent a potential threat to A. mellifera worldwide. The extreme lack of polymorphism in the K and J haplotypes outside of Asia, can now be plausibly explained as being due to genetic 'bottlenecks' that occurred in Asia before and after mites shifted from their original Eastern honeybee host. Apis mellifera / Apis cerana / Varroa / mitochondrial DNA/diversity

International audience; Pheromones are very important in animal communication. To learn more about the molecular basis of pheromone action, we studied the effects of a potent honey bee pheromone on brain gene expression. Brood pheromone (BP) caused changes in the expression of hundreds of genes in the bee brain in a manner consistent with its known effects on behavioral maturation. Brood pheromone exposure in young bees causes a delay in the transition from working in the hive to foraging, and we found that BP treatment tended to upregulate genes in the brain that are upregulated in bees specialized on brood care but downregulate genes that are upregulated in foragers. However, the effects of BP were age dependent; this pattern was reversed when older bees were tested, consistent with the stimulation of foraging by BP in older bees already competent to forage. These results support the idea that one way that pheromones influence behavior is by orchestrating large-scale changes in brain gene expression. We also found evidence for a relationship between cis and BP regulation of brain gene expression, with several cis-regulatory motifs statistically overrepresented in the promoter regions of genes regulated by BP. Transcription factors that target a few of these motifs have already been implicated in the regulation of bee behavior. Together these results demonstrate strong connections between pheromone effects, behavior, and regulation of brain gene expression.

The purpose of this study is to investigate the possibility to use acetylcholinesterase (AChE) as a biomarker of exposure to deltamethrin insecticide in the honeybee, Apis mellifera and to test its reliability in the presence of other contaminants, as carbamate insecticide. Joined actions of deltamethrin (pyrethroid) and pirimicarb (carbamate), alone or in association, are investigated on AChE activity in surviving and dead honeybees, with a special focus on the relative proportions of its membrane and soluble forms. At the 0.5X dose (12.5 ng of deltamethrin and/or 2.5 microg of pirimicarb per bee), the residual tissue AChE activity in dead bees was 78% with deltamethrin, 43% with pirimicarb and 33% with dual treatment. In surviving bees, tissue AChE activity represented 250%, and 270% of control AChE activity with deltamethrin and dual treatment, respectively. The analysis of membrane and soluble AChE forms revealed an increase in the soluble form in dead bees after deltamethrin and dual treatment. However, in vitro investigations showed no direct interaction of deltamethrin on soluble and membrane AChE activity. The results suggest that the action of deltamethrin on AChE activity, in honeybee intact organisms, could be due to indirect mechanisms. The duality of AChE response to deltamethrin exposure, exhibited by the possibility of increase (surviving bees) or decrease (dead bees) of its activity has been pointed out for the first time. The important increase in AChE activity in response to deltamethrin, not altered by pirimicarb treatment, suggests that AChE activity could represent a robust biomarker specific to deltamethrin exposure in living bees.

International audience; Two acetylcholinesterase (EC 3.1.1.7) membrane forms AChEm1 and AChEm2, have been characterised in the honey bee head. They can be differentiated by their ionic properties: AChEm1 is eluted at 220 mM NaCl whereas AChEm2 is eluted at 350 mM NaCl in anion exchange chromatography. They also present different thermal stabilities. Previous processing such as sedimentation, phase separation, and extraction procedures do not affect the presence of the two forms. Unlike AChEm1, AChEm2 presents reversible chromatographic elution properties, with a shift between 350 to 220 mM NaCl, depending on detergent conditions. Purification by affinity chromatography does not abolish the shift of the AChEm2 elution. The similar chromatographic behaviour of soluble AChE strongly suggests that the occurrence of the two membrane forms is not due to the membrane anchor. The two forms have similar sensitivities to eserine and BW284C51. They exhibit similar electrophoretic mobilities and present molecular masses of 66 kDa in SDS-PAGE and a sensitivity to phosphatidylinositol-specific phospholipase C in non-denaturing conditions, thus revealing the presence of a glycosyl-phosphatidylinositol anchor. We assume that bee AChE occurs in two distinct conformational states whose AChEm2 apparent state is reversibly modulated by the Triton X-100 detergent into AChEm1

La diversité du pollen a un impact sur la résistance aux stress: pesticides, pathogènes, famine, sous-population. (...)

National audience

The South West Indian Ocean (SWIO) islands are home to an exceptional flora and fauna and are considered as one the five most important biodiversity hotspots in the world. In most islands of this region, the honeybee Apis mellifera occupies diverse habitats. Regarding its ability as a generalist pollinator, honeybee interacts with native and highly endemic flora. Furthermore, this species is used by human for beekeeping as it is able to produce honey, pollen and other hive products. Within the large group of bees (Apidae), A. mellifera is a model of diversity that has diverged into several lineages and subspecies in its native range. Among the 28 recognized subspecies, A. m. unicolor has been described as endemic to Madagascar and belongs to the African A lineage. The Mascarenes, Comoros and Seychelles archipelagos surround this continental island but the A. mellifera populations present have been little or never studied. The aims of this thesis were to characterize the honeybee from the Mascarenes (La Réunion, Mauritius, Rodrigues), Comoros (Anjouan, Mohéli, Grande Comore, Mayotte) and Seychelles (Mahé, Praslin, La Digue) archipelagos by determining the evolutionary lineages and subspecies present. Secondly, a study of genetic diversity and structure were conducted on these same insular populations. For that, a large sampling was carried (n = 4095 colonies from the SWIO, and 238 from native continental areas) and was combined to molecular analyzes using mitochondrial markers (sequencing of the COI-COII intergenic region and ND2 gene) and nuclear markers (15 microsatellite loci). Three of the four evolutionary lineages (A, C and M) were detected in different proportions in the 10 studied islands. The African A lineage and A. m. unicolor subspecies were predominant in the SWIO excepted for Rodrigues exclusively from the European C lineage. All sampled colonies from the Seychelles and Comoros archipelagos belong to the African lineage while in La Réunion the proportion reach 95.2% and only 54.2% in Mauritius. The presence of the Z African sub-lineage has been described for the first time out of Africa in two Seychelles islands. Moreover, Comoros islands may constitute a contact area between the continental African lineage and A. m. unicolor populations (insular African lineage). The SWIO populations show high levels of nuclear genetic diversity and a structuration by island and archipelago. In addition, SWIO populations strongly differentiated from African and European continental populations. The combined results from different molecular markers favor the hypothesis of an ancient and natural colonization from Madagascar to La Réunion, Mauritius and Seychelles islands. Therefore, the previous referenced interactions between the honeybee and the endemic fauna and flora in the SWIO might be explained by a long cohabitation in addition to its generalist pollinator ability., Les îles du Sud-Ouest de l'océan Indien (SOOI) abritent une faune et une flore exceptionnelle et constituent l'un des cinq hotspot de biodiversité les plus importants au monde. L'abeille domestique Apis mellifera occupe divers habitats dans la majorité de ces îles et interagit avec une flore indigène et endémique. Elle est également exploitée par l'Homme pour l'apiculture. A. mellifera a divergé en plusieurs lignées évolutives et sous-espèces dans son aire d'origine. Parmi-elles, A. m. unicolor a été décrite comme endémique de Madagascar et appartient à la lignée africaine A. Les objectifs de cette thèse étaient de caractériser l'abeille dans les archipels des Mascareignes, Comores et Seychelles en identifiant les lignées évolutives et sous-espèces présentes avec des marqueurs mitochondriaux (région intergénique COI-COII, gène ND2). Dans un second temps, une étude de la diversité et de la structure génétique a été réalisée sur ces mêmes populations insulaires (15 microsatellites). Un total de 4095 colonies ont été échantillonnées dans le SOOI et 238 dans l'aire naturelle continentale. Trois des quatre lignées évolutives (A, C et M) ont été détectées dans les 10 îles étudiées et ce en différentes proportions. La lignée africaine A et A. m. unicolor sont prépondérantes dans le SOOI excepté à Rodrigues (100% lignée européenne C). Dans toutes les îles de l'archipel des Comores et des Seychelles, 100% des colonies échantillonnées appartiennent à la lignée A, 95,2% à La Réunion et seulement 54,2% à Maurice. Les îles de l'archipel des Comores constitueraient une zone de contact entre la lignée africaine continentale et les populations d'A. m. unicolor. La diversité génétique nucléaire est forte dans les archipels du SOOI et est structurée par îles et archipels. En outre, les populations du SOOI se différencient fortement des populations continentales africaines et européennes. La combinaison des différents marqueurs privilégie l'hypothèse d'une colonisation ancienne et naturelle d'A. m. unicolor depuis Madagascar à La Réunion, Maurice et aux Seychelles.

Recent studies have demonstrated a remarkable and unexpected complexity in social insect pheromone communication, particularly for honeybees (Apis mellifera L.). The intricate interactions characteristic of social insects demand a complex language, based on specialized chemical signals that provide a syntax that is deeper in complexity and richer in nuance than previously imagined. Here, we discuss this rapidly evolving field for honeybees, the only social insect for which any primer pheromones have been identified. Novel research has demonstrated the importance of complexity, synergy, context, and dose, mediated through spatial and temporal pheromone distribution, and has revealed an unprecedented wealth of identified semiochemicals and functions. These new results demand fresh terminology, and we propose adding “colony pheromone” and “passenger pheromone” to the current terms sociochemical, releaser, and primer pheromone to better encompass our growing understanding of chemical communication in social insects.

In social insects, larvae are completely dependent on adults to complete their development. In honey bees (Apis mellifera L.), larval development requires that larvae engage workers in nursing tasks rather than allocating energy in other activities (Le Conte and Hefetz, 2008). Indeed, in the absence of any constraint, workers tend to become active reproductive individual. The queen inhibits worker ovary development via pheromones (Hoover et al., 2003; Wossler and Crewe, 1999), but the inhibition of worker ovary development seems superior when bees are exposed to unsealed brood (Kropacova and Haslbachova, 1970, 1971). Components of the brood pheromone have already been identified and consist of a blend of 10 esters (Le Conte et al., 1989, 1990). Two of these low volatility compounds have been demonstrated to partially decrease worker ovary development (Mohammedi et al., 1998; Pankiw and Garza, 2007). Thus, we asked whether brood emits volatile compounds that could also have an effect on worker ovary activation. We identified a new highly volatile molecule from the larvae E-β-ocimene, that inhibits worker ovary maturation. We used Solid Phase Microextraction (SPME) (65 μm Carbowax) to sample volatiles emitted by different larval instars. We analyzed 20 larvae at stage 1, 2–3 or 10 larvae at stage 4–5. Larvae were kept in a 15 mL closed vial for 20 min in an incubator at 34 ◦C and 50% humidity (N = 8

International audience; The effects of the herbicide Paraquat were investigated in honey bee larvae with attention focused on oenocytes. Honey bee larvae were exposed to Paraquat at different concentrations in the food: 0, 0.001, 0.01, 0.1 and 1 mg/kg. In controls, between 24 h and 48 h, oenocytes grew from 630.1 to 1643.8 mm 2 while nuclei changed in size from 124.9 to 245.6 mm 2. At 24 h, Paraquat induced a slight decrease in the size of oenocytes and nuclei. N-acetylcysteine (NAC), an antioxidant substance, slightly lowered the effects of Paraquat. At 48 h, Paraquat elicited a strong concentration-dependent decrease in the size of oenocytes, even at the lowest concentration. NAC reversed the effect of Paraquat at a concentration of $0.01 mg/kg. This reversion suggested different modes of action of Paraquat, with an oxidant action prevalent at concentrations $0.01 mg/kg. This study is the first which reports an effect of a pesticide at the very low concentration of 1 ng/kg, a concentration below the detection limits of the most efficient analytic methods. It shows that chemicals, including pesticides, are likely to have a potential impact at such exposure levels. We also suggest that Paraquat could be used as a suitable tool for investigating the functions of oenocytes.

Review article; International audience; During their foraging activity, honey bees are often exposed to direct and residual contacts with pesticides, especially insecticides, all substances specifically designed to kill, repel, attract or perturb the vital functions of insects. Insecticides may elicit lethal and sublethal effects of different natures that may affect various biological systems of the honey bee. The first step in the induction of toxicity by a chemical is the interaction between the toxic compound and its molecular target. The action on the molecular target can lead to the induction of observable or non-visible effects. The toxic substance may impair important processes involved in cognitive functions, behaviour or integrity of physiological functions. This review is focused on the neural effects of insecticides that have repercussions on (a) cognitive functions, including learning and memory, habituation, olfaction and gustation, navigation and orientation; (b) behaviour, including foraging and (c) physiological functions, including thermoregulation and muscle activity.

International audience; Honey bee colonies (Apis mellifera) have been selected for low level of Nosema in Denmark over decades and Nosema is now rarely found in bee colonies from these breeding lines. We compared the immune response of a selected and an unselected honey bee lineage, taking advantage of the haploid males to study its potential impact on the tolerance toward Nosema ceranae, a novel introduced microsporidian pathogen. After artificial infections of the N. Ceranae spores, the lineage selected for Nosema tolerance showed a higher N. ceranae spore load, a lower mortality and an up-regulated immune response. The differences in the response of the innate immune system between the selected and unselected lineage were strongest at day six post infection. In particular genes of the Toll pathway were up-regulated in the selected strain, probably is the main immune pathway involved in N. ceranae infection response. After decades of selective breeding for Nosema tolerance in the Danish strain, it appears these bees are tolerant to N. ceranae infections

Article first published online: 1 MAY 2012; International audience; Honey bee societies (Apis mellifera), the ectoparasitic mite Varroa destructor, and honey bee viruses that are vectored by the mite, form a complex system of host–parasite interactions. Coevolution by natural selection in this system has been hindered for European honey bee hosts since apicultural practices remove the mite and consequently the selective pressures required for such a process. An increasing mite population means increasing transmission opportunities for viruses that can quickly develop into severe infections, killing a bee colony. Remarkably, a few subpopulations in Europe have survived mite infestation for extended periods of over 10 years without management by beekeepers and offer the possibility to study their natural host–parasite coevolution. Our study shows that two of these “natural” honey bee populations, in Avignon, France and Gotland, Sweden, have in fact evolved resistant traits that reduce the fitness of the mite (measured as the reproductive success), thereby reducing the parasitic load within the colony to evade the development of overt viral infections. Mite reproductive success was reduced by about 30% in both populations. Detailed examinations of mite reproductive parameters suggest these geographically and genetically distinct populations favor different mechanisms of resistance, even though they have experienced similar selection pressures of mite infestation. Compared to unrelated control colonies in the same location, mites in the Avignon population had high levels of infertility while in Gotland there was a higher proportions of mites that delayed initiation of egg-laying. Possible explanations for the observed rapid coevolution are discussed.

Published online: 18 march 2012; International audience; Social work force distribution in honeybee colonies critically depends on subtle adjustments of an age-related polyethism. Pheromones play a crucial role in adjusting physiological and behavioral maturation of nurse bees to foragers. In addition to primer effects of brood pheromone and queen mandibular pheromone—both were shown to influence onset of foraging—direct worker–worker interactions influence adult behavioral maturation. These interactions were narrowed down to the primer pheromone ethyl oleate, which is present at high concentrations in foragers, almost absent in young bees and was shown to delay the onset of foraging. Based on chemical analyses, physiological recordings from the antenna (electroantennograms) and the antennal lobe (calcium imaging), and behavioral assays (associative conditioning of the proboscis extension response), we present evidence that ethyl oleate is most abundant on the cuticle, received by olfactory receptors on the antenna, processed in glomeruli of the antennal lobe, and learned in olfactory centers of the brain. The results are highly suggestive that the primer pheromone ethyl oleate is transmitted and perceived between individuals via olfaction at close range.

Available online 19 April 2012; International audience; Social removal is often an adaptive response for preventing the entry and spread of parasitic infection between kin members of a group. Social isolation via removal or the switching of social tasks has also been observed in insect societies; however, the underlying mechanisms are unclear. We tested in honeybees the role of the immune system in physiological and behavioral modulation. Forager bees are often located in the outer area of the colony, and thus have reduced contacts with individuals of high importance, who are located in the inner area of the colony (e.g. queen and brood). We thus expected that an immune challenge would induce a forager profile. This was confirmed by measuring brain (foraging and malvolio gene expression), physiological (hypopharyngeal glands size) and behavioral (queen attendance) parameters of nurse/forager profiles after a treatment with an immune-activator (lipopolysaccharides). Our results support the idea that the interplay between the brain and immune system may be an important regulatory factor of social immunity in insects

National audience

International audience; In Brazil, as well as in other countries, the use of pesticides from the recent class of neonicotinoids surpasses those from organophosphates and pyrethroids. In this class, thiamethoxam is an insecticide used in Brazil mainly to control sucking insects in several crops such as citrus, coffee, soybean, bean and cotton. However, the honey bee Apis mellifera L., 1758, which has a great value as pollinator and is required for increasing the plant production, can be exposed to residues from treatments with neonicotinoids. Thus, this work aimed to determine the acute toxicity of thiamethoxam to the honeybee expressed as LD50. This value is then used as a reference dose to assess the sublethal effects of this pesticide on type B esterases from A. mellifera. Honey bee foragers were exposed, by contact application, to different doses of thiamethoxam and mortality was measured after 24 and 48 hours. The results show that the LD50 values at 24 and 48 hours are 11.13 ng a.i./bee (CL95% = 9.71 - 12.55; D.F. = 16 and χ2 = 10.628) and 12.67 ng a.i./bee (CL95% = 9.25 - 16.08; D.F. = 18 and χ2 = 17.506), respectively. When honeybee are exposed to sublethal doses of thiamethoxam (i.e. LD50/10 or LD50/20), acetylcholinesterase and carboxylesterase significantly decreased and represented 94% and 78% of control activity at 24 hours and 48 hours, respectively. Thus, these enzymes could be used as biomarkers of exposure to pesticides to help for a better honey bee management and to follow the environmental health

National audience

Background Malnutrition is a major factor affecting animal health, resistance to disease and survival. In honey bees (Apis mellifera), pollen, which is the main dietary source of proteins, amino acids and lipids, is essential to adult bee physiological development while reducing their susceptibility to parasites and pathogens. However, the molecular mechanisms underlying pollen's nutritive impact on honey bee health remained to be determined. For that purpose, we investigated the influence of pollen nutrients on the transcriptome of worker bees parasitized by the mite Varroa destructor, known for suppressing immunity and decreasing lifespan. The 4 experimental groups (control bees without a pollen diet, control bees fed with pollen, varroa-parasitized bees without a pollen diet and varroa-parasitized bees fed with pollen) were analyzed by performing a digital gene expression (DGE) analysis on bee abdomens. Results Around 36, 000 unique tags were generated per DGE-tag library, which matched about 8, 000 genes (60% of the genes in the honey bee genome). Comparing the transcriptome of bees fed with pollen and sugar and bees restricted to a sugar diet, we found that pollen activates nutrient-sensing and metabolic pathways. In addition, those nutrients had a positive influence on genes affecting longevity and the production of some antimicrobial peptides. However, varroa parasitism caused the development of viral populations and a decrease in metabolism, specifically by inhibiting protein metabolism essential to bee health. This harmful effect was not reversed by pollen intake. Conclusions The DGE-tag profiling methods used in this study proved to be a powerful means for analyzing transcriptome variation related to nutrient intake in honey bees. Ultimately, with such an approach, applying genomics tools to nutrition research, nutrigenomics promises to offer a better understanding of how nutrition influences body homeostasis and may help reduce the susceptibility of bees to (less virulent) pathogens.

Diplôme : Master

Diplôme : other; This study forms part of a policy for the conservation of different apoidea genera by means of description of the interactions between bees and the flowery arable plants of the herb layers in a environment of intensive cereal fields. Firstly, it has been written a qualitative list of the different types of wild plants and of the apoidea groups associated to them. This list, made up from bees being captured on patches or on the edges of cultivated fields, helped to establish what vegetal types are the most appropriate for bee-conservation. On the one hand, it was established that cornflowers and some kinds of asteraceae attract a greater diversity of bees. On the other hand, some other plants, which are more specialized, attract a few genera of bees which are more rare and therefore more sensible. Afterwards, the study focuses on cornflowers. The abundance of these different groups was analysed quantitatively according to the surface of the cornflower patches and to their flower density. This established that the density in flowers has got a positive impact on all bee genera studied contrary to the surface which benefits that at only some specific genera of bees.; Cette étude s'inscrit dans une logique de préservation des différents genres apoïdes en caractérisant les interactions entre les abeilles et adventices fleuries des strates herbacées vivant en plaine céréalière intensive. En premier lieu nous avons dressé de façon qualitative une liste des genres des diverses plantes sauvages et des cortèges d'apoïdes associés. Cette liste, élaborée à partir de captures d'abeilles effectuées sur patch ou bordures de champs en plaines agricoles, a permis de constater quels genres végétaux étaient les plus adéquats dans la préservation des abeilles. Il a ainsi été constaté que le bleuet et certains genres d’Astéracées attirent une grande diversité d'abeilles. D'autres végétaux plus spécialisés permettent quant à eux d'attirer quelques genres d'abeilles plus rares et donc plus sensibles. Par la suite un focus sur le bleuet a été réalisé. L'abondance des différents cortèges d'abeilles a été analysée quantitativement selon la surface des patches de bleuets et de leur abondance en fleur. Cela a permis de révéler que la densité en fleur possède un impact favorable sur tous les genres d'abeilles étudiés contrairement à la surface qui ne bénéficie qu'à certains genres d'abeilles.

Cette étude s'inscrit dans une logique de préservation des différents genres apoïdes en caractérisant les interactions entre les abeilles et adventices fleuries des strates herbacées vivant en plaine céréalière intensive. En premier lieu nous avons dressé de façon qualitative une liste des genres des diverses plantes sauvages et des cortèges d'apoïdes associés. Cette liste, élaborée à partir de captures d'abeilles effectuées sur patch ou bordures de champs en plaines agricoles, a permis de constater quels genres végétaux étaient les plus adéquats dans la préservation des abeilles. Il a ainsi été constaté que le bleuet et certains genres d’Astéracées attirent une grande diversité d'abeilles. D'autres végétaux plus spécialisés permettent quant à eux d'attirer quelques genres d'abeilles plus rares et donc plus sensibles. Par la suite un focus sur le bleuet a été réalisé. L'abondance des différents cortèges d'abeilles a été analysée quantitativement selon la surface des patches de bleuets et de leur abondance en fleur. Cela a permis de révéler que la densité en fleur possède un impact favorable sur tous les genres d'abeilles étudiés contrairement à la surface qui ne bénéficie qu'à certains genres d'abeilles., This study forms part of a policy for the conservation of different apoidea genera by means of description of the interactions between bees and the flowery arable plants of the herb layers in a environment of intensive cereal fields. Firstly, it has been written a qualitative list of the different types of wild plants and of the apoidea groups associated to them. This list, made up from bees being captured on patches or on the edges of cultivated fields, helped to establish what vegetal types are the most appropriate for bee-conservation. On the one hand, it was established that cornflowers and some kinds of asteraceae attract a greater diversity of bees. On the other hand, some other plants, which are more specialized, attract a few genera of bees which are more rare and therefore more sensible. Afterwards, the study focuses on cornflowers. The abundance of these different groups was analysed quantitatively according to the surface of the cornflower patches and to their flower density. This established that the density in flowers has got a positive impact on all bee genera studied contrary to the surface which benefits that at only some specific genera of bees.

Diplôme : Master

International audience

National audience

International audience; BACKGROUND: The honeybee, Apis mellifera, is undergoing a worldwide decline whose origin is still in debate. Studies performed for twenty years suggest that this decline may involve both infectious diseases and exposure to pesticides. Joint action of pathogens and chemicals are known to threaten several organisms but the combined effects of these stressors were poorly investigated in honeybees. Our study was designed to explore the effect of Nosema ceranae infection on honeybee sensitivity to sublethal doses of the insecticides fipronil and thiacloprid. METHODOLOGY/FINDING: Five days after their emergence, honeybees were divided in 6 experimental groups: (i) uninfected controls, (ii) infected with N. ceranae, (iii) uninfected and exposed to fipronil, (iv) uninfected and exposed to thiacloprid, (v) infected with N. ceranae and exposed 10 days post-infection (p.i.) to fipronil, and (vi) infected with N. ceranae and exposed 10 days p.i. to thiacloprid. Honeybee mortality and insecticide consumption were analyzed daily and the intestinal spore content was evaluated 20 days after infection. A significant increase in honeybee mortality was observed when N. ceranae-infected honeybees were exposed to sublethal doses of insecticides. Surprisingly, exposures to fipronil and thiacloprid had opposite effects on microsporidian spore production. Analysis of the honeybee detoxification system 10 days p.i. showed that N. ceranae infection induced an increase in glutathione-S-transferase activity in midgut and fat body but not in 7-ethoxycoumarin-O-deethylase activity. CONCLUSIONS/SIGNIFICANCE: After exposure to sublethal doses of fipronil or thiacloprid a higher mortality was observed in N. ceranae-infected honeybees than in uninfected ones. The synergistic effect of N. ceranae and insecticide on honeybee mortality, however, did not appear strongly linked to a decrease of the insect detoxification system. These data support the hypothesis that the combination of the increasing prevalence of N. ceranae with high pesticide content in beehives may contribute to colony depopulation.

Diplôme : DUT

International audience

Honeybee (Apis mellifera L.) populations have experienced serious losses in Europe and North America (Neumann & Carreck, 2010; Oldroyd, 2007). These losses highlights the potential risks for our natural and agricultural landscapes through lack of pollination, and the repercussions these would have for human activities and nutrition (Aizen & Harder, 2009; Gallai et al., 2009; Klein et al., 2007; Rader et al., 2009; Ollerton et al., 2011). There is a great deal of concerns about the decline of honeybees across the world and what has been termed colony collapse disorder in the USA. Honeybee health is influenced by biotic factors such as availability of resources, competitors, pathogens, parasites, and predators, and abiotic factors such as climate and pollutants. Colony losses are likely due to multiple factors (Oldroyd, 2007), and most research to date has focused on epidemiological studies affecting honeybee health (Cox-Foster et al., 2007; Johnson et al., 2009; Le Conte et al., 2010), and on the negative effects of agricultural pesticides (Decourtye & Devillers, 2010; Desneux et al., 2007; Johnson et al., 2010; Kevan, 1977). Although the putative causes of this decline are still being investigated, it has long been recognized that a lack of food, and particularly a dearth of pollen, within intensively farmed agricultural landscapes has contributed to the loss of colonies (Mattila & Otis, 2006; Maurizio, 1950; Naug, 2009). Beekeepers have frequently cited starvation and poor foraging conditions as the principal causes of the recent bee losses (Allier et al., 2010; vanEngelsdorp et al., 2007). Naug (2009) suggested that nutritional stress due to habitat loss has played an important role in honeybee colony collapse, and thereby stressed the usefulness of protecting and enhancing the availability of flower resources by using rules and policies for efficient management of agricultural farmlands. Decourtye et al. (2010) reviewed potential approaches to provide and maintain diverse floral resources in a landscape, giving particular consideration to herbaceous plants, to sustain bee populations, and support honeybee health and beekeeping. These approaches include the cultivation and maintenance of large strips (6-12 m in width) of native or non native melliferous plants maintained between crop fields, fallow areas, field margins, and conservation buffer strips. To set up an favourable landscape for honeybees

Diplôme : IUT

37 Annexes Diplôme : Licence

International audience; Global pollinators, like honeybees, are declining in abundance and diversity, which can adversely affect natural ecosystems and agriculture. Therefore, we tested the current hypotheses describing honeybee losses as a multifactorial syndrome, by investigating integrative effects of an infectious organism and an insecticide on honeybee health. We demonstrated that the interaction between the microsporidia Nosema and a neonicotinoid (imidacloprid) significantly weakened honeybees. In the short term, the combination of both agents caused the highest individual mortality rates and energetic stress. By quantifying the strength of immunity at both the individual and social levels, we showed that neither the haemocyte number nor the phenoloxidase activity of individuals was affected by the different treatments. However, the activity of glucose oxidase, enabling bees to sterilize colony and brood food, was significantly decreased only by the combination of both factors compared with control, Nosema or imidacloprid groups, suggesting a synergistic interaction and in the long term a higher susceptibility of the colony to pathogens. This provides the first evidences that interaction between an infectious organism and a chemical can also threaten pollinators, interactions that are widely used to eliminate insect pests in integrative pest management

Pheromones in social insects play a key role in the regulation of group homoeostasis. It is well-established that parasites can modify hormone signaling of their host, but less is known about the effect of parasites on pheromone signaling in insect societies. We, thus, tested in honey bees (Apis mellifera) the effect of the widespread parasite Nosema spp. on the production of ethyl oleate (EO), the only identified primer pheromone in honey bee workers. Since environmental stressors like pesticides also can weaken honey bees, we also analyzed the effect of imidacloprid, a neonicotinoid widely used in agriculture, on EO production. We show that, contrary to imidacloprid, Nosema spp. significantly altered EO production. In addition, the level of Nosema infection was correlated positively with the level of EO production. Since EO is involved in the regulation of division of labor among workers, our result suggests that the changes in EO signaling induced by parasitism have the potential to disturb the colony homoeostasis

Diplôme : Master; Like all bees (Apiformes), honey bees (Apis mellifera) feed on pollen which they must harvest to bring to their nest. To do so, pollen is acquired in flowers, brushed, gathered and compacted with nectar or honey into the corbiculae of the hind legs. The behaviours used during pollen manipulation and compaction have already been described repeatedly, but mainly based on visual observations. My goal was to record, describe and analyse these behaviours based on the recordings with a high speed camera. With these recordings, an ethogram of 12 behaviors was compiled, each behaviour with an average duration of only 17 to 73/100 of a second. The presence of some behaviours already described was confirmed, others were not, and some new behaviours were recorded such as the brushing of the mid legs by the front legs and, in strict nectar foragers, the brushing of the external surface of the hind legs by the mid legs. The analysis of the frequency distribution of these 12 behaviours highlighted a significant difference between foragers with pollen loads in their corbiculae and strict nectar foragers. This study is one of the first ones done on bees with this approach and it showed its possibilities as well as its limits when working under natural conditions; Comme toutes les abeilles (Apiformes), les abeilles domestiques (Apis mellifera) se nourrissent de pollen qu’elles doivent donc récolter pour le rapporter à leur nid. Pour se faire, le pollen est obtenu dans les fleurs, brossé, rassemblé et compacté avec du nectar ou du miel dans les corbicules des pattes postérieures. Les comportements impliqués dans la manipulation et l’agrégation du pollen ont déjà été souvent décrits, mais principalement à partir d’observations réalisées à l’oeil nu. Mon objectif était d’observer, de décrire et d’analyser ces comportements en utilisant une caméra à haute vitesse. A partir de ces enregistrements, un éthogramme de 12 comportements a été établi, chacun d’eux avec une durée moyenne de seulement 17 à 73 centièmes de seconde. La présence de certains comportements déjà décrits dans la littérature a été confirmée, d’autres ont été infirmé, et de nouveaux comportements ont été observés comme le brossage des pattes médianes par les pattes antérieures et, chez les butineuses de nectar strictes, le brossage de l’extérieur des pattes postérieures par les pattes médianes. L’analyse de la distribution des fréquences de ces 12 comportements a mis en évidence une différence significative entre les mouvements des pattes des butineuses qui possèdent des pelotes et ceux des butineuses strictes de nectar. Cette étude est l’une des premières effectuées sur abeilles avec cette approche et elle en montre les possibilités, mais aussi les limites en conditions naturelles.