Impact of Nutritional Stress on Honeybee Gut Microbiota, Immunity, and Nosema ceranae Infection

Honeybees are important pollinators, having an essential role in the ecology of natural and agricultural environments. Honeybee colony losses episodes reported worldwide and have been associated with different pests and pathogens, pesticide exposure, and nutritional stress. This nutritional stress is related to the increase in monoculture areas which leads to a reduction of pollen availability and diversity. In this study, we examined whether nutritional stress affects honeybee gut microbiota, bee immunity, and infection by Nosema ceranae, under laboratory conditions. Consumption of Eucalyptus grandis pollen was used as a nutritionally poor-quality diet to study nutritional stress, in contraposition to the consumption of polyfloral pollen. Honeybees feed with Eucalyptus grandis pollen showed a lower abundance of Lactobacillus mellifer and Lactobacillus apis (Firm-4 and Firm-5, respectively) and Bifidobacterium spp. and a higher abundance of Bartonella apis, than honeybees fed with polyfloral pollen. Besides the impact of nutritional stress on honeybee microbiota, it also decreased the expression levels of vitellogenin and genes associated to immunity (glucose oxidase, hymenoptaecin and lysozyme). Finally, Eucalyptus grandis pollen favored the multiplication of Nosema ceranae. These results show that nutritional stress impacts the honeybee gut microbiota, having consequences on honeybee immunity and pathogen development. Those results may be useful to understand the influence of modern agriculture on honeybee health.Fil: Castelli, L.. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Branchiccela, B.. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Garrido, Paula Melisa. Universidad Nacional de Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente; ArgentinaFil: Invernizzi, Ciro. No especifíca;Fil: Porrini, Martín Pablo. Universidad Nacional de Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Producción, Sanidad y Ambiente; ArgentinaFil: Romero, H.. No especifíca;Fil: Santos, E.. No especifíca;Fil: Zunino, P.. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Antúnez, Karina. Instituto de Investigaciones Biológicas "Clemente Estable"; Urugua

Hygromechanical behaviour of wooden panel paintings: classification of their deformation tendencies based on numerical modelling and experimental results

AbstractWooden panel paintings are among the most important historical and artistic artworks from the Middle Ages and the Renaissance period. Currently, they represent a challenge for conservators and scientists who face complex issues related to their conservation. Panel paintings can be considered multilayer objects, that for brevity can be considered to consist of a wooden support and various paint layers. The wooden support is known to be hygroscopic and is continuously seeking hygroscopic equilibrium with the humidity of the environment, thus it tends to deform. Based on various hygroscopic tests carried out on 6 real panel paintings chosen by expert restorers to represent different periods and construction techniques, this paper describes the deformation tendencies of the selected panel paintings. Among possible variables, three most important variables were identified: (a) tree ring orientation of the wooden support, (b) stiffness and (c) emissivity of the paint layers. The internal equilibrium of the forces, governed by the moisture gradients across the thickness of the wood, changes drastically according to the varying characterisation of these factors. To observe their individual contributions, the 6 panel paintings underwent various humidity cycles, were completely free to deform and were always in complete safety. To characterise the stiffness and emissivity of the paint layers, the 6 panel paintings underwent a few humidity cycles with the front face totally waterproofed; thus, the moisture exchange was forced from the back only, and one of the three variables was eliminated. A complex system emerges where the tree ring orientation of the wooden support, the stiffness and emissivity of the paint layers are strongly coupled and determine the deformation modes of the panel paintings. A numerical analysis was conducted to classify the various general deformation modes of panel paintings and the specific classification of the 6 real panel paintings analysed experimentally. The complexity of the interaction of the variables studied suggests that experimental procedures must be conducted in preparation for numerical analyses of real panel paintings

Unraveling honey bee–varroa destructor interaction: multiple factors involved in differential resistance between two uruguayan populations

The ectoparasite Varroa destructor is the greatest biotic threat of honey bees Apis mellifera in vast regions of the world. Recently, the study of natural mite-resistant populations has gained much interest to understand the action of natural selection on the mechanisms that limit the mite population. In this study, the components of the A. mellifera–V. destructor relationship were thoroughly examined and compared in resistant and susceptible honey bee populations from two regions of Uruguay. Mite-resistant honey bees have greater behavioral resistance (hygienic and grooming behaviors) than susceptible honey bees. At the end of the summer, resistant honey bees had fewer mites and a lower deformed wing virus (DWV) viral load than susceptible honey bees. DWV variant A was the only detected variant in honey bees and mites. Molecular analysis by Short Tandem Repeat showed that resistant honey bees were Africanized (A. m. scutellata hybrids), whereas susceptible honey bees were closer to European subspecies. Furthermore, significant genetic differentiation was also found between the mite populations. The obtained results show that the natural resistance of honey bees to V. destructor in Uruguay depends on several factors and that the genetic variants of both organisms can play a relevant rol

Genetic diversification of an invasive honey bee ectoparasite across sympatric and allopatric host populations

Invasive parasites are major threats to biodiversity. The honey bee ectoparasite, Varroa destructor, has shifted host and spread almost globally several decades ago. This pest is generally considered to be the main global threat to Western honey bees, Apis mellifera, although the damages it causes are not equivalent in all its new host’s populations. Due to the high virulence of this parasite and the viruses it vectors, beekeepers generally rely on acaricide treatments to keep their colonies alive. However, some populations of A. mellifera can survive without anthropogenic mite control, through the expression of diverse resistance and tolerance traits. Such surviving colonies are currently found throughout the globe, with the biggest populations being found in Sub- Saharan Africa and Latin America. Recently, genetic differences between mite populations infesting surviving and treated A. mellifera colonies in Europe were found, suggesting that adaptations of honey bees drive mite evolution. Yet, the prevalence of such co-evolutionary adaptations in other invasive populations of V. destructor remain unknown. Using the previous data from Europe and novel genetic data from V. destructor populations in South America and Africa, we here investigated whether mites display signs of adaptations to different host populations of diverse origins and undergoing differing management. Our results show that, contrary to the differences previously documented in Europe, mites infesting treated and untreated honey bee populations in Africa and South America are genetically similar. However, strong levels of genetic differentiation were found when comparing mites across continents, suggesting ongoing allopatric speciation despite a recent spread from genetically homogenous lineages. This study provides novel insights into the co-evolution of V. destructor and A. mellifera, and confirms that these species are ideal to investigate coevolution in newly established host- parasite systems.Agencia Nacional de Investigación e InnovaciónPrograma ECOS-Su

Genetic diversification of an invasive honey bee ectoparasite across sympatric and allopatric host populations.

Invasive parasites are major threats to biodiversity. The honey bee ectoparasite, Varroa destructor, has shifted host and spread almost globally several decades ago. This pest is generally considered to be the main global threat to Western honey bees, Apis mellifera, although the damages it causes are not equivalent in all its new host's populations. Due to the high virulence of this parasite and the viruses it vectors, beekeepers generally rely on acaricide treatments to keep their colonies alive. However, some populations of A. mellifera can survive without anthropogenic mite control, through the expression of diverse resistance and tolerance traits. Such surviving colonies are currently found throughout the globe, with the biggest populations being found in Sub-Saharan Africa and Latin America. Recently, genetic differences between mite populations infesting surviving and treated A. mellifera colonies in Europe were found, suggesting that adaptations of honey bees drive mite evolution. Yet, the prevalence of such co-evolutionary adaptations in other invasive populations of V. destructor remain unknown. Using the previous data from Europe and novel genetic data from V. destructor populations in South America and Africa, we here investigated whether mites display signs of adaptations to different host populations of diverse origins and undergoing differing management. Our results show that, contrary to the differences previously documented in Europe, mites infesting treated and untreated honey bee populations in Africa and South America are genetically similar. However, strong levels of genetic differentiation were found when comparing mites across continents, suggesting ongoing allopatric speciation despite a recent spread from genetically homogenous lineages. This study provides novel insights into the co-evolution of V. destructor and A. mellifera, and confirms that these species are ideal to investigate coevolution in newly established host-parasite systems

Impact of nutritional stress on the honeybee colony health

Honeybees Apis mellifera are important pollinators of wild plants and commercial crops. For more than a decade, high percentages of honeybee colony losses have been reported worldwide. Nutritional stress due to habitat depletion, infection by different pests and pathogens and pesticide exposure has been proposed as the major causes. In this study we analyzed how nutritional stress affects colony strength and health. Two groups of colonies were set in a Eucalyptus grandis plantation at the beginning of the flowering period (autumn), replicating a natural scenario with a nutritionally poor food source. While both groups of colonies had access to the pollen available in this plantation, one was supplemented with a polyfloral pollen patty during the entire flowering period. In the short-term, colonies under nutritional stress (which consumed mainly E. grandis pollen) showed higher infection level with Nosema spp. and lower brood and adult bee population, compared to supplemented colonies. On the other hand, these supplemented colonies showed higher infection level with RNA viruses although infection levels were low compared to countries were viral infections have negative impacts. Nutritional stress also had long-term colony effects, because bee population did not recover in spring, as in supplemented colonies did. In conclusion, nutritional stress and Nosema spp. infection had a severe impact on colony strength with consequences in both short and long-term

Perfiles virales de colonias susceptibles y sobrevivientes a Varroa destructor

Varroa destructor es la principal amenaza biótica de Apis mellifera, es vector de diversos virus y es letal si las colonias no son tratadas a tiempo. En Uruguay existe una población de abejas que sobreviven naturalmente a la parasitación con este ácaro sin necesidad de tratamientos. Este fenómeno estaría asociado a un mayor comportamiento higiénico de esas abejas; pero, además, podría deberse a la presencia de comunidades virales diferenciales asociadas a las colonias. El objetivo de este trabajo fue cuantificar y caracterizar los virus presentes en colonias de A. mellifera sobrevivientes y susceptibles a V. destructor de nuestro país. Para ello se tomaron muestras de abejas nodrizas de estas colonias en primavera y en otoño, y se realizó la detección y cuantificación absoluta mediante qPCR de los virus: de la Parálisis Aguda (ABPV), de las Celdas Reales Negras (BQCV), de las Alas Deformes (DWV) y de la cría ensacada (SBV). Paralelamente, muestras de esas mismas colonias fueron sometidas a protocolos de enriquecimiento de las partículas virales y posterior secuenciación masiva (Illumina). Los resultados de este trabajo nos permitieron realizar la caracterización genómica de los principales virus de interés apícola (ABPV, BQCV, DWV y SBV). A su vez, se observó que en otoño las colonias sobrevivientes presentaron menor nivel de infección para algunos virus comparado con las colonias susceptibles. Por último, la secuenciación masiva permitió la detección de algunos fragmentos de virus que aún no se habían detectado en nuestro país, como el Virus del Lago Sinaí y el Virus Filamentoso de Apis mellifera. Continuamos estudiando los perfiles virales de las colonias sobrevivientes y susceptibles a V. destructor con el fin de avanzar hacia un control sustentable de las poblaciones de ácaros.Agencia Nacional de Investigación e Innovació

Sanitary situation of honey bees in Uruguay: novelties of the last decade

En los últimos años, la apicultura en Uruguay se enfrenta con bajos rendimientos de producción de miel y pérdidas anuales de colonias que pueden alcanzar el 30%, estando los problemas sanitarios involucrados en buena parte de esta situación. A nivel mundial la investigación sobre los factores que amenazan a las poblaciones de abejas melíferas se ha ampliado, abarcando los problemas nutricionales, la respuesta inmune, la microbiota intestinal, la identificación de nuevos patógenos o variantes de los mismos, el efecto de los agroquímicos, y otros insectos que comparten patógenos con las abejas melíferas. Respecto a la varroosis la investigación se ha enfocado en las poblaciones de abejas sobrevivientes a Varroa destructor. En Uruguay, la investigación sobre salud de las abejas melíferas en los últimos 10 años ha sido muy prolífica abordando buena parte de los temas mencionados desde las condiciones particulares que presenta el país. Esta revisión sobre la situación sanitaria de las abejas melíferas en Uruguay se centra en resultados de investigaciones nacionales sobre las parasitosis y virosis más prevalentes, la identificación de un nuevo parásito, el efecto de la nutrición y el herbicida glifosato tanto en la microbiota intestinal como en la sanidad, el estudio de parásitos y virus de las abejas melíferas presentes en abejorros nativos del género Bombus, y la descripción de una enfermedad específica del país como es el Mal del Río. Se resalta la importancia de los diferentes resultados para la apicultura nacional y se ponen en contexto con la información internacional reciente.In recent years, beekeeping industry in Uruguay faces low honey production yields and annual colony losses that can reach 30%, and health problems are involved in much of this situation. Worldwide, research on the factors that threaten honey bee populations has expanded, encompassing nutritional problems, the immune response, the intestinal microbiota, identification of new pathogens or its variants, the effect of agrochemicals, and other insects that share pathogens with honey bees. Regarding varroosis, research has focused on the populations of bees surviving Varroa destructor. In Uruguay, research on the health of honey bees in the last 10 years has been very prolific, addressing a good part of the aforementioned issues taking into account the particular conditions that the country presents. This review on the health situation of honey bees in Uruguay focuses on the results of national research on the most prevalent parasitosis and virosis, the identification of a new parasite, the effect of nutrition and the herbicide glyphosate on the intestinal microbiota and on the health, the study of parasites and viruses of honey bees present in native bumblebees of the genus Bombus, and the description of the country-specific disease (River disease). The importance of the diverse results for national beekeeping is highlighted and put in context with recent international information