Synergistic effects between microplastics and glyphosate on honey bee larvae.

Microplastic (MPs) pollution has emerged as a global ecological concern, however, the impact of MPs exposure, particularly in conjunction with other pollutants such as glyphosate (GLY) on honey bee remains unknown. This study investigated the effects of exposure to different concentrations of MPs and their combination with GLY on honey bee larvae development, or during the larvae period, regulation of major detoxification, antioxidant and immune genes, and oxidative stress biomarkers. Results revealed that combined exposure to MPs and GLY decreased larvae survivorship and weight, while exposure to MPs alone showed no significant differences. Both MPs and GLY alone downregulated the defensin-1 gene, but only combined exposure with GLY downregulated the hymenoptaecin gene and increased catalase enzyme activity. The data suggest a synergistic effect of MPs and GLY, leading to immunosuppression and reduced larvae survival and weight. These findings highlight potential risks of two prevalent environmental pollutants on honey bee health.

Assessment of oxidative status, detoxification capacity and immune responsiveness in honey bees with ageing.

The honey bee (Apis mellifera L.), as an eusocial insect species, is an important model organism in research focusing on ageing and longevity, due to prominent seasonal lifespan plasticity within the worker caste (summer and winter worker bees). In this study, we employed a screening approach to evaluate several molecular parameters, providing comprehensive insights into the antioxidative (superoxide dismutase and catalase activity, reduced glutathione and sulfhydryl group content, total antioxidative capacity), detoxifying (glutathione S-transferase and acetylcholinesterase activity), and immune (phenol oxidase and glucose oxidase activity) status, as well as vitellogenin content, in the summer and winter generation of honey bees, across ageing stages and in two body compartments: the whole abdomen and the head. Summer worker bees were collected weekly for six weeks, while winter bees were collected monthly for five months. The results of our study clearly indicate a reduced overall antioxidative capacity of older groups of worker bees from both generations, while the parameters of immune responsiveness mostly contributed to the separation between the two generations based on season rather than age categories. Detoxification ability appeared to be more susceptible to environmental factors. An age-dependent increase in vitellogenin content was recorded in the abdomen, but without seasonal differences. These findings provide an excellent starting point for further investigations into age-related changes, particularly within the context of honey bee sociality.

Estimating genus-specific effects of non-native honey bees and urbanization on wild bee communities: A case study in Maryland, United States.

Non-native species have the potential to detrimentally affect native species through resource competition, disease transmission, and other forms of antagonism. The western honey bee (Apis mellifera) is one such species that has been widely introduced beyond its native range for hundreds of years. There are strong concerns in the United States, and other countries, about the strain that high-density, managed honey bee populations could pose to already imperiled wild bee communities. While there is some experimental evidence of honey bees competing with wild bees for resources, few studies have connected landscape-scale honey bee apiary density with down-stream consequences for wild bee communities. Here, using a dataset from Maryland, US and joint species distribution models, we provide the largest scale, most phylogenetically resolved assessment of non-native honey bee density effects on wild bee abundance to date. As beekeeping in Maryland primarily consists of urban beekeeping, we also assessed the relative impact of developed land on wild bee communities. Six of the 33 wild bee genera we assessed showed a high probability (> 90 %) of a negative association with apiary density and/or developed land. These bees were primarily late-season, specialist genera (several long-horned genera represented) or small, ground nesting, season-long foragers (including several sweat bee genera). Conversely, developed land was associated with an increase in relative abundance for some genera including invasive Anthidium and other urban garden-associated genera. We discuss several avenues to ameliorate potentially detrimental effects of beekeeping and urbanization on the most imperiled wild bee groups. We additionally offer methodological insights based on sampling efficiency of different methods (hand netting, pan trapping, vane trapping), highlighting large variation in effect sizes across genera. The magnitude of sampling effect was very high, relative to the observed ecological effects, demonstrating the importance of integrated sampling, particularly for multi-species or community level assessments.

Surviving high temperatures: The crucial role of vesicular inhibitory amino acid transporter in Asian honeybee, Apis cerana.

Asian honeybees (Apis cerana) play a crucial role as pollinators to service for the ecological stability. However, their proliferation and growth are significantly impacted by environmental temperature stress. This study delves into the function of the Apis cerana vesicular inhibitory amino acid transporter gene (AcVIAAT) in safeguarding Asian honeybees against high-temperature stress. The AcVIAAT gene exhibits positive responsiveness in honeybees subjected to varying thermal conditions by triggering the genes associated with oxidative stress. Molecular docking, co-immunoprecipitation, and ELISA verify the capacity of the AcVIAAT protein to interact with γ-aminobutyric acid (GABA), a key inhibitory neurotransmitter. Administering GABA to honeybees significantly improves their survival rate under high-temperature stress and also simultaneously upregulating oxidative stress-related genes. Therefore, these findings reveal that the AcVIAAT gene enhances the thermoregulatory capacity of honeybees by modulating oxidative stress-related genes through facilitating GABA transport. The characterization of six non-synonymous SNPs in the AcVIAAT gene among A.cerana populations distributed across both the northern and southern regions indicates a potential association between gene variation and environmental adaptation. Our results contribute to elucidating the molecular mechanisms underlying high-temperature tolerance in Asian honeybees and provide a promising genetic marker for enhancing heat tolerance through genetic improvement.

Neglecting non-bee pollinators may lead to substantial underestimation of competition risk among pollinators.

Due to the increasing pressures on bees, many beekeepers currently wish to move their managed livestock of Apis mellifera into little disturbed ecosystems such as protected natural areas. This may, however, exert detrimental competitive effects upon local wild pollinators. While it appears critical for land managers to get an adequate knowledge of this issue for effective wildlife conservation schemes, the frequency of this competition is not clear to date. Based on a systematic literature review of 96 studies, we assessed the frequency of exploitative competition between honey bees and wild pollinators. We found that 78% of the studies highlighted exploitative competition from honey bees to wild pollinators. Importantly, these studies have mostly explored competition with wild bees, while only 18% of them considered other pollinator taxa such as ants, beetles, bugs, butterflies, flies, moths, and wasps. The integration of non-bee pollinators into scientific studies and conservation plans is urgently required as they are critical for the pollination of many wild plants and crops. Interestingly, we found that a majority (88%) of these studies considering also non-bee pollinators report evidence of competition. Thus, neglecting non-bee pollinators could imply an underestimation of competition risks from honey bees. More inclusive work is needed to estimate the risks of competition in its entirety, but also to apprehend the context-dependency of competition so as to properly inform wildlife conservation schemes.

Symbiont-mediated antisense RNA delivery controls Nosema ceranae infections in Apis mellifera.

Nosema ceranae is a main parasite for honeybees (Apis mellifera) which causes colony collapse in spring. Effective management of N. ceranae infections in bees is imperative for beekeepers. RNA interference (RNAi) has been proven a promising method to control bee pathogens, including IAPV, Varroa destructor, and Nosema. Most studies in this field focused on oral inoculation of double-stranded RNA (dsRNA). We developed an easier method with long-term RNAi effects by engineering the bee symbiont, Bacillus subtilis, to deliver single-stranded antisense RNA (asRNA) in the bee guts, targeting N. ceranae genes. We interfered with the expression of a spore wall protein (SWP12) and a polar tube protein (PTP3) of N. ceranae, resulting in a 60.5% increase in bee lifespan and a 72.7% decrease in Nosema spore load. Our research introduced a novel approach to bee parasite control: B. subtilis-mediated asRNA delivery. Our strategy simplifies the procedure of RNAi, presenting a more efficient mechanism with both prophylactic and therapeutic effects on N. ceranae-infected bees.

Analysis of fast calcium dynamics of honey bee olfactory coding.

Odour processing exhibits multiple parallels between vertebrate and invertebrate olfactory systems. Insects, in particular, have emerged as relevant models for olfactory studies because of the tractability of their olfactory circuits. Here, we used fast calcium imaging to track the activity of projection neurons in the honey bee antennal lobe (AL) during olfactory stimulation at high temporal resolution. We observed a heterogeneity of response profiles and an abundance of inhibitory activities, resulting in various response latencies and stimulus-specific post-odour neural signatures. Recorded calcium signals were fed to a mushroom body (MB) model constructed implementing the fundamental features of connectivity between olfactory projection neurons, Kenyon cells (KC), and MB output neurons (MBON). The model accounts for the increase of odorant discrimination in the MB compared to the AL and reveals the recruitment of two distinct KC populations that represent odorants and their aftersmell as two separate but temporally coherent neural objects. Finally, we showed that the learning-induced modulation of KC-to-MBON synapses can explain both the variations in associative learning scores across different conditioning protocols used in bees and the bees' response latency. Thus, it provides a simple explanation of how the time contingency between the stimulus and the reward can be encoded without the need for time tracking. This study broadens our understanding of olfactory coding and learning in honey bees. It demonstrates that a model based on simple MB connectivity rules and fed with real physiological data can explain fundamental aspects of odour processing and associative learning.

Dimethyl sulfoxide, an alternative for control of Nosema ceranae infection in honey bees (Apis mellifera).

Nosema ceranae is a microsporidian parasite that threatens current apiculture. N. ceranae-infected honey bees (Apis mellifera) exhibit morbid physiological impairments and reduced honey production, malnutrition, shorter life span, and higher mortality than healthy honey bees. In this study, we found that dimethyl sulfoxide (DMSO) could enhance the survival rate of N. ceranae-infected honey bees. Therefore, we investigated the effect of DMSO on N. ceranae-infected honey bees using comparative RNA sequencing analysis. Our results revealed that DMSO was able to affect several biochemical pathways, especially the metabolic-related pathways in N. ceranae-infected honey bees. Based on these findings, we conclude that DMSO may be a useful alternative for treating N. ceranae infection in apiculture.

Spatiotemporal evolution of the distribution of Chronic bee paralysis virus (CBPV) in honey bee colonies.

Chronic bee paralysis virus (CBPV) is a Apis mellifera viral infectious disease, exhibiting dark and hairless abdomen in workers with tremors and ataxita. Clinical signs are also typically linked to adverse weather conditions and overcrowding in the hive. The disease occurs in spring but recently it has been observed cases increase and seasonality loss of the disease incidence. This study analyses the evolution of CBPV in Italy, through data collected from 2009 to 2023 within three monitoring projects comprising nationwide extended detection networks, aimed to investigate the evolution of the CBPV spatial distribution, identifying high-risk areas for the virus spread. This study highlights an increased risk over years. Prevalence increased from 4.3% during 2009-2010 to 84.7% during 2021-2023 monitoring years. CBPV outbreaks were irregular between investigated seasons, highlighting Spring and Autumn as the most susceptible seasons. Risk of CBPV infection has increased, reaching high-risk in last years of monitoring. Sequence analysis showed a high similarity to other isolated Italian CBPVs. The study offers an epidemiological insight into the aetiology of this disease. CBPV distribution is a prerequisite to predict its future spread and factors involved in its propagation not only in honey bees but also in other pollinators and environments.

One-step genome engineering in bee gut bacterial symbionts.

Mechanistic understanding of interactions in many host-microbe systems, including the honey bee microbiome, is limited by a lack of easy-to-use genome engineering approaches. To this end, we demonstrate a one-step genome engineering approach for making gene deletions and insertions in the chromosomes of honey bee gut bacterial symbionts. Electroporation of linear or non-replicating plasmid DNA containing an antibiotic resistance cassette flanked by regions with homology to a symbiont genome reliably results in chromosomal integration. This lightweight approach does not require expressing any exogenous recombination machinery. The high concentrations of large DNAs with long homology regions needed to make the process efficient can be readily produced using modern DNA synthesis and assembly methods. We use this approach to knock out genes, including genes involved in biofilm formation, and insert fluorescent protein genes into the chromosome of the betaproteobacterial bee gut symbiont Snodgrassella alvi. We are also able to engineer the genomes of multiple strains of S. alvi and another species, Snodgrassella communis, which is found in the bumble bee gut microbiome. Finally, we use the same method to engineer the chromosome of another bee symbiont, Bartonella apis, which is an alphaproteobacterium. As expected, gene knockout in S. alvi using this approach is recA-dependent, suggesting that this straightforward procedure can be applied to other microbes that lack convenient genome engineering methods. IMPORTANCE: Honey bees are ecologically and economically important crop pollinators with bacterial gut symbionts that influence their health. Microbiome-based strategies for studying or improving bee health have utilized wild-type or plasmid-engineered bacteria. We demonstrate that a straightforward, single-step method can be used to insert cassettes and replace genes in the chromosomes of multiple bee gut bacteria. This method can be used for investigating the mechanisms of host-microbe interactions in the bee gut community and stably engineering symbionts that benefit pollinator health.

Wing vein abnormality analysis in honeybee (Apis mellifera L. 1758) populations from Iran.

The insect wing is one of the most important characteristics that allowed insects to occupy most of the habitats on the planet. Honeybee wings has been the subject of studies on the venation abnormalities. A total of 424 honeybees from 14 locations were collected and all four wings were removed and examined for 19 abnormalities on the forewings and 6 abnormalities on the hindwings. In general, supernumerary veins were the most common abnormalities seen and abnormalities no. 23, 2, 6, 1, 5, 21, 10, 13 had the highest and abnormalities no. 11, 17, 18, 19, 20, and 25 had the lowest frequencies. All of the abnormalities had similar frequencies in the right and left wings in the population. In terms of correlation between 25 abnormalities, abnormality pairs AB3-AB13, AB6-AB7, AB7-AB8, AB10-AB12, AB16-AB17 on the forewing and AB2-AB23, AB12-AB20, AB12-AB24, AB13-AB21, AB16-AB25, and AB17-AB25 between the forewing and hindwing show significant positive correlations and abnormality pairs AB4-AB5, AB7-AB15 and AB8-AB9 on the forewing show significant negative correlations with each other. In terms of the differential occurrence of abnormalities , a few locations differed significantly from other locations. This study provides some insights into the nature of these abnormalities on the honeybee wings.

Melittin alcalase-hydrolysate: a novel chemically characterized multifunctional bioagent; antibacterial, anti-biofilm and anticancer.

The prevalent life-threatening microbial and cancer diseases and lack of effective pharmaceutical therapies created the need for new molecules with antimicrobial and anticancer potential. Bee venom (BV) was collected from honeybee workers, and melittin (NM) was extracted from BV and analyzed by urea-polyacrylamide gel electrophoresis (urea-PAGE). The isolated melittin was hydrolyzed with alcalase into new bioactive peptides and evaluated for their antimicrobial and anticancer activity. Gel filtration chromatography fractionated melittin hydrolysate (HM) into three significant fractions (F1, F2, and F3), that were characterized by electrospray ionization mass spectrometry (ESI-MS) and evaluated for their antimicrobial, anti-biofilm, antitumor, and anti-migration activities. All the tested peptides showed antimicrobial and anti-biofilm activities against Gram-positive and Gram-negative bacteria. Melittin and its fractions significantly inhibited the proliferation of two types of cancer cells (Huh-7 and HCT 116). Yet, melittin and its fractions did not affect the viability of normal human lung Wi-38 cells. The IC50 and selectivity index data evidenced the superiority of melittin peptide fractions over intact melittin. Melittin enzymatic hydrolysate is a promising novel product with high potential as an antibacterial and anticancer agent.

How stressors disrupt honey bee biological traits and overwintering mechanisms.

High winter mortality of honey bees (Apis mellifera) has been observed in temperate regions over the past 30 years. Several biotic and abiotic stressors associated with winter colony losses have been identified, but the mechanisms and interactions underlying their effects remain unclear. We reviewed the effects of stressors on key overwintering biological traits, distinguishing between individual and colony traits. We found that disturbances at the level of individual traits can be amplified when transmitted to colony traits. By analyzing these cascading effects, we propose a concept of a feedback loop mechanism of winter mortality. We found that population size, social thermoregulation and honey reserve are integrative traits and can predict overwintering failure. Furthermore, we identified social thermoregulation as a good candidate for an early warning indicator. We therefore discuss existing tools for monitoring hive temperature to help mitigate the current high winter mortality of honey bees and support the sustainability of beekeeping.

Physiological effects of field concentrations and sublethal concentrations of sulfoxaflor on Apis mellifera.

BACKGROUND: Bees (Apis mellifera), as important pollinators of agricultural crops, are at risk when pesticides are used. Sulfoxaflor is a new insecticide which acts on the nicotinic acetylcholine receptor (nAChR) in a similar way to neonicotinoids. The goal of this study is to evaluate the toxicity of sulfoxaflor and its effect on the A. mellifera exposure. RESULTS: Initially, developmental indicators such as larval survival, pupation, and eclosion were inhibited by 5.0 mg/L (field concentration) sulfoxaflor. In the pupal stage, fat content was significantly increased, while the glycogen content decreased. In addition, A. mellifera heads were treated with 2.0 mg/L (sublethal concentration) of sulfoxaflor and analyzed by RNA sequencing. The transcriptome results indicated that 2.0 mg/L amounts of sulfoxaflor have adverse effects on the immune, digestive, and nervous systems. Sulfoxaflor down-regulated the expression of many genes involved in immunity, detoxification, the myosin cytoskeleton, sensory neurons, and odor-binding proteins. CONCLUSION: Field concentration and sublethal concentration were used for the combined analysis of honeybees. The effect of sublethal concentration of sulfoxaflor on honeybees was studied for the first time from the perspective of transcriptome sequencing of honeybee head. A preliminary study was carried out on the stress of sulfoxaflor at sublethal concentration on honeybee workers, which has certain research significance and can provide theoretical basis for the use of sulfoxaflor in the field environment. © 2024 Society of Chemical Industry.

Semi-natural habitats mitigate the impact of food shortage on honey bees in farmlands.

Landscape simplification and the loss of semi-natural habitats are identified as important drivers of insect pollinator decline in farmlands, by disrupting the availability of floral resources and facilitating the occurrence of food shortages. Food shortages can lead to accelerated behavioral maturation in honey bees, with potential consequences for colony survival. However, little is known about the magnitude of behavioral maturation mediated by to food shortage under real field conditions, and whether it could be mitigated by the presence of semi-natural habitats. Here, we monitored the lifespan (LSP), age at first exit (AFE), foraging tenure, and foraging intensity of 1035 honey bees along a landscape gradient of semi-natural habitats in farmlands. We found a clear acceleration of behavioral maturation of bees during the food shortage season, with precocity in AFE between 6 and 10 days earlier and reduced LSP by 5 to 9 days, with no effect on foraging tenure or foraging intensity. We also found that higher proportions of semi-natural habitats mitigated behavioral maturation of bees by up to 6 days. Beyond the direct effects on adult bees, we found no delayed effect of larval feeding status on adult life-history traits or foraging behavior. Nevertheless, our results strongly advocate the implementation of policies aimed at increasing the coverage of semi-natural environments (e.g., grasslands, forests, hedgerows) in intensive agricultural landscapes to support honey bee survival and pollinator conservation.

The neonicotinoid acetamiprid reduces larval and adult survival in honeybees (Apis mellifera) and interacts with a fungicide mixture.

Plant protection products (PPPs), which are frequently used in agriculture, can be major stressors for honeybees. They have been found abundantly in the beehive, particularly in pollen. Few studies have analysed effects on honeybee larvae, and little is known about effects of insecticide-fungicide-mixtures, although this is a highly realistic exposure scenario. We asked whether the combination of a frequently used insecticide and fungicides would affect developing bees. Honeybee larvae (Apis mellifera carnica) were reared in vitro on larval diets containing different PPPs at two concentrations, derived from residues found in pollen. We used the neonicotinoid acetamiprid, the combined fungicides boscalid/dimoxystrobin and the mixture of all three substances. Mortality was assessed at larval, pupal, and adult stages, and the size and weight of newly emerged bees were measured. The insecticide treatment in higher concentrations significantly reduced larval and adult survival. Interestingly, survival was not affected by the high concentrated insecticide-fungicides-mixture. However, negative synergistic effects on adult survival were caused by the low concentrated insecticide-fungicides-mixture, which had no effect when applied alone. The lower concentrated combined fungicides led to significantly lighter adult bees, although the survival was unaffected. Our results suggest that environmental relevant concentrations can be harmful to honeybees. To fully understand the interaction of different PPPs, more combinations and concentrations should be studied in social and solitary bees with possibly different sensitivities.

Fecal transplant allows transmission of the gut microbiota in honey bees.

The study of the fecal microbiota is crucial for unraveling the pathways through which gut symbionts are acquired and transmitted. While stable gut microbial communities are essential for honey bee health, their modes of acquisition and transmission are yet to be confirmed. The gut of honey bees is colonized by symbiotic bacteria within 5 days after emergence from their wax cells as adults. Few studies have suggested that bees could be colonized in part via contact with fecal matter in the hive. However, the composition of the fecal microbiota is still unknown. It is particularly unclear whether all bacterial species can be found viable in the feces and can therefore be transmitted to newborn nestmates. Using 16S rRNA gene amplicon sequencing, we revealed that the composition of the honey bee fecal microbiota is strikingly similar to the microbiota of entire guts. We found that fecal transplantation resulted in gut microbial communities similar to those obtained from feeding gut homogenates. Our study shows that fecal sampling and transplantation are viable tools for the non-invasive analysis of bacterial community composition and host-microbe interactions. It also implies that contact of young bees with fecal matter in the hive is a plausible route for gut microbiota acquisition. IMPORTANCE: Honey bees are crucial pollinators for many crops and wildflowers. They are also powerful models for studying microbiome-host interactions. However, current methods rely on gut tissue disruption to analyze microbiota composition and use gut homogenates to inoculate microbiota-deprived bees. Here, we provide two new and non-invasive approaches that will open doors to longitudinal studies: fecal sampling and transplantation. Furthermore, our findings provide insights into gut microbiota transmission in social insects by showing that ingestion of fecal matter can result in gut microbiota acquisition.

Early exposure to glyphosate during larval development induces late behavioural effects on adult honey bees.

As the most abundant pollinator insect in crops, Apis mellifera is a sentinel species of the pollinator communities. In these ecosystems, honey bees of different ages and developmental stages are exposed to diverse agrochemicals. However, most toxicological studies analyse the immediate effects during exposure. Late effects during adulthood after early exposure to pollutants during larval development are poorly studied in bees. The herbicide glyphosate (GLY) is the most applied pesticide worldwide. GLY has been detected in honey and beebread from hives near treated crops. Alterations in growth, morphogenesis or organogenesis during pre-imaginal development could induce late adverse effects after the emergence. Previous studies have demonstrated that GLY alters honey bee development, immediately affecting survival, growth and metabolism, followed by late teratogenic effects. The present study aims to determine the late impact on the behaviour and physiology of adult bees after pre-imaginal exposure to GLY. For that, we reared brood in vitro or in the hive with sub-chronic exposure to the herbicide with the average detected concentration in hives. Then, all newly emerged bees were reared in an incubator until maturity and tested when they became nurse-aged bees. Three behavioural responses were assessed as markers of cognitive and physiological impairment. Our results show i) decreased sensitivity to sucrose regardless of the rearing procedure, ii) increased choice latency and locomotor alterations during chemotaxis and iii) impaired associative learning. These late toxicity signs could indicate adverse effects on task performance and colony efficiency.

Effects of a supplemented diet containing 7 probiotic strains (Honeybeeotic) on honeybee physiology and immune response: analysis of hemolymph cytology, phenoloxidase activity, and gut microbiome.

BACKGROUND: In this study, a probiotic mixture (Honeybeeotic) consisting of seven bacterial strains isolated from a unique population of honeybees (Apis mellifera ligustica) was used. That honeybee population was located in the Roti Abbey locality of the Marche Region in Italy, an area isolated from human activities, and genetic contamination from other honeybee populations. The aim was to investigate the effects of this probiotic mixture on the innate immunity and intestinal microbiome of healthy common honeybees in two hives of the same apiary. Hive A received a diet of 50% glucose syrup, while hive B received the same syrup supplemented with the probiotics, both administered daily for 1 month. To determine whether the probiotic altered the immune response, phenoloxidase activity and hemolymph cellular subtype count were investigated. Additionally, metagenomic approaches were used to analyze the effects on gut microbiota composition and function, considering the critical role the gut microbiota plays in modulating host physiology. RESULTS: The results revealed differences in hemocyte populations between the two hives, as hive A exhibited higher counts of oenocytoids and granulocytes. These findings indicated that the dietary supplementation with the probiotic mixture was safe and well-tolerated. Furthermore, phenoloxidase activity significantly decreased in hive B (1.75 ± 0.19 U/mg) compared to hive A (3.62 ± 0.44 U/mg, p < 0.005), suggesting an improved state of well-being in the honeybees, as they did not require activation of immune defense mechanisms. Regarding the microbiome composition, the probiotic modulated the gut microbiota in hive B compared to the control, retaining core microbiota components while causing both positive and negative variations. Notably, several genes, particularly KEGG genes involved in amino acid metabolism, carbohydrate metabolism, and branched-chain amino acid (BCAA) transport, were more abundant in the probiotic-fed group, suggesting an effective nutritional supplement for the host. CONCLUSIONS: This study advocated that feeding with this probiotic mixture induces beneficial immunological effects and promoted a balanced gut microbiota with enhanced metabolic activities related to digestion. The use of highly selected probiotics was shown to contribute to the overall well-being of the honeybees, improving their immune response and gut health.

Origins, diversity, and adaptive evolution of DWV in the honey bees of the Azores: the impact of the invasive mite Varroa destructor.

Deformed wing virus (DWV) is a honey bee virus, whose emergence from relative obscurity is driven by the recent host-switch, adaptation, and global dispersal of the ectoparasitic mite Varroa destructor (a highly efficient vector of DWV) to reproduction on honey bees (Apis mellifera). Our study examines how varroa affects the continuing evolution of DWV, using the Azores archipelago, where varroa is present on only three out of the eight Islands, as a natural experimental system for comparing different evolutionary conditions and trajectories. We combined qPCR of 494 honey bee colonies sampled across the archipelago with amplicon deep sequencing to reveal how the DWV genetic landscape is altered by varroa. Two of the varroa-free Islands were also free of DWV, while a further two Islands were intriguingly dominated by the rare DWV-C major variant. The other four Islands, including the three varroa-infested Islands, were dominated by the common DWV-A and DWV-B variants. The varroa-infested Islands had, as expected, an elevated DWV prevalence relative to the uninfested Islands, but not elevated DWV loads, due the relatively high prevalence and loads of DWV-C on the varroa-free Islands. This establishes the Azores as a stable refuge for DWV-C and provides the most convincing evidence to date that at least some major strains of DWV may be capable of not just surviving, but actually thriving in honey bees in the absence of varroa-mediated transmission. We did not detect any change in DWV genetic diversity associated with island varroa status but did find a positive association of DWV diversity with virus load, irrespective of island varroa status.