Adult Honey Bees Research Articles

Observation of Tropilaelaps mercedesae (Mesostigmata: Laelapidae) on Western honey bees (Apis mellifera) exiting colonies.

Tropilaelaps mercedesae (Delfinado and Baker) is an emerging parasitic mite that can severely impact the Western honey bee (Apis mellifera L.). While T. mercedesae has been reported to be expanding its geographical range, the routes of inter-colony dispersal between A. mellifera colonies are still largely unknown. In this study, we used funnel traps to collect foraging honey bees exiting their colonies before performing an alcohol wash to collect any phoretic T. mercedesae mites. We found T. mercedesae on exiting adult honey bees; however, they were only detected when a colony had an elevated T. mercedesae brood infestation. We show that T. mercedesae can exit colonies through phoresy on adult A. mellifera which demonstrates the potential of these mites to be spread through the natural movement of A. mellifera honey bees among colonies.

Effect of thymol and propolis extract on genotoxicity, biochemical activities and expression profile of some genes on honey bee, Apis mellifera, infected with Vairimorpha (Nosema) ceranae

BackgroundNosema ceranae, the predominant microsporidian parasite, weakens Apis mellifera honey bee colonies and reduces their productivity and reproduction. This research aims to detect the impact of thymol and propolis extracts on genotoxicity repair, oxidative enzymes, expression of some antimicrobial genes and some hypopharyngeal glands genes in N. ceranae-infected bees. Experimentally, infected honeybee colonies were divided into four groups: (1) untreated, (2) for propolis (3 g/L) treatment, (3) for thymol (0.1 g/L) treatment and (4) for mixed treatment with thymol and propolis. Workers from adult honeybee colonies, treated and untreated, were randomly sampled. The collected samples were used in studying the genotoxicity effect, the concentration of oxidative enzymes (superoxide-dismutases, glutathione S transferase, catalase and malondialdehyde (MDA)), measuring the relative expression of antimicrobial genes and hypopharyngeal glands genes major royal proteins 1 & 2 (MJRP1 and MJRP2).ResultsThe results show that thymol and propolis extract decreased genotoxicity effect, increased expression of antimicrobial genes, increased expression levels of MJRP1 and MJRP2 genes and decreased activities of oxidative enzymes when applied to Nosema-infected bees.ConclusionThymol and propolis extract positively affect honey bee health and mix of them. This study reveals that natural product extracts and their mixture may fight Nosema and prevent honey bee colonies decline and sudden death.

Effects of advanced chelate-based mineral supplement on adult worker honey bees’ (Apis mellifera L.) survival, nutritional indices, hypopharyngeal glands’ growth, energy reserve contents, and tolerance to dimethoate

This research aims to evaluate the effects of a chelated mineral diet supplement (hereinafter CMDS), namely Bonza bee which is designed based on the advanced chelate compounds technology, on adult worker honey bee’s (Apis mellifera L.) longevity, nutritional indices, hypopharyngeal glands’ (HPGs) growth, energy reserve contents, and tolerance to dimethoate. Newly emerged worker bees were confined in wooden laboratory cages and fed daily with 4 g of aqueous diets containing various concentrations of the CMDS (0, 0.2, 0.4, 0.5, 0.6, and 0.8% diet weight) for 21 days. Results of survival analysis revealed that providing the bees with diets containing 0.2 and 0.4% CMDS had no toxic effect, but their survival significantly declined as the concentration of the CMDS in the diets was increased. It was found that the bees consumed the diets in a CMDS concentration-dependent manner and they showed a significantly lower tendency to the diets with high concentrations of the CMDS. The maximum relative body growth rate was observed in the bees fed with a diet containing 0.4% CMDS. It was found that the diets containing 0.2 and 0.4% CMDS promoted the HPGs growth. The content of nutrient reserve macromolecules (protein, glycogen, and lipid) was significantly higher in the bees fed with the CMDS-supplemented diets. We also found that the bees fed the diet with 0.5% CMDS were more tolerant to the residue of sublethal concentration of dimethoate. We conclude, therefore, that dietary CMDS concentrations from 0.2 to 0.4% are optimal for the honey bee’s growth and health.

A honey bee-associated virus remains infectious and quantifiable in postmortem hosts.

Corpse-mediated pathogen transmission is a viable route through which naïve hosts can become infected, but its likelihood for honey bee-associated viruses is largely unknown. While these viruses can be easily detected in deceased bees, it remains unclear if they stay infectious within postmortem hosts or if enough viral RNA degradation-and subsequently virus inactivation-occurs post-host death to render these viruses inviable. This knowledge gap has important implications for how researchers perform honey bee virus studies and for our general understanding of honey bee virus transmission. To better understand the resiliency of honey bee-associated viruses within deceased hosts, we first tested the hypothesis that postmortem specimens, stored in colony-normal temperature and humidity conditions, can be reliably used to quantify virus abundance. To determine this, we experimentally-infected adult honey bees with Israeli acute paralysis virus (IAPV) and then measured the virus levels of individuals sampled live or at different postmortem time points (4, 12, 24, and 48 hours post-death) using RT-qPCR and a standard curve absolute quantification method. We found no significant differences based on when bees were sampled, indicating that postmortem honey bees are statistically comparable to using live-sampled bees and can be reliably used to quantify absolute IAPV abundance. We then performed a follow-up experiment that determined whether or not the IAPV detected in postmortem bees remained infectious over time. We found that IAPV extracted from postmortem bees remained highly infectious for at least 48 hours post-death, indicating that any viral RNA degradation that may have occurred during the postmortem interval did not adversely affect IAPV's overall infectivity. The results from this study suggest that IAPV is more resilient to degradation than previously assumed, support the use of postmortem bees for downstream IAPV analyses, and indicate that postmortem hosts can act as sources of IAPV infection for susceptible individuals.

Acetamiprid Exposure Disrupts Gut Microbiota in Adult and Larval Worker Honeybees (Apis mellifera L.).

Acetamiprid is a third-generation neonicotinoid insecticide that is now widely employed for the protection of crops grown in outdoor environments. This is because it is considerably less toxic to pollinating insects than other neonicotinoids. Previous studies have shown that acetamiprid has direct physiological effects on adult and larval bees. However, its effects on the potentially healthy gut microbiota of honeybees have not been fully elucidated. To further investigate the effects, adult and larval worker honeybees were exposed to sucrose solutions containing acetamiprid at concentrations of 0, 5, and 25 mg/L for a period of 7 days (adults) and 4 days (larvae). The results showed that acetamiprid exposure significantly disrupted the honeybees' intestinal microbiota. In adults, acetamiprid exposure led to a significant increase in the relative abundance of Commensalibacter, while the Bifidobacterium and Gilliamella levels decreased. In larvae, we observed significant changes in the microbial composition, notably a marked reduction in Bombella. Further analysis demonstrated that alterations in the gut microbiota of honeybee larvae were associated with disturbances in metabolic pathways that regulate energy metabolism and neurometabolism. These results suggest that acetamiprid affects bee health not only through direct physiological effects, but also through changes in the gut microbiota, which in turn affect the metabolic and immune function of bees. This study underscores the need to evaluate pesticides' risks from a microbiological standpoint and offers crucial insights into how acetamiprid impacts bee health by modifying the gut microbiota. These insights support the more comprehensive assessment of acetamiprid and similar pesticides regarding bee health.

A new variant of slow bee paralysis virus revealed by transcriptome analysis

Using NGS data from an RNA-seq library, we reveal a novel variant of slow bee paralysis virus (SBPV) in a pooled sample of adult honey bees (Apis mellifera) collected in southwest Germany. We provide its sequence (NCBI Accession No. PP100271) and demonstrate that it is infective for adult honey bees by feeding.

Managing the parasitic honey bee mite Tropilaelaps mercedesae through combined cultural and chemical control methods

The western honey bee (Apis mellifera) is severely impacted by the parasitic Tropilaelaps mercedesae mite, which has the capacity to outcompete Varroa destructor mites (the current leading cause of colony losses) and more rapidly overwhelm colonies. While T. mercedesae is native to Asia, it has recently expanded its geographic range and has the potential to devastate beekeeping worldwide if introduced to new regions. Our research exploited the dependence of T. mercedesae on developing honey bees (brood) by combining a cultural technique (brood break) with U.S. registered chemical products (oxalic acid or formic acid) to manage T. mercedesae infestation. To evaluate this approach, we compared four treatment groups: (1) Brood Break; (2) Brood Break + Formic Acid (FormicPro®); (3) Brood Break + Oxalic Acid dribble (Api-Bioxal®); and (4) untreated Control. We found that the mite infestation rate of worker brood in Control colonies rose from 0.4 to 15.25% over 60 days, whereas all other treatment groups had infestation rates under 0.11% on Day 60. Mite fall assessments showed similar results, whereby Control colonies had 15.48 mites fall per 24 h on day 60 compared to less than 0.2 mites for any other treatment group. Evaluation of colony strength revealed that Brood Break + Formic Acid colonies had slightly reduced adult honey bee populations. No treatment eliminated all mites, so additional measures may be needed to eradicate T. mercedesae if detected in countries that do not currently have T. mercedesae.

Metal concentration in honeybees along an urbanization gradient in Central Mexico

Urbanization is rapidly increasing worldwide, leading to rising levels of pollution, one of the major drivers of environmental change; yet little is known about the relationship between urbanization intensity and pollution levels in pollinator taxa. Toxic metals are among the most common contaminants in urban environments, but few data exist on their presence in the flora and fauna of cities in Latin America, one of the world's most urbanized and biologically diverse regions. In this study, we used an urban-rural gradient approach to analyze the relationship between the concentrations of eleven metals present in adult honeybees (Apis mellifera) and the degree of urbanization within twelve landscapes in the metropolitan area of Pachuca, Hidalgo, which forms part of the megalopolis of Mexico City. Metal concentrations were compared with previously reported values contrasting honeybees from urban and rural areas after standardizing urbanization levels among published reports. The concentrations of Ag, Cr, Cu, and Zn in honeybees increased significantly with the degree of urbanization. Urbanization was not found to influence the levels of Al, Ba, Cd, Mn, and Sr in honeybees. The maximum concentrations of six metals in our urban sites (Al, Ba, Cd, Cu, Mn, and Sr) were higher than the maximum values reported for bees in other urban areas. The concentrations of two metals measured in our study (Cr and Zn) were within the range of values previously published for urban areas. Compared to other studies, we did not detect Pb in the body of honeybees. We conclude that the concentrations of Ag, Cr, Cu, and Zn present in honeybees are a quantitative reflection of the degree of urbanization in central Mexico. Our results highlight the need to monitor metal emission sources in this and other areas and investigate their effects on bees and other pollinator taxa.

Differential impact of Paenibacillus infection on the microbiota of Varroa destructor and Apis mellifera

The Western honey bee (Apis mellifera) is a vital agricultural pollinator whose populations are threatened by the parasitic mite Varroa destructor and associated pathogens. While the impact of Paenibacillus species on honey bees, particularly Paenibacillus larvae causing American foulbrood, is documented, their effect on the microbiota of Varroa mites remains unclear. This study aimed to investigate the influence of Paenibacillus sp. on the bacterial communities of Varroa mites and adult honey bees. We hypothesized that Paenibacillus sp. would significantly alter the microbiota of Varroa mites but have minimal effect on that of adult honey bees. Utilizing 16S rRNA sequencing data from a previous study, we reanalyzed samples categorized into four groups based on Paenibacillus sp. infection load: highly infected and lowly infected honey bees (A. mellifera) and mites (V. destructor). Infection status was determined by Paenibacillus sp. read counts, with more than three reads indicating high infection. Microbial diversity was assessed using alpha and beta diversity metrics. Co-occurrence networks were constructed to visualize bacterial community assemblies, and network robustness was evaluated through node addition and removal tests. Keystone taxa were identified based on eigenvector centrality and relative abundance. Highly infected Varroa mites exhibited a significant reduction in alpha diversity and a markedly different bacterial community composition compared to lowly infected mites (p < 0.05). Their bacterial co-occurrence networks showed decreased connectivity and robustness, indicating a disruptive effect of Paenibacillus sp. In contrast, adult honey bees displayed no significant differences in alpha diversity or network structure between highly and lowly infected groups (p > 0.05), suggesting a resilient microbiota. Keystone taxa analysis revealed fewer central species in highly infected Varroa mites, potentially impacting network stability. High Paenibacillus sp. infection is associated with significant alterations in the microbiota of Varroa mites, disrupting bacterial communities and potentially affecting mite physiology. The microbiota of adult honey bees appears more robust against Paenibacillus sp. influence. These findings enhance our understanding of the complex interactions within the “honey bee–mite–microorganism” system and may inform future strategies for managing Varroa mite infestations and associated pathogens.

Megaselia scalaris and Senotainia tricuspis Infesting Apis mellifera: Detection by Quantitative PCR, Genotyping, and Involvement in the Transmission of Microbial Pathogens.

The Megaselia scalaris and Senotainia tricuspis parasitoid flies of the honeybee Apis mellifera were found to infest apiaries of different European and Mediterranean countries but their prevalence and impact on apiary health are little known. Therefore, in this study, quantitative PCR (qPCR)-based methods were developed for their rapid detection directly in hive matrices. The newly developed qPCR assays were targeted at the mitochondrial cytochrome oxidase subunit I (COI) gene for the M. scalaris and the cytochrome B (cytB) gene for the S. tricuspis. The tests were preliminarily applied to 64 samples of adult honeybees and hive debris collected in the Abruzzo and Molise regions, Central Italy, and the Republic of Kosovo showing that both flies occur in the two countries and more frequently in Italy. The positive apiaries in Italy were re-sampled by capturing viable forager bees and isolating emerging flies to carry out the genotyping and analyses aimed at defining if these flies can transmit honeybee pathogens. Genotyping based on the COI and cytB gene sequencing for M. scalaris and S. tricuspis, respectively, identified one S. tricuspis genotype and diverse genotypes of M. scalaris highly similar to those from distant countries. Some fly isolates harbored the DNA or RNA of honeybee microbial pathogens Paenibacillus larvae, deformed wing viruses A and B (DWVA and B), black queen cell virus (BQCV), chronic paralysis virus (CBPV), and Nosema ceranae. The results indicated that these parasites should be efficiently controlled in apiaries by using rapid detection methods to facilitate the large screening studies and early detection.

The selection traits of mite non-reproduction (MNR) and Varroa sensitive hygiene (VSH) show high variance in subsequent generations and require intensive time investment to evaluate

The honey bee ectoparasite Varroa destructor is the main cause of honey bee colony losses worldwide. Over the last decades, several projects have focused on improving the robustness of Apis mellifera against this parasitic mite. Selection traits, such as mite non-reproduction (MNR) and Varroa sensitive hygiene (VSH), are favored selection factors in Varroa resistance projects. VSH is a trait where adult honey bees remove the Varroa-infested brood. During this process, the female mites are arrested in their reproductive cycle leading to a reduction of the Varroa population within the bee colony. From 2019 to 2022, 1402 queens were instrumentally inseminated with single or multiple drones in a breeding program. Colonies headed by these queens were established annually, and the MNR and VSH levels were analyzed. VSH was evaluated in response to cells artificially infested with Varroa, and colonies with high VSH values were used to generate our selected VSH stock. Despite crossing high VSH drones and queens, we measured a remarkable heterogeneity of MNR and VSH in the next generation(s), most likely due to the well-described, high recombination rate in the honey bee genome. When assessed multiple times in the same colony, great variance between measurements was observed. Detailed evaluations of daughter colonies are thus required if selection programs want to breed colonies with reliable VSH traits. This constant need to evaluate all offspring to ensure the desirable resistance traits are present results in high workloads and great expenses in selection programs. Furthermore, such large-scale breeding programs are inefficient due to high fluctuations between measurements and generations, indicating we need to develop new approaches and improved methods for assessing Varroa resistance.

Pesticide exposure patterns in honey bees during migratory pollination

Monitoring pesticide exposures in honey bees provides fundamental risk information that informs efforts to improve regulatory policy, pesticide use, and beekeeping management so pollinators are protected in realistic field conditions. We investigated pesticide exposures to bee colonies while colonies moved along commercial migratory routes in 2022 and 2023 to pollinate multiple pollinator-dependent, high-value U.S. specialty crops (e.g., almonds in California and apples and cherries in Washington). We found evident pesticide exposure patterns, including increasing exposures (both levels and number of pesticides) to fungicides during almond pollination, higher exposures to insecticides and persistent exposures to fungicides during springtime fruit pollination, and declining exposures in summer. Exposure risk assessment by risk quotient (RQ) model based on residues in bee bread indicates no concern of acute toxicity to adult honey bees during pollination, however, during colony inspections we found severe brood mortality in fields associated with high exposure to buprofezin, an insect growth regulator (IGR) thought to be safe for adult bees, which is permitted for use any time across the season. Our results suggest a need to improve compliance with insecticide label requirements during tree fruit pollination and a need for further research into the negative impacts of IGR on colony health especially on immature bees to inform potential policy changes.

Flumethrin exposure perturbs gut microbiota structure and intestinal metabolism in honeybees (Apis mellifera)

Flumethrin mitigates Varroa’s harm to honeybee colonies; however, its residues in colonies threaten the fitness of honeybee hosts and gut microbiota. Our previous research has shown that flumethrin induces significant physiological effects on honeybee larvae; but the effects of flumethrin on the gut microbiota and metabolism of adult honeybees are still unknown. In this study, 1-day-old honeybees were exposed to 0, 0.01, 0.1, and 1 mg/L flumethrin for 14 days and the impacts of flumethrin on the intestinal system were evaluated. The results showed that exposure to 1 mg/L flumethrin significantly reduced honeybee survival and the activities of antioxidative enzymes (superoxide dismutase and catalase) and detoxification enzymes (glutathione S-transferase) in honeybee heads. Moreover, exposure to 0.01, 0.1, and 1 mg/L flumethrin significantly decreased the diversity of the honeybee gut microbiota. Results from untargeted metabolomics showed that long-term exposure to 0.01, 0.1, and 1 mg/L flumethrin caused changes in the metabolic pathways of honeybee gut microbes. Furthermore, increased metabolism of phenylalanine, tyrosine, and tryptophan derivatives was observed in honeybee gut microbes. These findings underscore the importance of careful consideration in using pesticides in apiculture and provide a basis for safeguarding honeybees from pollutants, considering the effects on gut microbes.

Development of germline progenitors in larval queen honeybee ovaries.

Honeybees (Apis mellifera) are a keystone species for managed pollination and the production of hive products. Eusociality in honeybees leads to much of the reproduction in a hive driven by the queen. Queen bees have two large active ovaries that can produce large numbers of eggs if conditions are appropriate. These ovaries are also active throughout the long lives of these insects, up to 5 years in some cases. Recent studies have indicated that the germline precursors of the adult honeybee queen ovary are organized into 8-cell clusters, joined together by a polyfusome; a cytoplasmic bridge. To understand the origin of these clusters, and trace the development of the honeybee queen ovary, we examined the cell types and regionalization of the developing larval and pupal queen ovaries. We used established (nanos and castor), and novel (odd skipped) gene expression markers to determine regions of the developing ovary. Primordial germline cells develop in the honeybee embryo and are organized into ovary structures before the embryo hatches. The ovary is regionalized by larval stage 3 into terminal filaments and germaria. At this stage, clusters of germline cells in the germaria are joined by fusomes and are dividing synchronously. The origin of the 8-cell clusters in the adult germarium is therefore during larval stages. On emergence, the queen ovary has terminal filaments and germaria but has not yet developed any vitellaria, which are produced after the queen embarks on a nuptial flight. The lack of germaria, and the storing of germline progenitors as clusters, may be adaptions for queen bees to endure the metabolic demands of a nuptial flight, as well as rapidly lay large numbers of eggs to establish a hive.

Full-Length Transcriptome Construction and Systematic Characterization of Virulence Factor-Associated Isoforms in Vairimorpha (Nosema) Ceranae.

Vairimorpha (Nosema) ceranae is a single-cellular fungus that obligately infects the midgut epithelial cells of adult honeybees, causing bee microsporidiosis and jeopardizing bee health and production. This work aims to construct the full-length transcriptome of V. ceranae and conduct a relevant investigation using PacBio single-molecule real-time (SMRT) sequencing technology. Following PacBio SMRT sequencing, 41,950 circular consensus (CCS) were generated, and 25,068 full-length non-chimeric (FLNC) reads were then detected. After polishing, 4387 high-quality, full-length transcripts were gained. There are 778, 2083, 1202, 1559, 1457, 1232, 1702, and 3896 full-length transcripts that could be annotated to COG, GO, KEGG, KOG, Pfam, Swiss-Prot, eggNOG, and Nr databases, respectively. Additionally, 11 alternative splicing (AS) events occurred in 6 genes were identified, including 1 alternative 5' splice-site and 10 intron retention. The structures of 225 annotated genes in the V. ceranae reference genome were optimized, of which 29 genes were extended at both 5' UTR and 3' UTR, while 90 and 106 genes were, respectively, extended at the 5' UTR as well as 3' UTR. Furthermore, a total of 29 high-confidence lncRNAs were obtained, including 12 sense-lncRNAs, 10 lincRNAs, and 7 antisense-lncRNAs. Taken together, the high-quality, full-length transcriptome of V. ceranae was constructed and annotated, the structures of annotated genes in the V. ceranae reference genome were improved, and abundant new genes, transcripts, and lncRNAs were discovered. Findings from this current work offer a valuable resource and a crucial foundation for molecular and omics research on V. ceranae.

Minibrain plays a role in the adult brain development of honeybee (Apis mellifera) workers.

The brain of adult honeybee (Apis mellifera) workers is larger than that of queens, facilitating behavioural differentiation between the castes. This brain diphenism develops during the pharate-adult stage and is driven by a caste-specific gene expression cascade in response to unique hormonal milieus. Previous molecular screening identified minibrain (mnb; DYRK1A) as a potential regulator in this process. Here, we used RNAi approach to reduce mnb transcript levels and test its role on brain diphenism development in honeybees. White-eyed unpigmented cuticle worker pupae were injected with dsRNA for mnb (Mnb-i) or gfp, and their phenotypes were assessed two and 8 days later using classic histological and transcriptomic analyses. After 2 days of the injections, Mnb-i bees showed 98% of downregulation of mnb transcripts. After 8 days, the brain of Mnb-i bees showed reduction in total volume and in the volume of the mushroom bodies (MB), antennal, and optic lobes. Additionally, signs of apoptosis were observed in the Kenyon cells region of the MB, and the cohesion of the brain tissues was affected. Our transcriptomic analyses revealed that 226 genes were affected by the knockdown of mnb transcripts, most of which allowing axonal fasciculation. These results suggest the evolutionary conserved mnb gene has been co-opted for promoting hormone-mediated developmental brain morphological plasticity generating caste diphenism in honeybees.

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.

Comparing the efficacy of alcohol wash and powdered sugar methods to dislodge the Varroa mite from the body of the adult honey bee

Comparing the efficacy of alcohol wash and powdered sugar methods to dislodge the Varroa mite from the body of the adult honey bee

Early-Life Sublethal Exposure to Thiacloprid Alters Adult Honeybee Gut Microbiota.

Thiacloprid, a neonicotinoid pesticide, is known to affect the gut microbiome of honeybees, yet studies often focus on immediate alternations during exposure, overlooking long-term microbiological impacts post-exposure. This study investigates the influences of sublethal thiacloprid administered during the larval developmental stage of honeybees on physiological changes and gut microbiota of adult honeybees. We found that thiacloprid exposure increased mortality and sugar intake in emerged honeybees. Using 16S rDNA sequencing, we analyzed intestinal microbial diversity of honeybees at one and six days post-emergence. Our findings reveal a significant but transient disruption in gut microbiota on day 1, with recovery from dysbiosis by day 6. This study emphasizes the importance of evaluating chronic sublethal exposure risks of thiacloprid to protect honeybee health.

A field realistic model to assess the effects of pesticides residues and adulterants on honey bee gene expression.

While studies on the sublethal effects of chemical residues in beeswax on adult honey bees are increasing, the study protocols assessing the impacts on honey bee brood in realistic conditions still need to be investigated. Moreover, little is known about the residue's effect on gene expression in honey bee brood. This study reports the effects of chlorpyriphos-ethyl, acrinathrin and stearin worker pupae exposure through contaminated or adulterated beeswax on the gene expression of some key health indicators, using a novel in vivo realistic model. Larvae were reared in acrinathrin (12.5, 25, 10 and 100 ppb) and chlorpyriphos-ethyl (5, 10, 500 and 5000 ppb) contaminated or stearin adulterated beeswax (3, 4, 5, 6 and 9%) in newly formed colonies to reduce the influence of external factors. On day 11, mortality rates were assessed. Honey bee pupae were extracted from the comb after 19 days of rearing and were analysed for the gene expression profile of four genes involved in the immune response to pathogens and environmental stress factors (Imd, dorsal, domeless and defensin), and two genes involved in detoxifications mechanisms (CYP6AS14 and CYP9Q3). We found no linear relation between the increase in the pesticide concentrations and the brood mortality rates, unlike stearin where an increase in stearin percentage led to an exponential increase in brood mortality. The immune system of pupae raised in acrinathrin contaminated wax was triggered and the expression of CYP6AS14 was significantly upregulated (exposure to 12.5 and 25 ppb). Almost all expression levels of the tested immune and detoxification genes were down-regulated when pupae were exposed to chlorpyrifos-contaminated wax. The exposure to stearin triggered the immune system and detoxification system of the pupae. The identification of substance-specific response factors might ultimately serve to identify molecules that are safer for bees and the ecosystem's health.