Kun Dong

Across agricultural systems, crop production relies heavily on insect-mediated pollination. Both honey bees and bumble bees contribute substantially to crop productivity, with honey bee colonies providing large foraging workforces. On the other hand, bumble bees’ specialized pollination behaviors offset the limitations of honey bees, making them especially well-suited for greenhouse production. However, pesticides may pose significant risks to bumble bee health. Here, we used 16S rRNA gene sequencing to examine the effects of treatment with cyfluthrin, atrazine, and prothioconazole on the gut bacterial community of the European bumble bee (Bombus terrestris Linnaeus, 1758). Only atrazine treatment elicited a concentration-dependent response in intake and mortality. In bumble bees that survived treatment with cyfluthrin and atrazine, beta diversity of the gut bacterial community was significantly altered. In contrast, prothioconazole significantly altered both alpha and beta diversity, suggesting a stronger impact on gut microbial structure. Cyfluthrin significantly increased the relative abundance of Proteobacteria while decreasing Firmicutes, atrazine significantly reduced Proteobacteria while increasing Firmicutes and Bacteroidota, and prothioconazole significantly reduced only Bacteroidota. At the genus level, cyfluthrin significantly decreased Lactobacillus and increased Pseudomonas and Brevundimonas, atrazine significantly increased Apibacter and Lactobacillus, and prothioconazole significantly decreased Apibacter and Bifidobacterium. Snodgrassella, Gilliamella, Apibacter, and Lactobacillus remained the dominant genera across all treatments. The results of this study clarify pesticide-specific effects on the bumble bee gut microbiome, providing exploratory evidence for potential modes of action and informing future risk-related studies.

Heavy metal pollution has emerged as a major challenge in global environmental science in the 21st century because of its extensive distribution, long-term environmental persistence, and non-degradability. As indispensable pollinators in ecosystems, honey bees have undergone marked population declines, a trend closely associated with multiple environmental stressors, including heavy metal contamination. Notably, lead (Pb), a widespread legacy toxic metal pollutant, is released into the environment through industrial emissions, vehicle exhaust, and other anthropogenic sources, contributing to long-term environmental contamination. Moreover, Pb can be transferred to honey bees through contaminated pollen and nectar. This exposure route may pose a risk to honey bee health, particularly under chronic or repeated exposure. This review synthesizes current evidence on Pb exposure routes, bioaccumulation, sublethal toxicity, and physiological responses in honey bees, while highlighting major uncertainties in colony-level risk assessment. Pb-associated physiological effects may impair individual bee health, but their long-term implications for colony health require further study.

Bumblebees are dominant pollinators threatened by environmental antibiotic residues. This study investigated sublethal chloramphenicol (12 and 120 μg/L) effects on Bombus terrestris after 15 days’ exposure. The results showed that chloramphenicol exposure had no significant effect on the survival rate and cumulative food intake of bumblebees, confirming the sublethal property of the tested concentrations. However, chloramphenicol significantly dysregulated the expression of genes related to learning–memory (DopR2, Oamb, NMDA), immunity (abaecin, defensin) and detoxification (cyp9Q6) in bumblebees. High-dose chloramphenicol significantly increased carboxylesterase activity and reduced malondialdehyde content, while superoxide dismutase activity remained unchanged. In addition, chloramphenicol exposure significantly reshaped the gut microbiota structure of bumblebees, reduced the abundance of core beneficial symbiotic bacteria, and increased the proportion of drug-resistant bacteria. Our findings indicate that sublethal concentrations of chloramphenicol can impair bumblebee health through multiple pathways, including regulating gene expression, altering antioxidant enzyme activity and disrupting gut microbiota homeostasis. This study provides multi-dimensional toxicological data and a scientific basis for the ecological risk assessment of agricultural antibiotic residues to pollinator insects.

Introduction: Heavy metal pollution poses a persistent global threat to pollinator health and biodiversity. Lead is environmentally stable and can induce multifaceted physiological disorders in pollinating insects. However, the comprehensive toxic impacts of lead on bumblebees, particularly the interconnections between host gene expression and gut microbiota, remain largely underexplored. Methods: In this study, Bombus terrestris individuals were chronically exposed to three lead concentrations (0.95, 3.6, and 80 mg/L), selected based on acute toxicity data and field-relevant pollution levels. Following oral exposure via sugar water, we examined the expression profiles of genes associated with learning and memory, detoxification, and immune defense, as well as structural alterations in gut microbial communities. Results: Lead exposure significantly altered the transcription of DopR1 , DopR2 , NMDA , GST , PPO , defensin , and Hymen . Gut microbiota profiling further revealed distinct operational taxonomic unit (OTU) distributions across treatment groups, indicating that lead exposure reshaped the diversity and community structure of bumblebee gut microbes. Discussion: These findings uncover the coordinated toxic responses of host genes and gut bacteria under lead stress, and provide critical insights for a more comprehensive assessment of the ecological risks that heavy metal pollution poses to bumblebee populations.

As the predominant native pollinator across Asia, Apis cerana is essential for the maintenance of biodiversity and agricultural productivity. The gut microbiota of honeybees plays a central role in host nutrition, detoxification, and immune function. p-Coumaric acid, a widespread phenolic acid enriched in pollen and nectar, has been reported to promote honeybee health by prolonging lifespan and increasing the expression of detoxification-related genes, hence improving tolerance to pesticides. Its influence on gut microbial communities, however, remains insufficiently characterized in A. cerana. This study evaluated the effects of dietary p-coumaric acid on survival, sucrose solution consumption, and gut microbiome composition in A. cerana workers using absolute quantification sequencing. Bees were provided sucrose solutions containing p-coumaric acid at concentrations of 41.0, 82.0, and 164.0 mg/L for durations of 5 and 10 days. The results indicated no effect on survival but revealed time-dependent changes in sucrose solution consumption. p-Coumaric acid exposure altered the abundance of non-core bacterial taxa, including Bombella and Apilactobacillus, whereas the core gut microbiota (Lactobacillus, Gilliamella, Snodgrassella, Apibacter, and Bifidobacterium) remained stable. These results suggest that p-coumaric acid modulates sucrose solution consumption and selectively influences non-core gut bacteria without disrupting survival or core microbiota stability, underscoring its role in regulating host–microbe interactions in honeybees.

The accumulation of cocoons within brood cells of old combs is a key factor causing a series of negative impacts on bee colonies. Previous studies did not sufficiently address this dynamic nature as the core microenvironment for preimaginal bee development. During this accumulation, the enrichment of potentially harmful microorganisms and chemical substances may pose a latent threat to colony health. This study combined microbiome and metabolomics analyses to systematically investigate the potential colony health risks posed by multi-generational accumulation of cocoons in Apis mellifera combs. The results demonstrated that with the growing number of brood rearing generations, the microbial diversity within the cocoons underwent significant shifts. For the bacterial community within multiple-generation cocoons, the Simpson index exhibited a significant increase, whereas indices including Sobs, Ace, and Chao showed significant decreases (p < 0.05). In the fungal community, the Shannon and Pielou_e indices significantly increased, while the Simpson and Faith_pd indices significantly declined (p < 0.05). Potential pathogens such as Melissococcus and the mycotoxin-producing fungus Wallemia became significantly enriched, reaching alarming relative abundances of 42.70% and 13.52%, respectively, in the multiple-generation cocoons. Metabolomic analysis further revealed the enrichment of 685 differential metabolites, including persistent exogenous pesticides such as cyanazine and pymetrozine, etc. Correlation analysis uncovered a significant positive relationship (r > 0.8) between these pesticide residues and pathogen abundance, indicating interactions between pollutants and pathogens that may exacerbate risks. This study reveals the aggravation of microecological imbalance and chemical pollution load within the cocoons of old combs and therefore provides strong scientific support for risk assessment of comb age in colony health management and offers practical guidance for the sustainable development of beekeeping.

Honeybees are vital pollinators that contribute substantially to global ecosystem stability and agricultural productivity. Camellia reticulata, a cross-pollinated crop species, depends on honeybees for successful reproduction. Apis cerana shows reluctance to pollinate C. reticulata, yet the molecular mechanisms underlying this phenomenon remain unexplored. In this study, we performed controlled feeding experiments in which adult worker A. cerana were supplied with stachyose, raffinose, and their combination. We assessed physiological traits including survival rate, sucrose solution consumption, and body weight gain, alongside histological changes in intestinal cell structures. We conducted RNA-seq of gut tissues as well as 16S rRNA sequencing and metabolomic profiling. Our findings revealed that the mixed oligosaccharide treatment significantly reduced the survival rate of workers, and three oligosaccharide treatments significantly reduced sucrose consumption in A. cerana. Both mixed and single-oligosaccharide treatments caused pronounced intestinal cell damage and disrupted the gut microbial community structure. Among the gut microbes, Gilliamella exhibited the most substantial decline in the stachyose group. Metabolomic analysis further demonstrated that oligosaccharide feeding significantly altered amino acid and galactose metabolism pathways, which may play critical roles in oligosaccharide utilization and directly influence honeybee survival. In summary, this study provides new insights into the molecular mechanisms underlying A. cerana mortality associated with C. reticulata pollination. These findings not only enhance our understanding of host-diet-microbiota interactions in honey bees but also offer a theoretical basis for the integrated management of A. cerana for C. reticulata pollination and the development of oligosaccharide-adapted bee diets.

Bumblebees are efficient pollinators of fruits and vegetables in greenhouses and field crops. However, pesticide use in agricultural landscapes is causing a sharp decline in pollinating insect populations. The impact of pesticides on bumblebee health is a growing concern. Cyfluthrin, atrazine, and prothioconazole are 3 commonly used pesticides in agricultural production. Although the Food and Agriculture Organization of the United Nations has published the acute median lethal dose (LD50) data for these 3 pesticides on Apis mellifera honey bee, there is still a lack of LD50 data for non-Apis bees, such as Bombus terrestris (Linnaeus, 1758). Therefore, this study determined the oral median lethal dose (LD50) of 3 pesticides, cyfluthrin, atrazine, and prothioconazole, in European bumblebees (Bombus terrestris). The active ingredient of each pesticide was first dissolved in dimethyl sulfoxide and then diluted in a sucrose solution to prepare the pesticide–sucrose mixture for feeding. The oral LD50 values of cyfluthrin for worker bees were 4.27, 3.36, and 2.16 μg/bee at 24, 48, and 72 h, respectively. The 24-h LD50 for virgin queens was 13.49 μg/bee. For 24-h exposures in worker bees, the oral LD50 values of atrazine, prothioconazole, and their mixture were 355.3, 530.0, and 480.4 μg/bee, respectively. Pesticide–sucrose solution intake decreased as pesticide concentration increased. This study provides a preliminary evaluation of the toxicity of 3 pesticide types on bumblebees and offers insight for improving the conservation and sustainability of pollinators in agriculture. Additionally, the findings contribute to regulatory assessments by providing crucial data on pesticide effects on B. terrestris, supporting more comprehensive and effective pesticide regulations.