Field agrochemical exposure impacts locomotor activity in wild bumblebees.

Agricultural intensification has been identified as one of the key causes of global insect biodiversity losses. These losses have been further linked to the widespread use of agrochemicals associated with modern agricultural practices. Many of these chemicals are known to have negative sublethal effects on commercial pollinators, such as managed honeybees and bumblebees, but less is known about the impacts on wild bees. Laboratory-based studies with commercial pollinators have consistently shown that pesticide exposure can impact bee behavior, with cascading effects on foraging performance, reproductive success, and pollination services. However, these studies typically assess only one chemical, neglecting the complexity of real-world exposure to multiple agrochemicals and other stressors. In the summer of 2020, we collected wild-foraging workers of the common eastern bumblebee, Bombus impatiens, from five squash (Cucurbita) agricultural sites (organic and conventional farms), selected to represent a range of agrochemical, including neonicotinoid insecticide, use. For each bee, we measured two behaviors relevant to foraging success and previously shown to be impacted by pesticide exposure: sucrose responsiveness and locomotor activity. Following behavioral testing, we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) chemical analysis to detect and quantify the presence of 92 agrochemicals in each bumblebee. Bees collected from our sites did not vary in pesticide exposure as expected. While we found a limited occurrence of neonicotinoids, two fungicides (azoxystrobin and difenoconazole) were detected at all sites, and the pesticide synergist piperonyl butoxide (PBO) was present in all 123 bees. We found that bumblebees that contained higher levels of PBO were less active, and this effect was stronger for larger bumblebee workers. While PBO is unlikely to be the direct cause of the reduction in bee activity, it could be an indicator of exposure to pyrethroids and/or other insecticides that we were unable to directly quantify, but which PBO is frequently tank-mixed with during pesticide applications on crops. We did not find a relationship between agrochemical exposure and bumblebee sucrose responsiveness. To our knowledge, this is the first evidence of a sublethal behavioral impact of agrochemical exposure on wild-foraging bees.

Effects of natural treatments on the varroa mite infestation levels and overall health of honey bee (Apis mellifera) colonies.

The survival of the honey bee (Apis mellifera), which has a crucial role in pollination and ecosystem maintenance, is threatened by many pathogens, including parasites, bacteria, fungi and viruses. The ectoparasite Varroa destructor is considered the major cause of the worldwide decline in honey bee colony health. Although several synthetic acaricides are available to control Varroa infestations, resistant mites and side effects on bees have been documented. The development of natural alternatives for mite control is therefore encouraged. The study aims at exploring the effects of cinnamon and oregano essential oils (EOs) and of a mixed fruit cocktail juice on mite infestation levels and bee colony health. A multi-method study including hive inspection, mite count, molecular detection of fungal, bacterial and viral pathogens, analysis of defensin-1, hymenoptaecin and vitellogenin immune gene expression, colony density and honey production data, was conducted in a 20-hive experimental apiary. The colonies were divided into five groups: four treatment groups and one control group. The treatment groups were fed on a sugar syrup supplemented with cinnamon EO, oregano EO, a 1:1 mixture of both EOs, or a juice cocktail. An unsupplemented syrup was, instead, used to feed the control group. While V. destructor affected all the colonies throughout the study, no differences in mite infestation levels, population density and honey yield were observed between treatment and control groups. An overexpression of vitellogenin was instead found in all EO-treated groups, even though a significant difference was only found in the group treated with the 1:1 EO mixture. Viral (DWV, CBPV and BQCV), fungal (Nosema ceranae) and bacterial (Melissococcus plutonius) pathogens from both symptomatic and asymptomatic colonies were detected.

Neonicotinoid exposure increases Varroa destructor (Mesostigmata: Varroidae) mite parasitism severity in honey bee colonies and is not mitigated by increased colony genetic diversity.

Agrochemical exposure is a major contributor to ecological declines worldwide, including the loss of crucial pollinator species. In addition to direct toxicity, field-relevant doses of pesticides can increase species' vulnerabilities to other stressors, including parasites. Experimental field demonstrations of potential interactive effects of pesticides and additional stressors are rare, as are tests of mechanisms via which pollinators tolerate pesticides. Here, we controlled honey bee colony exposure to field-relevant concentrations of 2 neonicotinoid insecticides (clothianidin and thiamethoxam) in pollen and simultaneously manipulated intracolony genetic heterogeneity. We showed that exposure increased rates of Varroa destructor (Anderson and Trueman) parasitism and that while increased genetic heterogeneity overall improved survivability, it did not reduce the negative effect size of neonicotinoid exposure. This study is, to our knowledge, the first experimental field demonstration of how neonicotinoid exposure can increase V. destructor populations in honey bees and also demonstrates that colony genetic diversity cannot mitigate the effects of neonicotinoid pesticides.

Relative impacts of Varroa destructor (Mesostigmata:Varroidae) infestation and pesticide exposure on honey bee colony health and survival in a high-intensity corn and soybean producing region in northern Iowa.

The negative effects of Varroa and pesticides on colony health and survival are among the most important concerns to beekeepers. To compare the relative contribution of Varroa, pesticides, and interactions between them on honey bee colony performance and survival, a 2-year longitudinal study was performed in corn and soybean growing areas of Iowa. Varroa infestation and pesticide content in stored pollen were measured from 3 apiaries across a gradient of corn and soybean production areas and compared to measurements of colony health and survival. Colonies were not treated for Varroa the first year, but were treated the second year, leading to reduced Varroa infestation that was associated with larger honey bee populations, increased honey production, and higher colony survival. Pesticide detections were highest in areas with high-intensity corn and soybean production treated with conventional methods. Pesticide detections were positively associated with honey bee population size in May 2015 in the intermediate conventional (IC) and intermediate organic (IO) apiaries. Varroa populations across all apiaries in October 2015 were negatively correlated with miticide and chlorpyrifos detections. Miticide detections across all apiaries and neonicotinoid detections in the IC apiary in May 2015 were higher in colonies that survived. In July 2015, colony survival was positively associated with total pesticide detections in all apiaries and chlorpyrifos exposure in the IC and high conventional (HC) apiaries. This research suggests that Varroa are a major cause of reduced colony performance and increased colony losses, and honey bees are resilient upon low to moderate pesticide detections.

Honey bee colony behavior and ontogeny are adversely affected when exposed to a pesticide-contaminated environment.

Honey bees exhibit age polyethism and thus have a predictable sequence of behaviors they express through developmental time. Numerous laboratory studies show exposure to pesticides may impair critical honey bee behaviors (brood care, foraging, egg-laying, etc.) that adversely affect colony productivity and survival. There are fewer studies that examine the impacts of pesticides in natural field settings, especially given the challenges of implementing treatment groups and controlling variables. This study helps address the need for impact studies on pollinators under field conditions to assess the consequences of chemical overuse and dependency in agricultural and urban landscapes. To assess the impact of systemic pesticides in a natural field setting on worker bee behavioral development, observation hives were established to monitor changes in behaviors of similarly aged workers and sister queens within 2 experimental groups: (i) colonies located near point-source systemic pesticide pollution (pesticide contaminated treatment), and (ii) colonies embedded within a typical Midwestern US agricultural environment (control). In this study, worker bees in the contaminated environment exhibited important and biologically significant behavioral differences and accelerated onset of hive tasks (i.e., precocious behavioral development) compared to similarly aged bees at the control site. Queen locomotion was largely unaffected; however, the egg-laying rate was reduced in queens at the contaminated (treated) site. These results show that environmental pesticide exposure can disrupt colony function and adversely affect worker bee behavioral maturation, leading to reduced worker longevity and decreased colony efficiency.

Toxic effects of acaricide fenazaquin on development, hemolymph metabolome, and gut microbiome of honeybee (Apis mellifera) larvae.

Fenazaquin, a potent insecticide widely used to control phytophagous mites, has recently emerged as a potential solution for managing Varroa destructor mites in honeybees. However, the comprehensive impact of fenazaquin on honeybee health remains insufficiently understood. Our current study investigated the acute and chronic toxicity of fenazaquin to honeybee larvae, along with its influence on larval hemolymph metabolism and gut microbiota. Results showed that the acute median lethal dose (LD50) of fenazaquin for honeybee larvae was 1.786 µg/larva, and the chronic LD50 was 1.213 µg/larva. Although chronic exposure to low doses of fenazaquin exhibited no significant effect on larval development, increasing doses of fenazaquin resulted in significant increases in larval mortality, developmental time, and deformity rates. At the metabolic level, high doses of fenazaquin inhibited nucleotide, purine, and lipid metabolism pathways in the larval hemolymph, leading to energy metabolism disorders and physiological dysfunction. Furthermore, high doses of fenazaquin reduced gut microbial diversity and abundance, characterized by decreased relative abundance of functional gut bacterium Lactobacillus kunkeei and increased pathogenic bacterium Melissococcus plutonius. The disrupted gut microbiota, combined with the observed gut tissue damage, could potentially impair food digestion and nutrient absorption in the larvae. Our results provide valuable insights into the complex and diverse effects of fenazaquin on honeybee larvae, establishing an important theoretical basis for applying fenazaquin in beekeeping.

Detrimental effects of amitraz exposure in honey bees (Apis mellifera) infected with Nosema ceranae.

In recent years, there has been growing concern on the potential weakening of honey bees and their increased susceptibility to pathogens due to chronic exposure to xenobiotics. The present work aimed to study the effects on bees undergoing an infection by Nosema ceranae and being exposed to a frequently used in-hive acaricide, amitraz. To achieve this, newly emerged bees were individually infected with N. ceranae spores and/or received a sublethal concentration of amitraz in their diets under laboratory conditions. Mortality, food intake, total volume excrement, body appearance, and parasite development were registered. Bees exposed to both stressors jointly had higher mortality rates compared to bees exposed separately, with no difference in the parasite development. An increase in sugar syrup consumption was observed for all treated bees while infected bees fed with amitraz also showed a diminishment in pollen intake. These results coupled with an increase in the total number of excretion events, alterations in behavior and body surface on individuals that received amitraz could evidence the detrimental action of this molecule. To corroborate these findings under semi-field conditions, worker bees were artificially infected, marked, and released into colonies. Then, they were exposed to a commercial amitraz-based product by contact. The recovered bees showed no differences in the parasite development due to amitraz exposure. This study provides evidence to which extent a honey bee infected with N. ceranae could potentially be weakened by chronic exposure to amitraz treatment.

Computational Modeling Oriented Substructure Splicing Application in the Identification of Thiazolidine Derivatives as Potential Low Honeybee Toxic Neonicotinoids.

With the aim of identifying novel neonicotinoid insecticides with low bee toxicity, a series of compounds bearing thiazolidine moiety, which has been shown to be low bee toxic, were rationally designed through substructure splicing strategy and evaluated insecticidal activities. The optimal compounds A24 and A29 exhibited LC50 values of 30.01 and 17.08 mg/L against Aphis craccivora, respectively. Electrophysiological studies performed on Xenopus oocytes indicated that compound A29 acted on insect nAChR, with EC50 value of 50.11 µM. Docking binding mode analysis demonstrated that A29 bound to Lymnaea stagnalis acetylcholine binding protein through H-bonds with the residues of D_Arg55, D_Leu102, and D_Val114. Quantum mechanics calculation showed that A29 had a higher highest occupied molecular orbit (HOMO) energy and lower vertical ionization potential (IP) value compared to the high bee toxic imidacloprid, showing potentially low bee toxicity. Bee toxicity predictive model also indicated that A29 was nontoxic to honeybees. Our present work identified an innovative insecticidal scaffold and might facilitate the further exploration of low bee toxic neonicotinoid insecticides.

Uncovering hidden dangers: The combined toxicity of abamectin and lambda-cyhalothrin on honey bees.

Studying the toxic effects of pesticides on bees has consistently been a prominent area of interest for researchers. Nonetheless, existing research has predominantly concentrated on individual toxicity assessments, leaving a gap in our understanding of mixed toxicity. This study delves into the individual and combined toxic effects of abamectin (ABA) and lambda-cyhalothrin (LCY) on honey bees (Apis mellifera) in laboratory settings. We discovered that ABA (96 h-LC50 value of 0.079 mg/L) exhibited greater acute toxicity to honey bees compared to LCY (96 h-LC50 value of 9.177 mg/L). Moreover, the mixture of ABA and LCY presented an acute antagonistic effect on honey bees. Additionally, our results indicated that exposure to LCY, at medium concentration, led to a reduction in the abundance of gut core bacterium Snodgrassella. However, an increase in the abundance of Bifidobacterium was noted when exposed to a medium concentration of LCY and its mixture with ABA. Transcriptomic analysis revealed significant regulation of certain genes in the medium concentration of all three treatments compared to the control group, primarily enriching in metabolism and immune-related pathways. Following chronic exposure to field-relevant concentrations of ABA, LCY, and their mixture, there were significant alterations in the activities of immunity-related enzyme polyphenol oxidase (PPO) and detoxification enzymes glutathione S-transferase (GST) and carboxylesterase (CarE). Additionally, the expression of four genes (abaecin, cyp9e2, cyp302a1, and GstD1) associated with immune and detoxification metabolism was significantly altered. These findings suggest a potential health risk posed by the insecticides ABA and LCY to honey bees. Despite exhibiting acute antagonistic effect, mixed exposure still induced damage to bees at all levels. This study advances our knowledge of the potential adverse effects of individual or combined exposure to these two pesticides on non-target pollinators and offers crucial guidance for the use of insecticides in agricultural production.

Multiple stresses induced by chronic exposure to flupyradifurone affect honey bee physiological states.

Flupyradifurone (FPF) has been reported to have a potential risk to terrestrial and aquatic ecosystems. In the present study, the effects of chronic FPF exposure on bees were systematically investigated at the individual behavioral, tissue, cell, enzyme activity, and the gene expression levels. Chronic exposure (14 d) to FPF led to reduced survival (12 mg/L), body weight gain (4 and 12 mg/L), and food utilization efficiency (4 and 12 mg/L). Additionally, FPF exposure (12 mg/L) impaired sucrose sensitivity and memory of bees. Morphological analysis revealed significant cellular and subcellular changes in brain neurons and midgut epithelial cells, including mitochondrial damage, nuclear disintegration, and apoptosis. FPF exposure (4 and 12 mg/L) led to oxidative stress, as evidenced by increased lipid peroxidation and alterations in antioxidant enzyme activity. Notably, gene expression analysis indicated significant dysregulation of apoptosis, immune, detoxification, sucrose responsiveness and memory-related genes, suggesting the involvement of different pathways in FPF-induced toxicity. The multiple stresses and potential mechanisms described here provide a basis for determining the intrinsic toxicity of FPF.

Unravelling the microplastic menace: Different polymers additively increase bee vulnerability.

Microplastics (MPs) are growing and ubiquitous environmental pollutants and represent one of the greatest contemporary challenges caused by human activities. Current research has predominantly examined the singular toxicological effects of individual polymers, neglecting the prevailing reality of organisms confronted with complex contaminant mixtures and potential synergistic effects. To fill this research gap, we investigated the lethal and sublethal effects of two common MPs, polystyrene (PS - 4.8-5.8 µm) and poly(methyl methacrylate) (PMMA - 1-40 µm), and their combination (MIX), on the pollinating insect Apis mellifera. For each treatment, we evaluated the oral toxicity of two ecologically relevant and one higher concentration (0.5, 5 and 50 mg/L) and analysed their effects on the immune system and worker survival. As immune activation can alter the cuticular hydrocarbon profile of honey bees, we used gas chromatography-mass spectrometry (GC-MS) to investigate whether MPs lead to changes in the chemical profile of foragers and behavioural assay to test whether such changes affect behavioural patterns of social recognition, undermining overall colony integrity. The results indicate an additive negative effect of PS and PMMA on bee survival and immune response, even at ecologically relevant concentrations. Furthermore, alterations in cuticle profiles were observed with both MPs at the highest and intermediate concentrations, with PMMA being mainly responsible. Both MPs exposure resulted in a reduction in the abundance of several cuticular compounds. Hive entry guards did not show increased inspection or aggressive behaviour towards exposed foragers, allowing them to enter the colony without being treated differently from uncontaminated foragers. These findings raise concerns not only for the health of individual bees, but also for the entire colony, which could be at risk if contaminated nestmates enter the colony undetected, allowing MPs to spread throughout the hive.

Combined effects of three insecticides with different modes of action on biochemical responses of the solitary bee Osmia bicornis.

Bees are simultaneously exposed to a variety of pesticides, which are often applied in mixtures and can cause lethal and sublethal effects. The combined effects of pesticides, however, are not measured in the current risk assessment schemes. Additionally, the sublethal effects of pesticides on a variety of physiological processes are poorly recognized in bees, especially in non-Apis solitary bees. In this study, we used a full-factorial design to examine the main and interactive effects of three insecticide formulations with different modes of action (Mospilan 20 SP, Sherpa 100 EC, and Dursban 480 EC) on bee biochemical processes. We measured acetylcholinesterase (AChE), glutathione S-transferase (GST) and esterase (EST) activities, as well as a nonenzymatic biomarker associated with energy metabolism, i.e., ATP level. All studied endpoints were affected by Sherpa 100 EC, and the activities of AChE and EST as well as ATP levels were affected by Dursban 480 EC. Moreover, complex interactions between all three insecticides affected ATP levels, showing outcomes that cannot be predicted when testing each insecticide separately. The results indicate that even if interactive effects are sometimes difficult to interpret, there is a need to study such interactions if laboratory-generated toxicity data are to be extrapolated to field conditions.

Assessing the effects of a commercial fungicide and an herbicide, alone and in combination, on Apis mellifera: Insights from biomarkers and cognitive analysis.

Agrochemicals play a vital role in protecting crops and enhancing agricultural production by reducing threats from pests, pathogens and weeds. The toxicological status of honey bees can be influenced by a number of factors, including pesticides. While extensive research has focused on the lethal and sublethal effects of insecticides on individual bees and colonies, it is important to recognise that fungicides and herbicides can also affect bees' health. Unfortunately, in the field, honey bees are exposed to mixtures of compounds rather than single substances. This study aimed to evaluate the effects of a commercial fungicide and a commercial herbicide, both individually and in combination, on honey bees. Mortality assays, biomarkers and learning and memory tests were performed, and the results were integrated to assess the toxicological status of honey bees. Neurotoxicity (acetylcholinesterase and carboxylesterase activities), detoxification and metabolic processes (glutathione S-transferase and alkaline phosphatase activities), immune system function (lysozyme activity and haemocytes count) and genotoxicity biomarkers (Nuclear Abnormalities assay) were assessed. The fungicide Sakura® was found to activate detoxification enzymes and affect alkaline phosphatase activity. The herbicide Elegant 2FD and the combination of both pesticides showed neurotoxic effects and induced detoxification processes. Exposure to the herbicide/fungicide mixture impaired learning and memory in honey bees. This study represents a significant advance in understanding the toxicological effects of commonly used commercial pesticides in agriculture and contributes to the development of effective strategies to mitigate their adverse effects on non-target insects.

Synergistic resistance of honeybee (Apis mellifera) and their gut microorganisms to fluvalinate stress.

Fluvalinate is widely used in the control of Varroa destructor, but its residues in colonies threaten honeybees. The effect of fluvalinate-induced dysbiosis on honeybee-related gene expression and the gut microenvironment of honeybees has not yet been fully elucidated. In this study, two-day-old larvae to seven-day-old adult worker bees were continuously fed different amounts of fluvalinate-sucrose solutions (0, 0.5, 5, and 50 mg/kg), after which the expression levels of two immune-related genes (Hymenoptaecin and Defensin1) and three detoxication-related genes (GSTS3, CAT, and CYP450) in worker bees (1, 7, and 20 days old) were measured. The effect of fluvalinate on the gut microbes of worker bees at seven days old also was explored using 16S rRNA Illumina deep sequencing. The results showed that exposure of honeybees to the insecticide fluvalinate affected their gene expression and gut microbial composition. As the age of honeybees increased, the effect of fluvalinate on the expression of Hymenoptaecin, CYP450, and CAT decreased, and the abundance of honeybee gut bacteria was affected by increasing the fluvalinate concentration. These findings provide insights into the synergistic defense of honeybee hosts against exogenous stresses in conjunction with honeybee gut microbes.

Interaction of acetamiprid, Varroa destructor, and Nosema ceranae in honey bees.

Health of honey bees is threatened by a variety of stressors, including pesticides and parasites. Here, we investigated effects of acetamiprid, Varroa destructor, and Nosema ceranae, which act either alone or in combination. Our results suggested that interaction between the three factors was additive, with survival risk increasing as the number of stressors increased. Although exposure to 150 µg/L acetamiprid alone did not negatively impact honey bee survival, it caused severe damage to midgut tissue. Among the three stressors, V. destructor posed the greatest threat to honey bee survival, and N. ceranae exacerbated intestinal damage and increased thickness of the midgut wall. Transcriptomic analysis indicated that different combinations of stressors elicited specific gene expression responses in honey bees, and genes involved in energy metabolism, immunity, and detoxification were altered in response to multiple stressor combinations. Additionally, genes associated with Toll and Imd signalling, tyrosine metabolism, and phototransduction pathway were significantly suppressed in response to different combinations of multiple stressors. This study enhances our understanding of the adaptation mechanisms to multiple stressors and aids in development of suitable protective measures for honey bees. ENVIRONMENTAL IMPLICATION: We believe our study is environmentally relevant for the following reasons: This study investigates combined effects of pesticide, Varroa destructor, and Nosema ceranae. These stressors are known to pose a threat to long-term survival of honey bees (Apis mellifera) and stability of the ecosystems. The research provides valuable insights into the adaptive mechanisms of honey bees in response to multiple stressors and developing effective conservation strategies. Further research can identify traits that promote honey bee survival in the face of future challenges from multiple stressors to maintain the overall stability of environment.

Imidacloprid effects on acetylcholinesterase and nicotinic acetylcholine receptor in Apis mellifera. Experimental and molecular modeling approaches.

Although the neonicotinoid insecticides have good selectivity towards insects rather than vertebrates, they have severe effects on honeybee production and pollination activities. Therefore, the effects of imidacloprid (IMI), the most used neonicotinoid, on the two main bioreceptors, acetylcholinesterase (AChE) and nicotinic acetylcholine receptor alpha subunit (nAChRα1) of honeybees were examined to identify their roles in honeybee toxicity and possible binding sites which assist in selecting and designing neonicotinoids. In vivo, IMI showed a high inhibitory effect on AChE (IC50 5.63 mg/L); however, the effect was much lower in vitro experiment (IC50 719 mg/L). This result induced us to examine the IMI effect on AChE gene expression which revealed that the AChE-2 gene expression was severely affected by IMI explaining the observed high enzyme inhibition. In addition, although toxicity increased by increasing exposure to IMI (LC50 2.9 mg/L after 4h and 0.75 mg/L after 48h), AChE was not elevated (IC50 5.63 and 5.52 mg/L respectively). Besides, Despite resuming most enzyme activity (77% during 2 h and 84.14% after 4 h), a high mortality level was observed with LC50 2.9 mg/L. These results reinforced that the observed high toxicity is a multifactor process. Accordingly, Molecular modeling and docking of IMI into honeybee AChE and nAChRα1were also performed to examine their possible interactions and identify the important binding sites. Results models indicated that the first two binding sites in AChE were found in the esteratic subunit in the active site explaining the observed in vitro inhibition. In nAChRα1, four of the highest five free energy binding sites are located in the large TM3-TM4 loop and one in the extracellular loops. Consequently, the present work revealed that IMI toxicity is attributed to various factors including direct interaction with both AChE and nAChRα1 as well as downregulating AChE-2 gene expression.

Exploring the effects of the acaricide cyflumetofen on the vital organs of the honey bee Apis mellifera (Hymenoptera: Apidae) workers.

Bees are important for maintaining ecosystems, pollinating crops and producing marketable products. In recent years, a decline in bee populations has been reported, with multifactorial causes, including the intensification of pesticide use in agriculture. Among pesticides, cyflumetofen is an insecticide and acaricide used in apple, coffee and citrus crops, whose main pollinator is the honey bee Apis mellifera. Therefore, this bee is a potential target of cyflumetofen during foraging. This study evaluated the histopathological and cytological damage in the midgut, hypopharyngeal glands and fat body of A. mellifera workers exposed to LC50 of cyflumetofen. The midgut epithelium of exposed bees presented cytoplasmic vacuolization, release of vesicles and cell fragments, which indicate autophagy, increased production of digestive enzymes and cell death, respectively. The cytological analysis of the midgut revealed the dilation of the basal labyrinth and the presence of spherocrystals in the digestive cells. The hypopharyngeal glands produced greater amounts of secretion in treated bees, whereas no changes were observed in the fat body. The results indicate that acute exposure to cyflumetofen negatively affect A. mellifera, causing damage to the midgut and changes in the hypopharyngeal glands, which may compromise the survival and foraging of this pollinator.

Effects of abamectin nanocapsules on bees through host physiology, immune function, and gut microbiome.

Pesticide usage is a common practice to increase crop yields. Nevertheless, the existence of pesticide residues in the surrounding environment presents a significant hazard to pollinators, specifically the potential undisclosed dangers related to emerging nanopesticides. This study examines the impact of abamectin nanocapsules (AbaNCs), created through electrostatic self-assembly, as an insecticide on honey bees. It was determined that AbaNCs upregulated detoxification genes, including CYP450, as well as antioxidant and immune genes in honey bees. Furthermore, AbaNCs affected the activity of crucial enzymes such as superoxide dismutase (SOD). Although no apparent damage was observed in bee gut tissue, AbaNCs significantly decreased digestive enzyme activity. Microbiome sequencing revealed that AbaNCs disrupted gut microbiome, resulting in a reduction of beneficial bacteria such as Bifidobacterium and Lactobacillus. Additionally, these changes in the gut microbiome were associated with decreased activity of digestive enzymes, including lipase. This study enhances our understanding of the impact of nanopesticides on pollinating insects. Through the revelation of the consequences arising from the utilization of abamectin nanocapsules, we have identified potential stress factors faced by these pollinators, enabling the implementation of improved protective measures.

Experimental Ecotoxicology Procedures Interfere with Honey Bee Life History.

Apis mellifera was used as a model species for ecotoxicological testing. In the present study, we tested the effects of acetone (0.1% in feed), a solvent commonly used to dissolve pesticides, on bees exposed at different developmental stages (larval and/or adult). Moreover, we explored the potential effect of in vitro larval rearing, a commonly used technique for accurately monitoring worker exposure at the larval stage, by combining acetone exposure and treatment conditions (in vitro larval rearing vs. in vivo larval rearing). We then analyzed the life-history traits of the experimental bees using radio frequency identification technology over three sessions (May, June, and August) to assess the potential seasonal dependence of the solvent effects. Our results highlight the substantial influence of in vitro larval rearing on the life cycle of bees, with a 47.7% decrease in life span, a decrease of 0.9 days in the age at first exit, an increase of 57.3% in the loss rate at first exit, and a decrease of 40.6% in foraging tenure. We did not observe any effect of exposure to acetone at the larval stage on the capacities of bees reared in vitro. Conversely, acetone exposure at the adult stage reduced the bee life span by 21.8% to 60%, decreased the age at first exit by 1.12 to 4.34 days, and reduced the foraging tenure by 30% to 37.7%. Interestingly, we found a significant effect of season on acetone exposure, suggesting that interference with the life-history traits of honey bees is dependent on season. These findings suggest improved integration of long-term monitoring for assessing sublethal responses in bees following exposure to chemicals during both the larval and adult stages. Environ Toxicol Chem 2024;43:1320-1331. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Comparing Sensitivity of Different Bee Species to Pesticides: A TKTD modeling approach.

Risk assessment for bees is mainly based on data for honey bees; however, risk assessment is intended to protect all bee species. This raises the question of whether data for honey bees are a good proxy for other bee species. This issue is not new and has resulted in several publications in which the sensitivity of bee species is compared based on the values of the 48-h median lethal dose (LD50) from acute test results. When this approach is used, observed differences in sensitivity may result both from differences in kinetics and from inherent differences in species sensitivity. In addition, the physiology of the bee, like its overall size, the size of the honey stomach (for acute oral tests), and the physical appearance (for acute contact tests) also influences the sensitivity of the bee. The recently introduced Toxicokinetic-Toxicodynamic (TKTD) model that was developed for the interpretation of honey bee tests (Bee General Uniform Threshold Model for Survival [BeeGUTS]) could integrate the results of acute oral tests, acute contact tests, and chronic tests within one consistent framework. We show that the BeeGUTS model can be calibrated and validated for other bee species and also that the honey bee is among the more sensitive bee species. In addition, we found that differences in sensitivity between species are smaller than previously published comparisons based on 48-h LD50 values. The time-dependency of the LD50 and the specifics of the bee physiology are the main causes of the wider variation found in the published literature. Environ Toxicol Chem 2024;43:1431-1441. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.