Adult Worker Honey Bees Research Articles

Antifungal Activity and Mechanism of Camphor Derivatives against Rhizoctonia solani: A Promising Alternative Antifungal Agent for Rice Sheath Blight.

Rice sheath blight, caused by the fungus Rhizoctonia solani, poses a significant threat to rice cultivation globally. This study aimed to investigate the potential mechanisms of action of camphor derivatives against R. solani. Compound 4o exhibited superior fungicidal activities in vitro (EC50 = 6.16 mg/L), and in vivo curative effects (77.5%) at 500 mg/L were significantly (P < 0.01) higher than the positive control validamycin·bacillus (66.1%). Additionally, compound 4o exhibited low cytotoxicity and acute oral toxicity for adult worker honeybees of Apis mellifera L. Mechanistically, compound 4o disrupted mycelial morphology and microstructure, increased cell membrane permeability, and inhibited both PDH and SDH enzyme activities. Molecular docking and molecular dynamics analyses indicated a tight interaction of compound 4o with PDH and SDH active sites. In summary, compound 4o exhibited substantial antifungal efficacy against R. solani, serving as a promising lead compound for further optimization of antifungal agents.

Analysis of X-ray irradiation effects on the mortality values and hemolymph immune cell composition of Apis mellifera and its parasite, Varroa destructor

Varroa destructor is one of the most destructive enemies of the honey bee, Apis mellifera all around the world. Several control methods are known to control V. destructor, but the efficacy of several alternative control methods remains unexplored. Irradiation can be one of these unknown solutions but before practical application, the effectiveness, and the physiological effects of ionizing radiation on the host and the parasite are waiting to be tested. Therefore, the objective of our study was to investigate the effects of different doses (15, 50, 100, and 150 Gy) of high-energy X-ray irradiation through mortality rates and hemocyte composition changes in A. mellifera workers and record the mortality rates of the parasite. The mortality rate was recorded during short-term (12, 24, and 48 h) and long-term periods (3, 6, 12, 18, and 24d).The sensitivity of the host and the parasite in case of the higher doses of radiation tested (50, 100, and 150 Gy) been demonstrated by total mortality of the host and 90 % of its parasite has been observed on the 18th day after the irradiation. V. destructor showed higher sensitivity (1.52-times higher than the adult honey bee workers) at the lowest dose (15 Gy). A. mellifera hemocytes were influenced significantly by radiation dosage and the elapsed time after treatment. The higher radiation doses increased plasmatocyte numbers in parallel with the decrease in prohemocyte numbers. On the contrary, the numbers of granulocytes and oencoytes increased in the treated samples, but the putative effects of the different dosages on the recorded number of these hemocyte types could not be statistically proven. In summary, based on the outcome of our study X-ray irradiation can be deemed an effective tool for controlling phoretic V. destructor. However, further research is needed to understand the physiological response of the affected organisms.

Memory consolidation in honey bees is enhanced by down-regulation of Down syndrome cell adhesion molecule and changes its alternative splicing.

Down syndrome cell adhesion molecule (Dscam) gene encodes a cell adhesion molecule required for neuronal wiring. A remarkable feature of arthropod Dscam is massive alternative splicing generating thousands of different isoforms from three variable clusters of alternative exons. Dscam expression and diversity arising from alternative splicing have been studied during development, but whether they exert functions in adult brains has not been determined. Here, using honey bees, we find that Dscam expression is critically linked to memory retention as reducing expression by RNAi enhances memory after reward learning in adult worker honey bees. Moreover, alternative splicing of Dscam is altered in all three variable clusters after learning. Since identical Dscam isoforms engage in homophilic interactions, these results suggest a mechanism to alter inclusion of variable exons during memory consolidation to modify neuronal connections for memory retention.

Impact of odorants on perception of sweetness by honey bees.

Organic volatiles produced by fruits can result in overestimation of sweetness by humans, but it is unknown if a comparable phenomenon occurs in other species. Honey bees collect nectar of varying sweetness at different flowering plants. Bees discriminate sugar concentration and generally prefer higher concentrations; they encounter floral volatiles as they collect nectar, suggesting that they, like humans, could be susceptible to sweetness enhancement by odorant. In this study, limonene, linalool, geraniol, and 6-methyl-5-hepten-2-ol were tested for their ability to alter behaviors related to perception of sweetness by honey bees. Honey bees were tested in the laboratory using proboscis extension response-based assays and in the field using feeder-based assays. In the laboratory assays, 6-methyl-5-hepten-2-ol and geraniol, but neither linalool nor limonene, significantly increased responses to low concentrations of sucrose compared with no odorant conditions in 15-day and 25-day-old adult worker honey bees, but not in 35-day-old bees. Limonene reduced responding in 15-day-old bees, but not in the older bees. There was no odorant-based difference in performance in field assays comparing geraniol and limonene with a no odorant control. The interaction of the tested plant volatiles with sucrose concentration revealed in laboratory testing is therefore unlikely to be a major determinant of nectar choice by honey bees foraging under natural conditions. Because geraniol is a component of honey bee Nasonov gland pheromone as well as a floral volatile, its impact on responses in the laboratory may reflect conveyance of different information than the other odorants tested.

Toxicity of spray adjuvants and tank mix combinations used in almond orchards to adult honey bees (Apis mellifera).

Commercial beekeepers transporting honey bees across the United States to provide almond pollination services have reported honey bee deaths, possibly due to pesticide applications made during crop bloom. Pesticides are often applied as "tank mixes", or mixtures of fungicides and insecticides combined into a single application. Spray adjuvants are often added to tank mixes to improve the application characteristics of a pesticide and include spreaders, stickers, or surfactants. The goal of this research was to determine toxicity of adjuvants to adult worker honey bees, both when applied alone and in adjuvant-pesticide tank mixtures. Field-relevant combinations of formulated products were applied to 3-day-old adult worker honey bees using a Potter Spray Tower, and mortality was assessed 48 h following exposure. Adjuvants tested included Activator-90, Attach, Choice Weather Master, Cohere, Dyne-Amic, Induce, Kinetic, LI 700, Liberate, Nu-Film P, PHT Latron B-1956, and Surf-90; fungicides tested include Luna Sensation (Fluopyram and Trifloxystrobin), Pristine (Pyraclostrobin and Boscalid), Tilt (Propiconazole), and Vangard (Cyprodinil), and insecticides tested include Altacor (Chlorantraniliprole), Intrepid 2F (Methoxyfenozide), and a positive control Mustang Maxx (Zeta-cypermethrin). Results demonstrated that exposure to some adjuvants causes acute honey bee mortality at near-field application rates, both when applied alone and in combination with pesticides. Some adjuvant-pesticide combinations demonstrated increased toxicity compared with the adjuvant alone, while others demonstrated decreased toxicity. A better understanding of adjuvant and adjuvant-pesticide tank mixture toxicity to honey bees will play a key role in informing "Best Management Practices" for pesticide applicators using spray adjuvants during bloom when honey bee exposure is likely.

Effects of fungicides propiconazole and Trichoderma spp. on the mortality and the physiological status of larvae and adult worker honey bees (Apis mellifera L.)

Exposure to pesticides may affect the survival and normal physiological functions of the honey bee (Apis mellifera L.). The fungicide propiconazole (PRO) and the biofungicide Trichoderma are widely used in agroecosystems, and their effects on the physiology of the honey bee have been largely neglected in risk assessment procedures. We investigated the mortality and variations in physiological biomarkers of honey bee larvae and newly emerged workers exposed to PRO and Trichoderma. Exceeding the field-recommended concentrations of Trichoderma decreased the survival of newly emerged bee workers significantly through oral exposure. PRO, however, showed no significant lethal effects. Contact or oral exposure to field-realistic concentrations of PRO and Trichoderma profoundly altered the activities of detoxification, antioxidative, and digestive enzymes along with energy reserve concentrations of honey bee larvae and adult workers. Integrated biological index (IBRv2) values suggested potential risks of PRO and Trichoderma to honey bees by impairing the physiological status of larvae and newly emerged workers.

Identification of ecdysone receptor target genes in the worker honey bee brains during foraging behavior

Ecdysone signaling plays central roles in morphogenesis and female ovarian development in holometabolous insects. In the European honey bee (Apis mellifera L.), however, ecdysone receptor (EcR) is expressed in the brains of adult workers, which have already undergone metamorphosis and are sterile with shrunken ovaries, during foraging behavior. Aiming at unveiling the significance of EcR signaling in the worker brain, we performed chromatin-immunoprecipitation sequencing of EcR to search for its target genes using the brains of nurse bees and foragers. The majority of the EcR targets were common between the nurse bee and forager brains and some of them were known ecdysone signaling-related genes. RNA-sequencing analysis revealed that some EcR target genes were upregulated in forager brains during foraging behavior and some were implicated in the repression of metabolic processes. Single-cell RNA-sequencing analysis revealed that EcR and its target genes were expressed mostly in neurons and partly in glial cells in the optic lobes of the forager brain. These findings suggest that in addition to its role during development, EcR transcriptionally represses metabolic processes during foraging behavior in the adult worker honey bee brain.

Evaluating the Impact of Commonly Used Pesticides on Honeybees (Apis mellifera) in North Gonder of Amhara Region, Ethiopia.

Global honeybee losses and colony decline are becoming continuous threat to the apicultural industry, as well as, for food security and environmental stability. Although the putative causes are still unclear, extensive exposure of bees to pesticides could be the possible factor for worldwide colony losses. This study was aimed at evaluating the impact of nine commonly used pesticide incidents on adult worker honeybees (A. mellifera) under the laboratory condition, in North Gonder of Amhara region, Ethiopia. Feeding test, contact test, and fumigation tests were carried out for each pesticide following the standard procedures, and each pesticide toxicity was compared to the standard toxic chemical, dimethoate 40% EC (positive control), and to 50% honey solution (negative control). The results revealed that all the tested pesticides caused significant deaths of the experimental bees (P < 0.05) in all the tests when compared to the negative control. Diazinon 60% EC, endosulfan 35% EC, and malathion 50% EC were appeared highly toxic causing 100% mortality of bees, while chlorsulfuron 75% WG killed 90% of the experimental bees as tested via feeding. On the other hand, agro-2, 4-D and its mixture with glycel 41% EC are moderately toxic, and mancozeb 80% WP and glycel 41% EC were slightly toxic to honeybees as compared to the positive control (dimethoate 40% EC). Suddenly, diazinon 60% EC and malathion 50% EC triggered 100% mortality of bees, while endosulfan 35% EC and chlorsulfuron 75% WG caused 63.63% and 90.82% of bee mortality, respectively, when evaluated via contact test. The fumigation test also showed that chlorsulfuron 75% WG, diazinon 60% EC, and endosulfan 35% EC caused 100%, 86.7%, and 65.6% mortality rate of bees. Our result also highlighted that tested LD50 of all pesticide incidents were significantly lower than the manufacturer-based LD50. This shows that local honeybees A. m. jemenetica are extremely sensitive to commonly used agricultural pesticides, which may affect the colony level due to the intensive application of these pesticides in Ethiopia.

Respiration levels of honey bee castes as a possible indicator in Varroa mite attraction

It has been demonstrated that fatty acids esters play an important role in the caste selection Varroa mites. However, there may be another mechanism of attraction in the preferred host location. We hypothesize that it may be due to differential respiration rates between larvae, but no investigations have been reported. This research was developed to determine if there is a measurable level and significant difference in honey bee caste respiration that may be exploited by Varroa mites in choice selection. In this study, we measured the respiration of all stages of the Western honey bee Apis mellifera, L. castes to determine the rate of continuous respiration. An assay was conducted using a portable photosynthesis system for gas exchange and chlorophyll fluorescence measurement (Li-Core LI-6400XT) to measure the respiration rate. In this study, a comparative analysis resulted in respiration levels that indicated a significant difference in the CO2 levels of adult worker (777.0 ± 0.002 μg CO2 g insect-1 min-1) and drone (375.5 µg CO2) honey bees. The comparison of worker (5.59 ± 0.002 μg CO2 g insect-1 min-1) and drone (7.20 ± 0.002 μg CO2 g insect-1 min-1) pupae showed no significant difference in the respiration levels; however, there was a noticeable difference in respiration levels of the worker (6.33 ± 0.002 μg CO2 g insect-1 min-1) and drone (10.07 ± 0.002 μg CO2 g insect-1 min-1) larvae. Future research will utilize the knowledge obtained to examine the mite’s attraction to the honey bee castes in host location. This information is a crucial step for the advancement of research studies and the development of management protocols for Varroa.

Genetic Polymorphism in Honey bee Apis cerana indica (F.) (Hymenoptera: Apidae) by Random amplified polymorphic DNA (RAPD) Markers

For pollination purpose and apiary by-products production Apis cerana indica is highly demanded honey bee in India. Honey bee is a polymorphic bee having three casts queen, workers and drones. In Apis cerana indica queen honey bee undergoes multiple mating with drones to gather genetic diversity in colony. Genomic DNA sample of adult drone and worker honey bees was used to study genetic polymorphism by Random amplified polymorphic DNA (RAPD) markers. Ten Primers of each containing different 10mer oligonucleotide sequence were used to generate RAPD profile. Present study observed the banding pattern for presence and absence of characters and find out the polymorphism information content (PIC) value generated by each primer. Low level of genetic polymorphism was found between workers and drones with 0.34984 PIC value.

Joint toxic effects of thiamethoxam and flusilazole on the adult worker honey bees (Apis mellifera L.)

Insect pollinators are routinely exposed to a complex mixture of many pesticides. However, traditional environmental risk assessment is only carried out based on ecotoxicological data of single substances. In this context, we aimed to explore the potential effects when worker honey bees (Apis mellifera L.) were simultaneously challenged by thiamethoxam (TMX) and flusilazole (FSZ). Results displayed that TMX possessed higher toxicity to A. mellifera (96-h LC50 value of 0.11 mg a. i. L−1) than FSZ (96-h LC50 value of 738 mg a. i. L−1). Furthermore, the mixture of TMX and FSZ exhibited an acute synergistic impact on the pollinators. Meanwhile, the activities of SOD, caspase 3, caspase 9, and PPO, as well as the expressions of six genes (abaecin, dorsal-2, defensin-2, vtg, caspase-1, and CYP6AS14) associated with oxidative stress, immune response, lifespan, cell apoptosis, and detoxification metabolism were noteworthily varied in the individual and mixture challenges than at the baseline level. These data revealed that it is imminently essential to investigate the combined toxicity of pesticides since the toxicity evaluation from individual compounds toward honey bees may underestimate the toxicity in realistic conditions. Overall, the present results could help understand the potential contribution of pesticide mixtures to the decline of bee populations.

Toxic evaluation of Proclaim Fit® on adult and larval worker honey bees.

Impacts to honey bees due to exposure to agricultural pesticides is one of the most serious threats to the beekeeping industry. Our research evaluated toxicity of the formulated insecticides Lufenuron+Emamectin benzoate (Proclaim Fit®) on the European honey bee Apis mellifera L. at field-realistic concentration (worst-case scenario). Newly emerged (≤24-h old) and forager (unknown age) worker bees were treated with the field recommended concentration of Proclaim Fit® using three routes of exposure including residual contact, oral, and spray within the laboratory. We also assessed the effects of Proclaim Fit® on the specific activity of some well-known detoxifying enzymes including α-esterase, β-esterase, and Glutathione S-transferase (GST) in the honey bees. In addition, toxicity of the formulation was tested on 4th instar larvae within the hive. Based on estimated median survival times (MSTs), Proclaim Fit® was highly toxic to the bees, especially when applied as spray. According to our estimated relative median potency (RMP) values, newly emerged bees were 1.72× more susceptible than foragers to Proclaim Fit® applied orally. Enzyme assays revealed the considerable involvement of the enzymes, especially GST and α-esterase, in detoxification of the Proclaim Fit®, but their activities were significantly influenced by route of exposure and age of bee. Notably, Proclaim Fit® was highly toxic to 4th instar honey bee larvae. Our results generally indicate a potent toxicity of Proclaim Fit® toward honey bees. Therefore, its application requires serious consideration and adherence to strict guidelines, especially during the flowering time of crops.

Impact of Imunit® insecticide on survival and detoxification enzymes activity of adult worker honey bee (Apis mellifera L.)

آلفاسایپرمترین+تفلوبنزورون (ایمونیت®) حشره‌کشی است که توسط سازمان حفظ نباتات ایران برای کنترل کرم میوه‌خوار (Helicoverpa armigera Hübner) در مزارع گوجه‌فرنگی توصیه می‌شود. در این پژوهش، تأثیر ایمونیت® روی نرخ بقای حشرات بالغ زنبورعسل کارگر (Apis mellifera L.) در شرایط آزمایشگاهی بررسی شد. زنبورهای تازه‌متولدشده (با سن کمتر از 24 ساعت) و چراگر (با سن بیشتر از 21 روز) به سه روش تماس با باقی‌مانده، گوارشی، و پاششی با دُز توصیه‌شدۀ مزرعه-ای این حشره‌کش تیمار شدند. همچنین، اثرات زیرکشندگی ایمونیت® روی فعالیت ویژه برخی از آنزیم‌های سم‌زُدا از قبیل آلفا-استراز، بتا-استراز، و گلوتاتیون اس-ترانسفراز مورد مطالعه قرار گرفت. آزمایش‌های زیست‌سنجی نشان داد که سمیت ایمونیت® با توجه به سن زنبور و روش استفاده از حشره‌کش فرق داشت. به استثنای روش پاششی، زنبورهای چراگر در مقایسه با زنبورهای تازه‌متولدشده از حساسیت بیشتری به این حشره‌کش برخوردار بودند. سمیت تماس با باقی‌مانده و پاششی ایمونیت® روی زنبورهای تازه‌متولدشده در مقایسه با سمیت گوارشی آن به طور معنی‌داری بیشتر بود، در حالی که زنبورهای چراگر بیشترین حساسیت را پس از تماس با باقی‌مانده این حشره‌کش نشان دادند. فعالیت آنزیم‌های سم‌زُدا نیز با توجه سن زنبورها و روش قرارگیری در معرض ایمونیت® تغییر پیدا کرد. به طور کلی، یافته‌های ما بیانگر پتانسیل بالای ایمونیت® برای ایجاد مسمومیت در زنبورعسل می‌باشد.

Impact of Imunit® insecticide on survival and detoxification enzymes activity of adult worker honey bee (Apis mellifera L.)

آلفاسایپرمترین+تفلوبنزورون (ایمونیت®) حشره‌کشی است که توسط سازمان حفظ نباتات ایران برای کنترل کرم میوه‌خوار (Helicoverpa armigera Hübner) در مزارع گوجه‌فرنگی توصیه می‌شود. در این پژوهش، تأثیر ایمونیت® روی نرخ بقای حشرات بالغ زنبورعسل کارگر (Apis mellifera L.) در شرایط آزمایشگاهی بررسی شد. زنبورهای تازه‌متولدشده (با سن کمتر از 24 ساعت) و چراگر (با سن بیشتر از 21 روز) به سه روش تماس با باقی‌مانده، گوارشی، و پاششی با دُز توصیه‌شدۀ مزرعه-ای این حشره‌کش تیمار شدند. همچنین، اثرات زیرکشندگی ایمونیت® روی فعالیت ویژه برخی از آنزیم‌های سم‌زُدا از قبیل آلفا-استراز، بتا-استراز، و گلوتاتیون اس-ترانسفراز مورد مطالعه قرار گرفت. آزمایش‌های زیست‌سنجی نشان داد که سمیت ایمونیت® با توجه به سن زنبور و روش استفاده از حشره‌کش فرق داشت. به استثنای روش پاششی، زنبورهای چراگر در مقایسه با زنبورهای تازه‌متولدشده از حساسیت بیشتری به این حشره‌کش برخوردار بودند. سمیت تماس با باقی‌مانده و پاششی ایمونیت® روی زنبورهای تازه‌متولدشده در مقایسه با سمیت گوارشی آن به طور معنی‌داری بیشتر بود، در حالی که زنبورهای چراگر بیشترین حساسیت را پس از تماس با باقی‌مانده این حشره‌کش نشان دادند. فعالیت آنزیم‌های سم‌زُدا نیز با توجه سن زنبورها و روش قرارگیری در معرض ایمونیت® تغییر پیدا کرد. به طور کلی، یافته‌های ما بیانگر پتانسیل بالای ایمونیت® برای ایجاد مسمومیت در زنبورعسل می‌باشد.

Metabolomics-Guided Comparison of Pollen and Microalgae-Based Artificial Diets in Honey Bees.

Managed honey bee colonies used for crop pollination are fed artificial diets to offset nutritional deficiencies related to land-use intensification and climate change. In this study, we formulated novel microalgae diets using Chlorella vulgaris and Arthrospira platensis (spirulina) biomass and fed them to young adult honey bee workers. Diet-induced changes in bee metabolite profiles were studied relative to a natural pollen diet using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) metabolomics. Untargeted analyses of pollen- and microalgae-fed bees revealed significant overlap, with 248 shared features determined by LC-MS and 87 shared features determined by GC-MS. Further metabolomic commonalities were evident upon subtraction of unique diet features. Twenty-five identified metabolites were influenced by diet, which included complex lipids, essential fatty acids, vitamins, and phytochemicals. The metabolomics results are useful to understand mechanisms underlying favorable growth performance as well as increased antioxidant and heat shock protein gene expression in bees fed the microalgae diets. We conclude that the tested microalgae have potential as sustainable feed additives and as a source of bee health-modulating natural products. Metabolomics-guided diet development could eventually help tailor feed interventions to achieve precision nutrition in honey bees and other livestock animals.

Worker bees (Apis mellifera) deprived of pollen in the first week of adulthood exhibit signs of premature aging

Pollinator populations, including bees, are in rapid decline in many parts of the world, raising concerns over the future of ecosystems and food production. Among the factors involved in these declines, poor nutrition deserves attention. The diet consumed by adult worker honeybees (Apis mellifera) is crucial for their behavioral maturation, i.e., the progressive division of labor they perform, such as nurse bees initially and later in life as foragers. Poor pollen nutrition is known to reduce the workers’ lifespan, but the underlying physiological and genetic mechanisms are not fully understood. Here we investigate how the lack of pollen in the diet of workers during their first week of adult life can affect age-related phenotypes. During the first seven days of adult life, newly emerged workers were fed either a pollen-deprived (PD) diet mimicking that of an older bee, or a control pollen-rich (PR) diet, as typically consumed by young bees. The PD-fed bees showed alterations in their fat body transcriptome, such as a switch from a protein-lipid based metabolism to a carbohydrate-based metabolism, and a reduced expression of genes involved with immune response. The absence of pollen in the diet also led to an accumulation of oxidative stress markers in fat body tissue and alterations in the cuticular hydrocarbon profiles, which became similar to those of chronologically older bees. Together, our data indicate that the absence of pollen during first week of adulthood triggers the premature onset of an aging-related worker phenotype.

Probiotic Potential and Effects on Gut Microbiota Composition and Immunity of Indigenous Gut Lactobacilli in Apis cerana.

This study aimed to investigate the probiotic potential of gut indigenous lactic acid bacteria (LAB) originated from Apis cerana. Six Limosilactobacillus reuteri and one Lactobacillus helveticus were isolated from gut samples of A. cerana adult worker bee. All isolates antagonized the growth of pathogens including Salmonella typhimurium, Escherichia coli, Shigella flexneri, and Flavobacterium frigidimaris, and L. helveticus KM7 showed the greatest antimicrobial activity among them. All strains were sensitive to cefotaxime, amoxicillin, cephalothin, penicillin G, kanamycin, and vancomycin, moderately sensitive to novobiocin and resistant to gentamicin. Six out of seven strains were sensitive to ampicillin. L. helveticus KM7 was chosen to evaluate in vivo probiotic effect of adult worker bees of A. cerana through fed sucrose syrup supplemented with KM7. Administration of KM7 increased survival rate and gut LAB but decreased gut fungi and Enterococcus in honeybees. Expressions of genes related to antimicrobial peptides (AMPs) including Abaecin and Defensin were also induced in the gut of honeybees. The results suggested that L. helveticus KM7 with greater probiotic properties could improve the survival rate of adult worker honeybees of A. cerana through regulating gut microbiota and AMPs genes expression.

Low-Level Fluvalinate Treatment in the Larval Stage Induces Impaired Olfactory Associative Behavior of Honey Bee Workers in the Field.

Simple SummaryThere may be high amounts of fluvalinate residue in bee colonies and products. It is usually used to control the varroa parasite on bees, but it may lead to adverse effects on both larvae and adults. In this study, we found that feeding with fluvalinate at a dose of 40 ng/larva could result in declined brood-capping, pupation, and eclosion rates. In addition, the olfactory associative behavior of adult bees was impaired after they were treated with a sublethal dose of 0.004 ng/larva in the larval stage. These findings suggest that a sublethal dose of fluvalinate given to larvae has a huge negative effect on adult honey bee workers, affecting their subsequent associative ability. It may further lead the entire colony to a detrimental developmental trend.Fluvalinate is a widely used insecticide for varroa mite control in apiculture. While most beekeepers have ignored the effects of low levels of fluvalinate on bees, this study aims to demonstrate its effects at very low concentrations. We first used fluvalinate doses ranging from 0.4 to 400 ng/larva to monitor the capping, pupation, and emergence rates of larval bees. Second, we used the honey bees’ proboscis extension reflex reaction to test the learning ability of adult bees that were exposed to fluvalinate doses from 0.004 to 4 ng/larva in the larval stage. The brood-capped rate of larvae decreased dramatically when the dose was increased to 40 ng/larva. Although no significant effect was observed on brood-capping, pupation, and eclosion rates with a dose of 4 ng/larva, we found that the olfactory associative behavior of adult bees was impaired when they were treated with sublethal doses from 0.004 to 4 ng/larva in the larval stage. These findings suggest that a sublethal dose of fluvalinate given to larvae affects the subsequent associative ability of adult honey bee workers. Thus, a very low dose may affect the survival conditions of the entire colony.

Antibiotics Alter the Expression of Genes Related to Behavioral Development in Honey Bees (Hymenoptera: Apidae).

Honey bees, as many species of social insects, display a division of labor among colony members based on behavioral specializations related to age. Adult worker honey bees perform a series of tasks in the hive when they are young (such as brood care or nursing) and at ca. 2–3 wk of age, shift to foraging for nectar and pollen outside the hive. The transition to foraging involves changes in metabolism and neuroendocrine activities. These changes are associated with a suite of developmental genes. It was recently demonstrated that antibiotics influence behavioral development by accelerating or delaying the onset of foraging depending on timing of antibiotic exposure. To understand the mechanisms of these changes, we conducted a study on the effects of antibiotics on expression of candidate genes known to regulate behavioral development. We demonstrate a delay in the typical changes in gene expression over the lifetime of the individuals that were exposed to antibiotics during immature stage and adulthood. Additionally, we show an acceleration in the typical changes in gene expression on individuals that were expose to antibiotics only during immature stage. These results show that timing of antibiotic exposure alter the typical regulation of behavioral development by metabolic and neuroendocrine processes.

Age and Season Effect the Timing of Adult Worker Honeybee Infection by Nosema ceranae.

The microsporidia Nosema ceranae is an intracellular parasite of honeybees’ midgut, highly prevalent in Apis mellifera colonies for which important epidemiological information is still unknown. Our research aimed at understanding how age and season influence the onset of infection in honeybees and its development in the colony environment. Adult worker honeybees of less than 24h were marked and introduced into 6 different colonies in assays carried out in spring and autumn. Bees of known age were individually analyzed by PCR for Nosema spp. infection and those resulting positive were studied to determine the load by Real Time-qPCR. The age of onset and development of infection in each season was studied on a total of 2401 bees and the probability and the load of infection for both periods was established with two statistical models. First N. ceranae infected honeybees were detected at day 5 post emergence (p.e.; spring) and at day 4 p.e. (autumn) and in-hive prevalence increased from that point onwards, reaching the highest mean infection on day 18 p.e. (spring). The probability of infection increased significantly with age in both periods although the age variable better correlated in spring. The N. ceranae load tended to increase with age in both periods, although the age-load relationship was clearer in spring than in autumn. Therefore, age and season play an important role on the probability and the development of N. ceranae infection in honeybees, bringing important information to understand how it spreads within a colony.