Bee Head Research Articles

Effect of industry on the content of fatty acids in the tissues of the honey-bee head

The tissues of the head of honey bees which are kept in the areas with a medium and low level of technogenic burden demonstrate the decrease in the contents of iron, zinc, copper, chromium, nickel, lead and cadmium in comparison with the tissues of the head of honey bees grown in areas with a high level of technogenic burden. Due to the activity of saturated fatty acids with the even and odd number of carbon atoms in chain, monounsaturated fatty acids of n-7 and n-9 families and polyunsaturated fatty acids of n-3 and n-6 families, the contents of anionic fatty acids, which are inaccessible for the bee body, decreases in the tissues of the head of honey bees which are kept in the areas with a medium and low level of technogenic burden in comparison with the tissues of the head of honey bees grown in areas with a high level of technogenic burden. 3. Monounsaturated fatty acids of n-7 and n-9 families and polyunsaturated fatty acids of n-3 and n-6 families in the tissues of the head of honey bees lead to increase of the total number of easily accessible non-esterified fatty acids for the honey bees which are kept in the areas with a medium and low level of technogenic burden in comparison with the tissues of the head of honey bees grown in areas with a high level of technogenic burden. Furthermore, the intensity of transformations of the non-esterified form of linolenic acid in its more long-chain and more unsaturated derivatives rises in the head tissues of the former. This fact indicates that the reduction of technogenic impact on the area results in the increase of the activity of desaturase in the tissues of the head of honey bees. The contents of heavy metals, anionic and non-esterified fatty acids in the tissues of the head of honey bees which are kept in the areas with low level of technogenic burden undergoes the most significant changes.

DNA methylation is maintained with high fidelity in the honey bee germline and exhibits global non-functional fluctuations during somatic development

BackgroundDNA methylation of active genes, also known as gene body methylation, is found in many animal and plant genomes. Despite this, the transcriptional and developmental role of such methylation remains poorly understood. Here, we explore the dynamic range of DNA methylation in honey bee, a model organism for gene body methylation.ResultsOur data show that CG methylation in gene bodies globally fluctuates during honey bee development. However, these changes cause no gene expression alterations. Intriguingly, despite the global alterations, tissue-specific CG methylation patterns of complete genes or exons are rare, implying robust maintenance of genic methylation during development. Additionally, we show that CG methylation maintenance fluctuates in somatic cells, while reaching maximum fidelity in sperm cells. Finally, unlike universally present CG methylation, we discovered non-CG methylation specifically in bee heads that resembles such methylation in mammalian brain tissue.ConclusionsBased on these results, we propose that gene body CG methylation can oscillate during development if it is kept to a level adequate to preserve function. Additionally, our data suggest that heightened non-CG methylation is a conserved regulator of animal nervous systems.

Pollination of Scutellaria mexicana (Lamiaceae) in Southern Nevada by Anthophora Bees

Scutellaria mexicana (Lamiaceae) is a common shrub in the Mojave and northern Sonoran Deserts in North America. The plant produces small tubular and bilabiate flowers that are nototribic by enclosing 2 pairs of stamens and a style within a hooded upper corolla lip. I investigated the pollination of the species in southern Nevada during April 2018 by aspirating insects from flowers. I estimated amounts of S. mexicana pollen on the front of the head and dorsum of the thorax, determined proportions of conspecific pollen on the head, thorax, and middle and hind legs, and examined correspondence between measurements of insect and flower structure. All insects collected on flowers were similarly sized bees in Anthophora (Apidae), mostly comprising A. coptognatha females, followed by A. centriformis males and females. Bees landed on flowers and fed on nectar with the front of the head against lobes that extended laterally from the base of the upper corolla lip. Large and varying amounts of conspecific pollen were carried on the head and thorax of bees, consistent with S. mexicana's nototribic flowers. Bees appeared specific to the plant because they carried high proportions of S. mexicana pollen. Proportions of conspecific pollen on bees differed among collection sites, likely due to different floral compositions. Lower proportions of conspecific pollen on the legs compared with the head or thorax indicated that pollen from plants other than S. mexicana was more likely to be transferred to the legs by bees of both sexes and transported to larvae by females. The length of Anthophora's long glossa corresponded to the depth of the corolla and the availability of nectar. The vertex of the head and anterior dorsum of the thorax of bees feeding on nectar would align with the anthers and stigma on the flowers. Scutellaria mexicana in southern Nevada appears to be dependent on Anthophora bees for pollination.

Exposure to sublethal concentrations of methoxyfenozide disrupts honey bee colony activity and thermoregulation.

Methoxyfenozide is an insect growth regulator (IGR) commonly used in agriculture to simultaneously control pests and preserve beneficial insect populations; however, its impact on honey bees in not fully understood. We conducted field and laboratory experiments to investigate bee health in response to field-relevant concentrations of this pesticide. Significant effects were observed in honey bee colony flight activity and thermoregulation after being exposed over 9 weeks to supplemental protein patty containing methoxyfenozide. Compared to bee colonies in the control group, colonies fed pollen patty with 200 ppb methoxyfenozide (as measured by residue analysis) had: 1) a significantly reduced rate of weight loss due to forager departure in the morning; and 2) higher temperature variability during the winter. Colonies in the 100 ppb (as measured by residue analysis) treatment group had values between the 200 ppb group and control for both response variables. The dusk break point, which is the time associated with the end of forager return, differed among all treatment groups but may have been confounded with direction the hives were facing. Bee colony metrics of adult bee mass and brood surface area, and measurements of bee head weight, newly-emerged bee weight, and hypopharyngeal gland size were not significantly affected by methoxyfenozide exposure, suggesting that there may be significant effects on honey bee colony behavior and health in the field that are difficult to detect using standard methods for assessing bee colonies and individuals. The second experiment was continued into the following spring, using the same treatment groups as in the fall. Fewer differences were observed among groups in the spring than the fall, possibly because of abundant spring forage and consequent reduced treatment patty consumption. Residue analyses showed that: 1) observed methoxyfenozide concentrations in treatment patty were about 18–60% lower than the calculated concentrations; 2) no residues were observed in wax in any treatment; and 3) methoxyfenozide was detected in bee bread only in the 200 ppb treatment group, at about 1–2.5% of the observed patty concentration.

Pollen reverses decreased lifespan, altered nutritional metabolism and suppressed immunity in honey bees (Apis mellifera) treated with antibiotics.

Nutrition is involved in regulating multiple aspects of honey bee biology such as caste, immunity, lifespan, growth and behavioral development. Deformed wing virus (DWV) is a major pathogenic factor which threatens honey bee populations, and its replication is regulated by the nutrition status and immune response of honey bees. The alimentary canal of the honey bee is home to a diverse microbial community that provides essential nutrients and serves to bolster immune responses. However, to what extent gut bacteria affect honey bee nutrition metabolism and immunity with respect to DWV has not been investigated fully. In this study, newly emerged worker bees were subjected to four diets that contained (1) pollen, (2) pollen and antibiotics, (3) neither pollen nor antibiotics or (4) antibiotics alone. The expression level of two nutrition genes target of rapamycin (tor) and insulin like peptide (ilp1), one nutritional marker gene vitellogenin (vg), five major royal jellyprotein genes (mrjp1-5), one antimicrobial peptide regulating gene relish (rel), and DWV virus titer and its replication intermediate, negative RNA strand, were determined by qRT-PCR from the honey bees at 7 days post-antibiotic treatment. Additionally, honey bee head mass and survival rate were measured. We observed that antibiotics decreased the expression of tor and rel, and increased DWV titer and its replication activity. Expression of ilp1, mrjp1-5 and vg, and honey bee head mass were also reduced compared with bees on a pollen diet. Antibiotics also caused a significant drop in survivorship, which could be rescued by addition of pollen to the diet. Of importance, pollen could partially rescue the loss of vg and mrjp2 while also increasing the head mass of antibiotic-treated bees. Our results illuminate the roles of bacteria in honey bee nutrition, metabolism and immunity, which confer the ability to inhibit virus replication, extend honey bee lifespan and improve overall health.

Sublethal effects of chronic exposure to CdO or PbO nanoparticles or their binary mixture on the honey bee (Apis millefera L.).

Cadmium and lead-based nanotechnologies are increasingly used in agricultural, industrial, and biological processes; however, potential adverse effects of nanomaterials on honey bees had not been assessed. In this study, effects of exposures to sublethal concentrations of PbO and CdO nanoparticles (NPs), either separately or in combination on honey bee (Apis mellifera) workers, were assessed. Honey bee workers were orally exposed for 9days under laboratory conditions to sublethal concentrations (20% of LC50) of CdO (0.01mg/ml-) and PbO (0.65mg/ml-) NPs either separately or combined. Effects on survival, feeding rate, activity of acetylcholinesterase (AChE), and expression of selected stress-related detoxifying enzymes were quantified. Survival and feeding rates decreased particularly in bees fed sugar syrup containing CdO NPs or binary mixtures of NPs of both metal oxides. Expressions of genes involved in detoxification of xenobiotics were affected by various combinations. Expression of catalase was 13.6-fold greater in bees consumed sugar syrup diet containing binary mixture of sublethal concentrations of both CdO and PbO NPs than it was in unexposed, control bees. AChE activity in heads of honey bees was inhibited by 3.8-, 3.0-, and 2.8-fold relative to control, respectively, in response to exposure to Cd or/and Pb oxide NPs. This result indicates potential neurotoxic effects of these NPs to honey bees. CdO NPs exhibited greater potency to honey bees. Overall, sublethal concentrations of CdO or/and PbO NPs resulted in detrimental effects on honeybee workers.

Maximum DNA Methylation Fidelity in the Germline Tolerates Global Non-Functional Gene Body Methylation Dynamics During Development

Although active genes frequently exhibit cytosine DNA methylation in animals and plants, the biological function of such methylation remains elusive. Here we explore the dynamic range of DNA methylation in honey bee, a model organism for gene body methylation. Our data show that CG-methylation in gene bodies globally fluctuates during honey bee development. However, these changes cause no gene expression alterations. Intriguingly, despite the global alterations, tissue-specific CG-methylation patterns of complete genes or exons are rare, implying robust maintenance of genic methylation during development. Additionally, we show that CG-methylation maintenance fluctuates in somatic cells, while reaching maximum fidelity in sperm cells. Based on these results, we propose that gene body CGmethylation can oscillate in organisms as long as it is being kept to an adequate level to preserve its function during development and its pattern across generations. Unlike CG-methylation, we discovered a non-CG methylation signal in bee heads that resembles the one found in mammalian brain tissue, suggesting that heightened non-CG methylation is a conserved regulator of animal nervous systems.

Validation of quantitative real-time PCR reference genes for the determination of seasonal and labor-specific gene expression profiles in the head of Western honey bee, Apis mellifera

Honey bee is not only considered an important pollinator in agriculture, but is also widely used as a model insect in biological sciences, thanks to its highly evolved sociality, specialization of labor division, and flexibility of colony management. For an intensive investigation of the seasonal and labor-dependent expression patterns of its genes, accurate quantification of the target gene transcription level is a fundamental step. To date, quantitative real-time PCR (qRT-PCR) has been widely used for rapid quantification of gene transcripts, with reliable reference gene(s) for normalization. To this end, in an attempt to search for reliable reference genes, the amplification efficiencies of six candidate reference genes (rp49, rpL32, rpS18, tbp, tub, and gapdh) were determined. Subsequently, four genes (rpL32, rpS18, tbp, and gapdh) with PCR efficiencies of 90% to 110% were evaluated for their expression stabilities with three programs (geNorm, NormFinder, and BestKeeper) and used for normalization of seasonal expression patterns of target genes in the forager and nurse heads. Although the three programs revealed slightly different results, two genes, rpS18 and gapdh, were suggested to be the optimal reference genes for qRT-PCR-based determination of seasonal and labor-specific gene expression profiles. Furthermore, the combined use of these two genes yielded a more accurate normalization, compared with the use of a single gene in the head of honey bee. The validated reference genes can be widely used for quantification of target gene expression in honey bee head although it is still remained to be elucidated the expression levels of the selected reference genes in specific tissues in head.

Compounds extracted from heads of African stingless bees (Hypotrigona species) as a prospective taxonomic tool

The European Union (EU) (Grant Contract No. DCI-FOOD/2013/313-659: African Reference Laboratory (with satellite stations) for the Management of Pollination Bee Diseases and Pests for Food Security); the South African National Research Foundation (NRF) Research Career Advancement Fellowship (Grant no: 91419) to AAY; NRF Incentive Funding for Rated Researchers to CWWP and AAY; UK Aid from the UK Government; Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC) and the Kenyan Government. The first author was supported by a German Academic Exchange Service (DAAD) In-Region Postgraduate Scholarship.

The microRNA ame-miR-279a regulates sucrose responsiveness of forager honey bees (Apis mellifera)

Increasing evidence demonstrates that microRNAs (miRNA) play an important role in the regulation of animal behaviours. Honey bees (Apis mellifera) are eusocial insects, with honey bee workers displaying age-dependent behavioural maturation. Many different miRNAs have been implicated in the change of behaviours in honey bees and ame-miR-279a was previously shown to be more highly expressed in nurse bee heads than in those of foragers. However, it was not clear whether this difference in expression was associated with age or task performance. Here we show that ame-miR-279a shows significantly higher expression in the brains of nurse bees relative to forager bees regardless of their ages, and that ame-miR-279a is primarily localized in the Kenyon cells of the mushroom body in both foragers and nurses. Overexpression of ame-miR-279a attenuates the sucrose responsiveness of foragers, while its absence enhances their sucrose responsiveness. Lastly, we determined that ame-miR-279a directly target the mRNA of Mblk-1. These findings suggest that ame-miR-279a plays important roles in regulating honey bee division of labour.

Bee visitors of Centaurea solstitialis L. (Asteraceae) in an urban environment in northwestern Turkey

Information on the pollination ecology and floral visitors of the noxious weed Centaurea solstitialis is available for several populations in its invasive range, but limited information is available in its native range, with most studies conducted on the Greek island of Lesvos. Herein, we document the visitation pattern of bees and explore the relationship of bee body size and nectar availability in weedy populations of C. solstitialis from an urban environment within its native range in northwestern Turkey. Studies were conducted at patches of C. solstitialis in abandoned lots at the Uludag University near the city of Bursa. A total of 41 species, including honey bees, belonging to five families and 19 genera were recorded. Small megachilid and halictid bee species were the most common visitors. Average nectar standing crop volume per floret was low (0.003–0.117 μL) and did not significantly vary throughout the day. Average bee head width significantly correlated with average nectar standing crop volume but did not significantly change throughout the day. Analyses of pollen loads as well as direct observations of bee foraging behavior indicate that a large number of bees visit C. solstitialis, primarily in search of nectar while carrying a large percentage of pollen grains of this plant species on their bodies. These results are similar to previous observations on a non-weedy population of C. solstitialis from the island of Lesvos.

Linking magnetite in the abdomen of honey bees to a magnetoreceptive function.

Previous studies of magnetoreception in honey bees, Apis mellifera, focused on the identification of magnetic material, its formation, the location of the receptor and potential underlying sensory mechanisms, but never directly linked magnetic material to a magnetoreceptive function. In our study, we demonstrate that ferromagnetic material consistent with magnetite plays an integral role in the bees' magnetoreceptor. Subjecting lyophilized and pelletized bee tagmata to analyses by a superconducting quantum interference device generated a distinct hysteresis loop for the abdomen but not for the thorax or the head of bees, indicating the presence of ferromagnetic material in the bee abdomen. Magnetic remanence of abdomen pellets produced from bees that were, or were not, exposed to the 2.2-kOe field of a magnet while alive differed, indicating that magnet exposure altered the magnetization of this magnetite in live bees. In behavioural two-choice field experiments, bees briefly exposed to the same magnet, but not sham-treated control bees, failed to sense a custom-generated magnetic anomaly, indicating that magnet exposure had rendered the bees' magnetoreceptor dysfunctional. Our data support the conclusion that honey bees possess a magnetite-based magnetoreceptor located in the abdomen.

Synthesis of Enantiopure Alicyclic Ethers and Their Activity on the Chemosensory Organ of the Ectoparasite of Honey Bees, Varroa destructor.

The preparation of enantiopure conformationally restricted alicyclic ethers and their inhibitory activities on the chemosensory organ of the Varroa destructor, a parasite of honey bees, are reported in this article. We tested the effect of enantiopure ethers of cis-5-(2'-hydroxyethyl)cyclopent-2-en-1-ol on the Varroa chemosensory organ by electrophysiology, for their ability to inhibit the responses to two honey bee-produced odors that are important for the mite to locate its host: nurse bee head space odor and (E)-β-ocimene, a honey bee brood pheromone. Previous work with the racemic compounds showed that they suppress the mite's olfactory response to its bee host, which led to incorrect host choice. Based on a structure-activity relationship, we predicted that the two most active compounds-cis-1-butoxy-5-(2'-methoxyethyl)cyclopent-2-ene, cy{4,1}, and (cis-1-ethoxy-5-(2'ethoxyethyl)cyclopent-2-ene, cy{2,2}-could have opposite active enantiomers. Here we studied the enantiomers of both ethers, whose preparation involved enzymatic resolution of racemic diol cis-5-(2'-hydroxyethyl)cyclopent-2-en-1-ol using Lipase AK with vinyl acetate. The racemic diol was prepared from commercially available 2,5-norbornadiene. We observed that the responses of the chemosensory organ to honey bee head space volatiles were significantly decreased by both enantiomers of cy{4,1} and cy{2,2}, but that responses to (E)-β-ocimene were decreased significantly only by (+)-cy{4,1} (1R,5S) and (-)-cy{2,2} (1S,5R) and not by their respective enantiomers. The importance of this result is that the racemates could be used to inhibit olfactory detection of bee odors by mites, without a loss in activity relative to the more expensive enantiopure compounds.

Secondary biomarkers of insecticide-induced stress of honey bee colonies and their relevance for overwintering strength

The evaluation of pesticide side-effects on honeybees is hampered by a lack of colony-level bioassays that not only are sensitive to physiological changes, but also allow predictions about the consequences of exposure for longer-term colony productivity and survival. Here we measured 28 biometrical, biochemical and behavioural indicators in a field study with 63 colonies and 3 apiaries. Colonies were stressed in early summer by feeding them for five days with either the carbamate growth regulator fenoxycarb or the neurotoxic neonicotinoid imidacloprid, or left untreated. Candidate stress indicators were measured 8–64 days later. We determined which of the indicators were influenced by the treatments, and which could be used as predictors in regression analyses of overwintering strength. Among the indicators influenced by fenoxycarb were the amount of brood in colonies as well as the learning performance and 24h-memory of bees, and the concentration of the brood food component 10HDA in head extracts. Imidacloprid significantly affected honey production, total number of bees and activity of the immune-related enzyme phenoloxidase in forager bee extracts. Indicators predictive of overwintering strength but unrelated to insecticide feeding included vitellogenin titer and glucose oxidase-activity in haemolymph/whole body-extracts of hive bees. Apart from variables that were themselves components of colony strength (numbers of bees/brood cells), the only indicator that was both influenced by an insecticide and predictive of overwintering strength was the concentration of 10HDA in worker bee heads. Our results show that physiological and biochemical bioassays can be used to study effects of insecticides at the colony level and assess the vitality of bee colonies. At the same time, most bioassays evaluated here appear of limited use for predicting pesticide effects on colony overwintering strength, because those that were sensitive to the insecticides were not identical with those that were predictive of colony overwintering. Our study therefore illustrates the difficulties involved in evaluating the economic/ecological significance of pesticide-induced stress in honey bee field studies.

Combined effect of pollen quality and thiamethoxam on hypopharyngeal gland development and protein content in Apis mellifera

Pollen diet is essential to nurse bees to develop hypopharyngeal glands (HPGs) and produce royal jelly to feed larvae. The effect of different diet regimes combined with pesticide exposure on the development of HPGs in honeybees was studied. In particular, a high-quality pollen mixture (high pollen diversity and protein content) and a low-quality diet (low pollen diversity and protein content) were combined with the chronic administration of thiamethoxam (10 and 40 μg/L). The impact of these stressors was evaluated by measuring the size of HPG acini and the total protein content of bee heads in 8- and 12-day-old bees. Bees fed with sub-lethal concentrations of thiamethoxam and with the low-quality diet exhibited smaller and irregularly shaped acini. The total protein content in bee head was also affected by pesticide administration, while the pollen quality did not cause significant modifications. In conclusion, these results highlighted the importance of the food quality, considered as nutritional value and pesticide contamination, for the physiological development of honeybees.

Multi-Drug Resistance Transporters and a Mechanism-Based Strategy for Assessing Risks of Pesticide Combinations to Honey Bees.

Annual losses of honey bee colonies remain high and pesticide exposure is one possible cause. Dangerous combinations of pesticides, plant-produced compounds and antibiotics added to hives may cause or contribute to losses, but it is very difficult to test the many combinations of those compounds that bees encounter. We propose a mechanism-based strategy for simplifying the assessment of combinations of compounds, focusing here on compounds that interact with xenobiotic handling ABC transporters. We evaluate the use of ivermectin as a model substrate for these transporters. Compounds that increase sensitivity of bees to ivermectin may be inhibiting key transporters. We show that several compounds commonly encountered by honey bees (fumagillin, Pristine, quercetin) significantly increased honey bee mortality due to ivermectin and significantly reduced the LC50 of ivermectin suggesting that they may interfere with transporter function. These inhibitors also significantly increased honey bees sensitivity to the neonicotinoid insecticide acetamiprid. This mechanism-based strategy may dramatically reduce the number of tests needed to assess the possibility of adverse combinations among pesticides. We also demonstrate an in vivo transporter assay that provides physical evidence of transporter inhibition by tracking the dynamics of a fluorescent substrate of these transporters (Rhodamine B) in bee tissues. Significantly more Rhodamine B remains in the head and hemolymph of bees pretreated with higher concentrations of the transporter inhibitor verapamil. Mechanism-based strategies for simplifying the assessment of adverse chemical interactions such as described here could improve our ability to identify those combinations that pose significantly greater risk to bees and perhaps improve the risk assessment protocols for honey bees and similar sensitive species.

Bumblebees taste protein quality difference

It's a sickening statistic: 50% of the UK's bee species have been lost since the 1950s and the number of honeybee hives in the US has plummeted from 6 million to 2.5 million. No matter where you are, bees and the agriculture that they support are at risk, so maintaining their health is of paramount importance. Sara Leonhardt from the University of Würzburg, Germany, explains that diet can significantly affect the insects’ health – high protein diets can shorten the life expectancy of adult honeybees while benefiting larvae – so bees would clearly benefit from being able to assess the quality and nutrient content of their food. However, Leonhardt says, ‘It remains unclear whether bees are actually able to perceive and assess the quality of pollen’. And even if they could, which senses might they use? Explaining that bumblebee foragers have to be able to assess the quality of the pollen and nectar that they deliver to the nest, because their nest mates do not provide feedback on the quality of the provisions, Leonhardt and Johannes Spaethe decided to ask bumblebees more about their ability to distinguish between the proteins in their diet.Snugly sitting the bees in a tube with their heads protruding from the end, Fabian Ruedenauer was able to take advantage of the bees’ tendency to stick out their tongues when they detect sugar to learn more about their preferences. Knowing that bumblebees can be trained to transfer their tongue extension behaviour to show when they recognise odours and flavours, Ruedenauer embarked on a painstaking set of experiments to test the insects’ ability to recognise proteins from different sources. Training the bees to recognise apple and almond pollen and the protein casein from milk, the team were pleased to see that the bees were capable of learning to recognise all three forms of protein. Then, Ruedenauer tested whether the bees could distinguish between the two pollens – which have different odours – by gently blowing a puff of pollen-flavoured air over the bee's head. Sure enough, the bumble bees could clearly distinguish between the two, sticking their tongues out whenever they encountered the pollen flavour that they had been trained to recall.But could the bees distinguish between pollen mixtures of different concentrations and if so, which senses would the insects use? Mixing pollen and cellulose in different proportions and blowing the mixture's odour over the faces of restrained bees, Ruedenauer could see that the bees were indifferent to the strength of the mixture, responding equally happily to both the strong and weak mixtures. However, when Rudenauer offered the bees the opportunity of tasting the mixture by dipping their antennae into the pollen/cellulose and casein/cellulose mixtures, the insects distinguished between the dilute and concentrated mixtures with ease. ‘Bumblebees are able to learn the odour of pollen and casein using olfactory cues, but can only differentiate between concentrations of these substances when they can touch the food,’ says Leonhardt.Having shown that the insects are capable of differentiating food with different protein contents, Leonhardt and her colleagues are now testing whether bumblebees are able to translate this into foraging practice by selecting better quality food when offered a choice. They also want to discover whether the foragers’ customers – the larvae that they supply – have an impact on the bees’ sensitivity to the quality of their foraged food.

Viral Infection Affects Sucrose Responsiveness and Homing Ability of Forager Honey Bees, Apis mellifera L.

Honey bee health is mainly affected by Varroa destructor, viruses, Nosema spp., pesticide residues and poor nutrition. Interactions between these proposed factors may be responsible for the colony losses reported worldwide in recent years. In the present study, the effects of a honey bee virus, Israeli acute paralysis virus (IAPV), on the foraging behaviors and homing ability of European honey bees (Apis mellifera L.) were investigated based on proboscis extension response (PER) assays and radio frequency identification (RFID) systems. The pollen forager honey bees originated from colonies that had no detectable level of honey bee viruses and were manually inoculated with IAPV to induce the viral infection. The results showed that IAPV-inoculated honey bees were more responsive to low sucrose solutions compared to that of non-infected foragers. After two days of infection, around 107 copies of IAPV were detected in the heads of these honey bees. The homing ability of IAPV-infected foragers was depressed significantly in comparison to the homing ability of uninfected foragers. The data provided evidence that IAPV infection in the heads may enable the virus to disorder foraging roles of honey bees and to interfere with brain functions that are responsible for learning, navigation, and orientation in the honey bees, thus, making honey bees have a lower response threshold to sucrose and lose their way back to the hive.

More than royal food - Major royal jelly protein genes in sexuals and workers of the honeybee Apis mellifera

BackgroundIn the honeybee Apis mellifera, female larvae destined to become a queen are fed with royal jelly, a secretion of the hypopharyngeal glands of young nurse bees that rear the brood. The protein moiety of royal jelly comprises mostly major royal jelly proteins (MRJPs) of which the coding genes (mrjp1-9) have been identified on chromosome 11 in the honeybee’s genome.ResultsWe determined the expression of mrjp1-9 among the honeybee worker caste (nurses, foragers) and the sexuals (queens (unmated, mated) and drones) in various body parts (head, thorax, abdomen). Specific mrjp expression was not only found in brood rearing nurse bees, but also in foragers and the sexuals.ConclusionsThe expression of mrjp1 to 7 is characteristic for the heads of worker bees, with an elevated expression of mrjp1-4 and 7 in nurse bees compared to foragers. Mrjp5 and 6 were higher in foragers compared to nurses suggesting functions in addition to those of brood food proteins. Furthermore, the expression of mrjp9 was high in the heads, thoraces and abdomen of almost all female bees, suggesting a function irrespective of body section. This completely different expression profile suggests mrjp9 to code for the most ancestral major royal jelly protein of the honeybee.

Behavioral plasticity in honey bees is associated with differences in brain microRNA transcriptome

Small, non-coding microRNAs (miRNAs) have been implicated in many biological processes, including the development of the nervous system. However, the roles of miRNAs in natural behavioral and neuronal plasticity are not well understood. To help address this we characterized the microRNA transcriptome in the adult worker honey bee head and investigated whether changes in microRNA expression levels in the brain are associated with division of labor among honey bees, a well-established model for socially regulated behavior. We determined that several miRNAs were downregulated in bees that specialize on brood care (nurses) relative to foragers. Additional experiments showed that this downregulation is dependent upon social context; it only occurred when nurse bees were in colonies that also contained foragers. Analyses of conservation patterns of brain-expressed miRNAs across Hymenoptera suggest a role for certain miRNAs in the evolution of the Aculeata, which includes all the eusocial hymenopteran species. Our results support the intriguing hypothesis that miRNAs are important regulators of social behavior at both developmental and evolutionary time scales.