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Dopamine (DA) regulates reproductive behavior and promotes maturation of the reproductive system in insects. In Drosophila , male courtship behavior is regulated by the protocerebral posteriolateral dopaminergic cluster neuron 2ab (PPL2ab). The ability to synthesize DA in the PPL2ab affects male-male and male-female courtship behavior. The DA level in the brain of adult male Drosophila influences sexual orientation; although, male-male courtship is induced when the DA level is too high or too low. DA also regulates changes in reproductive behavior and post-copulation behavior. As a neurohormone, DA regulates taste and smell perception in insects. In the central nervous system, DA regulation of reproductive behavior involves the DA/MH (molting hormone) receptor (DopEcR) and synergy between DA and ecdysone, with the tritocerebrum P1 neurons playing an important role in the male courtship information loop. DA can promote development in the eggs and regulate the reproductive state in social insects. The promotional effect of DA on egg development involves developmental stage differences in DA receptor expression and interactions among DA, juvenile hormone (JH), MH, and octopamine (OA). For example, the expression level of dopamine D2-like receptor (DD2R) in the corpora allata of D. melanogaster young females is far lower than that in sexually mature females. Meanwhile, the expression level of dopamine D1-like receptor (DopR) in young females is much higher than that in mature females. By contrast, the expression of DopR and DD2R in the fat body is the opposite to that in the corpora allata. The interactions among DA, JH, MH, and OA depend on the expression of certain genes and regulation of metabolic enzyme activity. In addition, the interactions among different hormones also involve the insulin-like signaling (ILPs) pathway. As to reproductive state regulation in social insects, it has been found that the reproductive state of worker bees is regulated by queen mandibular pheromone (QMP), larvae pheromones, and the ovarian DA D2 receptor gene. Research on DA regulation of insect reproduction will provide us with references for the development of new drugs, and for research on mechanisms in human brain science and nervous system diseases.

This research deals with the effect of pheromones, queen mandibular pheromone one gene expression of brain adult for workers honeybee Apis mellifera, these expressions can explain the response behavior induced by pheromones QMP, the impact of gene expression by affecting the movement of workers A. mellifera in the colony of honeybees in the case of the presence of the Queen. Queen's absence means the lack of workers as a result of the lack of pheromones (QMP) or the presence of a few compared to the presence of the Queen. The behavior of workers is linked to the existence of pheromones released by the Queen.

Recent work demonstrated that honey bee (Apis mellifera L.) queens reared in pesticide-laden beeswax exhibit significant changes in the composition of the chemicals produced by their mandibular glands including those that comprise queen mandibular pheromone, which is a critical signal used in mating as well as queen tending behavior. For the present study, we hypothesized that pesticide exposure during development would alter other queen-produced chemicals, including brood pheromone in immature queens, thus resulting in differential feeding of queen larvae by nurse workers, ultimately impacting adult queen morphology. We tested these hypotheses by rearing queens in beeswax containing field-relevant concentrations of (1) a combination of tau-fluvalinate and coumaphos, (2) amitraz, or (3) a combination of chlorothalonil and chlorpyrifos. These pesticides are ubiquitous in most commercial beekeeping operations in North America. We observed nurse feeding rates of queen larvae grafted into pesticide-laden beeswax, analyzed the chemical composition of larval queen pheromones and measured morphological markers in adult queens. Neither the nurse feeding rates, nor the chemical profiles of immature queen pheromones, differed significantly between queens reared in pesticide-laden wax compared to queens reared in pesticide-free wax. Moreover, pesticide exposure during development did not cause virgin or mated adult queens to exhibit differences in morphological markers (i.e., body weight, head width, or thorax width). These results were unexpected given our previous research and indicate that future work is needed to fully understand how pesticide exposure during development affects honey bee queen physiology, as well as how various adult queen quality metrics relate to each other.

Eusocial insect societies are defined by the reproductive division of labour, a social structure that is generally enforced by the reproductive dominant or ‘queen’. Reproductive dominance is maintained through behavioural dominance in some species as well as production of queen pheromones in others, or a mixture of both. Queen mandibular pheromone (QMP) is produced by honeybee (Apis mellifera) queens and has been characterised chemically. How QMP acts to repress worker reproduction, and how it has evolved this activity, remains less well understood. Surprisingly, QMP is capable of repressing reproduction in non-target arthropods which have not co-evolved with QMP, are never exposed to QMP in nature, and are up to 530 million years diverged from the honeybee. Here we show that, in Drosophila melanogaster, QMP treatment mimics nutrient limiting conditions, leading to disrupted reproduction. Exposure to QMP induces an increase in food consumption, consistent with that observed in D. melanogaster in response to starvation conditions. This response induces the activation of two checkpoints within the ovary that inhibit oogenesis. The first is the 2a/b ovarian checkpoint in the germarium, which reduces the flow of presumptive oocytes. A stage 9 ovarian checkpoint is also activated, causing degradation of oocytes. The magnitude of activation of both checkpoints is indistinguishable between QMP treated and starved individuals. As QMP seems to trigger a starvation response in an insect highly diverged from honeybees, we propose that QMP originally evolved by co-opting nutrition signalling pathways to regulate reproduction, a key step in the evolution of eusociality.

Eusociality is characterised by the reproductive division of labour; a dominant female (queen) or females are responsible for the majority of reproduction, and subordinate females are reproductively constrained. Reproductive constraint can be due to behavioural aggression and/or chemical cues, so-called queen pheromones, produced by the dominant females. In the honeybee, Apis mellifera, this repressive queen pheromone is queen mandibular pheromone (QMP). The mechanism by which honeybee workers are susceptible to QMP is not yet completely understood, however it is thought to be through olfaction via the antennae and/or gustation via trophallaxis. We have investigated whether olfaction is key to sensing of QMP, using both Drosophila melanogaster- a tractable non-eusocial insect which is also reproductively repressed by QMP- and the target species, A. mellifera worker honeybees. D. melanogaster are still capable of sensing and responding to QMP without their antenna and maxillary palps, and therefore without olfactory receptors. When worker honeybees were exposed to QMP but unable to physically interact with it, therefore required to use olfaction, they were similarly not reproductively repressed. Combined, these findings support either a non-olfactory based mechanism for the repression of reproduction via QMP, or redundancy via non-olfactory mechanisms in both D. melanogaster and A. mellifera. This study furthers our understanding of how species are susceptible to QMP, and provides insight into the mechanisms governing QMP responsiveness in these diverse species.

Queen mandibular pheromone (QMP) is a potent reproductive signal to which honey bee workers respond by suppressing their ovaries and adopting alloparental roles within the colony. This anti-ovarian effect of QMP on workers can, surprisingly, be induced in other insects, including fruit flies, in which females exposed to synthetic QMP develop smaller ovaries with fewer eggs. In this study, we use the Drosophila melanogaster model to identify the components of synthetic QMP required for the anti-ovarian effect. We found that virgin females respond strongly to 9-oxo-2-decenoic acid and 10-hydroxy-2-decenoic acid (10HDA), suggesting that the decenoic acid components of QMP are essential for the anti-ovarian response. Further, a nuclear factor of activated T-cells reporter system revealed neurones expressing the olfactory receptors Or-56a, Or-49b and Or-98a are activated by QMP in the antenna. In addition, we used olfactory receptor GAL4 drivers and a neuronal activator (a neuronal activating bacterial sodium channel) to test whether the candidate neurones are potential labelled lines for a decenoic acid response. We identified Or-49b as a potential candidate receiver of the 10HDA signal. Finally, the anti-ovarian response to synthetic QMP is not mediated by decreasing the titre of the reproductive hormones ecdysone and juvenile hormone.

Pheromones are used by many insects to mediate social interactions. In the highly eusocial honey bee ( Apis mellifera ) queen mandibular pheromone is involved in the regulation of reproduction and the rate of ageing of workers. The molecular mechanisms by which queen mandibular pheromone acts remain largely unknown. Here we investigate how genes responsible for epigenetic modifications to DNA, RNA and histones expressed in the brain of honey bee workers respond to the presence of queen mandibular pheromone. Several of these genes are upregulated in workers exposed to queen mandibular pheromone. This suggests that epigenetic mechanisms are mediated by pheromonal communication between queens and workers, and that the interaction of pheromone signalling and epigenetics may mediate some of the neural plasticity that underlies ageing-associated traits in social insects. We suggest that pheromonal communication systems, such as those used by social insects, evolved to respond to environmental clues by making use of epigenomic machineries.

The evolutionary origin of queen pheromones (QPs), which regulate reproductive division of labor in insect societies, has been explained by two evolutionary scenarios: the sender-precursor hypothesis and the sensory exploitation hypothesis. These scenarios differ in terms of whether the signaling system was built on preadaptations on the part of either the sender queens or the receiver workers. While some social insect QPs—such as cuticular hydrocarbons—were likely derived from ancestral fertility cues and evolved according to the former theory, the honeybee’s queen mandibular pheromone (QMP) has been suggested to act directly on preexisting gene-regulatory networks linked with reproduction. This is evidenced by the fact that QMP has been shown to also inhibit ovary activation in fruit flies, thereby implying exploitation of conserved physiological pathways. To verify whether QMP has similar effects on more closely related eusocial species, we here tested for QMP cross-activity in the bumblebee Bombus terrestris. Interestingly, we found that the non-native QMP blend significantly inhibited egg laying in both worker and queen bumblebees and caused accompanying shifts in ovary activation. The native bumblebee QP pentacosane, by contrast, only inhibited the reproduction of the workers. Overall, these findings support the hypothesis that honeybee QMP likely evolved via a route of sensory exploitation. We argue that such exploitation could allow social insect queens to produce compounds that manipulate the workers to remain sterile, but that a major hurdle would be that the queens themselves would have to be immune to such compounds. ispartof: Behavioral Ecology vol:31 issue:2 status: published

Queen pheromones effect the reproductive division of labour, a defining feature of eusociality. Reproductive division of labour ensures that one, or a small number of, females are responsible for the majority of reproduction within a colony. Much work on the evolution and function of these pheromones has focussed on Queen Mandibular Pheromone (QMP) which is produced by the Western or European honeybee (Apis mellifera). QMP has phylogenetically broad effects, repressing reproduction in a variety of arthropods, including those distantly related to the honeybee such as the fruit fly Drosophila melanogaster. QMP is highly derived and has little chemical similarity to the majority of hymenopteran queen pheromones which are derived from cuticular hydrocarbons. This raises the question of whether the phylogenetically widespread repression of reproduction by QMP also occurs with more basal saturated hydrocarbon-based queen-pheromones. Using D. melanogaster we show that saturated hydrocarbons, are incapable of repressing reproduction, unlike QMP. We also show no interaction between the four saturated hydrocarbons tested or between the saturated hydrocarbons and QMP, implying that there is no conservation in the mechanism of detection or action between these compounds. We propose that the phylogenetically broad reproductive repression seen in response to QMP is not a feature of all queen pheromones, but unique to QMP itself, which has implications for our understanding of how queen pheromones act and evolve.

Social insects have two or more female castes that exhibit extreme differences in their reproductive capacity. The molecular basis of these differences is largely unknown. In honeybees the egg yolk protein vitellogenin (Vg), has acquired regulatory functions that go beyond reproduction, including the regulation of aging and task polyethism. Vg is synthesised in the fat body of both queens and workers and in the ovaries of queens. Here we show that Vg is also expressed in worker ovaries and that ovary activation and environmental cues (both social and diet) modulate Vg expression. Workers that are fed Royal Jelly have higher expression of Vg than those not fed Royal Jelly. Surprisingly, we find that Vg expression is not corelated with worker ovary activation, which suggests that Vg has non-reproductive functions in worker’s ovaries. We also find that Royal Jelly in the diet disrupts the expression of likely regulators of Vg expression: Vitellogenin receptor ( VgR ), Krüppel-homolog 1 ( Kr-h1 ), DNA methyltransferase 3 ( Dnmt3 ) and the Forkhead box O transcription factor ( FoxO ). These results therefore support the ‘reproductive grand plan hypothesis’, which argues that genes that had reproductive functions in solitary ancestors have been co-opted for social functions in social insects.

International audience; AbstractThe number of female progeny that a honey bee (Apis mellifera) queen produces in her lifetime is directly dependent on the amount of semen she collects upon mating (i.e., insemination volume) and the number of viable sperm cells contained within the semen (i.e., sperm viability). Queen insemination volume has been shown to alter queen mandibular pheromone profiles, as well as worker behavior and physiology at the individual level. In order to determine if queen insemination volume has any colony-level effects, we compared the growth of newly established colonies headed by queens instrumentally inseminated with either a low volume (1.5 μL) or a high volume (9.0 μL) of pooled semen from May to October in 2013 and 2015. We did not find a significant effect of queen insemination volume on the production of worker comb, drone comb, stored food, worker population, or seasonal queen or colony survivorship. Therefore, we concluded that queen insemination volume does not seem to directly affect growth at the colony level, at least during a colony’s first year.

Exposing honey bees to isopentylacetate (IPA) can cause stress-related changes in learning performance. In bees of foraging age, IPA’s effects on learning are mimicked by C-type allatostatins (AstCC, AstCCC) injected into the brain. Here we ask whether allatostatins induce a similar response in young (6-day-old) bees and if so, whether their effects on learning performance are modulated by queen mandibular pheromone (QMP). We found that young bees exposed to IPA responded less to the conditioned stimulus during training than controls (Type 1-like stress response). AstCC treatment induced a similar response, but only in bees maintained without QMP. Bees exposed to QMP responded to AstCC with increased odour responsiveness and odour generalisation in the 1-h memory test (Type 2-like response). Type 2-like responses could be induced also by the A-type allatostatin, AstA. However, in bees exposed to QMP, AstA-induced odour generalisation was absent. Effects of AstCCC treatment in young bees were weak, indicating that responsiveness to this peptide changes with age. Our findings are consistent with the hypothesis that honey bee allatostatins play a role in stress reactivity, but suggest in addition that allatostatin signalling is age dependent and susceptible to modulation by pheromone released by the queen bee.

Floral nectar often contains chemicals that are deterrent to pollinators, presenting potential challenges to outcrossing plant species. Plants may be able to co-opt pollinator chemical signals to mitigate the negative effects of nectar deterrent compounds on pollination services. We found that buckwheat (Fagopyrum esculentum) and Mexican sunflower (Tithonia diversifolia) produce nectar with abundant phenolics, including three components of the Apis honeybee queen mandibular pheromone (QMP). In addition, these nectars contain a non-pheromonal phenolic, chlorogenic acid (CA), which was toxic to honeybees, and T. diversifolia nectar also contained isochlorogenic acid (IA). Fresh nectar or solutions containing nectar phenolics reduced Apis individual feeding compared to sucrose solutions. However, freely foraging bees preferred solutions with QMP components to control solutions, and QMP components over-rode or reversed avoidance of CA and IA. Furthermore, prior exposure to the presence or just the odor of QMP components removed the deterrent effects of CA and IA. By mimicking the honey bee pheromone blend, nectar may maintain pollinator attraction in spite of deterrent nectar compounds.

The objective of this study was to assess the effects of honey bees (Apis mellifera L.) with different grooming ability and queen pheromone status on mortality rates of Varroa mites (Varroa destructor Anderson and Trueman), mite damage, and mortality rates of honey bees. Twenty-four small queenless colonies containing either stock selected for high rates of mite removal (n = 12) or unselected stock (n = 12) were maintained under constant darkness at 5 °C. Colonies were randomly assigned to be treated with one of three queen pheromone status treatments: (1) caged, mated queen, (2) a synthetic queen mandibular pheromone lure (QMP), or (3) queenless with no queen substitute. The results showed overall mite mortality rate was greater in stock selected for grooming than in unselected stock. There was a short term transitory increase in bee mortality rates in selected stock when compared to unselected stock. The presence of queen pheromone from either caged, mated queens or QMP enhanced mite removal from clusters of bees relative to queenless colonies over short periods of time and increased the variation in mite mortality over time relative to colonies without queen pheromone, but did not affect the proportion of damaged mites. The effects of source of bees on mite damage varied with time but damage to mites was not reliably related to mite mortality. In conclusion, this study showed differential mite removal of different stocks was possible under low temperature. Queen status should be considered when designing experiments using bioassays for grooming response.

International audience; AbstractTo test the hypothesis that exposure to queen mandibular pheromone (QMP) modulates ecdysteroid production in adult worker honey bees, ecdysteroids were measured in hemolymph and other tissues of individual adult worker honey bees reared with or without QMP in cages and field colonies. Ecdysteroid titers were higher in caged workers exposed to QMP continuously from the first day of adult life than in workers reared without QMP. Statistical cluster analysis suggested the possibility that a subgroup of workers (“responders”) is more sensitive to QMP in this regard than other workers. In 12-day-old workers, ecdysteroid titers in workers reared in queenright (QR) colonies were similar to those observed in cages with QMP, but lower than those in queenless (QL) colonies. Differences in number of ovarioles or degree of ovarian activation did not correlate with hemolymph ecdysteroids. Previous studies have demonstrated ecdysteroids in hemolymph in very young adult workers and in workers in QL colonies; the present study indicates that production of ecdysteroids occurs in older adult worker honey bees in the absence of morphological signs of ovarian activation, with cage studies revealing a modulatory role for QMP masked in the complex environment of the hive.

In highly social bees, queen mandibular pheromone (QMP) is vital for colony life. Both Apis cerana (Ac) and Apis mellifera (Am) share an evolutionarily conserved set of QMP compounds: (E)-9-oxodec-2-enoic acid (9-ODA), (E)-9-hydroxydec-2-enoic acid (9-HDA), (E)-10-hydroxy-dec-2-enoic acid (10-HDA), 10-hydroxy-decanoic acid (10-HDAA), and methyl p-hydroxybenzoate (HOB) found at similar levels. However, evidence suggests there may be species-specific sensitivity differences to QMP compounds because Ac workers have higher levels of ovarian activation than Am workers. Using electroantennograms, we found species-specific sensitivity differences for a blend of the major QMP compounds and three individual compounds (9-HDA, 10-HDAA, and 10-HDA). As predicted, Am was more sensitive than Ac in all cases (1.3- to 2.7- fold higher responses). There were also species differences in worker retinue attraction to three compounds (9-HDA, HOB, and 10-HDA). In all significantly different cases, Am workers were 4.5- to 6.2-fold more strongly attracted than Ac workers were. Thus, Ac workers responded less strongly to QMP than Am workers, and 9-HDA and 10-HDA consistently elicited stronger antennal and retinue formation responses [corrected].

Queen pheromones, which signal the presence of a fertile queen and induce workers to remain sterile, play a key role in regulating reproductive division of labour in insect societies. In the honeybee, volatiles produced by the queen's mandibular glands have been argued to act as the primary sterility-inducing pheromones. This contrasts with evidence from other groups of social insects, where specific queen-characteristic hydrocarbons present on the cuticle act as conserved queen signals. This led us to hypothesize that honeybee queens might also employ cuticular pheromones to stop workers from reproducing. Here, we support this hypothesis with the results of bioassays with synthetic blends of queen-characteristic alkenes, esters and carboxylic acids. We show that all these compound classes suppress worker ovary development, and that one of the blends of esters that we used was as effective as the queen mandibular pheromone (QMP) mix. Furthermore, we demonstrate that the two main QMP compounds 9-ODA and 9-HDA tested individually were as effective as the blend of all four major QMP compounds, suggesting considerable signal redundancy. Possible adaptive reasons for the observed complexity of the honeybee queen signal mix are discussed. ispartof: Proceedings Of The Royal Society B-Biological Sciences vol:286 issue:1905 ispartof: location:England status: published

Here, we examine effects of the steroid hormone, 20-hydroxyecdysone (20-E), on associative olfactory learning in the honeybee, Apis mellifera. 20-E impaired the bees’ ability to associate odors with punishment during aversive conditioning, but did not interfere with their ability to associate odors with a food reward (appetitive learning). The steroid had a significant impact also on the expression of amine-receptor genes in centers of the brain involved in the formation and recall of associative olfactory memories (mushroom bodies). 20-E increased expression of the dopamine receptor gene, Amdop2, and reduced the expression of the putative dopamine/ecdysone receptor gene, Amgpcr19. Interestingly, Amgpcr19 tended to be highly expressed in the brains of foragers that exhibited strong aversive learning, but expressed at lower levels in bees that performed well in appetitive learning assays. In 2-d-old bees, transcript levels of the same gene could be reduced by queen mandibular pheromone, a pheromone that blocks aversive learning in young worker bees. As ecdysteroid levels rise to a peak ∼2 d after adult emergence and then fall to low levels in foragers, we examined aversive learning also in young worker bees. Aversive learning performance in 2-d-old bees was consistently poor. The results of this study indicate that learning in honeybees can be modulated by ecdysteroids. They highlight, in addition, a potential involvement of the putative dopamine/ecdysone receptor, AmGPCR19, in hormonal regulation of associative olfactory learning in the honeybee.

A key feature of eusocial insects is their reproductive division of labour. The queen signals her fecundity to her potentially reproductive daughters via a pheromone, which renders them sterile. In contrast, solitary insects lack division in reproductive labour and there is no such social signalling or need for ovary-regulating pheromones. Nonetheless, females from both non-social and eusocial lineages are expected to regulate their ovaries to maximize inclusive lifetime reproductive success. It is not known, however, whether the underlying networks that regulate ovary activation are homologous between non-social and eusocial taxa, especially when these taxa are phylogenetically distant. In this study, we provide evidence that solitary fruit flies may share a conserved ovary-regulating pathway witha eusocial honeybee,Apis melliferaL.(Hymenoptera: Apidae).Specifically,wedemonstrate that honey bee queen mandibular pheromone (QMP) inhibits fly ovaries in much the same way as it suppresses worker ovaries. Drosophila melanogasterMeigen (Diptera: Drosophilidae) exposed to sufficientdosesofQMPshowedareductioninovarysize,producedfewereggs,andgeneratedfewerviable offspring, relative to unexposed controls. Drosophila melanogaster therefore responds to an interspecific social cue to which it would not normally be exposed. Although we cannot strictly rule out an incidental effect, this conspicuous response suggests that these two species may share an underlying mechanism for ovary regulation. Why a non-social species of fly responds to a highly social bee’s pheromone is not clear, but one possibility is that solitary and social insects share pathways associated with female reproduction, as predicted by the ‘groundplan’ hypothesis of social evolution.

If eusociality evolved through modification of pre-social mechanisms for regulating personal reproduction, then even insects like Drosophila may be vulnerable to latent effects of 'queen' pheromone. Here, I test if male fruit flies respond to a eusocial queen bee pheromone. I found that male flies were attracted to queen bee pheromone, and pheromone-treated males raised the intensity of their courting towards conspecific females. These novel observations from Drosophila suggest that male flies have the capacity to respond to queen pheromone in a manner that is comparable to the native response from male (drone) bees. I therefore optimized a nuclear factor of activated T-cell (NFAT) system to label olfactory neurons that are putatively responsive to the pro-reproductive pheromone. The NFAT reporter system implicates three neurons (Or-49b, Or-56a, Or-98a) that, if shown to function similarly in drones, will validate my use of Drosophila to probe otherwise unknown mechanisms of social bee communication.

International audience; Chemical communication is one of the most fascinating areas of social insect science among which honeybee is the most known model. More than 50 pheromonal compounds had been identified in the honeybee, most of them triggering releaser effects to the receivers, and the queen mandibular pheromone had been the first primer pheromone identified in the animal kingdom. This chapter focuse on the latest findings in this topic, particulary the discovery of brood pheromones and the worker inhibitor pheromones regulating behavioral development of the nurse workers. We describe the finding of chemicals produced by the honeybee larvae involved in their recognition by the varroa mite. This work lead to the characterization of a brood pheromone involved in the recognition of the larvae and their needs by the workers and having primer effects on hypopharyngeal gland secretions and ovary development. This blend of chemical compounds also delays the age at first foraging, so that the larvae can manipulate the workers to achieve their needs. One compound of this blend ethyl oleate (EO), had been found to be produced by forager bees to regulate the behavioral development of younger bees.So, the same compound, EO, is produced by different members in the colonies, the larvae and the foragers, to regulate the equilibrium between nurses and foragers, thus optimizing colony development. Potential uses of those pheromonal compounds in beekeeping are discussed.

The presence of the honey bee queen reduces worker ovary activation. When the queen is healthy and fecund, this is interpreted as an adaptive response as workers can gain fitness from helping the queen raise additional offspring, their sisters. However, when the queen is absent, workers activate their ovaries and lay unfertilized eggs that become males. Queen pheromones are recognised as a factor affecting worker ovary activation. Recent work has shown that queen mandibular pheromone composition changes with queen mating condition and workers show different behavioural responses to pheromone extracts from these queens. Here, we tested whether workers reared in colonies with queens of different mating condition varied in level of ovary activation. We also examined the changes in the chemical composition of the queen mandibular glands to determine if the pheromone blend varied among the queens. We found that the workers activated their ovaries when queens were unmated and had lower ovary activation when raised with mated queens, suggesting that workers detect and respond adaptively to queens of differing mating status. Moreover, variation in queen mandibular gland’s chemical composition correlated with the levels of worker ovary activation. Although correlative, this evidence suggests that queen pheromone may act as a signal of queen mating condition for workers, in response to which they alter their level of ovary activation.

We recently identified changes in amine-receptor gene expression in the antennae of the honey bee that correlate with shifts in the behavioural responsiveness of worker bees towards queen mandibular pheromone. Here we examine whether variations in expression of amine-receptor genes are related to age and/or to behavioural state. Colonies with a normal age structure were used to collect bees of different ages, as well as pollen foragers of unknown age. Single- and double-cohort colonies were established also to generate nurses and pollen foragers of the same age. Amdop1 was the only gene examined that showed no significant change in expression levels across the age groups tested. However, expression of this gene was significantly higher in 6-day-old nurses than in pollen foragers of the same age. Levels of expression of Amdop2 were very variable, particularly during the first week of adult life, and showed no correlation with nursing or foraging behaviour. Amdop3 and Amtyr1 expression levels changed dramatically with age. Interestingly, Amtyr1 expression was significantly higher in 15-day-old pollen foragers than in same-age nurses, whereas the opposite was true for Amoa1. While Amoa1 expression in the antennae was lower in 6- and 15-day-old pollen foragers than in nurses of the same age, differences in gene expression levels between nurses and pollen foragers could not be detected in 22-day-old bees. Our data show dynamic modulation of gene expression in the antennae of worker bees and suggest a peripheral role for biogenic amines in regulating behavioural plasticity in the honey bee.

Honey bee colonies consist of tens of thousands of workers and a single reproductive queen that produces a pheromone blend which maintains colony organization. Previous studies indicated that the insemination quantity and volume alter queen mandibular pheromone profiles. In our 11-month long field study we show that workers are more attracted to high-volume versus low-volume inseminated queens, however, there were no significant differences between treatments in the number of queen cells built by workers in preparation for supersedure. Workers exposed to low-volume inseminated queens initiated production of queen-like esters in their Dufour's glands, but there were no significant difference in the amount of methyl farnesoate and juvenile hormone in worker hemolymph. Lastly, queen overwintering survival was unexpectedly lower in high-volume inseminated queens. Our results suggest that the queen insemination volume could ultimately affect colony health and productivity.

Several lines of evidence support genetic links between ovary size and division of labor in worker honey bees. However, it is largely unknown how ovaries influence behavior. To address this question, we first performed transcriptional profiling on worker ovaries from two genotypes that differ in social behavior and ovary size. Then, we contrasted the differentially expressed ovarian genes with six sets of available brain transcriptomes. Finally, we probed behavior-related candidate gene networks in wild-type ovaries of different sizes. We found differential expression in 2151 ovarian transcripts in these artificially selected honey bee strains, corresponding to approximately 20.3% of the predicted gene set of honey bees. Differences in gene expression overlapped significantly with changes in the brain transcriptomes. Differentially expressed genes were associated with neural signal transmission (tyramine receptor, TYR ) and ecdysteroid signaling; two independently tested nuclear hormone receptors ( HR46 and ftz-f1 ) were also significantly correlated with ovary size in wild-type bees. We suggest that the correspondence between ovary and brain transcriptomes identified here indicates systemic regulatory networks among hormones (juvenile hormone and ecdysteroids), pheromones (queen mandibular pheromone), reproductive organs and nervous tissues in worker honey bees. Furthermore, robust correlations between ovary size and neuraland endocrine response genes are consistent with the hypothesized roles of the ovaries in honey bee behavioral regulation. * Egf : epidermal growth factor E75 : ecdysone-induced protein 75 : FDR false discovery rate ftz-f1 : ftz transcription factor-1 GO : gene ontology GPCR : G protein-coupled receptor HR46 : hormone receptor-like in 46 JH : juvenile hormone JHi-26 : juvenile hormone-inducible protein 26 LAO : large ovary LSD : least significant difference MRJP : major royal jelly protein MRJP1 : major royal jelly protein 1 OR : olfactory receptor PDK1 : phosphoinositide-dependent kinase-1 QMP : queen mandibular pheromone QTL : quantitative trait loci RQ : relative quantification SMO : small ovary TYR : tyramine receptor gene

SUMMARY Worker honey bees undergo a socially regulated, highly stable lipid loss as part of their behavioral maturation. We used large-scale transcriptomic and proteomic experiments, physiological experiments and RNA interference to explore the mechanistic basis for this lipid loss. Lipid loss was associated with thousands of gene expression changes in abdominal fat bodies. Many of these genes were also regulated in young bees by nutrition during an initial period of lipid gain. Surprisingly, in older bees, which is when maximum lipid loss occurs, diet played less of a role in regulating fat body gene expression for components of evolutionarily conserved nutrition-related endocrine systems involving insulin and juvenile hormone signaling. By contrast, fat body gene expression in older bees was regulated more strongly by evolutionarily novel regulatory factors, queen mandibular pheromone (a honey bee-specific social signal) and vitellogenin (a conserved yolk protein that has evolved novel, maturation-related functions in the bee), independent of nutrition. These results demonstrate that conserved molecular pathways can be manipulated to achieve stable lipid loss through evolutionarily novel regulatory processes.

While chemical communication regulates individual behavior in a wide variety of species, these communication systems are most elaborated in insect societies. In these complex systems, pheromones produced by the reproductive individuals (queens) are critical in establishing and maintaining dominant reproductive status over hundreds to thousands of workers. The proximate and ultimate mechanisms by which these intricate pheromone communication systems evolved are largely unknown, though there has been much debate over whether queen pheromones function as a control mechanism or as an honest signal facilitating cooperation. Here, we summarize results from recent studies in honey bees, bumble bees, wasps, ants and termites. We further discuss evolutionary mechanisms by which queen pheromone communication systems may have evolved. Overall, these studies suggest that queen-worker pheromone communication is a multi-component, labile dialog between the castes, rather than a simple, fixed signal-response system. We also discuss future approaches that can shed light on the proximate and ultimate mechanisms that underlie these complex systems by focusing on the development of increasingly sophisticated genomic tools and their potential applications to examine the molecular mechanisms that regulate pheromone production and perception.

International audience; Honey bee colonies are characterised by well-developed reproductive division of labour between the queen and workers. Here, we test whether this reproductive division of labour is evident in both the socially parasitic workers that invade a colony as well as in their offspring generation. We infected six Apis mellifera scutellata host colonies with pseudo-clonal socially parasitic Cape honeybee workers (Apis mellifera capensis). We show that the first generation of socially parasitic workers can monopolize reproduction within host colonies. Of the initially invading parasites, 94.4% became reproductive pseudoqueens with activated ovaries and produced queen-like pheromones. Their offspring, however, had much lower levels of ovary activation (3.1%), yet 89% showed fatty acid synthesis typical of the queen substance (9-oxo-2(E)-decenoic acid) biochemical pathway. However, in these second-generation workers, the last oxidation step from the precursor (9-hydroxy-2(E)-decenoic acid) to the queen substance was interrupted and appears to be required for reproductive dominance in honeybee workers. Our data show that despite the absence of genetic diversity, residual queen mandibular pheromone (QMP) variation is sufficient to establish reproductive dominance hierarchies among parasitic workers. Consequently, QMP produced by a group of workers can maintain reproductive division of labour in queenless honeybee colonies.

International audience; The ability to distinguish between members of a social group and unfamiliar individuals is a critical element of social behaviour. Social insects can differentiate between nestmates and non-nestmates via recognition cues, which in most species are cuticular hydrocarbons. Cuticular hydrocarbon patterns are altered by genotype and environmental conditions, but it is unclear whether colony social conditions can also affect nestmate interactions. Honeybee queens produce pheromones that regulate many aspects of worker behaviour, physiology and colony organization. A five-component blend, queen mandibular pheromone (QMP), produces many of the effects of a live queen. We found that QMP treatment alters how resident bees interact with intruder bees, based on standard nestmate recognition assays. However, QMP does not appear to alter the ability of bees to distinguish between nestmates and non-nestmates, or general aggression levels. Rather, QMP exposure significantly alters cuticular hydrocarbon patterns of worker bees, suggesting that QMP-treated nestmates are no longer recognized as nestmates by untreated bees, and vice versa. Thus, queen pheromone can have significant effects on nestmate recognition and interactions in honeybees, which may be important for colony cohesion. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

It is generally accepted that young worker bees ( Apis mellifera L.) are highly attracted to queen mandibular pheromone (QMP). Our results challenge this widely held view. We have found that unless young workers are exposed to QMP early in adult life, they, like foragers, avoid contact with this pheromone. Our data indicate that responses to QMP are regulated peripherally, at the level of the antennal sensory neurons, and that a window of opportunity exists in which QMP can alter a young bee's response to this critically important pheromone. Exposing young bees to QMP from the time of adult emergence reduces expression in the antennae of the D1-like dopamine receptor gene, Amdop1 . Levels of Amdop3 transcript, on the other hand, and of the octopamine receptor gene Amoa1 , are significantly higher in the antennae of bees strongly attracted to QMP than in bees showing no attraction to this pheromone. A decline in QMP attraction with age is accompanied by a fall in expression in worker antennae of the D2-like dopamine receptor, Am DOP3, a receptor that is selectively activated by QMP. Taken together, our findings suggest that QMP's actions peripherally not only suppress avoidance behavior, but also enhance attraction to QMP, thereby facilitating attendance of the queen.