Social Modulation of Stress Reactivity and Learning in Young Worker Honey Bees

Alarm pheromone and its major component isopentylacetate induce stress-like responses in forager honey bees, impairing their ability to associate odors with a food reward. We investigated whether isopentylacetate exposure decreases appetitive learning also in young worker bees. While isopentylacetate-induced learning deficits were observed in guards and foragers collected from a queen-right colony, learning impairments resulting from exposure to this pheromone could not be detected in bees cleaning cells. As cell cleaners are generally among the youngest workers in the colony, effects of isopentylacetate on learning behavior were examined further using bees of known age. Adult workers were maintained under laboratory conditions from the time of adult emergence. Fifty percent of the bees were exposed to queen mandibular pheromone during this period, whereas control bees were not exposed to this pheromone. Isopentylacetate-induced learning impairments were apparent in young (less than one week old) controls, but not in bees of the same age exposed to queen mandibular pheromone. This study reveals young worker bees can exhibit a stress-like response to alarm pheromone, but isopentylacetate-induced learning impairments in young bees are suppressed by queen mandibular pheromone. While isopentylacetate exposure reduced responses during associative learning (acquisition), it did not affect one-hour memory retrieval.     

Social Insect Pheromones: Their Chemistry and Function

Exocrine secretions of social insects are often characterizedby extraordinarily complex mixtures of natural products. Thus,chemical communication in social insects must be interpretedin terms of signals generated by multicomponent systems, theindividual constituents of which can affect the informationalcontent of the message. Alarm pheromones have been identified chiefly in three subfamiliesof ants and their distribution appears to be chemosystematicallysignificant. Myrmicine genera emphasize 3-alkanones as alarmreleasers, whereas methyl ketones, primarily of terpenoidalorigin, are widely utilized as alarm pheromones in the subfamilyDolichoderinae. Formicine species may employ formic acidas analarm pheromone in addition to the compounds produced in themandibular and Dufour's glands. The mandibular gland pheromonesare chiefly acyclic monoterpene aldehydes (e.g., citronellal)which are relatively low boiling compounds. Higher boiling n-alkanesare produced in the Dufour's glands and may serve as more persistentreleasers of alarm behavior. Alarm pheromones as well as thecaste-specific pheromones of male bees and ants, probably alsoserve as defensive products. In many cases it is likely thatpheromones were originally utilized as defensive compounds andtheir communicative function is a secondary development.     

Stingless bees (<Emphasis Type="Italic">Scaptotrigona pectoralis</Emphasis>) learn foreign trail pheromones and use them to find food

Foragers of several species of stingless bees (Hymenoptera, Apidae and Meliponini) deposit pheromone marks in the vegetation to guide nestmates to new food sources. These pheromones are produced in the labial glands and are nest and species specific. Thus, an important question is how recruited foragers recognize their nestmates’ pheromone in the field. We tested whether naïve workers learn a specific trail pheromone composition while being recruited by nestmates inside the hive in the species Scaptotrigona pectoralis. We installed artificial scent trails branching off from trails deposited by recruiting foragers and registered whether newly recruited bees follow these trails. The artificial trails were baited with trail pheromones of workers collected from foreign S. pectoralis colonies. When the same foreign trail pheromone was presented inside the experimental hives while recruitment took place a significant higher number of bees followed the artificial trails than in experiments without intranidal presentation. Our results demonstrate that recruits of S. pectoralis can learn the composition of specific trail pheromone bouquets inside the nest and subsequently follow this pheromone in the field. We, therefore, suggest that trail pheromone recognition in S. pectoralis is based on a flexible learning process rather than being a genetically fixed behaviour.     

Effects of insemination quantity on honey bee queen physiology

Mating has profound effects on the physiology and behavior of female insects, and in honey bee (Apis mellifera) queens, these changes are permanent. Queens mate with multiple males during a brief period in their early adult lives, and shortly thereafter they initiate egg-laying. Furthermore, the pheromone profiles of mated queens differ from those of virgins, and these pheromones regulate many different aspects of worker behavior and colony organization. While it is clear that mating causes dramatic changes in queens, it is unclear if mating number has more subtle effects on queen physiology or queen-worker interactions; indeed, the effect of multiple matings on female insect physiology has not been broadly addressed. Because it is not possible to control the natural mating behavior of queens, we used instrumental insemination and compared queens inseminated with semen from either a single drone (single-drone inseminated, or SDI) or 10 drones (multi-drone inseminated, or MDI). We used observation hives to monitor attraction of workers to SDI or MDI queens in colonies, and cage studies to monitor the attraction of workers to virgin, SDI, and MDI queen mandibular gland extracts (the main source of queen pheromone). The chemical profiles of the mandibular glands of virgin, SDI, and MDI queens were characterized using GC-MS. Finally, we measured brain expression levels in SDI and MDI queens of a gene associated with phototaxis in worker honey bees (Amfor). Here, we demonstrate for the first time that insemination quantity significantly affects mandibular gland chemical profiles, queen-worker interactions, and brain gene expression. Further research will be necessary to elucidate the mechanistic bases for these effects: insemination volume, sperm and seminal protein quantity, and genetic diversity of the sperm may all be important factors contributing to this profound change in honey bee queen physiology, queen behavior, and social interactions in the colony.     

How honeybee queen attendants become ordinary workers

Honeybee queen attendants disperse queen pheromones to supplement pheromone dispersal by direct queen-worker contacts. With time they lose their dispersal function exponentially due mainly to volatilization of queen pheromones carried on their bodies. The elimination of those airborne pheromones together with the air while ventilating the hive is balanced by pheromone release by the queen. This equilibrium results in a certain level of queen pheromones in the broodnest. The change of the pheromone level (for example, due to loss of the colony of its queen) can serve as a signal to alter the behaviour of the workers and the state of the colony.     

昆虫聚集信息素

昆虫聚集信息素是昆虫重要的信息化学物质之一,对昆虫的聚集行为有重要意义。近三十年来,国外鉴定了多种昆虫聚集信息素,主要成分为一些烃、醇、醛、酮、酯、酸、酸酐、胺以及腈类化合物,但其在有害生物可持续治理中的应用潜能尚未充分利用;昆虫聚集信息素的来源多样,除蛹外,多个虫态均有聚集信息素释放,有些学者甚至把一些寄主释放的挥发物作为聚集信息素的组分;同种昆虫,不同生理状态,其聚集信息素可以完全不同或同一信息化学物质的功能不同;但是,并非所有昆虫的聚集行为均为聚集信息素调节,利他素、性信息素以及报警信息素等其它信息化学物质均能导致一些昆虫的聚集。本文综述了5目17科55种昆虫的聚集信息素。     

Quantitative trait loci influencing honeybee alarm pheromone levels.

Quantitative trait loci (QTL) mapping procedures were used to identify loci that influence the levels of alarm pheromones found in the stinging apparatus of worker honeybees. An F1 queen was produced from a cross between a queen of European origin and a drone descended from an African subspecies. Haploid drones from the hybrid queen were individually backcrossed to European queens to produce 172 colonies. Samples of stings were taken from backcross workers of these colonies. Alarm pheromone levels were determined by gas chromatography. RAPD markers were scored from the haploid drone fathers of these colonies. The multiple-QTL model (MQM) of MapQTL was used to identify QTLs that influence the levels of four alarm pheromone components. Seven independent, potential QTLs were identified with LOD scores greater than two, and one at LOD 1.88. We identified one QTL for n-decyl acetate, three for n-octanol, four for isopentyl acetate, and one for hexyl acetate. One region of linkage group XI shows a strong influence on body size and the levels of three alarm pheromone components. This locus explained 40% of the variance for the amount of n-decyl acetate (LOD 6.57). In general, the QTLs influencing alarm pheromone levels were independent of previously identified loci that influenced the stinging behavior of these colonies. The only exception was a potential locus influencing levels of n-octanol, which was inversely correlated with stinging behavior.     

Elimination of sexual brood in the Argentine antLinepithema humile: queen effect and brood recognition

Mated queens of the antLinepithema humile (Iridomyrmex humilis Mayr) introduced into dequeened colony fragments rearing sexual brood elicited worker aggression resulting in queen larvae being bitten and eliminated. By contrast, male larvae were spared. Regarding queen brood, killing mainly concerned small and medium sized larvae. A large proportion of the large larvae escaped extermination, and prepupae and pupae were spared. These data suggest that workers were able to discriminate sex, caste and age of the brood. That a queen pheromone may be involved was shown by experiments using whole or cut corpses that were either rinsed or not rinsed in pentane. The pheromone eliciting worker aggressive behaviour was shown to act over a short distance, suggesting that it is somewhat volatile. Similarities and differences between this new queen pheromone and other known queen pheromones acting on queen production or worker attraction are discussed as well as the origin of the signals underlying the recognition of the larval classes.     

农业昆虫气味受体功能研究进展

昆虫主要依靠嗅觉系统寻找食物、发现配偶、控制交配、选择产卵地、逃避天敌等,因此嗅觉系统对昆虫的繁殖和生存至关重要。气味受体(odorant receptor, OR)是嗅觉系统中的关键成分之一,可被信息化合物激活引发特定行为产生。随着测序技术的发展,大量的农业昆虫的基因组和转录组被测序,从测序数据中分析获得了它们的OR家族。现在OR功能研究经常用到外源表达系统和CRISPR/Cas9系统。外源表达系统结合记录系统可用于目标OR表达和配体筛选,CRISPR/Cas9系统可从昆虫染色体上敲除目标OR基因,进而利用电生理技术和行为学实验研究其功能。本文系统总结了鳞翅目、直翅目、半翅目、双翅目、膜翅目和鞘翅目6个目30个种的农业昆虫OR的气味分子反应谱及功能,尤其是鳞翅目农业昆虫。农业昆虫的性信息素往往是由雌虫产生的两种或两种以上成分按一定比例组成的混合物,包括在种间生殖隔离中起作用的行为拮抗剂。每个种因此具有多个性信息素的受体,共同感受这些信息素信息,调控种内和种间性行为。有些OR可调谐至主要针对植物挥发物,包括花香气味,在寄主植物选择和雌虫选择产卵地等行为中起作用。聚集信息素受体可特异地被聚集信息素激活,引起聚集行为;报警信息素受体可特异地被报警信息素激活,引起排斥行为。研究农业昆虫OR的气味分子反应谱和功能可为开发在害虫防控中应用的性诱剂、食诱剂、拒食剂、聚集信息素等奠定理论基础。最后我们对未来的主要研究方向提出了以下建议：(1)开发新的外源OR表达系统;(2)研究在雌虫中特异调谐至针对雄虫产生的性信息素的性信息素受体的功能;(3)探讨OR与气味分子之间特异性相互作用的分子机制。     

白蚁信息素研究进展

白蚁是最古老的社会性昆虫, 其社会性的维持需要信息素的相互作用。本文回顾了近年来国内外白蚁信息素研究的最新进展, 内容涉及白蚁踪迹信息素、 性信息素、 告警信息素和促食信息素的功能、 化学成分及产生信息素的外分泌腺。白蚁分泌信息素的腺体主要有背板腺、 腹板腺、 后腹板腺、 额腺和唾腺。绝大多数白蚁信息素是挥发性物质。白蚁在化学通讯上存在节俭策略, 即同一种化合物由不同的白蚁种类的不同外分泌腺分泌, 可具有不同的功能。总结了各类信息素在白蚁物种间、 同一物种的品级间和性别间的异同和作用方式, 强调了白蚁信息素的反应阈值、 最佳浓度、 有效期和物种特异性对其功能的影响。目前对白蚁信息素的研究尚处于起步阶段, 其研究成果对等翅目系统发育研究和白蚁防治具有重要的意义。文章最后展望了白蚁信息素在白蚁防治上的应用前景。     

Suppression of queen rearing in European and Africanized honey beesApis mellifera L. by synthetic queen mandibular gland pheromone

Summary Queen rearing is suppressed in honey bees (Apis mellifera L.) by pheromones, particularly the queen's mandibular gland pheromone. In this study we compared this pheromonally-based inhibition between temperate and tropically-evolved honey bees. Colonies of European and Africanized bees were exposed to synthetic queen mandibular gland pheromone (QMP) for ten days following removal of resident queens, and their queen rearing responses were examined. Queen rearing was suppressed similarly in both European and Africanized honey bees with the addition of synthetic QMP, indicating that QMP acts on workers of both races in a comparable fashion. QMP completely suppressed queen cell production for two days, but by day six, cells containing queen larvae were present in all treated colonies, indicating that other signals play a role in the suppression of queen rearing. In queenless control colonies not treated with QMP, Africanized bees reared 30% fewer queens than Europeans, possibly due to racial differences in response to feedback from developing queens and/or their cells. Queen development rate was faster in Africanized colonies, or they selected older larvae to initiate cells, as only 1 % of queen cells were unsealed after 10 days compared with 12% unsealed cells in European colonies.     

Queen pheromones affecting the production of queen-like secretion in workers

The honeybee queen pheromones promote both worker sterility and worker-like pheromone composition; in their absence workers become fertile and express the queen pheromones. Which of the queen pheromones regulate worker pheromone expression and how, is still elusive. Here we investigated how two queen pheromones, the mandibular and Dufour’s, singly or combined, affect worker ovarian activation and occurrence of queen-like Dufour’s esters. Although queen mandibular pheromone (QMP) alone, or combined with Dufour’s secretion, inhibited to some extent worker reproduction, neither was as effective as the queen. The effect of the queen pheromones on worker pheromone expression was limited to workers with developed ovaries. Here too, QMP and Dufour’s combined had the greatest inhibitory effect. In contrast, treatment with Dufour’s alone resulted in augmentation of esters in the workers. This is another demonstration that a pheromone emitted by one individual affects the rates of its production in another individual. Ester production was tightly coupled to ovarian development. However fertile workers from queenright or QMP-treated colonies had significantly higher amounts of esters in their Dufour’s gland than untreated queenless colonies. The fact that the queen or QMP exert greater suppression on signal production than on ovary activation, suggests disparate regulatory pathways, and presents a challenging ultimate as well as proximate questions.     

A conserved class of queen pheromones? Re-evaluating the evidence in bumblebees (Bombus impatiens)

The regulation of reproductive division of labour is a key component in the evolution of social insects. Chemical signals are important mechanisms to regulate worker reproduction, either as queen-produced pheromones that coercively inhibit worker reproduction or as queen signals that honestly advertise her fecundity. A recent study suggested that a conserved class of hydrocarbons serve as queen pheromones across three independent origins of eusociality. In bumblebees (Bombus terrestris), pentacosane (_C25) was suggested to serve as a queen pheromone. Here, we repeat these studies using a different species of bumblebee (Bombus impatiens) with a more controlled experimental design. Instead of dequeened colonies, we used same-aged, three-worker queenless groups comprising either experienced or naive workers (with/without adult exposure to queen pheromone). We quantified three hydrocarbons (_C23, _C25 and _C27) on the cuticular surfaces of females and tested their effects on the two worker types. Our results indicate differences in responses of naive and experienced workers, genetic effects on worker reproduction, and general effects of hydrocarbons and duration of egg laying on ovary resorption rates. However, we found no evidence to support the theory that a conserved class of hydrocarbons serve as queen pheromones or queen signals in Bombus impatiens.     

Chemical Profiles of Two Pheromone Glands Are Differentially Regulated by Distinct Mating Factors in Honey Bee Queens (Apis mellifera L.)

Pheromones mediate social interactions among individuals in a wide variety of species, from yeast to mammals. In social insects such as honey bees, pheromone communication systems can be extraordinarily complex and serve to coordinate behaviors among many individuals. One of the primary mediators of social behavior and organization in honey bee colonies is queen pheromone, which is produced by multiple glands. The types and quantities of chemicals produced differ significantly between virgin and mated queens, and recent studies have suggested that, in newly mated queens, insemination volume or quantity can affect pheromone production. Here, we examine the long-term impact of different factors involved during queen insemination on the chemical composition of the mandibular and Dufour''s glands, two of the major sources of queen pheromone. Our results demonstrate that carbon dioxide (an anesthetic used in instrumental insemination), physical manipulation of genital tract (presumably mimicking the act of copulation), insemination substance (saline vs. semen), and insemination volume (1 vs. 8 µl) all have long-term effects on mandibular gland chemical profiles. In contrast, Dufour''s gland chemical profiles were changed only upon insemination and were not influenced by exposure to carbon dioxide, manipulation, insemination substance or volume. These results suggest that the chemical contents of these two glands are regulated by different neuro-physiological mechanisms. Furthermore, workers responded differently to the different mandibular gland extracts in a choice assay. Although these studies must be validated in naturally mated queens of varying mating quality, our results suggest that while the chemical composition of Dufour''s gland is associated with mating status, that of the mandibular glands is associated with both mating status and insemination success. Thus, the queen appears to be signaling both status and reproductive quality to the workers, which may impact worker behavior and physiology as well as social organization and productivity of the colony.     

cGMP modulates responses to queen mandibular pheromone in worker honey bees

Responses to social cues, such as pheromones, can be modified by genotype, physiology, or environmental context. Honey bee queens produce a pheromone (queen mandibular pheromone; QMP) which regulates aspects of worker bee behavior and physiology. Forager bees are less responsive to QMP than young bees engaged in brood care, suggesting that physiological changes associated with behavioral maturation modulate response to this pheromone. Since 3′,5′-cyclic guanosine monophosphate (cGMP) is a major regulator of behavioral maturation in workers, we examined its role in modulating worker responses to QMP. Treatment with a cGMP analog resulted in significant reductions in both behavioral and physiological responses to QMP in young caged workers. Treatment significantly reduced attraction to QMP and inhibited the QMP-mediated increase in vitellogenin RNA levels in the fat bodies of worker bees. Genome-wide analysis of brain gene expression patterns demonstrated that cGMP has a larger effect on expression levels than QMP, and that QMP has specific effects in the presence of cGMP, suggesting that some responses to QMP may be dependent on an individual bees’ physiological state. Our data suggest that cGMP-mediated processes play a role in modulating responses to QMP in honey bees at the behavioral, physiological, and molecular levels.     

Anarchistic queen honey bees have normal queen mandibular pheromones

Summary. Anarchistic honey bees are a line developed by recurrent selection in which workers frequently lay eggs. In unselected colonies, workers refrain from reproduction in response to pheromonal signals that indicate the presence of brood and a queen. We show that queen type (anarchistic or wild type) has no effect on rates of ovary activation of anarchistic or wild type workers. In addition, we show that an important component of the queens signalling system, the queen mandibular gland pheromone, is similar in wild type and anarchistic queens. Anarchistic larvae do not inhibit worker ovary development to the same degree as wild type larvae, however all colonies in this experiment contained only wild type larvae. Anarchistic workers had greater rates of ovary activation than wild type workers in colonies headed by either queen type. We therefore conclude that there must be differences in the transmission or reception of queen pheromones, or worker sensitivity to these compounds. These results clearly demonstrate that anarchy is a complex syndrome, not simply the result of reduced pheromone production by anarchist queens and larvae.Received 23 December 2003; revised 14 May 2004; accepted 1 June 2004.     

Seasonal variation in the titers and biosynthesis of the primer pheromone ethyl oleate in honey bees

Honey bees allocate tasks along reproductive and non-reproductive lines: the queen mates and lays eggs, whereas the workers nurse the brood and forage for food. Among workers, tasks are distributed according to age: young workers nurse and old workers fly out and forage. This task distribution in the colony is further regulated by an increase in juvenile hormone III as workers age and by pheromones. One such compound is ethyl oleate (EO), a primer pheromone that delays the onset of foraging in young workers. EO is produced by foragers when they are exposed to ethanol (from fermented nectar) while gathering food. EO is perceived by younger bees via olfaction. We describe here the seasonal variation of EO production and the effects of Methoprene, a juvenile hormone analog. We found that honey bee workers biosynthesize more EO during the growing season than during the fall and winter months, reaching peak levels at late spring or summer. When caged workers were fed with syrup+d(6)-ethanol, labeled EO accumulated in the honey crop and large amounts exuded to the exoskeleton. Exuded levels were high for several hours after exposure to ethanol. Treatment with Methoprene increased the production of EO in worker bees, by speeding up its movement from biosynthetic sites to the exoskeleton, where EO evaporates. Crop fluid from bees collected monthly during the growing season showed a modest seasonal variation of in vitro EO biosynthetic activity that correlated with the dry and sunny periods during which bees could forage.     

A single sex pheromone receptor determines chemical response specificity of sexual behavior in the silkmoth Bombyx mori

In insects and other animals, intraspecific communication between individuals of the opposite sex is mediated in part by chemical signals called sex pheromones. In most moth species, male moths rely heavily on species-specific sex pheromones emitted by female moths to identify and orient towards an appropriate mating partner among a large number of sympatric insect species. The silkmoth, Bombyx mori, utilizes the simplest possible pheromone system, in which a single pheromone component, (E, Z)-10,12-hexadecadienol (bombykol), is sufficient to elicit full sexual behavior. We have previously shown that the sex pheromone receptor BmOR1 mediates specific detection of bombykol in the antennae of male silkmoths. However, it is unclear whether the sex pheromone receptor is the minimally sufficient determination factor that triggers initiation of orientation behavior towards a potential mate. Using transgenic silkmoths expressing the sex pheromone receptor PxOR1 of the diamondback moth Plutella xylostella in BmOR1-expressing neurons, we show that the selectivity of the sex pheromone receptor determines the chemical response specificity of sexual behavior in the silkmoth. Bombykol receptor neurons expressing PxOR1 responded to its specific ligand, (Z)-11-hexadecenal (Z11-16:Ald), in a dose-dependent manner. Male moths expressing PxOR1 exhibited typical pheromone orientation behavior and copulation attempts in response to Z11-16:Ald and to females of P. xylostella. Transformation of the bombykol receptor neurons had no effect on their projections in the antennal lobe. These results indicate that activation of bombykol receptor neurons alone is sufficient to trigger full sexual behavior. Thus, a single gene defines behavioral selectivity in sex pheromone communication in the silkmoth. Our findings show that a single molecular determinant can not only function as a modulator of behavior but also as an all-or-nothing initiator of a complex species-specific behavioral sequence.     

Wild genius - domestic fool? Spatial learning abilities of wild and domestic guinea pigs

Background

In social insects, the queen is essential to the functioning and homeostasis of the colony. This influence has been demonstrated to be mediated through pheromone communication. However, the only social insect for which any queen pheromone has been identified is the honey bee (Apis mellifera) with its well-known queen mandibular pheromone (QMP). Although pleiotropic effects on colony regulation are accredited to the QMP, this pheromone does not trigger the full behavioral and physiological response observed in the presence of the queen, suggesting the presence of additional compounds. We tested the hypothesis of a pheromone redundancy in honey bee queens by comparing the influence of queens with and without mandibular glands on worker behavior and physiology.

Results

Demandibulated queens had no detectable (E)-9-oxodec-2-enoic acid (9-ODA), the major compound in QMP, yet they controlled worker behavior (cell construction and queen retinue) and physiology (ovary inhibition) as efficiently as intact queens.

Conclusions

We demonstrated that the queen uses other pheromones as powerful as QMP to control the colony. It follows that queens appear to have multiple active compounds with similar functions in the colony (pheromone redundancy). Our findings support two hypotheses in the biology of social insects: (1) that multiple semiochemicals with synonymous meaning exist in the honey bee, (2) that this extensive semiochemical vocabulary exists because it confers an evolutionary advantage to the colony.