Socially cued anticipatory adjustment of female signalling effort in a moth

Juvenile population density has profound effects on subsequent adult development, morphology and reproductive investment. Yet, little is known about how the juvenile social environment affects adult investment into chemical sexual signalling. Male gumleaf skeletonizer moths, Uraba lugens, facultatively increase investment into antennae (pheromone receiving structures) when reared at low juvenile population densities, but whether there is comparable adjustment by females into pheromone investment is not known. We investigate how juvenile population density influences the ‘calling'' (pheromone-releasing) behaviour of females and the attractiveness of their pheromones. Female U. lugens adjust their calling behaviour in response to socio-sexual cues: adult females reared in high juvenile population densities called earlier and for longer than those from low juvenile densities. Juvenile density also affected female pheromonal attractiveness: Y-maze olfactometer assays revealed that males prefer pheromones produced by females reared at high juvenile densities. This strategic investment in calling behaviour by females, based on juvenile cues that anticipate the future socio-sexual environment, likely reflects a response to avoid mating failure through competition with neighbouring signallers.     

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。     

Does the scent of a potential mate prevent the resorption of oocytes by apoptosis in Nauphoeta cinerea?

Abstract  We expect organisms to have evolved mechanisms to gather and use the information available within their environments, to steer resource investment decisions toward the traits that will give the greatest fitness returns. Pheromones are social signals, a common purpose of which is to act as indicators of mate presence. Consequently, pheromones have the potential to act as signals to increase or maintain reproductive investment over that of competing life-history traits. In the cockroach, Nauphoeta cinerea (Oliver), females pay costs of maintaining investment in reproduction when there are no males, and males produce pheromones that are known to effect female reproductive outcomes. Whether the pheromones have an influence on resource physiology is unknown. We subjected newly eclosed females to either a synthetic blend of male pheromones or control. We dissected females at 7, 12, 17 or 22 days. We measured apoptosis levels and size of all oocytes within the vitellerium, and measured dry fat body mass. Synthetic male pheromone blend did not have an effect on any measure of female reproductive or somatic resource physiology. Although negative results are always problematic, the success of the synthetic pheromone method in the past suggests that females may be insensitive to male pheromones in the pre-oviposition period, and may rely on mating stimulus rather than pheromone as the cue for oocyte maintenance and growth. Previous studies reporting effects of male pheromones on female reproduction suggest that the period of pheromone sensitivity may be between mating and birth.     

Stable eusociality via maternal manipulation when resistance is costless

In many eusocial species, queens use pheromones to influence offspring to express worker phenotypes. Although evidence suggests that queen pheromones are honest signals of the queen's reproductive health, here I show that queen's honest signalling can result from ancestral maternal manipulation. I develop a mathematical model to study the coevolution of maternal manipulation, offspring resistance to manipulation and maternal resource allocation. I assume that (i) maternal manipulation causes offspring to be workers against offspring's interests; (ii) offspring can resist at no direct cost, as is thought to be the case with pheromonal manipulation; and (iii) the mother chooses how much resource to allocate to fertility and maternal care. In the coevolution of these traits, I find that maternal care decreases, thereby increasing the benefit that offspring obtain from help, which in the long run eliminates selection for resistance. Consequently, ancestral maternal manipulation yields stable eusociality despite costless resistance. Additionally, ancestral manipulation in the long run becomes honest signalling that induces offspring to help. These results indicate that both eusociality and its commonly associated queen honest signalling can be likely to originate from ancestral manipulation.     

Natural ligands of hamster aphrodisin

The chemical nature of vertebrate pheromones remains largely to be deciphered. Hamster aphrodisin is a rare instance of mammal proteinaceous sexual pheromone. This protein, found in vaginal secretions, facilitates the mounting behaviour of males via activation of a specialized sensory structure named the vomeronasal organ, which activates the accessory olfactory bulb. Since it might carry small pheromonal ligands due to its lipocalin structure, we analysed organic extracts from natural aphrodisin. We identified five predominant compounds specifically bound onto natural aphrodisin as 1-hexadecanol (44.7%), 1-octadecanol (19.5%), Z-9-octadecen-1-ol (18.2%), E-9-octadecen-1-ol (15.4%) and hexadecanoic acid (2.2%). Interestingly, these compounds are also described as part of insect pheromone blends, disclosing the continuing story of amazing coincidences of chemical communication shared by mammals and insects.     

The lack of chiral specificity in a termite queen pheromone

The queens of many social insects produce pheromones that influence the behaviour and physiology of colony members. Pheromones produced by queens have long been considered as the prime factor inhibiting the differentiation of new reproductive individuals. A volatile pheromone consisting of a blend of n‐butyl‐n‐butyrate and 2‐methyl‐1‐butanol comprises a queen pheromone that inhibits the differentiation of female neotenic reproductives (secondary queens) of a termite Reticulitermes speratus. 2‐Methyl‐1‐butanol is the first chiral molecule to be identified as a primer pheromone in social insects, which presents the intriguing question of whether enantiomeric composition plays a role in caste regulation. In the present study, we report that the (R)‐ and (S)‐enantiomers and the racemic mixture of 2‐methyl‐1‐butanol show significant inhibitory effects on the differentiation of new female neotenics in combination with n‐butyl‐n‐butyrate, whereas no significant difference in inhibitory activity is observed among them. These results suggests that termites recognize 2‐methyl‐1‐butanol as a queen signal but they do not distinguish between the stereostructures of the enantiomers.     

Evolutionarily stable communication between kin: a general model

At present, the most general evolutionary theory of honest communication is Grafen''s model of Zahavi''s ''handicap'' signalling system, in which honesty of signals about the signaller''s quality (e.g. mate suitability or fighting ability) is maintained by the differentially high cost of signals to signallers having lower quality. The latter model is here further generalized to include any communication between signallers and receivers that are genetically related (e.g. parents and begging offspring, cooperative or competing siblings). Signalling systems involving relatives are shown to be evolutionarily stable, despite a potential pay-off for false signalling, if the Zahavian assumption of differential signal costs holds and there are diminishing reproductive returns to the signaller as the receiver''s assessed value of its attribute increases, or if, regardless of whether the Zahavian assumption holds, signallers with high values of the attribute benefit more from a given receiver assessment than signallers with low values (e.g. begging chicks that are hungrier benefit more from being fed). In stable systems of signalling among kin, it is also shown to be generally true that (i) levels of signalling and thus observed signal costs will decline as relatedness increases or as the receiver''s reproductive penalty for erroneous assessment increases, and (ii) receivers will consistently, altruistically overestimate the true value of the signalled attribute.     

Induction of meiotic disturbances in spermatocytes I by pheromones as an inhibiting mechanism of male reproductive function in house mice

The influence of pheromons on reproduction and other important physiological characteristics has been reported for many mammalian species. However, mechanisms of this action at the level of target cells still remain unclear. A study was made of the influence of non-identified pheromones from adult males and a female pheromone 2,5-dimethylpyrazine on germ cells of CBA inbred strain mice. Cytogenetic analysis shows a significant increase in such meiotic disturbances as multivalent associations and autsomal univalents 24 h after exposure to pheromonal cues. Results of in situ hybridization show that the level of c-fos and c-jun expression is significantly higher 3.5 h after exposure to pheromones of adult males. It is likely that destabilization of chromosomal apparatus in dividing meiotic cells forms the basis of some reproductive effects of murine pheromones. Possible mechanisms of pheromone influence on reproduction are discussed.     

Changes in juvenile hormone biosynthetic rate and whole body content in maturing virgin queens of Solenopsis invicta

Studies were conducted on the physiological and hormonal changes following the release of alates from developmentally suppressive pheromones produced by mature queens of the fire ant Solenopsis invicta Buren. Winged virgin queens were removed from the pheromonal signal and placed in colony fragments. The time for dealation, degree of ovarian development, and biosynthesis rate and whole body content of juvenile hormone (JH) were measured. The production rate and content of JH were highly correlated. Dealation and the initiation of oviposition corresponded to peak production of JH. JH production rose sharply following separation from the natal nest, peaking after 3 days. After 8 days of isolation, JH production gradually subsided to levels similar to that found in pre-release queens, but began to increase again after 12 days. Mature queens had highly elevated levels of JH relative to recently dealate females, probably reflecting the increased reproductive capability of these older females. The results support the hypothesis that the pheromone released by functional queens inhibits reproduction in virgin alates by suppressing corpora allata activity and the production of JH.     

The receptor channel formed by ppk25, ppk29 and ppk23 can sense the Drosophila female pheromone 7,11‐heptacosadiene

In Drosophila, pheromones play a crucial role in regulating courtship behaviors. In males, female aphrodisiac pheromones promote male‐female courtship, and male antiaphrodisiac pheromones inhibit male‐male courtship. Previous studies have reported that receptor proteins belonging to the pickpocket (ppk) family, ionotropic receptor family and gustatory receptor family are required for pheromone detection and normal courtship. However, none of them has been shown to be sufficient for sensing pheromones after ectopic expression in originally unresponsive cells. “M” cells are activated by male antiaphrodisiac pheromones but not female aphrodisiac pheromones, and the activated cells inhibit male‐male courtship. In our study, male flies with ectopic expression of ppk25, ppk29 and ppk23 in “M” cells showed decreased male‐female courtship. Using an in vivo calcium imaging approach, we found that the “M” cells expressing these three ppks were significantly activated by the female aphrodisiac pheromone 7,11‐heptacosadiene (7,11‐HD). Our results indicate that a sodium channel consisting, at minimum, of ppk25, ppk29 and ppk23, can sense 7,11‐HD, most likely as a receptor. Our findings may help us gain insights into the molecular mechanisms of pheromonal functions.     

Male-male pheromone signalling in a lekking Drosophila

Interest in sex pheromones has mainly been focused on mate finding, while relatively little attention has been given to the role of sex pheromones in mate choice and almost none to competition over mates. Here, we study male response to male pheromones in the lekking Drosophila grimshawi, where males deposit long-lasting pheromone streaks that attract males and females to the leks and influence mate assessment. We used two stocks of flies and both stocks adjusted their pheromone depositing behaviour in response to experimental manipulation, strongly indicating male ability to distinguish between competitors from qualitative differences in pheromone streaks alone. This is the first example of an insect distinguishing between individual odour signatures. Pheromone signalling influenced competition over mates, as males adjusted their investment in pheromone deposition in response to foreign pheromone streaks. Both sexes adapt their behaviour according to information from olfactory cues in D. grimshawi, but the relative benefits from male-female, as compared to male-male signalling, remain unknown. It seems likely that the pheromone signalling system originally evolved for attracting females to leks. The transition to a signalling system for conveying information about individuals may well, however, at least in part have been driven by benefits from male-male signalling.     

Olfactory stress and modification of phagocytosis in peripheral blood cells of adult male mice]

Data on pheromonal influence on phagocytic activity of leukocytes in peripheral blood of adult randombred and CBA male mice have been obtained. The identified mouse pheromone 2,5-dimethylpyrazine was used, which induces some physiological effects associated with reproduction in both mouse males and females. Significant differences in spontaneous level of phagocytosis were between inbred CBA and randombred animals: the frequency of phagocytic cells was lower in CBA males by 1.4 times. The substance tested here induces phagocytosis in randombred (by 1.7 times) males. A low dose of 2,5-dimethylpyrazine (similar to the natural pheromone concentration) induces a higher increase in phagocytic activity by leukocytes. Possible mechanisms of pheromonal action on phagocytosis are discussed with the perspectives of finding highly effective immunomodulators among mammalian pheromones.     

PHEROMONES AND CHEMICAL ECOLOGY OF LOCUSTS

Modern studies of chemical ecology and behaviour of the locusts Schistocerca gregaria and Locusta migratoria in the laboratory need to be more closely coupled with field experiments and observations. The life history relating to oviposition, transformation to gregarious phases, and adult maturation mediated by pheromones is reviewed. The principles of pheromone isolation and identification are discussed. The long-term effects of the gregarization pheromone on the physiology are presented, with discussion of morphological changes, chiasma frequency increases, and synchronization of moulting induced by the pheromone. Isolation of the purported gregarization pheromone, locustol, from faeces is discussed in regard to inconsistent effects. Other more immediate effects of the pheromone on the social (gregarious) behaviour and the isolation of possible pheromone components different from but related to locustol are presented. It is stressed that more rigorous isolation studies should be undertaken to resolve conflicting reports and methodological problems. The possibility of an anti-gregarization pheromone or solitarizing pheromone is discounted. The source and biosynthesis of locustol (or gregarization pheromone) from degradation of lignin by symbiotic bacteria is discussed. Theories of reception of the gregarization pheromone such as inhalation through the spiracles or sensory perception by the antennae are presented. Also an internal mechanism involving cAMP and/or corpora allata may be induced by gregarization pheromone to effect the physiological phase changes. The advantages to an individual of reception of the gregarization pheromone from a group of gregarious and pre-migrating locusts is discussed. Also the possible benefits of gregarious behaviour, phase polymorphism and migration are dealt with. An adult (sexual) maturation pheromone has long-term effects on reducing the period of maturation, and immediate effects on the behavioural vibration response. The epidermal source of the pheromone and glandular cells responsible for the production of the pheromone are discussed. The reception and internal mechanisms of response via the corpora allata are mentioned. The benefits to individuals of synchronized and rapid adult maturation in a gregarious group are considered. An oviposition-stimulating pheromone produced by the male accessory reproductive glands appears to be a proteinaceous substance of large molecular weight. On the other hand, an oviposition-aggregating pheromone volatilizes from epidermal areas of either sex and causes higher oviposition rates in the area of release. The behavioural and ecological aspects of this pheromone are discussed. Several other possible pheromones and semiochemicals are discussed, such as a long-range sex pheromone, sex-recognition pheromone, grass odours and feeding stimulants and deterrents. Several possible control strategies using locust pheromones are considered. The general conclusion is that the chemical isolation of the various pheromones is necessary before further progress can be achieved on the source and biosynthesis of pheromone, reception of pheromone, behavioural effects of pheromone, and control measures.     

Peripheral, central and behavioral responses to the cuticular pheromone bouquet in Drosophila melanogaster males

Pheromonal communication is crucial with regard to mate choice in many animals including insects. Drosophila melanogaster flies produce a pheromonal bouquet with many cuticular hydrocarbons some of which diverge between the sexes and differently affect male courtship behavior. Cuticular pheromones have a relatively high weight and are thought to be -- mostly but not only -- detected by gustatory contact. However, the response of the peripheral and central gustatory systems to these substances remains poorly explored. We measured the effect induced by pheromonal cuticular mixtures on (i) the electrophysiological response of peripheral gustatory receptor neurons, (ii) the calcium variation in brain centers receiving these gustatory inputs and (iii) the behavioral reaction induced in control males and in mutant desat1 males, which show abnormal pheromone production and perception. While male and female pheromones induced inhibitory-like effects on taste receptor neurons, the contact of male pheromones on male fore-tarsi elicits a long-lasting response of higher intensity in the dedicated gustatory brain center. We found that the behavior of control males was more strongly inhibited by male pheromones than by female pheromones, but this difference disappeared in anosmic males. Mutant desat1 males showed an increased sensitivity of their peripheral gustatory neurons to contact pheromones and a behavioral incapacity to discriminate sex pheromones. Together our data indicate that cuticular hydrocarbons induce long-lasting inhibitory effects on the relevant taste pathway which may interact with the olfactory pathway to modulate pheromonal perception.     

蛾类性信息素生物合成途径及其调控

蛾类通过产生和识别物种特异性性信息素来引发后续交配行为,因此它在两性交配行为中至关重要.它们具有不同碳链长度、末端官能团、不同双键位置和构型等化学结构特征,本文详细讨论了不同蛾类性信息素的合成途径以及催化每一步反应的相关酶系,列举了15种夜蛾科不同亚科常见物种的性信息素组分及其比例,总结了产生特定比例性信息素的可能原因,查阅了夜蛾科不同物种已经鉴别的性信息素,并按照不同亚科、不同官能团和碳链长度对其进行分类,归纳了同一物种及其亲缘物种性信息素组分和比例的变异,总结了产生变异的分子机理,讨论了性信息素变异和物种进化的关系.最后以生物合成激活神经肽(PBAN)为主, 介绍了其调控途径和机制.本文旨在以不同的蛾类性信息素合成途径为线索,从共有合成途径出发深入了解其规律和共性,从特异合成途径出发探究物种间的进化和变异,展望未来的研究方向及其应用.     

Effects of Contact and Ingestion Exposure to Formulated CheckMate® LBAM-F and Unformulated LBAM Mating Pheromones on Adult Worker Honeybees,Apis mellifera (Hymenoptera: Apidae)

Acute 7-day toxicity tests evaluating adverse effects from contact and ingestion exposure to light brown apple moth (LBAM) pheromones and time-released microencapsulated LBAM pheromones in CheckMate® LBAM-F (Checkmate) were conducted on newly emerged honeybees (less than 24 h old). Contact studies exposed bees to 1× and 10× the CheckMate label application rate. Ingestion studies exposed bees to CheckMate formulations, and active (pheromone) ingredients (a.i.) at 0.1%, 1.0%, and 10% concentrations by weight in solid food. Bees ingested approximately 39% of their body weight during the tests. Mortality ranged from 2–10% in three of four contact and ingestion exposure trials. Trial 1, which utilized a different feeding design, showed higher mortality in both control and test replicates (9–28%). One-way ANOVA tests indicated no significant difference in mortality between control and treatment replicates in the four trials. Bees were subjected to one-time CheckMate contact exposures of up to 0.49 mg/kg-bee, and average pheromone and formulation ingestion exposures of up to 56 (0.1%), 611 (1.0%), and 6,282 (10%) mg/kg-bee-day. LBAM pheromones and microencapsulated pheromones proved to be non-toxic to honeybees when sprayed with 10× the field application rate, or when ingested in food at concentrations of up to 10% by weight.     

Food collection and response to pheromones in an ant species exposed to electromagnetic radiation

We used the ant species Myrmica sabuleti as a model to study the impact of electromagnetic waves on social insects' response to their pheromones and their food collection. We quantified M. sabuleti workers' response to their trail, area marking and alarm pheromone under normal conditions. Then, we quantified the same responses while under the influence of electromagnetic waves. Under such an influence, ants followed trails for only short distances, no longer arrived at marked areas and no longer orientated themselves to a source of alarm pheromone. Also when exposed to electromagnetic waves, ants became unable to return to their nest and recruit congeners; therefore, the number of ants collecting food increases only slightly and slowly. After 180 h of exposure, their colonies deteriorated. Electromagnetic radiation obviously affects social insects' behavior and physiology.     

Genetic independence of female signal form and male receiver design in the almond moth, Cadra cautella

Efficient signalling requires coordination of signal form and receiver design. To maintain signal function, parallel changes in signaller and receiver traits are required. Genetic correlation and co-evolution among signal and response traits have been proposed to preserve signal function (i.e. coordination) during the evolution of mate recognition systems. Empirical studies have provided support for both mechanisms; however, there is debate regarding the interpretation of some of these studies. Tests for a genetic correlation typically hybridize divergent signalling systems and look at hybrid signal form and receiver design, or impose artificial selection on signal form and look for an indirect response to selection in receiver design. Some of the hybridization studies did not achieve reassortment of genes from the parental types, whereas some of the artificial selection studies incorporated random mating in their designs. As a result of these limitations, the hybridization studies cannot discriminate between genetic correlation and co-evolution with primarily additive genetic effects underlying signal and response traits. Similarly, the artificial selection experiments cannot discriminate between genetic correlation because of linkage disequilibrium and co-evolution. This study examined the mating preferences of male almond moths, Cadra cautella, before and after female moths were artificially selected (using a design incorporating assortative mating) for novel pheromone blend ratios. Our results demonstrate the absence of a genetic correlation between signal and response traits in the almond moth.     

Effects of aggregation pheromone on individual behaviour and food web interactions: a field study on Drosophila

Abstract.  1. The effects of an aggregation pheromone on individual behaviour and food web interactions were investigated in two ecological communities, using Drosophila melanogaster and D. simulans as focal species.
2. Fruit substrates with aggregation pheromone were significantly more attractive to adult D. melanogaster and D. simulans than control fruit substrates, and the response was positively dose dependent. Competing species and natural enemies were also significantly attracted to substrates with the aggregation pheromone of D. melanogaster and D. simulans .
3. Significantly more eggs were deposited on pheromone-treated fruits than on control fruits, and the microdistribution of eggs within fruits was correlated to the microdistribution of the pheromone. The aggregation pheromone induced more females to share the breeding site.
4. The extremely high densities of fruit flies in the large aggregations appeared to reduce the oviposition rate of females. Physical interactions with conspecific and heterospecifics were frequently observed in the aggregations, and often led to patch leaving of the fruit flies.
5. Competition for food among larvae occurred at high densities and parasitism was density dependent. Aggregation pheromones can be directly responsible for these patterns through their effects on the con- and heterospecific behaviour.
6. The combined results show that aggregation pheromones affect a multitude of aspects in the ecology of interacting animals. The importance of incorporating the communication signals in ecological theory of aggregations is discussed.     

Evidence of a Male Sex Pheromone in the Round Goby (Neogobius melanostomus)

The reproductive success of the round goby (Neogobius melanostomus), an invasive fish, may be mediated by the use of pheromones. We hypothesized that reproductive male (RM) round gobies release sex pheromone to which reproductive females (RF) respond. In this study, we compared behavioural and electrophysiological responses of reproductive and non-reproductive female round gobies to conspeci fic males. Results of behavioural experiments in the laboratory showed that RF spent significantly more time near the source of the male odour compared with odours from control water. However, RF did not distinguish between odours from non-reproductive male (non-RM) water and control water. Non-reproductive females (non-RF) were not attracted to odours released from RM or non-RM water. Results of electro-olfactogram (EOG) responses showed that both RF and non-RF discriminated between HPLC fractionated RM and non-RM odours. However, the EOG responses of RF were about eight-fold higher than non-RF exposed to RM odours. These findings confirm that RM round gobies release a pheromone signal that attracts RF. The results of this research may be useful in developing control strategy using natural pheromones to disrupt the reproductive behaviour of the invasive round goby and to curtail its effects on native species. An erratum to this article is available at .