Aging modulates cuticular hydrocarbons and sexual attractiveness in Drosophila melanogaster

Cuticular composition: An alternative taxonomic approach to differentiate between Argas arboreus and Argas persicus ticks (Acari: Argasidae)

Argas arboreus and A. persicus are blood sucking ectoparasites on domestic birds in Egypt. They cause anemia in birds, in addition to transmitting a variety of pathogens that leads to economical loss in the poultry industry. It is difficult for non-taxonomists to differentiate between these species because of minor morphological characters. Therefore, it is very important to identify tick species for developing a suitable strategy to reduce risks to poultry wealth. This study characterized the female cuticular hydrocarbons of two Argas species using gas chromatography-mass spectrometry. Sixty different hydrocarbons were exclusively identified in A. arboureus, whereas only 51 in A. persicus. Some of the hydrocarbon compounds were stage-specific ones that differentiate between two species. Others shared between all feeding stages of both species that improved they are closely related ones. Genetic variability recorded its maximum value between unfed stages of the two species, and similarity reached only 25 %. The present study provides the first chemotaxonomic data to differentiate between two closely related Argas species according to their cuticular hydrocarbons. Therefore, hydrocarbon composition seems to be a promising tool available as a taxonomic character, in addition improved that feeding stage was the susceptible one to be controlled.

Unlocking the Secrets of Insects: The Role of Mass Spectrometry to Understand the Life of Insects

Chemical signaling is crucial during the insect lifespan, significantly affecting their survival, reproduction, and ecological interactions. Unfortunately, most chemical signals insects use are impossible for humans to perceive directly. Hence, mass spectrometry has become a vital tool by offering vital insight into the underlying chemical and biochemical processes in various variety of insect activities, such as communication, mate recognition, mating behavior, and adaptation (defense/attack mechanisms), among others. Here, we review different mass spectrometry-based strategies used to gain a deeper understanding of the chemicals involved in shaping the complex behaviors among insects and mass spectrometry-based research in insects that have direct impact in global economic activities.

Complexity of Chemical Emissions Increases Concurrently with Sexual Maturity in Heliconius Butterflies

Pheromone communication is widespread among animals. Since it is often involved in mate choice, pheromone production is often tightly controlled. Although male sex pheromones (MSPs) and anti-aphrodisiacs have been studied in some Heliconius butterfly species, little is known about the factors affecting their production and release in these long-lived butterflies. Here, we investigate the effect of post-eclosion age on chemical blends from pheromone-emitting tissues in Heliconius atthis and Heliconius charithonia, exhibiting respectively free-mating and pupal-mating strategies that are hypothesised to differently affect the timing of their pheromone emissions. We focus on two different tissues: the wing androconia, responsible for MSPs used in courtship, and the genital tip, the production site for anti-aphrodisiac pheromones that affect post-mating behaviour. Gas chromatography-mass spectrometric analysis of tissue extracts from virgin males and females of both species from day 0 to 8 post-eclosion demonstrates the following. Some ubiquitous fatty acid precursors are already detectable at day 0. The complexity of the chemical blends increases with age regardless of tissue or sex. No obvious difference in the time course of blend production was evident between the two species, but female tissues in H. charithonia were more affected by age than in H. atthis. We suggest that compounds unique to male androconia and genitals and whose amount increases with age are potential candidates for future investigation into their roles as pheromones. While this analysis revealed some of the complexity in Heliconius chemical ecology, the effects of other factors, such as the time of day, remain unknown.

Behavioural consequences of intraspecific variability in a mate recognition signal

Mate recognition is paramount for sexually reproducing animals, and many insects rely on cuticular hydrocarbons (CHCs) for close-range sexual communication. To ensure reliable mate recognition, intraspecific sex pheromone variability should be low. However, CHCs can be influenced by several factors, with the resulting variability potentially impacting sexual communication. While intraspecific CHC variability is a common phenomenon, the consequences thereof for mate recognition remain largely unknown. We investigated the effect of CHC variability on male responses in a parasitoid wasp showing a clear-cut within-population CHC polymorphism (three distinct female chemotypes, one thereof similar to male profiles). Males clearly discriminated between female and male CHCs, but not between female chemotypes in no-choice assays. When given a choice, a preference hierarchy emerged. Interestingly, the most attractive chemotype was the one most similar to male profiles. Mixtures of female CHCs were as attractive as chemotype-pure ones, while a female-male mixture negatively impacted male responses, indicating assessment of the entire, complex CHC profile composition. Our study reveals that the evaluation of CHC profiles can be strict towards 'undesirable' features, but simultaneously tolerant enough to cover a range of variants. This reconciles reliable mate recognition with naturally occurring variability.

Learning from fights: Males' social dominance status impact reproductive success in Drosophila melanogaster

In animals, the access to vital resources often relies on individuals' behavioural personality, strength, motivation, past experiences and dominance status. Dominant individuals would be more territorial, providing them with a better access to food resources and mate. The so-called winner and loser effects induce individuals' behavioural changes after experiencing a victory or a defeat, and lead to an individual persistent state influencing the outcome of subsequent fights. However, whether and how development of winner and loser effects affect individuals' fitness is controversial. The aim of this study is to evaluate how individuals' fitness can be influenced by previous fighting experience in Drosophila melanogaster. In this study, we assess various behavioural performances as indicators for dominant and subordinate fitness. Our results show that subordinates are less territorial than dominants although their locomotor abilities are not affected. We also demonstrate that in a non-competitive context, experiencing a defeat reduces males' motivation to court females but not the reproductive success while in a competitive context, it negatively affects males' reproductive success. However, we found no impact upon either males' ability to distinguish potential mates nor on females' choice of a specific mating partner. Overall, these results indicate that previous defeats reduce reproductive success, a commonly used estimate of individual fitness.

Bacterial and fungal components of the microbiome have distinct roles in Hawaiian drosophila reproduction

The microbiome provides numerous physiological benefits for host animals. The role of bacterial members of microbiomes to host physiology is well-documented. However, much less is known about the contributions and interactions of fungal members, even though fungi are integral components of many microbiomes, including those of humans and insects. Here, we used antibacterial and antifungal drugs to manipulate the gut microbiome of a Hawaiian picture-wing Drosophila species, Drosophila grimshawi, and identified distinct effects for each treatment on microbiome community stability, reproduction, and lipid metabolism. Female oogenesis, fecundity, and mating drive were significantly diminished with antifungal treatment. In contrast, male fecundity was affected by antibacterial but not antifungal treatment. For males and females, simultaneous treatment with both antibacterial and antifungal drugs resulted in severely reduced fecundity and changes in fatty acid levels and composition. Microbial transplants using frass harvested from control flies partially restored microbiome composition and female fecundity. Overall, our results reveal that antibacterial and antifungal treatments have distinct effects on host fecundity, mating behavior, and lipid metabolism, and that interkingdom interactions contribute to microbial community stability and reproduction.

The neuropeptide drosulfakinin enhances choosiness and protects males from the aging effects of social perception

The motivation to reproduce is a potent natural drive, and the social behaviors that induce it can severely impact animal health and lifespan. Indeed, in Drosophila males, accelerated aging associated with reproduction arises not from the physical act of courtship or copulation but instead from the motivational drive to court and mate. To better understand the mechanisms underlying social effects on aging, we studied male choosiness for mates. We found that increased activity of insulin-producing cells (IPCs) of the fly brain potentiated choosiness without consistently affecting courtship activity. Surprisingly, this effect was not caused by insulins themselves, but instead by drosulfakinin (DSK), another neuropeptide produced in a subset of the IPCs, acting through one of the two DSK receptors, CCKLR-17D1. Activation of Dsk+ IPC neurons also decreased food consumption, while activation of Dsk+ neurons outside of IPCs affected neither choosiness nor feeding, suggesting an overlap between Dsk+neurons modulating choosiness and those influencing satiety. Broader activation of Dsk+ neurons (both within and outside of the IPCs) was required to rescue the detrimental effect of female pheromone exposure on male lifespan, as was the function of both DSK receptors. The same broad set of Dsk+ neurons was found to reinforce normally aversive feeding interactions, but only after exposure to female pheromones, suggesting that perception of the opposite sex gates rewarding properties of these neurons. We speculate that broad Dsk+ neuron activation is associated with states of satiety and social experience, which under stressful conditions is rewarding and beneficial for lifespan.

The Cuticular Hydrocarbons of Dasineura Oleae Show Differences Between Sex, Adult Age and Mating Status

In insects, cuticular lipids prevent water loss and act as semiochemicals. Because of their ecological function, the profile change across the insects' sex and development offers insight into insect biology and possible tools for pest management. Here, the first work on cecidomyiid cuticular extracts is proposed considering Dasineura oleae (Diptera: Cecidomyiidae) males and females at different adult ages (0-12 h, 12-24 h, 24-36 h) and distinct sexual conditions (virgin and mated). A set of 49 compounds were recorded (12 alkanes, 1 monomethyl alkane, 11 fatty acids, 4 esters, 1 aldehyde, 1 allylbenzene, 1 amine, 1 flavonoid, 1 ketone, 1 phenol, 1 steradiene, 1 sterol, 1 terpene, 1 triterpene and 11 unknown compounds), and 18 of them showed significant differences between groups. Among alkanes, hexacosane (nC26) exhibited a decreasing trend from the youngest to the oldest females, while pentacosane (nC25) and nonacosane (nC29) showed a decreasing trend from 0 to 12 h to 12-24 h virgin females. In addition, nonadecane (nC19) was significantly more abundant in the youngest males compared to older males and females. The alkanes nC25, nC26 and nC29 have been reported to be age-related also in other dipterans, while nC19 has been described as gender-specific chemical cue for platygastrid parasitoids. Further behavioural trials and analyses are required to assign the specific ecological roles to the characterized compounds. Our results may contribute to develop new low-impact control strategies relying on the manipulation of D. oleae's chemical communication (e.g. disruption of mating or species recognition). HIGHLIGHTS: • Cuticular hydrocarbons are often involved in dipteran intraspecific communication. • We explored the cuticular profile of D. oleae at different age, sex, mating condition. • Five alkanes and one mono-methyl alkane showed differences among groups. • Linoleic acid is the most abundant compound in virgins, absent in mated insects. • Eleven compounds disappear in mated insects, but were present in all virgins.

Bacterial and fungal components of the gut microbiome have distinct, sex-specific roles in Hawaiian Drosophila reproduction

Gut microbiomes provide numerous physiological benefits for host animals. The role of bacterial members of microbiomes in host physiology is well-documented. However, much less is known about the contributions and interactions of fungal members of the microbiome even though fungi are significant components of many microbiomes, including those of humans and insects. Here, we used antibacterial and antifungal drugs to manipulate the gut microbiome of a Hawaiian picture-wing Drosophila species, D. grimshawi, and identified distinct, sex-specific roles for the bacteria and fungi in microbiome community stability and reproduction. Female oogenesis, fecundity and mating drive were significantly diminished when fungal communities were suppressed. By contrast, male fecundity was more strongly affected by bacterial but not fungal populations. For males and females, suppression of both bacteria and fungi severely reduced fecundity and altered fatty acid levels and composition, implicating the importance of interkingdom interactions on reproduction and lipid metabolism. Overall, our results reveal that bacteria and fungi have distinct, sexually-dimorphic effects on host physiology and interkingdom dynamics in the gut help to maintain microbiome community stability and enhance reproduction.

Endocrine Regulation of Lifespan in Insect Diapause

Diapause is a physiological adaptation to conditions that are unfavorable for growth or reproduction. During diapause, animals become long-lived, stress-resistant, developmentally static, and non-reproductive, in the case of diapausing adults. Diapause has been observed at all developmental stages in both vertebrates and invertebrates. In adults, diapause traits weaken into adaptations such as hibernation, estivation, dormancy, or torpor, which represent evolutionarily diverse versions of the traditional diapause traits. These traits are regulated through modifications of the endocrine program guiding development. In insects, this typically includes changes in molting hormones, as well as metabolic signals that limit growth while skewing the organism's energetic demands toward conservation. While much work has been done to characterize these modifications, the interactions between hormones and their downstream consequences are incompletely understood. The current state of diapause endocrinology is reviewed here to highlight the relevance of diapause beyond its use as a model to study seasonality and development. Specifically, insect diapause is an emerging model to study mechanisms that determine lifespan. The induction of diapause represents a dramatic change in the normal progression of age. Hormones such as juvenile hormone, 20-hydroxyecdysone, and prothoracicotropic hormone are well-known to modulate this plasticity. The induction of diapause-and by extension, the cessation of normal aging-is coordinated by interactions between these pathways. However, research directly connecting diapause endocrinology to the biology of aging is lacking. This review explores connections between diapause and aging through the perspective of endocrine signaling. The current state of research in both fields suggests appreciable overlap that will greatly contribute to our understanding of diapause and lifespan determination.

Aging-Related Variation of Cuticular Hydrocarbons in Wild Type and Variant Drosophila melanogaster

The cuticle of all insects is covered with hydrocarbons which have multiple functions. Cuticular hydrocarbons (CHCs) basically serve to protect insects against environmental harm and reduce dehydration. In many species, some CHCs also act as pheromones. CHCs have been intensively studied in Drosophila species and more especially in D. melanogaster. In this species, flies produce about 40 CHCs forming a complex sex- and species-specific bouquet. The quantitative and qualitative pattern of the CHC bouquet was characterized during the first days of adult life but remains unexplored in aging flies. Here, we characterized CHCs during the whole-or a large period of-adult life in males and females of several wild type and transgenic lines. Both types of lines included standard and variant CHC profiles. Some of the genotypes tested here showed very dramatic and unexpected aging-related variation based on their early days' profile. This study provides a concrete dataset to better understand the mechanisms underlying the establishment and maintenance of CHCs on the fly cuticle. It could be useful to determine physiological parameters, including age and response to climate variation, in insects collected in the wild.

Endosymbiotic male-killing Spiroplasma affect the physiological and behavioural ecology of Macrocheles-Drosophila interactions

While many arthropod endosymbionts are vertically transmitted, phylogenetic studies reveal repeated introductions of hemolymph-dwelling Spiroplasma into Drosophila. Introductions are often attributed to horizontal transmission via ectoparasite vectors. Here, we test if mites prefer to infect Spiroplasma poulsonii MSRO infected flies, and if MSRO infection impairs fly resistance against secondary mite (Macrocheles subbadius) attack. First we tested if mites prefer MSRO+ or MSRO- flies using pair-wise-choice tests across fly ages. We then tested whether mite preferences are explained by changes in fly physiology, specifically increased metabolic rate (measured as CO₂ production). We hypothesize that this preference is due in part to MSRO+ flies expressing higher metabolic rates. However, our results showed mite preference depended on an interaction between fly age and MSRO status: mites avoided 14-days old MSRO+ flies relative to MSRO- flies (31% infection), but prefered MSRO+ flies (64% infection) among 26-day old flies. Using flow-through respirometry, we found 14 day-old MSRO+ flies had higher CO₂ emissions than MSRO- flies (32% greater), whereas at 26 days old the CO₂ production among MSRO+ flies was 20% lower than MSRO- flies. Thus, mite preferences for high metabolic rate hosts did not explain the infection biases in this study. To assess changes in susceptibility to infection, we measured fly endurance using geotaxis assays. Older flies had lower endurance consistent with fly senescence, and this effect was magnified among MSRO+ flies. Given the biological importance of male-killing Spiroplasma, potential changes in the interactions of hosts and potential vectors could impact the ecology and evolution of host species. Importance Male-killing endosymbionts are transmitted mother to daughter and kill male offspring. Despite these major ecological effects, how these endosymbionts colonize new host species is not always clear. Mites are sometimes hypothesized to transfer these bacteria between hosts/host species. Here we test if 1) if mites prefer to infect flies that harbour Spiroplasma poulisoni MSRO and 2) if flies infected with MSRO are less able to resist mite infection. Our results show that flies infected with MSRO have weaker anti-mite resistance but the mite preference/aversion for MSRO+ flies varied with fly age. Given the fitness and population impacts of male-killing Spiroplasma, changes in fly-mite interactions have implications for the ecology and evolution of these symbioses.

Inheritance of pheromone profiles from aged D. melanogaster

Through aging, D. melanogaster males and females change their social spacing. Flies are initially more social, but reduce sociability as they grow older. This preferred social space is inherited in their progeny. Here, we report that in females, the profiles of cuticular hydrocarbons (CHC), which are known to promote social interaction between individuals, similarly are affected by age. Importantly, for a subset of those CHC, the progeny's CHC levels are comparable to those of their parents, suggesting that parental age influences offspring CHC expression. Those data establish a foundation to identify the relationship between CHC levels and social spacing, and to understand the mechanisms of the inheritance of complex traits.

Social perception of young adults prolongs the lifespan of aged Drosophila

Lifespan is modulated at distinct levels by multiple factors, including genetic backgrounds, the environment, behavior traits, metabolic status, and more interestingly, sensory perceptions. However, the effects of social perception between individuals living in the same space remain less clear. Here, we used the Drosophila model to study the influences of social perception on the lifespan of aged fruit flies. We found the lifespan of aged Drosophila is markedly prolonged after being co-housed with young adults of the same gender. Moreover, the changes of lifespan were affected by several experimental contexts: (1) the ratios of aged and young adults co-housed, (2) the chronological ages of two populations, and (3) the integrity of sensory modalities. Together, we hypothesize the chemical/physical stimuli derived from the interacting young adults are capable of interfering with the physiology and behavior of aged flies, ultimately leading to the alteration of lifespan.

Mating behaviour, mate choice and female resistance in the bean flower thrips (Megalurothrips sjostedti)

Many species of thrips (Thysanoptera) in the family Thripidae form mating aggregations, but the adaptive significance of these aggregations and the extent of male and female mate choice is poorly understood. We studied the mating behaviour of the bean flower thrips Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), which forms male aggregations and occurs across sub-Saharan Africa. We tested whether males choose mates by female age or mating status. No-choice mating bioassays with one male and one female were used to simulate the way males usually encounter only one female at a time in aggregations in the field. Virgin females violently resisted mating attempts by males, but we found no compelling evidence to establish whether this was indiscriminate or was screening suitable males. Younger males (1–2 days old) did not discriminate females by age (1–2 or 7–10 days old), but older males (7–10 days old) avoided mating with older females. Any male choice by female mating status (virgin or mated) was weak or absent. The mating behaviour of M. sjostedti shows broad similarities with that of other thrips species that form aggregations, but also shows some distinct and novel differences, which can help our understanding of the adaptive significance of aggregations.

Common features of aging fail to occur in Drosophila raised without a bacterial microbiome

Lifespan is limited both by intrinsic decline in vigor with age and by accumulation of external insults. There exists a general picture of the deficits of aging, one that is reflected in a pattern of age-correlated changes in gene expression conserved across species. Here, however, by comparing gene expression profiling of Drosophila raised either conventionally, or free of bacteria, we show that ∼70% of these conserved, age-associated changes in gene expression fail to occur in germ-free flies. Among the processes that fail to show time-dependent change under germ-free conditions are two aging features that are observed across phylogeny, declining expression of stress response genes and increasing expression of innate immune genes. These comprise adaptive strategies the organism uses to respond to bacteria, rather than being inevitable components of age-dependent decline. Changes in other processes are independent of the microbiome and can serve as autonomous markers of aging of the individual.

Cuticular hydrocarbons on old museum specimens of the spiny mason wasp, Odynerus spinipes (Hymenoptera: Vespidae: Eumeninae), shed light on the distribution and on regional frequencies of distinct chemotypes

The mason wasp Odynerus spinipes shows an exceptional case of intrasexual cuticular hydrocarbon (CHC) profile dimorphism. Females of this species display one of two CHC profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC–MS the CHC profile of 1042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC profile dimorphism that O. spinipes females exhibit.

Cuticular hydrocarbons for identifying Sarcophagidae (Diptera)

The composition and quantity of insect cuticular hydrocarbons (CHCs) can be species-specific as well as sexually dimorphic within species. CHC analysis has been previously used for identification and ageing purposes for several insect orders including true flies (Diptera). Here, we analysed the CHC chemical profiles of adult males and females of eleven species of flesh flies belonging to the genus Sarcophaga Meigen (Sarcophagidae), namely Sarcophaga africa (Wiedemann), S. agnata Rondani, S. argyrostoma Robineau-Desvoidy, S. carnaria (Linnaeus), S. crassipalpis Macquart, S. melanura Meigen, S. pumila Meigen, S. teretirostris Pandellé, S. subvicina Rohdendorf, S. vagans Meigen and S. variegata (Scopoli). Cuticular hydrocarbons extracted from pinned specimens from the collections of the Natural History Museum, London using a customised extraction technique were analysed using Gas Chromatography-Mass Spectrometry. Time of preservation prior to extraction ranged between a few weeks to over one hundred years. CHC profiles (1) allowed reliable identification of a large majority of specimens, (2) differed between males and females of the same species, (3) reliably associated males and females of the same species, provided sufficient replicates (up to 10) of each sex were analysed, and (4) identified specimens preserved for up to over one hundred years prior to extraction.

Seven Questions on the Chemical Ecology and Neurogenetics of Resource-Mediated Speciation

Adaptation to different environments can result in reproductive isolation between populations and the formation of new species. Food resources are among the most important environmental factors shaping local adaptation. The chemosensory system, the most ubiquitous sensory channel in the animal kingdom, not only detects food resources and their chemical composition, but also mediates sexual communication and reproductive isolation in many taxa. Chemosensory divergence may thus play a crucial role in resource-mediated adaptation and speciation. Understanding how the chemosensory system can facilitate resource-mediated ecological speciation requires integrating mechanistic studies of the chemosensory system with ecological studies, to link the genetics and physiology of chemosensory properties to divergent adaptation. In this review, we use examples of insect research to present seven key questions that can be used to understand how the chemosensory system can facilitate resource-mediated ecological speciation in consumer populations.

Post-eclosion temperature effects on insect cuticular hydrocarbon profiles

The insect cuticle is the interface between internal homeostasis and the often harsh external environment. Cuticular hydrocarbons (CHCs) are key constituents of this hard cuticle and are associated with a variety of functions including stress response and communication. CHC production and deposition on the insect cuticle vary among natural populations and are affected by developmental temperature; however, little is known about CHC plasticity in response to the environment experienced following eclosion, during which time the insect cuticle undergoes several crucial changes. We targeted this crucial to important phase and studied post-eclosion temperature effects on CHC profiles in two natural populations of Drosophila melanogaster. A forty-eight hour post-eclosion exposure to three different temperatures (18, 25, and 30°C) significantly affected CHCs in both ancestral African and more recently derived North American populations of D. melanogaster. A clear shift from shorter to longer CHCs chain length was observed with increasing temperature, and the effects of post-eclosion temperature varied across populations and between sexes. The quantitative differences in CHCs were associated with variation in desiccation tolerance among populations. Surprisingly, we did not detect any significant differences in water loss rate between African and North American populations. Overall, our results demonstrate strong genetic and plasticity effects in CHC profiles in response to environmental temperatures experienced at the adult stage as well as associations with desiccation tolerance, which is crucial in understanding holometabolan responses to stress.

Influence of Age and Mating Status on Pheromone Production in a Powderpost Beetle Lyctus africanus (Coleoptera: Lyctinae)

Simple Summary

Powderpost beetles, such as Lyctus africanus, are a common pest group for dried cured wood. The damage is slow and inconspicuous; thus, the infestation is mostly identified belatedly due to a lack of knowledge of how to locate and monitor it. L. africanus produces a pheromone, a chemical compound to attract other beetles. This pheromone has been determined and suggested as a monitoring tool for L. africanus. Here, we examined the physiological and behavioral parameters that affect pheromone production. We found that food availability may affect pheromone production in adult L. africanus males. In addition, of three components in male L. africanus aggregation pheromones, major compounds 2 (3-pentyl dodecanoate) and 3 (3-pentyl tetradecanoate) may be affected by age, not mating status, while compound 1 (2-propyl dodecanoate) was produced steadily and was affected by mating status. This suggests compounds 2 and 3 might have an important function in aggregation behavior, especially in signaling for mating opportunities. We also were able to clarify the minor effect of compound 1 in the aggregation pheromone of L. africanus, although not its role. The present information will be helpful in understanding the chemical communication of these insects, which may be important for the development of improved pheromone-based management strategies for controlling Lyctus beetles.

Abstract

Powderpost beetles such as Lyctus africanus are a common pest group for dried cured wood, causing significant harm to wood and wood products. We examined the life span and effects of aging and mating status on pheromone production in the powderpost beetle L. africanus (Coleoptera: Lyctinae). Experiments compared starved and unstarved male groups, and chemical analysis was used to determine factors affecting pheromone production. Regarding lifespan, male beetles provided food survived up to 14 weeks, while starved beetles died before the fifth week. Thus, an adult L. africanus male may require food throughout its lifespan, and food availability may affect pheromone production. There was no significant difference in the quantity of two major pheromone compounds, compound 2 (3-pentyl dodecanoate) and 3 (3-pentyl tetradecanoate) between mated and un-mated males. On the other hand, a minor compound, compound 1 (2-propyl dodecanoate) showed increased quantity after mating. The two major compounds were produced in low amounts by young L. africanus beetles, increasing until the fifth week, and beginning to decrease at the ninth week. The minor compound was produced steadily without significant change up to 9 weeks. Our results represent a step forward in the knowledge of the chemical communication of this important pest.

The evolution of sexually dimorphic cuticular hydrocarbons in blowflies (Diptera: Calliphoridae)

Cuticular hydrocarbons (CHCs) are organic compounds found on the cuticles of all insects which can act as close-contact pheromones, while also providing a hydrophobic barrier to water loss. Given their widespread importance in sexual behaviour and survival, CHCs have likely contributed heavily to the adaptation and speciation of insects. Despite this, the patterns and mechanisms of their diversification have been studied in very few taxa. Here, we perform the first study of CHC diversification in blowflies, focussing on wild populations of the ecologically diverse genus Chrysomya. We convert CHC profiles into qualitative and quantitative traits and assess their inter- and intra-specific variation across 10 species. We also construct a global phylogeny of Chrysomya, onto which CHCs were mapped to explore the patterns of their diversification. For the first time, we demonstrate that blowflies express an exceptional diversity of CHCs, which have diversified in a nonphylogenetic and punctuated manner, are species-specific and sexually dimorphic. It is likely that both ecological and sexual selection have shaped these patterns of CHC diversification, and our study now provides a comprehensive framework for testing such hypotheses.

On the use of private versus social information in oviposition site choice decisions by Drosophila melanogaster females

Individuals are faced with decisions throughout their lifetimes, and the choices they make often have important consequences toward their fitness. Being able to discern which available option is best to pursue often incurs sampling costs, which may be largely avoided by copying the behavior and decisions of others. Although social learning and copying behaviors are widespread, much remains unknown about how effective and adaptive copying behavior is, as well as the factors that underlie its expression. Recently, it has been suggested that since female fruit flies (Drosophila melanogaster) appear to rely heavily on public information when selecting oviposition sites, they are a promising model system for researching patch-choice copying, and more generally, the mechanisms that control decision making. Here, we set out to determine how well female distinguish between socially produced cues, and whether females are using “relevant” signals when choosing an oviposition site. We found that females showed a strong preference for ovipositing on media patches that had been previously occupied by ovipositing females of the same species and diet over other female outgroups. However, in a separate assay, we observed that females favored ovipositing on media patches that previously housed virgin males over those exhibiting alternative conspecific signals. Our results confirm that females use cues left behind by other flies when choosing between potential oviposition sites, though their prioritization of these signals raises serious questions as to whether fruit flies are employing copying behavior, or are instead responding to signals that may not be of relevance to oviposition site suitability.

Desiccation resistance is an adaptive life-history trait dependent upon cuticular hydrocarbons, and influenced by mating status and temperature in D. melanogaster

Terrestrial insects are susceptible to desiccation and conserve internal water stores by preventing the loss of water due to transpiration across the cuticle. The epicuticle, a thin waxy layer on the outer surface of the insect cuticle is comprised primarily of a complex blend of cuticular hydrocarbons (CHCs) and is integral to preventing cuticular water loss. How the composition of epicuticular lipids (quantity and quality of the specific hydrocarbons) relates to desiccation resistance, however, has been difficult to determine. Here, we establish a model system to test the capacity of CHCs to protect against desiccation in the vinegar fly, Drosophila melanogaster. Using this system, we demonstrate that the oenocytes and CHCs produced by these cells are critically important for desiccation resistance, as measured by survival under desiccative conditions. Additionally, we show that both mating status and developmental temperature influence desiccation resistance. Prior mating increased desiccation survival through the direct transfer of CHCs between sexual partners, as well as through a female-specific response to a male-derived factor transferred during copulation. Together, our results demonstrate that desiccation resistance is an adaptive life-history trait dependent upon CHCs and influenced by prior social interactions and environmental conditions.

Drosophila Sexual Attractiveness in Older Males Is Mediated by Their Microbiota

Age is well known to be a basis for female preference of males. However, the mechanisms underlying age-based choices are not well understood, with several competing theories and little consensus. The idea that the microbiota can affect host mate choice is gaining traction, and in this study we examine whether the male microbiota influences female preference for older individuals in the fruit fly Drosophila pseudoobscura. We find that an intact microbiota is a key component of attractiveness in older males. However, we found no evidence that this decrease in older male attractiveness was simply due to impaired microbiota generally reducing male quality. Instead, we suggest that the microbiota underlies an honest signal used by females to assess male age, and that impaired microbiota disrupt this signal. This suggests that age-based preferences may break down in environments where the microbiota is impaired, for example when individuals are exposed to naturally occurring antibiotics, extreme temperatures, or in animals reared in laboratories on antibiotic supplemented diet.

Neuronal Mechanisms that Drive Organismal Aging Through the Lens of Perception

Sensory neurons provide organisms with data about the world in which they live, for the purpose of successfully exploiting their environment. The consequences of sensory perception are not simply limited to decision-making behaviors; evidence suggests that sensory perception directly influences physiology and aging, a phenomenon that has been observed in animals across taxa. Therefore, understanding the neural mechanisms by which sensory input influences aging may uncover novel therapeutic targets for aging-related physiologies. In this review, we examine different perceptive experiences that have been most clearly linked to aging or age-related disease: food perception, social perception, time perception, and threat perception. For each, the sensory cues, receptors, and/or pathways that influence aging as well as the individual or groups of neurons involved, if known, are discussed. We conclude with general thoughts about the potential impact of this line of research on human health and aging.

Social behavior and aging: A fly model

The field of behavioral genetics has recently begun to explore the effect of age on social behaviors. Such studies are particularly important, as certain neuropsychiatric disorders with abnormal social interactions, like autism and schizophrenia, have been linked to older parents. Appropriate social interaction can also have a positive impact on longevity, and is associated with successful aging in humans. Currently, there are few genetic models for understanding the effect of aging on social behavior and its potential transgenerational inheritance. The fly is emerging as a powerful model for identifying the basic molecular mechanisms underlying neurological and neuropsychiatric disorders. In this review, we discuss these recent advancements, with a focus on how studies in Drosophila melanogaster have provided insight into the effect of aging on aspects of social behavior, including across generations.

Past and present resource availability affect mating rate but not mate choice in Drosophila melanogaster

The choices of when, where, and with whom to mate represent some of the most important decisions an individual can make to increase their fitness. Several studies have shown that the resources available to an individual during development can dramatically alter their mating rate later in life, and even the choice of mate. However, an individual's surroundings and available resources can change rapidly, and it is not clear how quickly the redistribution of resources towards reproduction can change. To address this important question, we measured mating rate and mate choice among Drosophila melanogaster males that were manipulated in terms of both past resources (control vs. starvation) and the resources available during mate choice (food vs. no food). We found that males given access to ample resources prior to mate choice showed higher mating rates than those that were starved, in agreement with previous studies. However, we also found that this effect can be reversed quickly, as starved males given the opportunity to mate in a high-quality environment mated at frequencies equivalent to their fed counterparts. Although past and present resources affected mating rate, they did not affect mate choice, as males mated with high-quality females at high frequencies regardless of their condition and environment. Our results show that both current condition as well as the promise of future resources can dramatically influence individuals' investment into reproduction and that such mating decisions are extremely plastic and reliant on environmental cues.

Dehydration triggers ecdysone-mediated recognition-protein priming and elevated anti-bacterial immune responses in Drosophila Malpighian tubule renal cells

Background

Drosophila is a powerful model for the study of factors modulating innate immunity. This study examines the effect of water-loss dehydration on innate immune responsiveness in the Drosophila renal system (Malpighian tubules; MTs), and how this leads to elevated host defense and contributes to immunosenescence.

Results

A short period of desiccation-elevated peptidoglycan recognition protein-LC (PGRP-LC) expression in MTs, increased antimicrobial peptide (AMP) gene induction, and protected animals from bacterial infection. We show that desiccation increased ecdysone synthesis in MTs, while inhibition of ecdysone synthesis or ecdysone receptor expression, specifically within MTs, prevented induction of PGRP-LC and reduced protection from bacterial infection. Additionally, aged flies are constitutively water-stressed and have elevated levels of ecdysone and PGRP-LC. Conversely, adults aged at high relative humidity show less water loss and have reduced expression of PGRP-LC and AMPs.

Conclusions

The Drosophila renal system is an important contributor to host defense and can modulate immune responses in an organ autonomous manner, responding to environmental changes such as desiccation. Desiccation primes immune responsiveness by elevating PGRP-LC expression specifically in MTs. In response to desiccation, ecdysone is produced in MTs and acts in a paracrine fashion to increase PGRP-LC expression, immune responsiveness, and improve host defense. This activity of the renal system may contribute to the immunosenescence observed in Drosophila.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0532-5) contains supplementary material, which is available to authorized users.

The role of cuticular hydrocarbons in mate recognition in Drosophila suzukii

Cuticular hydrocarbons (CHCs) play a central role in the chemical communication of many insects. In Drosophila suzukii, an economically important pest insect, very little is known about chemical communication and the possible role of CHCs. In this study, we identified 60 CHCs of Drosophila suzukii and studied their changes in function of age (maturation), sex and interactions with the opposite sex. We demonstrate that age (maturation) is the key factor driving changes in the CHC profiles. We then test the effect on courtship behaviour and mating of six CHCs, five of which were positively associated with maturation and one negatively. The results of these experiments demonstrate that four of the major CHC peaks with a chain length of 23 carbons, namely 9-tricosene (9-C23:1), 7-tricosene (7-C23:1), 5-tricosene (5-C23:1) and tricosane (n-C23), negatively regulated courtship and mating, even though all these compounds were characteristic for sexually mature flies. We then go on to show that this effect on courtship and mating is likely due to the disruption of the natural ratios in which these hydrocarbons occur in Drosophila suzukii. Overall, these results provide key insights into the cuticular hydrocarbon signals that play a role in D. suzukii mate recognition.

Larval Diet Affects Male Pheromone Blend in a Laboratory Strain of the Medfly, Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly (medfly) Ceratitis capitata is a polyphagous pest of fruits and crops with a worldwide distribution. Its ability to use different larval hosts may have multiple effects, including impacts on adult reproductive biology. The male sex pheromone, which plays a key role in attracting both other males to lekking arenas and females for mating, is a mixture of chemical compounds including esters, acids, alkanes and terpenes known to differ between laboratory strains and wild-type populations. The relationship between larval diet and adult pheromone composition remains unexplored. Here, we investigated the effect of larval diet, including laboratory media and fresh fruits, on the composition of the male pheromone mixture. Using Headspace Solid Phase Microextraction we collected the pheromone emitted by males reared as larvae on different substrates and found both qualitative and quantitative differences. A number of alkanes appeared to be typical of the pheromone of males reared on wheat bran-based larval medium, and these may be cuticular hydrocarbons involved in chemical communication. We also detected differences in pheromone composition related to adult male age, suggesting that variations in hormonal levels and/or adult diet could also play a role in determining the chemical profile emitted. Our findings highlight the plasticity of dietary responses of C. capitata, which may be important in determining the interactions of this pest with the environment and with conspecifics. These results also have applied relevance to increase the mating competitiveness of mass-reared C. capitata used in Sterile Insect Technique programs.

Phenotypic Plasticity of Cuticular Hydrocarbon Profiles in Insects

The insect integument is covered by cuticular hydrocarbons (CHCs) which provide protection against environmental stresses, but are also used for communication. Here we review current knowledge on environmental and insect-internal factors which shape phenotypic plasticity of solitary living insects, especially herbivorous ones. We address the dynamics of changes which may occur within minutes, but may also last weeks, depending on the species and conditions. Two different modes of changes are suggested, i.e. stepwise and gradual. A switch between two distinct environments (e.g. host plant switch by phytophagous insects) results in stepwise formation of two distinct adaptive phenotypes, while a gradual environmental change (e.g. temperature gradients) induces a gradual change of numerous adaptive CHC phenotypes. We further discuss the ecological and evolutionary consequences of phenotypic plasticity of insect CHC profiles by addressing the question at which conditions is CHC phenotypic plasticity beneficial. The high plasticity of CHC profiles might be a trade-off for insects using CHCs for communication. We discuss how insects cope with the challenge to produce and "understand" a highly plastic, environmentally dependent CHC pattern that conveys reliable and comprehensible information. Finally, we outline how phenotypic plasticity of CHC profiles may promote speciation in insects that rely on CHCs for mate recognition.

Drosophila as a holistic model for insect pheromone signaling and processing

In recent years, research into the chemical ecology of the vinegar fly, Drosophila melanogaster, has yielded a wealth of information on the neural substrates that detect and process pheromones and control behavior. The studies reveal at the cellular and molecular level how behavioral responses to pheromones are initiated and modulated by social, environmental, and physiological factors. By taking into account both the complexity of the chemical world and the intricacies of the animal's physiological state, the emerging holistic perspective provides insight not only into chemical communication but more generally, how organisms balance internal and external signals when making behavioral decisions.

Sex-Specific Routes To Immune Senescence In Drosophila melanogaster

Animal immune systems change dramatically during the ageing process, often accompanied by major increases in pathogen susceptibility. However, the extent to which senescent elevations in infection mortality are causally driven by deteriorations in canonical systemic immune processes is unclear. We studied Drosophila melanogaster and compared the relative contributions of impaired systemic immune defences and deteriorating barrier defences to increased pathogen susceptibility in aged flies. To assess senescent changes in systemic immune response efficacy we injected one and four-week old flies with the entomopathogenic fungus Beauveria bassiana and studied subsequent mortality; whereas to include the role of barrier defences we infected flies by dusting the cuticle with fungal spores. We show that the processes underlying pathogen defence senescence differ between males and females. Both sexes became more susceptible to infection as they aged. However, we conclude that for males, this was principally due to deterioration in barrier defences, whereas for females systemic immune defence senescence was mainly responsible. We discuss the potential roles of sex-specific selection on the immune system and behavioural variation between males and females in driving these different senescent trends.

Tissue-specific insulin signaling mediates female sexual attractiveness

Individuals choose their mates so as to maximize reproductive success, and one important component of this choice is assessment of traits reflecting mate quality. Little is known about why specific traits are used for mate quality assessment nor about how they reflect it. We have previously shown that global manipulation of insulin signaling, a nutrient-sensing pathway governing investment in survival versus reproduction, affects female sexual attractiveness in the fruit fly, Drosophila melanogaster. Here we demonstrate that these effects on attractiveness derive from insulin signaling in the fat body and ovarian follicle cells, whose signals are integrated by pheromone-producing cells called oenocytes. Functional ovaries were required for global insulin signaling effects on attractiveness, and manipulations of insulin signaling specifically in late follicle cells recapitulated effects of global manipulations. Interestingly, modulation of insulin signaling in the fat body produced opposite effects on attractiveness, suggesting a competitive relationship with the ovary. Furthermore, all investigated tissue-specific insulin signaling manipulations that changed attractiveness also changed fecundity in the corresponding direction, pointing to insulin pathway activity as a reliable link between fecundity and attractiveness cues. The cues themselves, cuticular hydrocarbons, responded distinctly to fat body and follicle cell manipulations, indicating independent readouts of the pathway activity from these two tissues. Thus, here we describe a system in which female attractiveness results from an apparent connection between attractiveness cues and an organismal state of high fecundity, both of which are created by lowered insulin signaling in the fat body and increased insulin signaling in late follicle cells.

Post-mating shift towards longer-chain cuticular hydrocarbons drastically reduces female attractiveness to males in a digger wasp

Females of most aculeate Hymenoptera mate only once and males are therefore under a strong competitive pressure which is expected to favour the evolution of rapid detection of virgin females. In several bee species, the cuticular hydrocarbon (CHC) profile exhibited by virgin females elicits male copulation attempts. However, it is still unknown how widespread this type of sexual communication is within Aculeata. Here, we investigated the use of CHCs as mating cues in the digger wasp Stizus continuus, which belongs to the family (Crabronidae) from within bees arose. In field experiments, unmanipulated, recently emerged virgin female dummies promptly elicit male copulation attempts, whereas 1-4days old mated females dummies were still attractive but to a much lesser extent. In contrast, old (10-15days) mated female dummies did not attract males at all. After hexane-washing, attractiveness almost disappeared but could be achieved by adding CHC extracts from virgin females even on hexane-washed old mated females. Thus, the chemical base of recognition of females as appropriate mating partner by males is coded in their CHC profile. Accordingly, differences in CHC profiles can be detected between sexes, with males having larger amounts of alkenes and exclusive long-chain alkanes, and within females specially according to their mating status. Shortly after mating, almost all of the major hydrocarbons found on the cuticle of females undergo significant changes in their abundance, with a clear shift from short-chain to long-chain linear and methyl-branched alkanes. The timely detection of virgin females by males in S. continuus could be advantageous within the narrow period of female emergence, when male-male competition is strongest.

Sexual selection, sexual isolation and pheromones in Drosophila melanogaster strains after long-term maintaining on different diets

Evolution of reproductive isolation may be a consequence of a variety of signals used in courtship and mate preferences. Pheromones play an important role in both sexual selection and sexual isolation. The abundance of pheromones in Drosophila melanogaster may depend on different environmental factors, including diet. The aim of this study was to ascertain to which degree principal pheromones affect sexual selection in D. melanogaster. We used D. melanogaster strains reared for 14 years on four substrates: standard cornmeal substrate and those containing tomato, banana and carrot. We have previously determined that long-term maintaining of these dietary strains resulted in differences in their cuticular hydrocarbons profile (CHs). In this work, we have tested the level of sexual selection and sexual isolation between aforementioned strains. We found that the high levels of cis-vaccenyl acetate, 7-pentacosene and 7,11-nonacosadiene in the strain reared on a substrate containing carrot affected the individual attractiveness and influenced sexual isolation between flies of this strain and flies reared on a substrate containing banana. Based on these results, long-term different diets, may contribute, to sexual behaviour of D. melanogaster via the effects of principal pheromones.

Mate choice in fruit flies is rational and adaptive

According to rational choice theory, beneficial preferences should lead individuals to sort available options into linear, transitive hierarchies, although the extent to which non-human animals behave rationally is unclear. Here we demonstrate that mate choice in the fruit fly Drosophila melanogaster results in the linear sorting of a set of diverse isogenic female lines, unambiguously demonstrating the hallmark of rational behaviour, transitivity. These rational choices are associated with direct benefits, enabling males to maximize offspring production. Furthermore, we demonstrate that female behaviours and cues act redundantly in mate detection and assessment, as rational mate choice largely persists when visual or chemical sensory modalities are impaired, but not when both are impaired. Transitivity in mate choice demonstrates that the quality of potential mates varies significantly among genotypes, and that males and females behave in such a way as to facilitate adaptive mate choice.

A characteristic of rational behaviour is that it is transitive, such that preferences are ranked in a strict linear order. Here, Arbuthnott and colleagues show that mate choice in the fruit fly, Drosophila melanogaster, is transitive at the population level and that preferred mates produce more offspring.

Neuroligins Nlg2 and Nlg4 Affect Social Behavior in Drosophila melanogaster

The genome of Drosophila melanogaster includes homologs to approximately one-third of the currently known human disease genes. Flies and humans share many biological processes, including the principles of information processing by excitable neurons, synaptic transmission, and the chemical signals involved in intercellular communication. Studies on the molecular and behavioral impact of genetic risk factors of human neuro-developmental disorders [autism spectrum disorders (ASDs), schizophrenia, attention deficit hyperactivity disorders, and Tourette syndrome] increasingly use the well-studied social behavior of D. melanogaster, an organism that is amenable to a large variety of genetic manipulations. Neuroligins (Nlgs) are a family of phylogenetically conserved postsynaptic adhesion molecules present (among others) in nematodes, insects, and mammals. Impaired function of Nlgs (particularly of Nlg 3 and 4) has been associated with ASDs in humans and impaired social and communication behavior in mice. Making use of a set of behavioral and social assays, we, here, analyzed the impact of two Drosophila Nlgs, Dnlg2 and Dnlg4, which are differentially expressed at excitatory and inhibitory central nervous synapses, respectively. Both Nlgs seem to be associated with diurnal activity and social behavior. Even though deficiencies in Dnlg2 and Dnlg4 appeared to have no effects on sensory or motor systems, they differentially impacted on social interactions, suggesting that social behavior is distinctly regulated by these Nlgs.

Steroid Hormone Signaling Is Essential for Pheromone Production and Oenocyte Survival

Many of the lipids found on the cuticles of insects function as pheromones and communicate information about age, sex, and reproductive status. In Drosophila, the composition of the information-rich lipid profile is dynamic and changes over the lifetime of an individual. However, the molecular basis of this change is not well understood. To identify genes that control cuticular lipid production in Drosophila, we performed a RNA interference screen and used Direct Analysis in Real Time and gas chromatography mass spectrometry to quantify changes in the chemical profiles. Twelve putative genes were identified whereby transcriptional silencing led to significant differences in cuticular lipid production. Amongst them, we characterized a gene which we name spidey, and which encodes a putative steroid dehydrogenase that has sex- and age-dependent effects on viability, pheromone production, and oenocyte survival. Transcriptional silencing or overexpression of spidey during embryonic development results in pupal lethality and significant changes in levels of the ecdysone metabolite 20-hydroxyecdysonic acid and 20-hydroxyecdysone. In contrast, inhibiting gene expression only during adulthood resulted in a striking loss of oenocyte cells and a concomitant reduction of cuticular hydrocarbons, desiccation resistance, and lifespan. Oenocyte loss and cuticular lipid levels were partially rescued by 20-hydroxyecdysone supplementation. Taken together, these results identify a novel regulator of pheromone synthesis and reveal that ecdysteroid signaling is essential for the maintenance of cuticular lipids and oenocytes throughout adulthood.

Pheromones are used by many animals to control social behaviors such as mate choice and kin recognition. The pheromone profile of insects is dynamic and can change depending on environmental, physiological, and social conditions. While many genes responsible for the biosynthesis of insect pheromones have been identified, much less is known about how pheromone production is systemically regulated over the lifetime of an animal. In this work, we identify 12 genes in Drosophila melanogaster that play a role in pheromone production. We characterized the function of one gene, which we name spidey, and which encodes a steroid dehydrogenase. Silencing spidey expression during the larval stage results in the rapid inactivation of an essential insect steroid, 20-hydroxyecdysone, and developmental arrest. In adults, spidey is needed for maintaining the viability of oenocytes, specialized cells that produce pheromones and also regulate energy homeostasis. Our work reveals a novel role for ecdysteroids in the adult animal and uncovers a regulatory mechanism for oenocyte activity. Potentially, ecdysteroid signaling serves as a mechanism by which environmental or social conditions shape pheromone production. Exploitation of this conserved pathway could be useful for interfering with the mating behavior and lifespan of disease-bearing insects or agricultural pests.

'Does my Diet Affect my Perfume?' Identification and Quantification of Cuticular Compounds in Five Drosophila melanogaster Strains Maintained over 300 Generations on Different Diets

Cuticular hydrocarbons (CHCs) in Drosophila melanogaster represent the basis of chemical communication being involved in many important biological functions. The aim of this study was to characterize chemical composition and variation of cuticular profiles in five D. melanogaster strains. These strains were reared for approximately 300 generations on five diets: standard cornmeal medium and substrates prepared with apple, banana, tomato, and carrot. Differences in quantity and/or quality in CHCs were assumed as a result of activation of different metabolic pathways involved in food digestion and adaptations to the particular diet type. In total, independently of sex and strain, 66 chemical compounds were identified. In females of all strains, 60 compounds were identified, while, in males, 47 compounds were extracted. Certain new chemical compounds for D. melanogaster were found. MANOVA confirmed that CHC amounts significantly depend on sex and substrates, as well as on their interactions. Discriminant analysis revealed that flies belonging to 'apple' and 'carrot' strains exhibited the most noticeable differences in CHC repertoires. A non-hydrocarbon pheromone, cis-vaccenyl acetate (cVA) also contributed to the variation in the pheromone bouquet among the strains. Variability detected in CHCs and cVA may be used in the explanation of differences in mating behaviour previously determined in analyzed fly strains.