Cuticular Hydrocarbons

The integrity of ant colonies depends exclusively on social relatonships
between their individuals, especially the ability of communicaton between group members, which is mainly mediated through chemical signals. Another important feature of ant behavior is territory defense, since they need to gather large amounts of food to feed their larvae, males and breeding females. Thereby, ants might display behavioral strategies to defend their territories from intruders. Here we investgated whether Ectatomma brunneum displays the Dear Enemy Phenomenon, what is the relatonship between Cutcular Hydrocarbon compositon and levels of aggression during their intraspecifc interactons and which compounds and/or classes of compounds might be the most important to modulate the level of aggression. To test our hypothesis, we evaluated the levels of aggression through behavioral observatons during interactons between 23 pairs of colonies nested in two distnct sites at varied distances. Then, we analyzed the cutcular chemical profle of the individuals involved in the interactons, and compared these results with the levels of aggression displayed between colonies tested. The results allow us to confrm our hypothesis that the DEP occurs in E. brunneum. The higher tolerance between closer colonies can be explained due to their kinship level in additon to sharing the same microhabitats. The results also showed there are signifcant differences in CHCs profles, especially between colonies nested at relatvely greater distances, and it is likely that differences in content of some branched alkanes are the most important to establish these differences and, therefore, the levels of aggression during the interactons.

Removal of Polycyclic Aromatic Hydrocarbons (PAHs) from the environment is important because of their potentially deleterious affect human health. Biological methods that was applied in the present study is typically contain microbial processes. It is the most innocuous and effective Original Research Article

Our aim was to test the existence of Gestalt colony odour in Camponotus fellah. We isolated individual workers to prevent trophallaxis, allogrooming and body contact. After 20 days, the cuticular hydrocarbon profile of the isolated ants diverged from that of the parent colony. Moreover, each isolated individual had its own specific blend. This procedure showed that after about 20 days of isolation there was a turnover of the colony odour, revealing the genetically expressed hydrocarbon profile of each individual. It also showed that the cuticular hydrocarbon profile is polymorphic, and that its homogeneity within a colony is maintained by frequent exchanges of hydrocarbons between workers. Behavioural observations of resident workers, in their nest, towards nestmates reintroduced after isolation indicated that a short isolation period (3–5 days), which induced a minor change in hydrocarbon profile, provoked frequent trophallactic solicitations. These were likely to permit the isolated ants to readjust their hydrocarbon profile to that of the ants in the mother colony. Longer isolation periods (20–40 days) induced a greater change in hydrocarbon profile and made the residents intolerant towards their introduced nestmates. Therefore, our results clearly support the existence of a Gestalt colony odour in C. fellah. They also show that since individual hydrocarbon production is dynamic, workers are obliged to exchange hydrocarbons continually (mainly by trophallaxis) in order to be in the Gestalt, and properly integrate into the colony.

Colony integrity and survival in honeybees is regulated by chemical signals that are actively produced by glands and syner-gically transmitted between the members. A number of these signals regulate the typical age-related division of labor among the worker bees performing different tasks at different ages. In this study, the analysis of the cuticular profiles in Apis mellifera ligus-tica Spinola, 1806 workers at various tasks (newly emerged, nurse and forager bees) was performed using in vivo solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). The use of in vivo SPME shed new light on the complexity of the molecular pattern on the epicuticle of honeybees. The identified molecules are mainly hydrocarbons, saturated and unsaturated carboxylic acids, and to a less extent, esters, sterols, aldehydes, and alcohols. Their relative abundance between the three task groups was evaluated using descriptive statistics and multivariate pattern recognition analysis (i.e., principal component analysis, PCA, and linear discriminant analysis, LDA). Eleven molecules namely nonacosane, pentacosane, (Z)-12-penta-cosene, 11-tricosene, 11-methylnonacosane, squalene, 13-methyl-heptacosane, heptacosane, heneicosane, docosane and tricosane, occur with high frequency in newly emerged, nurse, and forager bees. The compounds that contributed the most for the separation of the three task groups in the PCA were pentacosane, (Z)-12-pen-tacosene, 13-methylheptacosane and squalene; while for LDA, nonacosane, 11-methylnonacosane and pentacosane were the molecules that contributed most to the discrimination.

The condition dependence of male sexual traits plays a central role in sexual selection theory. Relatively little, however, is known about the condition dependence of chemical signals used in mate choice and their subsequent effects on male mating success. Furthermore, few studies have isolated the specific nutrients responsible for condition-dependent variation in male sexual traits. Here, we used nutritional geometry to determine the effect of protein (P) and carbohydrate (C) intake on male cuticular hydrocarbon (CHC) expression and mating success in male decorated crickets (Gryllodes sigillatus). We show that both traits are maximized at a moderate-to-high intake of nutrients in a P:C ratio of 1 : 1.5. We also show that female precopulatory mate choice exerts a complex pattern of linear and quadratic sexual selection on this condition-dependent variation in male CHC expression. Structural equation modelling revealed that although the effect of nutrient intake on mating success is mediated through condition-dependent CHC expression, it is not exclusively so, suggesting that other traits must also play an important role. Collectively, our results suggest that the complex interplay between nutrient intake, CHC expression and mating success plays an important role in the operation of sexual selection in G. sigillatus.

Nasonia (Hymenoptera: Pteromalidae) is a genus of parasitoid wasps, which is fast emerging as a model system for evolutionary, genetic, developmental and host-endosymbiont interaction studies. In this study, we report a new species, Nasonia oneida, distinguish its behavioral, genetic and morphological features, and characterize its pre-mating and post-mating isolation with the other Nasonia species. Phylogenetic analyses indicate that N. oneida is the sister species to Nasonia giraulti with its own uniquely distinct cuticular hydrocarbon profiles, behavioral characteristics and subtle morphological differences. An important characteristic of N. oneida is the strong mate discrimination shown by the females against all the other Nasonia species. A genetic analysis of this phenotype by interspecies hybridization indicates that this strong discriminating phenotype is recessive. A formal species description of N. oneida Raychoudhury & Desjardins is also provided.

Queens in many social insects are known to maintain their status through chemicals (pheromones) and cuticular hydrocarbons and have been the focus of many investigations that have looked at the chemicals involved in queen signaling. In the primitively eusocial wasp Ropalidia marginata Lepeletier (Hymenoptera: Vespidae), the Dufour's gland has been shown to be involved in queen signaling, and Dufour's gland hydrocarbons have been found to be correlated with fertility. Hence, this study analyzed the cuticle of R. marginata along with the Dufour's gland in order to compare their hydrocarbon profiles. The results show that the Dufour's gland and cuticle contained the same set of hydrocarbons in similar proportions (for the majority of compounds). Patterns pertaining to fertility signaling present in cuticular hydrocarbons were also similar to those present in the Dufour's gland hydrocarbons. Furthermore, the haemolymph contained the same hydrocarbons as found in the Dufour's gland and cuticle in similar proportions, thereby providing an explanation as to why the hydrocarbon profiles of the Dufour's gland and cuticle are correlated.

The social life of animals depends on communication between individuals. Recent studies in Drosophila melanogaster demonstrate that various behaviors are influenced by social interactions. For example, courtship is a social interaction mediated by pheromonal signaling that occurs more frequently during certain times of the day than others. In adult flies, sex pheromones are synthesized in cells called oenocytes and displayed on the surface of the cuticle. Although the role of Drosophila pheromones in sexual behavior is well established, little is known about the timing of these signals or how their regulation is influenced by the presence of other flies. Results: We report that oenocytes contain functional circadian clocks that appear to regulate the synthesis of pheromones by controlling the transcription of desaturase1 (desat1), a gene required for production of male cuticular sex pheromones. Moreover, levels of these pheromones vary throughout the day in a pattern that depends on the clock genes and most likely also depends on the circadian control of desat1 in the oenocytes. To assess group dynamics, we manipulated the genotypic composition of social groups (single versus mixed genotypes). This manipulation significantly affects clock gene transcription both in the head and oenocytes, and it also affects the pattern of pheromonal accumulation on the cuticle. Remarkably, we found that flies in mixed social groups mate more frequently than do their counterparts in uniform groups. Conclusions: These results demonstrate that social context exerts a regulatory influence on the expression of chemical signals, while modulating sexual behavior in the fruit fly.

The composition of the cuticular wax varies from species to species as well as the developmental stage of the organ. In the present study, the variation in the pattern of accumulation of C28 and > C28 chain length of the cuticular wax compounds in the two contrasting Musa species for wax content has been examined—Musa balbisiana ‘Bee heekela’ (BB genome) (with high wax content) and Musa acuminata ssp. Burmannicoides Colla—‘Calcutta-4’ (AA genome) (with low wax content). These two species are the progenitors for the modern cultivated banana. Using GC–MS analysis, 40 different cuticular wax compounds from five different leaf developmental stages in these two musa species were identified. Around tenfold higher accumulation of C28 length compounds was found in ‘Calcutta-4’ as compared to that of ‘Bee hee kela’. In case of ‘Bee hee kela’,  > C28 length compounds were in large proportion compared to C28 length wax compounds. The qPCR analysis was carried out for the gene CUT1/CER6/KCS6 which are involved in the fatty acid elongation step of cuticular wax biosynthesis. A higher expression in the 2nd (young), 4th and 6th (old) fully expanded leaves of high wax genotype ‘Bee hee kela’ with 1.57083, 9.71512, and 1.44963 fold change, whereas a lower expression of 0.9151, 4.8785, and 1.2321 fold change in low wax genotype ‘Calcutta-4’, respectively, was observed. A negative relationship between the gene expression and C28 wax compounds’ accumulation was observed, indicating the importance of the expression of CUT1/CER6/KCS6 gene for elongation of C28 to > C28 cuticular wax compounds. The current study suggest that CUT1/CER6/KCS6 from ‘Bee heekela’ would be a good contributor for higher cuticular wax with higher > C28 compounds, thus, finally, contributing for higher leaf water retention capacity their by conferring drought tolerance helping in the future banana improvement programs.

Sex pheromones are vital in communication between individuals belonging to opposite sexes and form an integral part of the reproductive biology of various species. Among insects, sexual dimorphism in CHCs has been reported from diverse taxa spanning seven different orders, and thereby CHCs have been implicated as sex pheromones. Because males and females of the primitively eusocial wasp Ropalidia marginata touch each other with their antennae during mating, before engaging in sperm transfer, a sex pheromone that is perceived via contact chemosensation through the antennae can possibly exist in this species. Since CHCs have been implied as sex pheromones in various insects (including hymenopterans), and since sexual dimorphism of CHCs should be an obligatory prerequisite for them to act as sex pheromones, we investigated whether males and females of R. marginata differ in their CHC profiles. We found only nonvolatile CHCs, and our results show absence of sexual dimorphism in CHCs, suggesting that CHCs do not function as sex pheromone in this species. A behavioral assay failed to show presence of mate attraction at a distance, thereby showing the absence of volatile long-distance mate attraction cues (that may originate from sources other than and in addition to CHCs).

Drosophila Cuticular Hydrocarbons (CH) influence courtship behaviour, mating, aggregation, oviposition, and resistance to desiccation. We measured levels of 24 different CH compounds of individual male D. melanogaster hourly under a variety of environmental (LD/DD) conditions. Using a model-based analysis of CH variation, we developed an improved normalization method for CH data, and show that CH compounds have reproducible cyclic within-day temporal patterns of expression which differ between LD and DD conditions. Multivariate clustering of expression patterns identified 5 clusters of co-expressed compounds with common chemical characteristics. Turnover rate estimates suggest CH production may be a significant metabolic cost. Male cuticular hydrocarbon expression is a dynamic trait influenced by light and time of day; since abundant hydrocarbons affect male sexual behavior, males may present different pheromonal profiles at different times and under different conditions.

Drosophila Cuticular Hydrocarbons (CH) influence courtship behaviour, mating, aggregation, oviposition, and resistance to desiccation. We measured levels of 24 different CH compounds of individual male D. melanogaster hourly under a variety of environmental (LD/DD) conditions. Using a model-based analysis of CH variation, we developed an improved normalization method for CH data, and show that CH compounds have reproducible cyclic within-day temporal patterns of expression which differ between LD and DD conditions. Multivariate clustering of expression patterns identified 5 clusters of co-expressed compounds with common chemical characteristics. Turnover rate estimates suggest CH production may be a significant metabolic cost. Male cuticular hydrocarbon expression is a dynamic trait influenced by light and time of day; since abundant hydrocarbons affect male sexual behavior, males may present different pheromonal profiles at different times and under different conditions.

Chemical communication mediates social interactions in insects . For the fruit fly, D. melanogaster, the chemical display is a key fitness trait because it leads to mating. An exchange of cues that resembles a dialogue between males and females is enacted by pheromones, chemical signals that pass between individual flies to alter physiology and behavior . Chemical signals also affect the timing of locomotor activity [4] and sleep . We investigated genetic and environmental determinants of chemical communica-

Drosophila Cuticular Hydrocarbons (CH) influence courtship behaviour, mating, aggregation, oviposition, and resistance to
desiccation. We measured levels of 24 different CH compounds of individual male D. melanogaster hourly under a variety of
environmental (LD/DD) conditions. Using a model-based analysis of CH variation, we developed an improved normalization
method for CH data, and show that CH compounds have reproducible cyclic within-day temporal patterns of expression which
differ between LD and DD conditions. Multivariate clustering of expression patterns identified 5 clusters of co-expressed
compounds with common chemical characteristics. Turnover rate estimates suggest CH production may be a significant
metabolic cost. Male cuticular hydrocarbon expression is a dynamic trait influenced by light and time of day; since abundant
hydrocarbons affect male sexual behavior, males may present different pheromonal profiles at different times and under
different conditions.