Cuticular Hydrocarbon Mixtures Research Articles

Consistency of Cuticular Hydrocarbon Mixtures of Five Reticulitermes (Blattodea: Rhinotermitidae) Taxa From Northern California: Similarity Among Colonies and Seasonal Variation.

Cuticular hydrocarbon (CHC) mixtures from workers of five distinct CHC phenotypes of Reticulitermes Holmgren 1913 from two locations in northern California were examined from monthly collections taken over a 3-yr period. The objectives of this study were (1) to identify and quantify variations of the CHCs of multiple colonies of each of these phenotypes (= species or subspecies) to demonstrate consistency, (2) to assess the potential of CHC mixtures to separate or identify colonies within each phenotype, and (3) to detect any temporal changes in each of the hydrocarbons in the CHC mixtures. Nonmetric multidimensional scaling of all CHC mixtures of all samples collected at both locations separated the samples into five clearly visible, different groups of CHC phenotypes (taxa or species) of Reticulitermes. The degree of variability of the CHC mixtures among colonies of each phenotype was such that nonmetric multidimensional scaling did not separate or identify colonies. Strong seasonal fluctuations were evident in some of the CHCs of all five phenotypes and were significantly consistent with a sine curve. Maximum proportions of seasonal CHCs within a phenotype occurred in all seasons of the year but occurred mostly in the winter and summer. In general, the CHCs displaying maximum values in the winter were short-chained (C23-C27) methyl-branched alkanes, whereas the CHCs displaying maximum values in the summer were long-chained (C35-C43) methyl-branched alkanes, which likely influences water retention. These consistent chemical fingerprints are probably responsible for inter-phenotype recognition patterns and are thus useful for chemical taxonomy.

The scent of symbiosis: gut bacteria may affect social interactions in leaf-cutting ants

Animal gut microbiota affect host physiology and behaviour. In social insects, where colony level integrity is preserved via a nestmate discrimination system based on cuticular hydrocarbon mixtures, microorganismal effects may therefore influence social dynamics. Although nestmate recognition has undergone a thorough exploration during the last four decades, few studies have investigated the putative role of gut microbes. Here, we integrated 16S rRNA-based microbial community profiling, chemical and behavioural approaches to test whether gut microbes affect nestmate recognition in Acromyrmex echinatior leaf-cutting ants. Treating workers with a sterile diet or with antibiotics resulted in a substantial alteration of their gut microbial communities. In pairwise social interactions, untreated versus antibiotic-treated nestmates behaved more aggressively than other nestmate and non-nestmate pairs, suggesting that bacterial suppression may alter chemical social cues and trigger aggressive behaviour. Chemical analyses of treated individuals revealed a decrease in the abundance of two metapleural gland antifungal compounds, and confirmed the correspondence between aggression levels and chemical profile differences. Feeding microbiota-remodelled ants with conspecific faecal droplets partially restored the original bacterial communities. Ants fed with faecal droplets from different colonies were unusually aggressive compared to pairs fed with faecal droplets from the same colony. We cannot exclude confounding effects resulting from the potentially harmful action of antibiotics on ant hosts. However, our results suggest a correlation between chemical profiles and the presence of certain microbial species in the gut, which may affect nestmate recognition and division of labour. This opens novel questions about the role of symbiotic microorganisms in the evolution of social insect behaviour.

Learning and discrimination of cuticular hydrocarbons in a social insect

Social insect cuticular hydrocarbon (CHC) mixtures are among the most complex chemical cues known and are important in nest-mate, caste and species recognition. Despite our growing knowledge of the nature of these cues, we have very little insight into how social insects actually perceive and discriminate among these chemicals. In this study, we use the newly developed technique of differential olfactory conditioning to pure, custom-designed synthetic colony odours to analyse signal discrimination in Argentine ants, Linepithema humile. Our results show that tri-methyl alkanes are more easily learned than single-methyl or straight-chain alkanes. In addition, we reveal that Argentine ants can discriminate between hydrocarbons with different branching patterns and the same chain length, but not always between hydrocarbons with the same branching patterns but different chain length. Our data thus show that biochemical characteristics influence those compounds that ants can discriminate between, and which thus potentially play a role in chemical signalling and nest-mate recognition.

Polistes dominulus (Hymenoptera, Vespidae) Larvae Show Different Cuticular Patterns According to their Sex: Workers Seem Not Use This Chemical Information

During reproductive phase, larvae of male and female are intermingled in nest of social wasps. Workers care for and feed larvae that gives them an opportunity to bias investment with respect to sex, or even to kill some larvae, if they can distinguish between immature males and females. Cuticular hydrocarbon (CHC) mixtures are the most studied cues for species, nestmate, and caste recognition in social Hymenoptera. In this study, we investigate the paper wasp Polistes dominulus to see if male and female larvae show different patterns of CHCs and if workers are able to discriminate between male and female larvae on this basis. We performed gas chromatography-mass spectrometry analysis on cuticular extracts of larvae, and then we genotyped them to assign sex. We found sex-based variation in CHC-profiles sufficient for discrimination. However, our behavioral assays do not support the view that adults discriminate between male and female larvae within nests.

<I>Reticulitermes</I> (Isoptera: Rhinotermitidae) in Arizona: Multiple Cuticular Hydrocarbon Phenotypes Indicate Additional Taxa

Abstract Current taxonomic and biogeographical information on Reticulitermes in the United States suggests the only species found in Arizona is Reticulitermes tibialis Banks. Reticulitermes occurs naturally throughout Arizona with the exception of much of the Sonoran and Colorado deserts. Collections of Reticulitermes from disparate locations in Arizona and neighboring states were made to characterize their cuticular hydrocarbons for taxonomic purposes. We identified five phenotypes based on cuticular hydrocarbon mixtures of worker termites. The predominant hydrocarbons in AZ-A have 25 and 27 carbons in the parent chain, including 5,17-dimeC27. The late-eluting compounds are composed primarily of dienes, trienes, a homologous series of internally branched mono- and dimethylalkanes, and 5,17-dimethylalkanes. AZ-B differs from AZ-A by lacking the late-eluting dienes and trienes and by producing smaller amounts of hydrocarbons with 27 carbons in the parent chain. The cuticular hydrocarbons in AZ-C are compos...

Cuticular Hydrocarbons of Polistes dominulus as a Biogeographic Tool: A Study of Populations from the Tuscan Archipelago and Surrounding Areas

In social insects, the types and proportions of epicuticular lipids may exhibit significant diversity as a result of factors such as age, sex, caste, rank, nest, and relatedness. It is known that these variations can be used by social insects to acquire information regarding conspecific individuals. Recent findings have shown that different populations of Polistes dominulus (Christ.) have distinctly different chemical cuticular profiles, and that wasps are able to recognize individuals of their own population. In this study, we showed that cuticular hydrocarbon patterns of Polistes dominulus are consistent with similarities among northern Tyrrhenian islands, as reported in previous biogeographic studies. Indeed, our findings indicate that cuticular hydrocarbon mixtures of P. dominulus from Capraia and Corsica are grouped together by cluster analysis, while those from Elba and Giglio cluster with cuticular profiles of the mainland wasps (Venturina).

Cuticular hydrocarbons suggest three lineages in Reticulitermes ( Isoptera:Rhinotermitidae) from North America

Cuticular hydrocarbon mixtures can be used to discriminate insect taxa. They have utility for determining phylogenetic relationships where they are independent characters with discrete states and represent a hierarchical distribution of shared, derived characters. We report inferred degrees of relatedness among the chemical phenotypes of Reticulitermes from PAUP (phylogenetic analysis using parsimony) analyses of cuticular hydrocarbon characters. One hundred and forty-one Reticulitermes colonies collected from California, Georgia, New Mexico, Arizona and Nevada were used. Initial maximum parsimony analyses sorted the 141 colonies into 26 chemical phenotypes. Subsequent analyses, using the ancestral species Coptotermes formosanus and Heterotermes sp. as outgroups, sorted Reticulitermes taxa into three major lineages, each characterized by a different set of dominant methyl-branched or unsaturated hydrocarbon components. Reticulitermes in lineage I have cuticular hydrocarbon mixtures with a preponderance of internally branched monomethylalkanes and 11,15-dimethylalkanes. Those in lineage II are defined by a preponderance of 5-methylalkanes and 5,17-dimethylalkanes. Taxa in lineage III are characterized by the predominance of olefins and a relative paucity of n-alkanes and methyl-branched alkanes. Bootstrap analyses and decay indices provided statistical support and robustness for these chemical-based relationships.

Cuticular hydrocarbons of termites of the Hawaiian Islands.

Seven species of termites (Isoptera) belonging to three families are found in the Hawaiian Islands. The Kalotermitidae include Neotermes connexus Snyder, Cryptotermes brevis (Walker), Cryptotermes cynocephalus Light, Incisitermes immigrans Snyder, and the recently introduced Incisitermes minor (Hagen). Zootermopsis angusticollis (Hagen), a native of the Pacific Coastal region of North America has become established on Maui and is the sole representative of the Termopsidae. The only rhinotermitid known to be established in the Hawaiian Islands is Coptotermes formosanus Shiraki. A closely related species, Coptotermes vastator Light, has been reported from the Hawaiian Islands, but not recently documented. Cuticular hydrocarbon mixtures were characterized for each of the established and introduced species, as well as for C. vastator from Guam. The diversity of the hydrocarbon mixtures was extreme. At least half the hydrocarbons of C. brevis, C. cynocephalus, I. immigrans, and N. connexus are olefins. C. formosanus and C. vastator make no olefins, but methyl-branched alkanes comprise ca. 95% and 85% of their hydrocarbon mixtures, respectively. Blends of abundant hydrocarbons are species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers, or imagoes. Cuticular hydrocarbon mixtures appear to correlate with habitat requirements.

Cuticular Hydrocarbons of Reticulitermes (Isoptera: Rhinotermitidae) from Northern California Indicate Undescribed Species

Cuticular hydrocarbon mixtures of Reticulitermes samples from disparate locations in northern California were characterized and correlated with species determinations. Literature records indicate that there are two extant species of Reticulitermes in northern California: Reticulitermes hesperus Banks and R. tibialis Banks. We identified five distinct hydrocarbon phenotypes in Reticulitermes from northern California. Termites were diagnosed morphologically as R. tibialis for all five cuticular hydrocarbon phenotypes based on available keys to soldiers. Commonly accepted distributions of Reticulitermes in northern California indicate that our primary collection sites should only produce R. hesperus. On the basis of cuticular hydrocarbons alone we suggest that there are two or more undescribed taxa of Reticulitermes in northern California, or that described species of Reticulitermes occur in northern California, but have never been noticed before. Therefore, we conclude that the taxonomy of Reticulitermes in North America is in need of revision.

Pattern of recovery of species‐specific cuticular hydrocarbon mixtures by Reticulitermes santonensis and Reticulitermes lucifugus grassei after being removed from a mixed group. Is the acquisition of allospecific hydrocarbons reversible?

Each of the termite species Reticulitermes santonensis and Reticulitermes lucifugus grassei has its own particular cuticular chemical profile. When members of the two species are placed together to form artificially mixed species groups, their chemical profiles undergo changes: Each species acquires all the hydrocarbons which initially characterized the other species. When the members of a mixed group which had been kept together for 24 h were split into two homospecific groups, the cuticular profiles of the members of both groups immediately showed a sharp drop in both the homospecific and allospecific components. In R. santonensis, the homospecific hydrocarbons subsequently increased in quantity, reaching values which were higher on the 33rd day after the separation than those initially recorded in this species; whereas in R. lucifugus grassei, the homospecific hydrocarbon proportions were still lower on the 33rd day than the initial values. In both species, the allospecific hydrocarbon levels began to increase sharply on the 5th day after separation, and the homospecific products still showed no tendency to return to the initial proportions 33 days after separation. In the light of these results, some hypotheses are put forward as to what mechanisms might posibly regulate the hydrocarbon profiles of these two species. Arch. Insect Biochem. Physiol. 35:237-259, 1997.© 1997 Wiley-Liss, Inc.

Pattern of recovery of species-specific cuticular hydrocarbon mixtures by Reticulitermes santonensis and Reticulitermes lucifugus grassei after being removed from a mixed group. Is the acquisition of allospecific hydrocarbons reversible?

Each of the termite species Reticulitermes santonensis and Reticulitermes lucifugus grassei has its own particular cuticular chemical profile. When members of the two species are placed together to form artificially mixed species groups, their chemical profiles undergo changes: Each species acquires all the hydrocarbons which initially characterized the other species. When the members of a mixed group which had been kept together for 24 h were slit into two homospecific groups, the cuticular profiles of the members of both groups immediately showed a sharp drop in both the homospecific and allospecific components. In R. santonensis, the homospecific hydrocarbons subsequently increased in quantity, reaching values which were higher on the 33rd day after the separation than those initially recorded in this species; whereas in R. lucifugus grassei, the homospecific hydrocarbon proportions were still lower on the 33rd day than the initial values. In both species, the allospecific hydrocarbon levels began to increase sharply on the 5th day after separation, and the homospecific products still showed no tendency to return to the initial proportions 33 days after separation. In the light of these results, some hypotheses are put forward as to what mechanisms might possibly regulate the hydrocarbon profiles of these two species.

Cuticular Hydrocarbons of Termites of the British Virgin Islands

A survey of the termites (Isoptera) of 17 islands of the British Virgin Island (BVI) complex yielded eight taxa belonging to three families. The Kalotermitidae include Neotermes mona (Banks), Cryptotermes brevis (Walker), Procryptotermes corniceps (Snyder), and an undetermined species of Incisitermes, likely Incisitermes nr snyderi (Light) or I. incisus (Silvestri). The only rhinotermitid collected is an undetermined species of Heterotermes (Froggatt). Parvitermes wolcotti (Snyder), Nasutitermes costalis (Holmgren), and N. acajutlae (Holmgren) comprise the Termitidae. Cuticular hydrocarbon mixtures were characterized for each of the taxa. Blends of abundant hydrocarbons are species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers, or imagoes, although the species of Incisitermes were not separable on the basis of cuticular hydrocarbons.

Plasticity of the Cuticular Hydrocarbon Profile of the Slave-Making Ant Polyergus Rufescens Depending on the Social Environment

Analysis of cuticular hydrocarbon mixtures of the slave-making ant Polyergus rufescens and the Formica rufibarbis or F. cunicularia slaves with which it was living either naturally or after the slave species had been experimentally exchanged showed that cohabitation induced no qualitative homogenization of these species' cuticular signatures. The proportions of hydrocarbons common to both species tended however to be adjusted (in the case of the natural associations) or readjusted (in that of the experimental associations), especially in Polyergus towards those of their partners.On the other hand, differences were observed between the cuticular profiles of Polyergus and their Formica slaves which had been living separately from the original colony for several weeks in an experimental group, and those of the members of the original colony. The changes in the cuticular profiles occurred synchronously in all the individual members of the group.Comparisons between the cuticular versus postpharyngeal slave-maker and slave mixtures showed the existence of qualitative differences between the two mixtures. This indicates that the postpharyngeal glands are not directly involved in the production of the cuticular signatures. Some possible explanations for these results are discussed.

Intercaste, intercolony, and temporal variation in cuticular hydrocarbons ofCopotermes formosanus shiraki (Isoptera: Rhinotermitidae)

We characterized the variation in cuticular hydrocarbon mixtures between seven colonies of the Formosan subterranean termite,Coptotermes formosanus Shiraki, from the same population. We report differences between castes, between colonies, and within the population over time to assess seasonality. Colonies ofC. formosanus from Oahu, Hawaii, were sampled for 25 months. Each month, one sample each of 200 workers, 50 soldiers, nymphs, or alates from each colony was subjected to gas chromatography-mass spectrometry (GC-MS) analysis of the cuticular hydrocarbons. We resolved 39 individual peaks and identified 52 individual or isomeric mixtures of hydrocarbons. Onlyn-alkanes and methyl-branched alkanes occur; no olefins were found. Internally branched monomethylalkanes were the most abundant class of hydrocarbons, representing 45% to 50% of the total 9-;11-;13-Methyl-heptacosane accounted for over 30% of the total hydrocarbon for all castes. 2-Methyl- and 3-methylalkanes comprise approximately 30% of the total. Internally branched dimethylalkanes constitute 15% to 20% of the total cuticular hydrocarbon. Only one trimethylalkane, 13,15,17-trimethylnonacosane, was found in small amounts. The hydrocarbon mixtures of all four castes were similar. Quantitative differences in hydrocarbon mixtures among the castes were easily displayed using canonical discriminant analysis. Soldiers and workers are significantly different from one another and from nymphs and alates. Nineteen peaks are statistically significant between workers and soldiers. Nymphs and alates were not statistically different. We detected statistically significant quantitative differences between colonies in 18 peaks for workers and 12 peaks for soldiers. Each of the colonies ofC. formosanus can be separated from the others by the proportions of their hydrocarbon components. We detected statistically significant differences between months of the year for 12 peaks for workers and four peaks for soldiers; two peaks each for workers and soldiers showed distinct, seasonal trends. This seasonal shift in proportions of hydrocarbons correlates with the production of alates.

Selective adaptation of the cuticular hydrocarbon profiles of the slave-making ants Polyergus rufescens Latr. and their Formica rufibarbis Fab. and F. Cunicularia Latr. slaves

The results of comparisons between the cuticular hydrocarbon mixtures of the slave-making ants Polyergus rufescens, their Formica rufibarbis and F. cunicularia slaves and between slave and free-living workers (which were probably related to one another) from each Formica species showed the following. (1) Several products were common to all three species. (2) Each òf the two Formica species had its own particular products. (3) The Polyergus cuticular mixture did not contain any species-specific hydrocarbons but had some components in common with either rufibarbis or cunicularia. Because these products were present in Polyergus, whichever Formica species they enslaved, Polyergus must be able to synthesize their own cuticular hydrocarbons. (4) Cohabitation with another species as the result of slave making had no qualitative effects on the individual cuticular hydrocarbon mixtures: their composition was the same in the Polyergus whether living with F. rufibarbis or F. cunicularia and in the Formica of each species whether free living or enslaved. (5) The Polyergus resembled their Formica slaves, however, due to a tendency to adjust the proportions of some of the common hydrocarbons to those of their slaves; this tendency seems to have been reciprocal, although it was less marked in the case of the Formica. (6) The chemical signatures of mixed colonies inhabited by the same slave species depended mainly on the cuticular characteristics of the Formica slaves but also on those of the Polyergus, which differed from one colony to another. The finding that cuticular hydrocarbon mixtures of individuals of both species (slaves and slave makers) interacting within a mixed colony kept their species-specific hydrocarbons while the proportions of the common products showed a tendency to adapt to those of the other species suggests that there exists a selective mechanism probably involving the regulation of the synthesis of these products.

Climate and cuticular hydrocarbon variation in Rhipicephalus sanguineus ticks (Acari: Ixodidae).

An association between the climate and variation of the cuticular hydrocarbon pattern was found for several populations of Rhipicephalus sanguineus ticks. Extreme parameters of climate (absolute minimal and maximal temperatures) correlated positively with six compounds (mainly methylalkanes) detected in cuticular hydrocarbon mixtures. In the light of work conducted on cuticular transpiration in arthropods and biochemical phase changes in cuticle lipids, it is suggested that the adaptation of ticks to potential colonization areas is accomplished by detectable changes in cuticular hydrocarbon relationships. These tick strains can be biochemically determined and their adaptation potential, analyzed.

Cuticular Hydrocarbons as Chemotaxonomic Characters for Bark Beetles: Dendroctonus ponderosae, D. jeffreyi, D. brevicomis, and D. frontalis (Coleoptera: Scolytidae)

Cuticular hydrocarbons were extracted from adults of the sibling species Dendroctonus ponderosae Hopkins and D. jeffreyi Hopkins and from the closely related species D. brevicomis LeConte and D. frontalis Zimmermann. Four distinct chemical mixtures of cuticular hydrocarbons were identified by gas chromatography-mass spectrometry. Five classes of hydrocarbons were present: n -alkanes, alkenes, terminally branched methylalkanes, internally branched monomethylalkanes, and dimethylalkanes. Each of the two species pairs, D. ponderosae-D. jeffreyi and D. brevicomis-D. frontalis, had similar hydrocarbon profiles, yet unique hydrocarbon components were found. The best hydrocarbons for separating D. ponderosae and D. jeffreyi are the 3,7-dimethylalkanes. Obvious diagnostic hydrocarbon components are the 3,X-dimethylnonacosanes in D. frontalis and the homologous series of n -alkanes from n -hentriacontane to n -pentatriacontane in D. brevicomis . Host tree and geographic location did not qualitatively affect the cuticular hydrocarbon composition of D. frontalis. Hydrocarbon patterns of male and female D. frontalis were qualitatively and quantitatively similar. The species-specific nature of cuticular hydrocarbon mixtures in these four species and their potential for nondestructive species discrimination are discussed.

Cuticular hydrocarbons of adult Cylindrinotus laevioctostriatus (Goeze) and Phylan gibbus (Fabricius) (Coleoptera: Tenebrionidae)

The cuticular hydrocarbon mixtures of adult Cylindrinotus laevioctostriatus (CL) and Phylan gibbus (PG) were analysed by gas chromatography (GC) and by combined gas chromatography-mass spectrometry (GC-MS). The mixtures comprise: n- alkanes (C 23–C 31; CL, 13%, PG, 18%), 3-methylalkanes (CL, C 26–C 32, 27%; PG, C 26–C 33, 2%), internally branched monomethylalkanes (C 26–C 35; CL, 18%, PG, 21%), dimethylalkanes (CL, C 28–C 39, 33%; PG, C 25–C 37, 46%) and trimethylalkanes (CL, C 34–C 38, 7%; PG, C 32–C 38, 10%). Comparison of the cuticular hydrocarbons of nine tenebrionid species shows that each species has a distinctive hydrocarbon composition and that the hydrocarbon mixtures of congeneric species show greater qualitative and quantitative similarities than those of more distantly related species.