Cuticular hydrocarbons of four populations ofCoptotermes formosanus Shiraki in the united states

The degree of similarity among cuticular hydrocarbon profiles of four populations ofCoptotermes formosanus Shiraki in the United States is reported. Sixteen individual or isomeric mixtures of hydrocarbons were identified by gas chromatography-mass spectrometry. Hydrocarbon components consist ofn-alkanes, 2-methylalkanes, 3-methylalkanes, internally branched monomethylalkanes on carbons 9–15, and dimethylalkanes. The predominant hydrocarbons have 27 carbons in the parent chain. Methyl-branched hydrocarbons are more abundant thann-alkanes. No qualitative differences were apparent in the hydrocarbon components of workers or soldiers from any of the four populations. Quantitative differences in the hydrocarbon components separate castes and populations into different concentration profiles. Stepwise discriminant analysis and canonical discriminant analysis were used to choose and display seven hydrocarbon components for workers and three for soldiers that best reveal the differences among populations. Within-population variation is low compared to the differences among populations. These results suggest thatC. formosanus from Hallandale, Florida; New Orleans, Louisiana; and Lake Charles, Louisiana, are not related to those from Honolulu, Hawaii, and probably originated from other geographical locations.Isoptera: Rhinotermitidae.     

Cuticular Hydrocarbons of the Dampwood Termite, Zootermopsis nevadensis: Caste Differences and Role of Lipophorin in Transport of Hydrocarbons and Hydrocarbon Metabolites

The epicuticular and internal hydrocarbons (HC) from different castes of the dampwood termite Zootermopsis nevadensis were analyzed by gas chromatography–mass spectrometry. The epicuticular HC profiles of workers and alates contained large proportions of n-heneicosane (n-C21), 5-methylheneicosane (5-MeC21), and 5,17- and 5,15-dimethylheneicosane (5,17-, 5,15-diMeC21). Sixty-three HC peaks were identified as normal-, monomethyl-, dimethyl-, and trimethylalkanes up to 41 carbons long. The HC content of the internal tissues was significantly greater than on the epicuticle in all castes examined (2.8-fold in female alates, 5.7-fold in male alates, and 13.7-fold in workers). The hemolymph of all castes, including workers, soldiers, nymphs, and female and male alates, contained large amounts of HC and all hemolymph samples had nearly identical HC profiles. However, the hemolymph profile was remarkably different from the cuticular profile. KBr equilibrium gradient ultracentrifugation of worker hemolymph showed that all HC were associated with a high-density lipophorin (density of 1.12 ± 0.005 g/ml) consisting of two subunits, apolipophorin-I (220 kDa) and apolipophorin-II (82 kDa). After topical application of radiolabeled 3,11-dimethylnonacosane, a HC that is closely related to a native HC, all the internalized HC and radiolabeled lipid metabolites that were recovered from the hemolymph were associated with lipophorin. These findings are consistent with the hypothesis that lipophorin transports HC and some HC metabolites through the hemolymph from the sites of synthesis to the integument and from the integument to metabolic and excretory tissues. In many social insects, different castes have different relative proportions of the same HC and lipophorin appears to play an important role in regulation of the externalization and internalization of HC and, therefore, in the attainment of caste-specific chemical profiles.     

Cuticular Surface Hydrocarbons of Desert Locust Nymphs, Schistocerca gregaria, and Their Effect on Phase Behavior

The quantity of cuticular hydrocarbons is higher in solitarious nymphs of the desert locust, Schistocerca gregaria, compared to gregarious nymphs, but the total hydrocarbon fraction of solitarious nymphs does not significantly divert behavioral transition of isolated nymphs to the gregarious phase, while gregarious hydrocarbon extracts do. This suggests that qualitative differences in composition are responsible for the biological effect. The profile of cuticular hydrocarbon components is similar in the two phases, but some peak ratios differ. Crowding of solitarious nymphs leads to rapid changes in the profile of the hydrocarbon fraction, suggesting that specific hydrocarbons are produced and secreted as a consequence. Isolating previously crowded nymphs has an opposite effect. The composition of cuticular hydrocarbons from the migratory locust, Locusta migratoria, which differs considerably from that of S. gregaria, does not induce the gregarious behavioral phase in solitarious nymphs of the latter.     

Hydrocarbons ofNasutitermes acajutlae and comparison of methodologies for sampling cuticular hydrocarbons of caribbean termites for taxonomic and ecological studies

Using data from the arboreal nestingNasutitermes acajutlae (Holmgren), we propose standard collection and extraction methodology for characterization of cuticular hydrocarbons of termites under field conditions in the tropics. Specifically, we evaluated: (1) the effect of the duration and the number of extractions; (2) the effect of drying termites before extraction; (3) the effect of sample size; (4) the effect of solvents (ethanol versus hexane) on cuticular hydrocarbon profiles. Olefins comprise ca. 70% of the cuticular hydrocarbons ofN. acajutlae. Hydrocarbons consist of two distinct groups: early-eluting components, primarilyn-alkanes and methyl-branched alkanes, and late-eluting compounds, which consist almost exclusively of unsaturated components with one to six double bonds. Soldiers have more early-eluting compounds than workers or alates. Nests from the same island had qualitatively similar, but quantitatively dissimilar hydrocarbon mixtures. Brief extractions of 300 live workers in 10 ml of hexane for only 20 sec produced a hydrocarbon mixture equivalent to a 10-min extraction. Long-term extraction of 300 workers in hexane for two years resulted in different mixtures of hydrocarbons. Drying workers tended to enhance extraction of the less abundant unsaturated compounds such as C_41.4 and C_41.5. A single extraction of a minimum of 100 workers (live or dried), with hexane for 20 sec to 10 min is best; these extraction regimes resulted in mixtures of hydrocarbons that are quantitatively very similar. For quantitative comparisons, extracts from dried samples should not be compared to those from live samples. Storage in ethanol caused numerous unidentified, nonhydrocarbon compounds to be extracted either from the cuticle or from internal tissues.     

Cuticular hydrocarbons of dampwood termites,Zootermopsis: Intra- and intercolony variation and potential as taxonomic characters

Colonies ofZootermopsis were collected from the central Sierra Nevada and the Monterey Penninsula in California, and from southern Arizona. Cuticular hydrocarbons were identified by gas chromatography-mass spectrometry (GC-MS) and quantified by gas-liquid chromatography (GLC) for each caste of all colonies. Four consistent and distinct cuticular hydrocarbon patterns, or chemical phenotypes, were identified. Unique and abundant monomethyl- and dimethylalkanes, and ann-alkene provided easy separation of the various phenotypes. Significant differences in the proportions of the various components were found among castes within a colony and colonies within phenotypes from California. Differences in the hydrocarbon proportions for castes were not consistent between colonies. The current taxonomy of the genusZootermopsis recognizes three species. Our identification of four consistent, unique cuticular hydrocarbon phenotypes from the three described species should alert systematists and others to a major concern. If there are truly only three extant species, then the hypothesis that cuticular hydrocarbon profiles in this genus are species specific is not acceptable. Conversely, if cuticular hydrocarbon profiles are truly species specific, then there is at least one new, undescribed species ofZootermopsis.Isoptera: Termopsidae.     

Cuticular hydrocarbons and defensive compounds ofReticulitermes flavipes (Kollar) andR. santonensis (feytaud): Polymorphism and chemotaxonomy

Colonies ofReticulitermes flavipes andR. santonensis were collected from the southeastern United States (Georgia) and the southwest of France (Charente-maritime). Defensive compounds and cuticular hydrocarbons were identified by gas chromatography-mass spectrometry and quantified by gas chromatography using an internal standard for each caste and all colonies. These analyses show that although the cuticular hydrocarbons ofR. santonensis in Europe andR. flavipes in Georgia are identical, their relative proportions are different. However, the defensive compounds synthesized by their soldiers are different. A strong chemical polymorphism between sympatric colonies ofR. flavipes in the SW United States was detected in terms of both the hydrocarbons of the workers and soldiers and in the defensive secretions of the soldiers. The six defensive secretion phenotypes are based on the presence or absence of terpenes whereas the cuticular hydrocarbon phenotypes are based on significant differences in the proportions of the various components. A multivariate analysis (analysis of principal components) clearly permitted discrimination of four phenotypes (three inR. flavipes and one inR. santonensis) without intermediates. The hydrocarbons responsible for these variations were identified, and it was shown that the variations are neither seasonal nor geographic. The phenotypes of the cuticular hydrocarbons (workers and soldiers) and defensive compounds are linked in each colony, forming in three groups inR. flavipes Georgia, one subdivided into four subgroups according to the defensive secretion phenotypes. The role of these polymorphisms is discussed and ethological tests indicate that the chemical polymorphism do not determine aggressive behavior. The taxonomic significance of these results is considered and two hypothesis are formulated: (1) We only detected a strong genetic polymorphism in one unique species, and we believe thatR. santonensis was introduced into Europe in the last century from oneR. flavipes colony. (2) Chemical variability characterizes the sibling species that can be grouped into the same subspeciesR. flavipes. Unknown mechanisms of reproductive isolation separate them.     

Quantitative Changes in Hydrocarbons over Time in Fecal Pellets of Incisitermes minor May Predict Whether Colonies Are Alive or Dead

Hydrocarbon mixtures extracted from fecal pellets of drywood termites are species-specific and can be characterized to identify the termites responsible for damage, even when termites are no longer present or are unable to be recovered easily. In structures infested by drywood termites, it is common to find fecal pellets, but difficult to sample termites from the wood. When fecal pellets appear after remedial treatment of a structure, it is difficult to determine whether this indicates that termites in the structure are still alive and active or not. We examined the hydrocarbon composition of workers, alates, and soldiers of Incisitermes minor (Hagen) (family Kalotermitidae) and of fecal pellets of workers. Hydrocarbons were qualitatively similar among castes and pellets. Fecal pellets that were aged for periods of 0, 30, 90, and 365 days after collection were qualitatively similar across all time periods, however, the relative quantities of certain individual hydrocarbons changed over time, with 19 of the 73 hydrocarbon peaks relatively increasing or decreasing. When the sums of the positive and negative slopes of these 19 hydrocarbons were indexed, they produced a highly significant linear correlation (R ²?=?0.89). Consequently, the quantitative differences of these hydrocarbons peaks can be used to determine the age of worker fecal pellets, and thus help determine whether the colony that produced them is alive or dead.     

Novel internally branched,internal alkenes as major components of the cuticular hydrocarbons of the primitive australian antNothomyrmecia macrops Clark (Hymenoptera: Formicidae)

Internally mono- and dimethyl branched, internal alkenes, which constitute most of the cuticular hydrocarbon present on workers of the primitive Australian antNothomyrmecia macrops Clark, have been identified by gas chromatography-mass spectrometry. They are the first such alkenes reported from insects. Also present are alkanes with similar carbon skeletons. The hydrocarbon patterns of three separateNothomyrmecia colonies were very similar.     

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 Hydrocarbon Composition Reflects Genetic Relationship Among Colonies of the Introduced Termite Reticulitermes santonensis Feytaud

Nestmate recognition plays a key role in kin selection to maintain colony integrity in social insects. Previous studies have demonstrated that nestmate recognition is dependent on detection of cuticular hydrocarbons. However, the absence of intraspecific aggression between some colonies of Isoptera and social Hymenoptera questions whether kin recognition must occur in social insects. The purpose of this study was to determine if cuticular hydrocarbon similarity and high genetic relatedness could explain the lack of intraspecific aggression among and within colonies of the introduced subterranean termite Reticulitermes santonensis. We performed both GC analysis of cuticular hydrocarbons and genotyping by using 10 DNA microsatellite loci on the same 10 workers from each of 14 parisian colonies. Multivariate analyses demonstrated correspondence between cuticular hydrocarbon patterns and genetic variation. By using a redundancy analysis combining chemical and genetic data, we found that a few hydrocarbons (mainly short vs. long chains; saturated vs. unsaturated alkanes) were associated with most genetic variation. We also found a strong positive correlation between chemical and genetic distances between colonies, thus providing evidence of a genetic basis for cuticular hydrocarbon variation. However, genetic distance did not account for all chemical variation, thus suggesting that some hydrocarbon variation was environmentally derived. Investigation at the intracolony level indicated that cuticular hydrocarbons did not depend on colony social structure. Based on our findings, we speculate that the absence of intraspecific aggression in R. santonensis may result from a loss of diversity in genetically derived recognition compounds in this species that presumably descended from R. flavipes populations imported from North America.     

Harvester Ants Utilize Cuticular Hydrocarbons in Nestmate Recognition

Cuticular hydrocarbons appear to play a role in ant nestmate recognition, but few studies have tested this hypothesis experimentally with purified hydrocarbon extracts. We exposed captive colonies of the harvester ant Pogonomyrmex barbatus to small glass blocks coated with whole cuticular lipid extracts and the purified hydrocarbon portion of extracts from nestmate and nonnestmate workers. As an estimate of agonistic behavior, we measured the proportion of ants in contact with blocks that flared their mandibles. Blocks coated with cuticular extracts from nonnestmates were contacted by more workers in one of two experiments and elicited higher levels of aggression in both experiments than blocks bearing extracts from nestmates. The cuticular hydrocarbon fraction of extracts alone was sufficient to elicit agonistic behavior toward nonnestmates. The results demonstrate that harvester ants can perceive differences in cuticular hydrocarbon composition, and can use those differences in nestmate recognition.     

Temporal changes in colony cuticular hydrocarbon patterns ofSolenopsis invicta

Heritable cuticular hydrocarbon patterns ofSolenopsis invicta workers are consistent within colonies for a given sampling time but vary sufficiently from colony to colony to distinguish the colonies from each other. In addition, cuticular hydrocarbon patterns change within colonies over time. Nestmate recognition cues found on the individual's cuticle, can be from heritable or environmental sources, and are a subset of colony odor. The cuticular hydrocarbons can be used as a model for heritable nestmate recognition cues. We propose that because potential nestmate recognition cues, both environmental and genetic, are dynamic in nature rather than static, during its lifetime a worker must continually update its perception (template) of colony odor and nestmate recognition cues.     

Cuticular hydrocarbons of the paper wasp,Polistes fuscatus: A search for recognition pheromones

The cuticular chemicals of 124 individual wasps (foundresses and workers) from 23 colonies ofPolistes fuscatus were analyzed. The compounds identified, all of which were hydrocarbons, were similar to those of other vespid wasps in that the bulk of the hydrocarbons were 23–33 carbons in chain length. However, the hydrocarbon profile ofP. fuscatus differed from those of its congeners in its proportions of straight-chain alkanes, methylalkanes, and alkenes. Three of the 20 identified hydrocarbons, 13- and 15-MeC₃₁, 11,15- and 13,17-diMeC₃₁, and 13-, 15-, and 17-MeC₃₃, had properties postulated for recognition pheromones: colony specificity, efficacy in assigning wasps to the appropriate colony, heritability, lack of differences between foundresses and workers, and distinctive stereochemistry.     

Nestmate recognition cues in laboratory and field colonies ofSolenopsis invicta buren (Hymenoptera: Formicidae)

Laboratory-rearedSolenopsis invicta workers were tested for the ability to discriminate nestmates from nonnestmate conspecifics. Postcontact aggressive response to workers from local field colonies was significantly greater than the response to lab-reared workers, even when the latter were selected from colonies originating hundreds of miles away. Behavioral observations support the conclusion that lab-reared ants were less distinctive than field-collected ants with respect to recognition cues detectable on the cuticle. Potential environmental factors affecting colony odor are discussed. In addition, gas-liquid Chromatographic and statistical analyses of the majorS. invicta cuticular hydrocarbons indicate that cuticular hydrocarbon pattern was a poor predictor of laboratory colony response to field colony workers.     

Functional subcaste discrimination (foragers and brood-tenders) in the antCamponotus vagus scop.: polymorphism of cuticular hydrocarbon patterns

In the antCamponotus vagus, when selected foragers that had been earlier removed from the foraging arena and brood-tenders that had been earlier removed from the nest were placed together in a foraging arena, most of the brood-tenders and only a few of the selected foragers were carried back to the nest by nonselected foragers. We hypothesize that cuticular hydrocarbons serve as a cue that allows foragers to discriminate between members of their own subcaste and brood-tenders. It has been established that the proportions of certain hydrocarbons, which are the same regardless of the colony studied, vary from one worker subcaste to another and thus constitute a specific chemical signature. These hydrocarbons belong to a wide range of chemical families (alkanes, monomethylalkanes, and dimethylalkanes). The greatest differences between the two subcastes were observed on the thorax of workers. Principal component analyses performed on the hydrocarbons (or hydrocarbon combinations) corresponding to the 45 main peaks in the cuticular profiles of the head and thorax of brood-tenders and foragers of several colonies show that there exist quantitative differences between the various signatures that characterize the colony, the worker subcastes, and the various body parts within the same species, which can be classified in a hierarchy where the differences between worker subcastes are less pronounced than those between body parts or between colonies.     

Cuticular Hydrocarbon Phenotypes Do not Indicate Cryptic Species in Fungus-Growing Termites (Isoptera: Macrotermitinae)

In several termite species, distinct differences in the composition of cuticular hydrocarbons among colonies correspond to high genetic divergence of mitochondrial DNA sequences. These observations suggest that hydrocarbon phenotypes represent cryptic species. Different cuticular hydrocarbon phenotypes also are found among colonies of fungus-growing termites of the genus Macrotermes. To determine if these hydrocarbon differences in Macrotermes also indicate cryptic species, we sequenced the mitochondrial CO I gene from species in West and East Africa. Among individuals of a supposed species but belonging to different cuticular hydrocarbon phenotypes, the genetic distances are much smaller than distances between species. Unlike what has been observed in other termites, Macrotermes hydrocarbon phenotypes do not represent cryptic species. Our findings suggest fundamental differences in the evolution and/or function of cuticular hydrocarbons among different termite lineages. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Surface hydrocarbon components of two species ofNasutitermes from Trinidad

Colonies ofNasutitermes costalis (Holmgren) andN. ephratae (Holmgren) were collected from five locations in Trinidad. Cuticular hydrocarbons were characterized by gas chromatography-electron impact mass spectrometry and quantified by capillary gas chromatography. Sixteen major components were identified; all but one component (12, 16-dimethyltriacontane) were common to both species. The methyl-branched hydrocarbons were predominant inN. costalis, while the majority of the hydrocarbon components inN. ephratae weren-alkanes. One hydrocarbon (11,15-dimethylheptacosane) was found in abundance in samples ofN. ephratae from Trinidad but was not previously reported from collections of this species in Panama. In addition to the morphology of the soldiers and alates and the architecture of the arboreal nests,N. costalis andN. ephratae from Trinidad can easily be separated by chromatograms of the hydrocarbons.N. costalis has an enormous 13,17-dimethylhentriacontane peak (mean = 42.4% of total hydrocarbon). InN. ephratae this peak is much smaller and the 12,16-dimethyltriacontane peak is completely missing.N. costalis from Trinidad andN. corniger from Panama appear to have cuticular hydrocarbon profiles that are more similar to one another than are those ofN. ephratae from Trinidad and Panama.Isoptera: Termitidae: Nasutitermitinae.     

Cuticular hydrocarbons of the eastern subterranean termite,Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Major cuticular hydrocarbon components in several castes ofReticulitermes flavipes (Kollar) have been identified and quantitated. Types of hydrocarbons present includen-alkanes, 2-methylalkanes, 3-methylalkanes, 5-methylalkanes, an alkene, and an alkadiene, with a range in carbon numbers from C₂₁ to C₂₆, This is the first report on insect cuticular hydrocarbons in which both 2- and 3-methylalkanes are present, as well as the first report of an insect with a conjugated alkadiene.     

Task-Related Differences in the Cuticular Hydrocarbon Composition of Harvester Ants, Pogonomyrmex barbatus

Colonies of the harvester ant, Pogonomyrmex barbatus, perform a variety of tasks. The behavior of an individual worker appears to depend on its recent history of brief contacts with ants of the same and other task groups. The purpose of this study was to determine whether task groups differ in cuticular hydrocarbon composition. We compared the cuticular hydrocarbon composition of ants collected under natural conditions as they performed one of three tasks: patrolling (locating food sources), foraging, or nest maintenance. Task groups differed significantly in the relative proportions of classes of hydrocarbon compounds, as well as in individual compounds. Relative to nest maintenance workers, foragers and patrollers had a higher proportion of straight-chain alkanes relative to monomethylalkanes, dimethylalkanes, and alkenes. There was no significant difference in the chain length of n-alkanes among the task groups. Foragers did not differ in hydrocarbon composition from patrollers. Colonies differed significantly from one another in hydrocarbon composition, but task groups differed in consistent ways from colony to colony, suggesting that the mechanism responsible for task-related hydrocarbon composition was the same in all colonies. P. barbatus workers switch tasks during their lifetimes, suggesting that cuticular hydrocarbon composition changes during adulthood as well. Nest maintenance workers are probably younger than foragers and patrollers and perform very little of their work outside of the nest. Task-related hydrocarbon differences detected here may be associated with worker age, and/or the abiotic characteristics (temperature, humidity, and ultraviolet light) of the interior and exterior work environments.     

Role of cuticular hydrocarbons of aphid parasitoids in their relationship to aphid-attending ants

Lysiphlebus cardui, the dominant aphidiid parasitoid of the black bean aphid,Aphis fabae cirsiiacanthoidis (Afc), on creeping thistle, is able to forage in ant-attended aphid colonies without being attacked by ants. Several behavioral observations and experimental studies led to the hypothesis thatL. cardui mimics the cuticular hydrocarbon profile of its host aphid. Chemical analysis of the cuticular extracts revealed that bothL. cardui and Afc exclusively possess saturated hydrocarbons:n-alkanes, monomethyl (MMA), dimethyl (DMA), and trimethyl alkanes (TMA). Comparison of the hydrocarbon profiles of parasitoid and aphid showed great qualitative resemblance between parasitoid and host:L. cardui possesses almost all host-specific compounds in addition to species-specific hydrocarbons of mainly higher molecular weight (>C₃₀). However, there is a lesser quantitative correspondence between parasitoid and host aphid. Furthermore, we analyzed the cuticular hydrocarbon profile of another parasitoid of Afc,Trioxys angelicae. This aphidiid species is vigorously attacked and finally killed by honeydewcollecting ants when encountered in aphid colonies. Its cuticular hydrocarbon profile is characterized by the presence of large amounts of (Z)-11-alkenes of chain lenghts C₂₇, C₂₉, C₃₁, and C₃₃, in addition to alkanes and presumably trienes. The role of the unsaturated hydrocarbons onT. angelicae as recognition cues for aphid-attending ants is discussed.