Cuticular hydrocarbons as cues of sex and health condition in Polistes dominula wasps

International audienceIn the paper wasp Polistes dominula, cuticular hydrocarbons play a critical role 14 to acquire information regarding conspecific individuals. However, the relationship 15 between cuticular hydrocarbons, health status and male sexually selected traits is poorly 16 investigated. In this study, we characterized the cuticular hydrocarbon profile of adult 17 male and female wasps, infected or not by the strepsipteran endoparasite Xenos 18 vesparum, to assess whether the chemical signature provides information about sex and 19 health status (parasite infection). Moreover, we tested whether the chemical profile 20 reflects male quality as measured via morphological and behavioural (sexually 21 selected) traits at leks. Our results showed that males and females had similar total 22 amount of CHCs, quantitatively different profiles and, to a lesser extent, sex specific 23 chemical compounds. Cuticular profiles were influenced by the strepsipteran infection

Friends and Foes from an Ant Brain's Point of View – Neuronal Correlates of Colony Odors in a Social Insect

Background: Successful cooperation depends on reliable identification of friends and foes. Social insects discriminate colony members (nestmates/friends) from foreign workers (non-nestmates/foes) by colony-specific, multi-component colony odors. Traditionally, complex processing in the brain has been regarded as crucial for colony recognition. Odor information is represented as spatial patterns of activity and processed in the primary olfactory neuropile, the antennal lobe (AL) of insects, which is analogous to the vertebrate olfactory bulb. Correlative evidence indicates that the spatial activity patterns reflect odor-quality, i.e., how an odor is perceived. For colony odors, alternatively, a sensory filter in the peripheral nervous system was suggested, causing specific anosmia to nestmate colony odors. Here, we investigate neuronal correlates of colony odors in the brain of a social insect to directly test whether they are anosmic to nestmate colony odors and whether spatial activity patterns in the AL can predict how odor qualities like ‘‘friend’’ and ‘‘foe’’ are attributed to colony odors. Methodology/Principal Findings: Using ant dummies that mimic natural conditions, we presented colony odors and investigated their neuronal representation in the ant Camponotus floridanus. Nestmate and non-nestmate colony odors elicited neuronal activity: In the periphery, we recorded sensory responses of olfactory receptor neurons (electroantennography), and in the brain, we measured colony odor specific spatial activity patterns in the AL (calcium imaging). Surprisingly, upon repeated stimulation with the same colony odor, spatial activity patterns were variable, and as variable as activity patterns elicited by different colony odors. Conclusions: Ants are not anosmic to nestmate colony odors. However, spatial activity patterns in the AL alone do not provide sufficient information for colony odor discrimination and this finding challenges the current notion of how odor quality is coded. Our result illustrates the enormous challenge for the nervous system to classify multi-component odors and indicates that other neuronal parameters, e.g., precise timing of neuronal activity, are likely necessary for attribution of odor quality to multi-component odors

Biosystematics of Reticulitermes termites in Europe: morphological, chemical and molecular data

In Europe the most abundant naturally residing termite is the subterranean genus Reticulitermes (Rhinotermitidae). Six phenotypes of Reticulitermes have been identified on the basis of morphological, chemical (cuticular hydrocarbons and soldier defensive secretions), and molecular (enzymatic alleles and mitochondrial ND1 sequence) features. They are R. santonensis in western France, R. grassei in southwestern France, northwestern and southern Spain and Portugal, R. banyulensis in northeastern Spain, central area of the Iberian Peninsula and southwestern France, R. lucifugus in Italy and southeastern France, R. balkanensis in the Balkans and R. sp. nov., a recently identified urban phenotype resembling R. balkanensis, in northern Italy and southeastern France. R. santonensis is close kin to the American species R. flavipes. R. grassei, R. banyulensis and R. lucifugus belong to the same species complex. R. balkanensis and the new phenotype R. sp. nov. are close to R. santonensis regarding cuticular hydrocarbons, to the lucifugus complex regarding DNA and to R. clypeatus from Israel regarding morphology. The species status of these genotypes has been confirmed by the mechanisms of species isolation. Prevention of hybridization depends on the method of colony formation in each species. Swarming dates, differences in pheromones, and infertility prevent hybridization by sexual alates. Interspecific aggression between workers prevents hybridization by necotenics. Behavioral and molecular studies have provided many data on the genetic structure of nests, which varies according to species and location. All colonies of R. santonensis are open all year. The colonies of R. grassei in southern areas and all colonies of R. banyulensis are closed families with generally a single reproductive couple. The colonies of R. grassei in northern areas and the colonies of R. lucifugus are open in the summer and closed in the winter. Based on the here presented data, the taxonomy and the speciation of the Reticulitermes genus in Europe are discussed

Interspecific variation in terpenoid composition of defensive secretions of European Reticulitermes termites

Sixteen terpene compounds were isolated from the soldier defensive secretions of seven European termite taxa of the genus Reticulitermes (Isoptera, Rhinotermitidae). We describe species-specific mixtures of monoterpenes (alpha-pinene, beta-pinene, limonene), sesquiterpenes (germacrene C, germacrene A, germacrene B, beta-selinene, delta-selinene, gamma-selinene, (E)-beta-farnesene, gamma-cadinene, nerolidol), diterpenes (geranyl linalool, geranyl geraniol, geranyl geranial), and one sesterterpene (geranyl farnesol). Compounds were purified by HPLC and their structures determined by means of MS spectrometry, or 1D and 2D NMR spectroscopy. Comparison of two different analytical approaches, GC-MS and HPLC with subsequent NMR spectroscopy, revealed Cope rearrangement of germacrene A, germacrene B, and germacrene C to the respective beta-elemene, gamma-elemene, and delta-elemene under GC conditions, thus demonstrating the limits for this analytical approach. The species-specific compound composition provides insight into taxonomy and species origin of European Reticulitermes. The biological significance of the species-specific composition of Reticulitermes defensive secretions is briefly discussed