Task-Specific Recognition Signals Are Located on the Legs in a Social Insect

Task allocation ensures a high level of organization within social insect colonies. Workers reveal their task assignment through cuticular hydrocarbon (CHC) signals. The source and chemical composition of these signals are largely unknown. We ask whether task recognition signals are located on particular body parts of workers of Australian meat ants (Iridomyrmex purpureus). We analyzed the CHC profile on the antennae, legs, and abdomens of workers engaged in different tasks. Discriminant analysis showed that the leg profile is the best indicator of task identification. Behavioral assays confirmed this finding: workers typically reacted differently to non-nestmates engaged in different tasks, but not if the CHCs on the legs of their opponents were removed by a solvent. Lasso and Elastic-Net Regularized Generalized Linear Model (GLMNET) revealed which CHC components show the highest correlation in task and nestmate recognition, suggesting that social insects can simultaneously convey different CHC signals on different body parts, thereby allowing efficient signaling and signal perception.a University of Melbourne Postgraduate Scholarship and a Holsworth Wildlife Research Endowment (to QW)

Data from: Location-specific cuticular hydrocarbon signals in a social insect

Social insects use cuticular hydrocarbons (CHCs) to convey different social signals, including colony or nest identity. Despite extensive investigations, the exact source and identity of CHCs that act as nest-specific identification signals remain largely unknown. Perhaps this is because studies that identify CHC signals typically use organic solvents to extract a single sample from the entire animal, thereby analysing a cocktail of chemicals that may serve several signal functions. We took a novel approach by first identifying CHC profiles from different body parts of ants (Iridomyrmex purpureus), then used behavioural bioassays to reveal the location of specific social signals. The CHC profiles of both workers and alates varied between different body parts, and workers paid more attention to the antennae of non-nestmate and the legs of nestmate workers. Workers responded less aggressively to non-nestmate workers if the CHCs on the antennae of their opponents were removed with a solvent. These data indicate that CHCs located on the antennae reveal nestmate identity and, remarkably, that antennae both convey and receive social signals. Our approach and findings could be valuably applied to chemical signaling in other behavioural contexts, and provide insights that were otherwise obscured by including chemicals that either have no signal function or may be used in other contexts

Ant behaviour and chemical ananlysis data

This file contains the behaviour data, including how ants direct different number of antennation behaviour towards different body parts of its opponents; the antennation behaviour and length of display behaviour when the ant's antennae have been amputated or washed with hexane.This file also contains chemical analysis data from GC-FID, how the cuticular hydrocarbon signals on different body parts are different, and data of antennae, legs, and abdomen collected from single ants

Localization of oleuropeyl glucose esters and a flavanone to secretory cavities of Myrtaceae.

We report the widespread occurrence of structurally diverse oleuropeyl glucose esters, including the new diester eucaglobulin B, localized specifically to the essential oil secretory cavities of myrtaceous species. Clear taxonomic patterns in the composition of cavity extracts within the genus Eucalyptus are shown with species from subgenus Symphyomyrtus dominated by oleuropeyl glucose esters and species from subgenus Eucalyptus dominated instead by the flavanone, pinocembrin. We also examined the intra-species occurrence of oleuropeyl glucose esters by quantifying the abundant constituents cuniloside B and froggattiside A in trees from two populations of Eucalyptus polybractea R.T. Baker. All trees contained both compounds, which were positively correlated with total essential oil concentration. This apparent ubiquity of oleuropeyl glucose esters at both intra- and inter-specific levels in Eucalyptus is indicative of important physiological or ecological functions. The significance of their prevalence and the sequestration of these esters and also pinocembrin to the extracellular domain of secretory cavities is discussed in light of their potential biological activities and our findings that they are spatially segregated to the exterior of cavity lumina. The localization of oleuropeyl glucose esters to a specific and isolatable tissue type has the potential to aid in future elucidation of function and biosynthesis

Chemical structures of flavonoids quantified from foliar secretory cavities of 11 species within <i>E</i>. subg. <i>Eucalyptus</i>.

<p>Dashed lines denote characteristic fragmentation patterns of flavanones and flavones observed in ESI-LCMS/MS.</p

Taxonomic classification of the <i>Eucalyptus</i> species sampled in this study.

<p>Species were chosen based on gland size and abundance and ease of isolation. Average leaf and gland parameters are presented. LMA, leaf mass per unit area.</p

Relationship between quantifiable constituents per gland and the estimated gland lumen volume for 11 species within <i>E</i>. subg. <i>Eucalyptus</i>.

<p>Quantifiable constituents were flavanonoids, monoterpenes, sesquiterpenes and triketones. Lumen data are the means (± 1 SE) of 30 cavities. Dotted line represents an idealised 1 to 1 relationship between lumen volume and total gland constituents, assuming an average constituent density of 1 μg per nl.</p