Changes in the cuticular hydrocarbon profile associated with the molting cycle correlate with the hydrocarbon profile of the fungus cultivated by the ant Atta sexdens

摘要

Leaf-cutting ants live in obligate mutualism with a basidiomycete fungus that they use as a rearing site and food resource. Chemical analyses of the fungus gardens kept by these ants have revealed the presence of hydrocarbons that also occur in the epicuticle of the ants. However, whether it is the fungus or the ants which are the ultimate producers of these compounds is not yet clear. To shed light on the chemoecological aspects of the symbiotic relationship between ant and fungus, in the present study, we aimed to characterize the changes in the cuticular chemical profiles during larval-to-adult molting of Atta sexdens workers, which allowed us to investigate how these changes were correlated with the chemical profile of fungal cultivars. The results show that cuticular hydrocarbon profiles of ants were comprised of linear and branched alkanes that varied significantly, according to developmental stages, with several ant-specific hydrocarbons being identified as the most representative ones. The chemical profile of symbiotic fungus was predominantly comprised of linear alkanes, which also occurred in the cuticle of the ants. Chemical distances calculated with the chemical profiles of the analyzed groups revealed a great similarity between the hydrocarbon profile of symbiotic fungus and those of the ants, especially at the earliest stages of ants' development, when mainly linear alkanes were identified. However, as individuals progressed through developmental stages, the chemical profiles increased in difference, due to the fact that several branched alkanes were found in great proportions in the cuticle of the ants. These findings suggest that the intimate relationship between brood and fungus might shape the hydrocarbon profile of both species, and the possible scenarios for the transference of these substances are discussed.