Chemical signals of Apis mellifera iberiensis: glandular pheromones versus in vivo emission of volatiles compounds
Résumé
The communication in social insets, particularly honeybees, is regulated by a complex language mediated by chemical signals, mostly pheromones. Those can be highly volatile, with low molecular weights and fast diffusion in air or less volatile, heavier, adsorbed on the surface of the body and passed through direct body contact or during food transfer [1]. Honeybee pheromone research has been focused mostly in the compounds present in solvent-derived extracts of glands or body parts, rather than the volatiles emitted in vivo. Although many chemicals have been identified, the understanding of the entire profile emitted by honeybees is crucial to disclose the complex chemical language observed in social hymenoptera. The aim of this work was to characterize the queen and alarm pheromone of Apis mellifera iberiensis, the native honeybee subspecies of Iberian Peninsula, through glandular extraction vs in vivo collection of the emitted volatiles. For queen pheromone, the glandular experiments were conducted in unmated/established mated queens by extraction procedures [2], while emitted volatiles, were collected in vivo by SPME. Similarly, the alarm pheromone produced in the glands was studied by removal and solvent extraction of forager bees sting apparatus, while in vivo experiments were conducted through SPME (with electrical stimulus). Chemical analysis was performed by GC-MS. Concerning the queen pheromone, the results obtained through glandular extraction showed a different composition, with a typical queen mandibular pheromone profile, mainly composed by (E)-9-oxodec-2-enoic acid, (E)-9-hydroxydec-2-enoic acid, methyl p-hydroxybenzoate and 4-hydroxy3methoxyphenylethanol, comparing to the volatiles collected in vivo, where the main compounds were octanal, octanol, nonanal, decanal and decanol. On the other hand, the analysis of the sting apparatus extract vs in vivo volatiles showed a more similar profile, with isopentyl acetate, octanol, 2-nonanol, benzyl acetate and n-octyl acetate in its composition.