Evaluation of the Mandibular Pheromones Produced by Queens of Africanized and European Honeybees under Normal Conditions and During Absconding Processes by HPLC-UV Methodology

Pheromones are essential for colony organization in honeybees. The pheromones 9-ODA ((E)-9-oxodec-2-enoic acid) and 9-HDA ((E)-9-hydroxydec-2-enoic acid), produced by the mandibular gland of the queen, have various functions within the colony, including inhibition of ovarian development of workers, attraction of swarms, and stabilization of the cluster group. An example of reaction of the colony to adverse conditions is absconding, which is defined as mass exit of all of the adult individuals, leaving even brood and food. In this study, the pheromones 9-ODA and 9-HDA were determined in virgin and normal mated, egg-laying European Carniolan and Africanized queens, as well as in mated queens that were in absconding colonies, using liquid chromatography with UV detection developed methodology. Absconding was induced by maintaining free-flying five-standard-Langstroth-frame colonies in a chamber artificially heated to 45 ºC. The obtained results showed that the amount of 9-ODA in Africanized queens (6.56 µg bee^-1) is very low compared with European queens. However, large amounts of 9-HDA were found in the queens of absconding Africanized swarms (107.4 µg bee^-1). According to our results, the quantities of 9-ODA and 9-HDA in Africanized honeybees in Brazil may be contributing to the high rates of absconding, promoting low effect of stabilizing agent, and high effect of attraction of dispersers cluster.

Keywords:
pheromones; absconding; European bees; Africanized bees; 9-ODA; 9-HDA; liquid chromatography