Correlation between octopaminergic signalling and foraging task specialisation in honeybees.

Regulation of pollen and nectar foraging in honeybees is linked to differences in the sensitivity to the reward. Octopamine (OA) participates in the processing of reward-related information in the bee brain, being a candidate to mediate and modulate the division of labour among pollen and nectar foragers. Here we tested the hypothesis that OA affects the resource preferences of foragers. We first investigated whether oral administration of OA is involved in the transition from nectar to pollen foraging. We quantified the percentage of OA-treated bees that switched from a sucrose solution to a pollen feeder when the sugar concentration was decreased experimentally. We also evaluated if feeding the colonies sucrose solution containing OA increases the rate of bees collecting pollen. Finally, we quantified OA and tyramine (TYR) receptor genes expression of pollen and nectar foragers in different parts of the brain, as a putative mechanism that affects the decision-making process regarding the resource type collected. Adding OA in the food modified the probability that foragers switch from nectar to pollen collection. The proportion of pollen foragers also increased after feeding colonies with OA-containing food. Furthermore, the expression level of the AmoctαR1 was upregulated in foragers arriving at pollen sources compared with those arriving at sugar-water feeders. Using age-matched pollen and nectar foragers that returned to the hive, we detected an upregulated expression of a TYR receptor gene in the suboesophageal ganglia. These findings support our prediction that OA signalling affects the decision in honeybee foragers to collect pollen or nectar.