Combined secondary compounds naturally found in nectars enhance honeybee cognition and survival

The alkaloid caffeine and the amino acid arginine are present as secondary compounds in nectars of some flower species visited by pollinators. Each of these compounds affects honeybee appetitive behaviors by improving its foraging activity and learning. While caffeine potentiates responses of mushroom body neurons involved in honeybee learning processes, arginine acts as precursor of nitric oxide enhancing the protein synthesis involved in memory formation. Despite existing evidence on how these compounds affect honeybee cognitive abilities individually, the effect of their mixtures on this matter is still unknown. We evaluated acquisition and memory retention in classical olfactory conditioning procedure, in which reward (sucrose solution) contained traces of caffeine, arginine or mixtures of both. The results indicate that the presence of the single compounds and their most concentrated mixture increases bees’ learning performance. However, memory retention, measured at short- and long-term, increases significantly only in those treatments offering mixtures in the reward. Additionally, the most concentrated mixture triggers a significant survival rate in the conditioned bees. Thus, some nectar compounds, when combined, show synergistic effects on cognitive abilities and survival in an insect.