The Influence of Gustatory and Olfactory Experiences on Responsiveness to Reward in the Honeybee

Gabriela P Ramírez,Walter M Farina,Vanesa M Fernández,Andrés S Martínez,Gonzalo Corti Bielsa

doi:10.1371/journal.pone.0013498

Abstract

BackgroundHoneybees (Apis mellifera) exhibit an extraordinarily tuned division of labor that depends on age polyethism. This adjustment is generally associated with the fact that individuals of different ages display different response thresholds to given stimuli, which determine specific behaviors. For instance, the sucrose-response threshold (SRT) which largely depends on genetic factors may also be affected by the nectar sugar content. However, it remains unknown whether SRTs in workers of different ages and tasks can differ depending on gustatory and olfactory experiences.MethodologyGroups of worker bees reared either in an artificial environment or else in a queen-right colony, were exposed to different reward conditions at different adult ages. Gustatory response scores (GRSs) and odor-memory retrieval were measured in bees that were previously exposed to changes in food characteristics.Principal FindingsResults show that the gustatory responses of pre-foraging-aged bees are affected by changes in sucrose solution concentration and also to the presence of an odor provided it is presented as scented sucrose solution. In contrast no differences in worker responses were observed when presented with odor only in the rearing environment. Fast modulation of GRSs was observed in older bees (12–16 days of age) which are commonly involved in food processing tasks within the hive, while slower modulation times were observed in younger bees (commonly nurse bees, 6–9 days of age). This suggests that older food-processing bees have a higher plasticity when responding to fluctuations in resource information than younger hive bees. Adjustments in the number of trophallaxis events were also found when scented food circulated inside the nest, and this was positively correlated with the differences in timing observed in gustatory responsiveness and memory retention for hive bees of different age classes.ConclusionsThis work demonstrates the accessibility of chemosensory information in the honeybee colonies with respect to incoming nectar. The modulation of the sensory-response systems within the hive can have important effects on the dynamics of food transfer and information propagation.

Highlights

A key organizational principle of most real-world networks such as metabolic and social networks is that the majority of members are involved in few interactions, while a very small number are responsible for most the connections [1]
Seven day-old bees reared under laboratory conditions decreased their Gustatory response scores (GRSs) after an increase in sucrose concentration, while no changes over time were found after a decrease in concentration
The GRS of 14-dayold bees changed in response to both an increase and decrease in sucrose content. 14-day old bees decreased their GRSs after an increase in the sucrose concentration of the food (K–W: H = 19.55, p,0.001, N = 77, Fig. 1C), and increased their GRSs after a decrease in sucrose content (K–W: H = 20.39, p,0.001, N = 96; Fig. 1D)

Summary

Introduction

A key organizational principle of most real-world networks such as metabolic and social networks is that the majority of members are involved in few interactions, while a very small number are responsible for most the connections [1]. The average bee is involved in a few trophallaxis events, while a rather small number of workers participate in many trophallaxis events This is the case for older pre-foraging worker hive bees that are approximately two weeks old and behave as food receivers. Their function is to unload freshly-collected food from incoming foragers and pass it on to other nest mates, an activity of crucial importance to ensure a fast flow of food and information within the hive [4,6,7]. The sucrose-response threshold (SRT) which largely depends on genetic factors may be affected by the nectar sugar content It remains unknown whether SRTs in workers of different ages and tasks can differ depending on gustatory and olfactory experiences

Methods

Results

Conclusion