Assessment of Appetitive Behavior in Honey Bee Dance Followers

Impact of odorants on perception of sweetness by honey bees

Organic volatiles produced by fruits can result in overestimation of sweetness by humans, but it is unknown if a comparable phenomenon occurs in other species. Honey bees collect nectar of varying sweetness at different flowering plants. Bees discriminate sugar concentration and generally prefer higher concentrations; they encounter floral volatiles as they collect nectar, suggesting that they, like humans, could be susceptible to sweetness enhancement by odorant. In this study, limonene, linalool, geraniol, and 6-methyl-5-hepten-2-ol were tested for their ability to alter behaviors related to perception of sweetness by honey bees. Honey bees were tested in the laboratory using proboscis extension response-based assays and in the field using feeder-based assays. In the laboratory assays, 6-methyl-5-hepten-2-ol and geraniol, but neither linalool nor limonene, significantly increased responses to low concentrations of sucrose compared with no odorant conditions in 15-day and 25-day-old adult worker honey bees, but not in 35-day-old bees. Limonene reduced responding in 15-day-old bees, but not in the older bees. There was no odorant-based difference in performance in field assays comparing geraniol and limonene with a no odorant control. The interaction of the tested plant volatiles with sucrose concentration revealed in laboratory testing is therefore unlikely to be a major determinant of nectar choice by honey bees foraging under natural conditions. Because geraniol is a component of honey bee Nasonov gland pheromone as well as a floral volatile, its impact on responses in the laboratory may reflect conveyance of different information than the other odorants tested.

In search of behavioral and brain processes involved in honey bee dance communication

Honey bees represent an iconic model animal for studying the underlying mechanisms affecting advanced sensory and cognitive abilities during communication among colony mates. After von Frisch discovered the functional value of the waggle dance, this complex motor pattern led ethologists and neuroscientists to study its neural mechanism, behavioral significance, and implications for a collective organization. Recent studies have revealed some of the mechanisms involved in this symbolic form of communication by using conventional behavioral and pharmacological assays, neurobiological studies, comprehensive molecular and connectome analyses, and computational models. This review summarizes several critical behavioral and brain processes and mechanisms involved in waggle dance communication. We focus on the role of neuromodulators in the dancer and the recruited follower, the interneurons and their related processing in the first mechano-processing, and the computational navigation centers of insect brains.

Early olfactory, but not gustatory processing, is affected by the selection of heritable cognitive phenotypes in honey bee

Associative learning enables animals to predict rewards or punishments by their associations with predictive stimuli, while non-associative learning occurs without reinforcement. The latter includes latent inhibition (LI), whereby animals learn to ignore an inconsequential 'familiar' stimulus. Individual honey bees display heritable differences in expression of LI. We examined the behavioral and neuronal responses between honey bee genetic lines exhibiting high and low LI. We observed, as in previous studies, that high LI lines learned a familiar odor more slowly than low LI bees. By measuring gustatory responses to sucrose, we determined that perception of sucrose reward was similar between both lines, thereby not contributing to the LI phenotype. We then used extracellular electrophysiology to determine differences in neural responses of the antennal lobe (AL) to familiar and novel odors between the lines. Low LI bees responded significantly more strongly to both familiar and novel odors than the high LI bees, but the lines showed equivalent differences in response to the novel and familiar odors. This work suggests that some effects of genotype are present in early olfactory processing, and those effects could complement how LI is manifested at later stages of processing in brains of bees in the different lines.

Spare to share? How does interindividual variation in metabolic rate influence food sharing in the honeybee?

A central benefit of group living is the cooperative acquisition and sharing of resources but the costs associated with these processes can set up a potential conflict between individual and group level fitness. Within a honeybee colony, the task of resource acquisition is relegated to the foragers and any interindividual differences in their metabolic rate and the consequent carbohydrate demand may pose a constraint on the amount of resources they can contribute to the colony. We investigated whether the carbohydrate demand of a forager is a function of her metabolic rate and if this impacts the amount of food she shares with the nestmates. Our results show that the sucrose consumption rates of foragers with high metabolic rates did not meet their carbohydrate demand, placing them at an energy deficit while those with lower metabolic rates had an energy surplus. Our food sharing experiments showed a trend but did not detect a significant difference among individuals with different consumption rates in terms of the amount of food they shared with their nestmates. These results suggest that honeybee foragers with different metabolic rates are likely to differ in terms of whether they have an energy surplus or deficit, but more long-term datasets may be required to detect how this may influence food sharing.

Honey bee workers generate low-frequency vibrations that are reliable indicators of their activity level

In social insects, the tuning of activity levels among different worker task groups, which constitutes a fundamental basis of colony organization, relies on the exchange of reliable information on the activity level of individuals. The underlying stimuli, however, have remained largely unexplored so far. In the present study, we describe low-frequency thoracic vibrations generated by honey bee workers (Apis mellifera) within the colony, whose velocity amplitudes and main frequency components significantly increased with the level of an individual's activity. The characteristics of these vibrations segregated three main activity level-groups: foragers, active hive bees, and inactive hive bees. Nectar foragers, moreover, modulated their low-frequency vibrations during trophallactic food unloading to nestmates according to the quality of the collected food. Owing to their clear association with the activity level of an individual and their potential perceptibility during direct contacts, these low-frequency thoracic vibrations are candidate stimuli for providing unambiguous local information on the motivational status of honey bee workers.