Circadian Rhythms and Sleep in Honey Bees

Abstract

The circadian clock of the honey bee is involved in complex behaviors and is socially regulated. Initial molecular characterization suggests that in many ways the clock of the bee is more similar to mammals than to Drosophila. Foragers rely on the circadian clock to anticipate day–night fluctuations in their environment, time visits to flowers, and for time compensation when referring to the sun in sun-compass orientation and dance language communication. Both workers and queens show plasticity in circadian rhythms. In workers, circadian rhythms are influenced by task specialization and regulated by direct contact with the brood; nurse bees tend the brood around the clock with no circadian rhythms in behavior or clock gene expression. An important function of the circadian clock is the regulation of sleep. Bees show a clear sleep state with a characteristic posture, reduced muscle tonus, and elevated response threshold. Honey bee sleep is a dynamic process with common transitions between stages of deep and light sleep. The sleep stages of workers active around-the-clock are overall similar to foragers. Sleep deprivation leads to an increase in the expression of sleep characteristics the following day, and may interfere with some learning paradigms. This review shows that the honey bee is an excellent model with which to study circadian rhythms and sleep in an ecologically and socially relevant context. Future research needs to deepen our understanding of these fascinating behaviors, reveal their neuronal and molecular bases, and explore their interactions with other physiological processes.