The social clock of the bee

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Guy Bloch

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Circadian clocks enable organisms to anticipate predicted changes in their environment and coordinate endogenous processes with external day-night cycles. In spite of the evidence for the importance of circadian rhythms for survival and health, recent studies in an ecologically-relevant context show that in nature many animal species show extended periods of activity around-the-clock with attenuated circadian rhythms and no ill effects. For example, social insects such as honey bees, bumble bees, and several species of ants show remarkable socially-regulated plasticity in circadian rhythms. Forager bees typically have strong circadian rhythms that are needed for time-compensated sun-compass navigation and for timing visits to flowers ("time memory"). “Nurse” workers on the other hand, tend brood around-the-clock which is thought to improve the quality of brood care. We discovered that some clocks in the brain of nurse bees continue to tick in the constantly dark and thermoregulated environment of the hive, and are synchronized ("entrained") by social time-givers in the nest. These findings raise many questions including: How does circadian plasticity manifest at the molecular level? Which are the endogenous processes for which circadian regulation is essential? Why do nurses need a clock? Do around-the-clock active nurse bees sleep? And what are the social signals that entrain the circadian clocks of nest bees? To answer these questions we use an integrative, multi-level approach, combining sociobiology, animal behaviour, physiology, neuroanatomy, and functional genomics. In my talk I will answer some of these questions and present the state of the art of our research.