Klein, B. A. 2006. Caste-Dependent Change in the Sleep of a Worker Honey Bee. SLEEP. 29:A32

Klein, B. A. 2006. Caste-dependent change in the sleep of a worker honey bee. SLEEP. 29:A32.

Caste-Dependent Change In The Sleep Of A Worker Honey Bee Klein, Barrett A. Ecology, Evolution and Behavior, University of Texas at Austin, Austin, TX, USA.

Introduction : The study of insect sleep has begun to offer tractable, evolutionarily significant perspectives on the behavior of sleep. Honey bees (Apis mellifera) have a long history of sleep research. Workers experience a division of labor that is largely determined by age, beginning adulthood as cell-cleaners, later tending immatures as nurse bees, then storing food, and ending their lives foraging for food. This temporal succession of tasks (cell-cleaner, nurse, food-storer, forager) correlates, at least in part, with changing sleep patterns. Honey bee foragers sleep at predictable times during the night, but the younger nurse bees do not show periodic bouts of relative immobility. No one has explicitly documented the sleep dynamics of non-foraging bees, including the remaining two worker castes (cell-cleaners and food-storers), leaving gaps in our understanding of sleep’s role across members of a colony. I examined a colony of worker honey bees for caste-dependent sleep signs.

Methods : A collaborator and I individually marked members of a freely-foraging colony of honey bees and recorded the frequency of superficial sleep signs of individuals from different castes throughout a 72h period (3sec/h x 40 bees) and a series of 24h periods (30min/h x 1 bee of each caste). To examine change throughout individual bees' lifetimes, we recorded superficial sleep signs for periods of 48h (15min x 2 bees/h x 3weeks) as workers aged and changed tasks, to determine to what degree sleep habits differ among the 4 worker castes. States of (relative) immobility were categorized by posture (body either lifted above substrate or prone), or antennal motility (none, small flicks, or large movements).

Results : All four honey bee worker castes exhibited superficial sleep signs as adults. As bees aged and performed different tasks, however, they spent more time in a sleep-state (7%, 9%, 13%, 29%). Rhythmic patterns of immobility-mobility were not found in the young cell-cleaners or in the nurse bees, but began to take shape in the food-storers (P=.0013), and rhythmicity was obvious in the foragers (P<.0001).

Conclusion : Honey bee workers differ in duration and rhythmicity of sleep signs with respect to their caste. Understanding the frequency and degree to which individuals of different castes within a society sleep is the starting point from which one can test and understand the nature of sleep and its impact on the behavior and ecology of societies, and the societally-based purpose(s) of sleep.

Support: Environmental Science Institute, The University of Texas at Austin, Department of Ecology, Evolution and Behavior