We measured seasonal variation in the locomotor behavior of newly emerged adult honey bee workers in the laboratory. Analyses of bees from 12 colonies, 7 of which were tested once and 5 tested more than once, revealed seasonal changes in the free-running period (FRP) of the rhythm for locomotor behavior, with an increase from spring to summer. At the same time there was a decrease in the age at onset of circadian rhythmicity. There were no seasonal changes in overall levels of locomotor activity. Temperature and photoperiod, the only factors known to mediate plasticity in the insect clock, cannot account for the observed seasonal variation because bees were maintained under constant conditions. In a second experiment we found no differences in the FRP of nurses and foragers obtained from colonies maintained in a 12h light: 12h dark illumination regime. These findings suggest that exposure to unknown cues during pre-adult stages may affect the circadian behavior of adult bees.
Bibliographical noteFunding Information:
We thank Ravid Sachar and Niv Bachanof for observations and assistance with the bees. Financial support was provided by NIH grant GM57196 (GER), and Israel-US Binational Science Foundation (BSF) grant 2001022 (GB and GER).
- Circadian rhythm
- Developmental plasticity
- Division of labor
- Free running period
- Honey bees