Figure 4.

Nurse bees show circadian rhythms in locomotor activity shortly after transfer from a LD illuminated hive to a constant laboratory environment. A, Representative double-plot actograms for locomotor activity of a nurse (left, R47; data for the same bee are shown in Fig. 1 A), a nurse-age bee that was restricted to a broodless comb in the hive (middle, W20; data for the same bee are shown in Fig. 1 B), and a forager (right). Bees were monitored individually under constant conditions in the laboratory. The y-axis shows the days after removal from the hive. The height of the small bars for each day corresponds to locomotor activity in a 10 min bin. Horizontal bars at the top of the plot correspond to the illumination regime in the observation hive: striped bars, subjective day, filled bars, subjective night. The arrows point to the data acquisition start time. B, Summary of locomotor activity during the first 3 d in the laboratory for bees from colony H7 that were removed from the hive at noon. All the bees were significantly more active during the subjective day (gray bar) than during the subjective night (filled bar). This difference was already visible on the first day of isolation (Paired t tests, two-tailed,*p < 0.01; **p < 0.001). The subjective day and night were based on the Free Running Period (τ) of each bee. Similar results were obtained for bees from colonies S26 and S77 (see supplemental Fig. S3A, available at www.jneurosci.org as supplemental material).