Laboratory versus nature: the two sides of the Drosophila circadian clock.

The daily pattern of animal behavior is thought to be of potential enormous importance for survival. Here, we compared the daily activity pattern of Drosophila melanogaster wild-type flies and the clock-impaired mutants, per(01) and Clk(Jrk) , under pseudo-natural conditions and laboratory conditions with natural-like temperature profiles. We found that clock-impaired flies respond stronger to changes in the environment, namely temperature increases, than wild-type flies. We hypothesize that the circadian clock may suppress unproductive activity in response to temperature fluctuations but that such suppression can be overcome in extreme conditions that are likely life-threatening for the flies. Thus, possessing a clock seems to be of adaptive significance.