The locomotor activity rhythm of Drosophila melanogaster is controlled by a dual oscillator system

Wild-type fruit flies show a pronounced bimodal locomotor activity pattern under light-dark conditions. This pattern seems to be due to two oscillator y components - the morning and evening oscillators. Whereas the evening osc illator is controlled by the well studied clock gene period, the morning os cillator appears independent of the period gene. The present study shows th at per(0) mutants retain the morning oscillator. The latter is apparently n ot strong enough to drive rhythmic activity under conditions of constant da rkness. However, under light-dark conditions the activity of per(0) mutants is entrained whereby the onset of activity depends on the Zeitgeber period . This behaviour is characteristic of circadian oscillators. The nature of the morning oscillator and its putative relationship to the photoperiodic t iming is discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.