PHASE SHIFTING OF ECLOSION IN DROSOPHILA PSEUDOOBSCURA AS A FUNCTION OF ENERGY OF LIGHT PULSE

The phase shifting effect of different energies of blue light pulses has been determined at two points in the circadian eclosion cycle of Drosophila pseudoobscura. At circadian time CT 16 as well as CT 20 no significant effect is found at energies up to 102ergs/cm2. Higher energies given at CT 16 delay phase, at CT 20 advance phase relative to a control. Figs. 1 and 2 show the amount of phase shift as a function of the energy of the light pulse for the fourth peak. These figures also show a plateau in the response to energies above 104ergs/cm2, i. e. phase-shifting response saturates around this energy. In contrast to earlier findings, phase shifting light pulses at CT 16 did not lead to a constant residual phase shift in respect to a control. Possible explanations are discussed. © 1969 Springer-Verlag.