ARE THE EFFECTS OF LIGHT ON PHASE AND PERIOD OF THE GONYAULAX CLOCK MEDIATED BY DIFFERENT PATHWAYS

The effects of different wavelengths of light on period, phase shifting, entrainment and after-effects of the circadian clock of the motile marine dinoflagellate Gonyaulax polyedra are described. Phase shifting and entrainment by light can be explained by the action of a single blue sensitive light input pathway. However, tonic effects of light on the period under free-running conditions, and also after-effects on period resulting from single 4 h light exposures, appear to involve two input pathways with different absorption and temperature characteristics. These results suggest different mechanisms for the control of phase and period of the circadian clock.