Resetting the Biological Clock in Gonyaulax with Ultraviolet Light

Abstract

Short exposures to ultraviolet light bring about stable changes in the phase of the rhythms of luminescence and cell division in Gonyaulax polyedra, presumably resetting the biological clock. The amount of change in the phase depends upon the length of the exposure to ultraviolet light and the time in the diurnal cycle at which irradiation occurs. The phase is always advanced by ultraviolet light. The phase shift is complete shortly after the end of irradiation, and does not appear to be photoreversible.