Photomotile responses of Blepharisma Japonicum I: action spectra determination and time-resolved fluorescence of photoreceptor pigments

The light-induced avoiding reaction of Blepharisma Japonicum was investigated by means of microscope videorecording techniques. The percentage of photoreacting cells and the lag time between stimulus onset and reaction were measured as a function of the fluence rate and of the light stimulus wavelength. Action spectra indicate that the red pigment blepharismin is the photoreceptor pigment for this photoresponse. The fluorescence lifetimes and quantum yields of ethanol-extracted pigments and cold-extruded pigment granules were measured by means of a phase-modulation spectrofluorometer. The fluorescence lifetime and quantum yield of the pigment in granules are half those of pigments in ethanol solution. This could be in agreement with the hypothesis that blepharismin is the photoreceptor pigment for the observed photobehaviour.