ACTION SPECTRA OF THE PHOTOPHOBIC RESPONSE OF BLUE AND RED FORMS OF BLEPHARISMA-JAPONICUM

When exposed, in the presence of molecular oxygen, to light intensities of the order of 3-30 W m-2, the ciliate Blepharisma japonicum changes its color from red to blue, because of the photooxidation of the photoreceptor pigment, blepharismin, to oxyblepharismin. Both red- and blue-pigmented cells show step-up photophobic responses. The action spectra of the light-dependent behavior of the red and the blue form of Blepharisma have been determined; their structure is very similar to that of the absorption spectra of the red and blue pigment, respectively. These findings suggest that the photosensing and phototransducing properties of blepharismin are maintained in its photooxidized form, oxyblepharismin.