title: Euglena: the photoreceptor system for phototaxis.
abstract: The photoreceptor structures (eyespot-paraflagellar body-flagellum) for Euglena phototaxis were investigated by electron microscopy. The paraflagellar body--the photoreceptor--is a highly ordered crystalline lamellar structure. Optical diffraction of the electron micrographs and resulting filtered images of the paraflagellar body suggest that it is formed of rods in a helical arrangement. The action spectra for phototaxis, the in situ spectrum by microspectrophotometry of the paraflagellar body, and flavin analysis of the organism indicate that the photoreceptor molecule is a flavoprotein. The phototaxis action spectrum is similar to the spectrum for O2 evolution and implies that similar molecules participate in the photo processes. As a result, a photochemical scheme is suggested in which a photo-excited flavin and a cytochrome participate in the photoprocess. The photochemistry and photoreceptor structures for Euglena phototaxis are likened to a photoneuro sensory cell.
mesh_terms: D000818:Animals; D005056:Euglena gracilis / Q000032:analysis / Q000502:physiology / Q000648:ultrastructure*; D005407:Flagella / Q000648:ultrastructure; D005415:Flavins / Q000032:analysis; D008027:Light; D010786:Photoreceptor Cells / Q000032:analysis / Q000648:ultrastructure*; D013054:Spectrophotometry, Atomic
chemical_list: D005415:Flavins