Phototactic Orientation in Plasmodia of the Acellular Slime Mold, Physarum polycephalum

Phototactic orientation to lateral light was studied in plasmodiaof the yellow-pigmented strain (CL) and a white mutant of theslime mold Physarum polycephalum. The orientation changes wereperformed by either a turn or a reversal of the internal polarityof the plasmodium. Fluence rate-response curves for white andmonochromatic light showed positive phototaxis with low fluencerates and negative phototaxis with higher ones. The wavelengthdependences for both strains were similar and indicated thepredominant role of a UV/blue light-absorbing photoreceptor,which was not the same as one of the yellow pigments found inthe wild-type strains. Wavelengths >500 nm induced only aninsignificant effect. The control of the motor apparatus andthe possible linkage of the photoresponse with the other sensoryprocesses known in Physarum are discussed. (Received June 3, 1983; Accepted October 11, 1983)