Identification of a birefringent structure which appears and disappears in accordance with the shuttle streaming inPhysarum plasmodia

Summary R-HMM (rhodamine-heavy meromyosin) stained the birefringent fibrous structure which appears and disappears cyclically in parallel with the periodic shuttle streaming in the plasmodium ofPhysarum polycephalum. In addition, 0.6 M KI readily made the birefringent fibrils fade away. These results clearly show that the birefringent fibrils are composed of actin filaments and prove the possibility of actin filaments to alter in the aggregation state during the cyclic production of the motive force responsible for the cytoplasmic streaming.