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Locomotive Mechanism of Physarum Plasmodia Based on Spatiotemporal Analysis of Protoplasmic Streaming

Kenji Matsumoto ^*, Seiji Takagi  and Toshiyuki Nakagaki  

^* Department of Mathematics, Research Institute of Electronic Sciences, and Creative Research Initiative Sousei, Hokkaido University, Sapporo, Japan

Correspondence: Address reprint requests to Toshiyuki Nakagaki, Tel.: 81-11-706-9211; E-mail: nakagaki{at}es.hokudai.ac.jp.

We investigate how an amoeba mechanically moves its own center of gravity using the model organism Physarum plasmodium. Time-dependent velocity fields of protoplasmic streaming over the whole plasmodia were measured with a particle image velocimetry program developed for this work. Combining these data with measurements of the simultaneous movements of the plasmodia revealed a simple physical mechanism of locomotion. The shuttle streaming of the protoplasm was not truly symmetric due to the peristalsis-like movements of the plasmodium. This asymmetry meant that the transport capacity of the stream was not equal in both directions, and a net forward displacement of the center of gravity resulted. The generality of this as a mechanism for amoeboid locomotion is discussed.