Perception in an Amoeboid Cell

Abstract

How is the sensed information processed and organized to bring about tactic beavior in an amoeboid cell? Cell shape and the motile activity oscillated with a period of several minutes during locomotion in various amoeboid cells, suggesting that oscillation forms a basis for amoeboid behavior. In addition, the whole amoeboid cell should be a coordinative assembly of interacting self-sustained oscillators, because each contractile element within the cell has oscillatory characteristics. With use of a computer image processing, we studied the responses of a giant amoeboid cell, the plasmodium of Physarum polycephalum, to local external stimuli as a dynamic cooperative behavior in thousands of oscillators. Much earlier than the behavior took place, new waves began to propagate within the cell, the phase gradient vectors pointing away from attractive stimuli and toward repulsive ones. Moreover, by applying oscillatory stimuli locally we were able to control the direction of the behavior at will as long as the intrinsic oscillation entrained to the external. Therefore, the sensed information is integrated at the level of interacting oscillators. Part of chemical nature of the oscillation and its role are also clarified.