Information Propagation by Spatio-Temporal Pattern Change of Ca²⁺ Concentration throughout Physarum polycephalum with Repulsive Stimulation

抄録

The development of a spatio-temporal pattern of Ca²⁺ concentration (Ca²⁺ pattern) in the plasmodium of Physarum polycephalum during repulsive response was studied using fura-2. In the migrating cell, the gradient of the Ca²⁺ concentration (Ca²⁺ gradient) immediately showed a decrease in local concentration in the area (S-site) stimulated by 50 mM KCl. The concentration rose and then decreased in a site neighboring the S-site. This transient increase of Ca²⁺ concentration, the duration of which was approx. 10 minutes, was propagated to the site most distant from the S-site. There, the Ca²⁺ concentration gradually rose and remained at a high level. Twenty-five minutes after stimulation, a new Ca²⁺ gradient was established throughout the plasmodium. The migratory direction of the cell as a whole then changed. In this process, although the period of Ca²⁺ oscillation changed at the S-site, this change was only local to the site. During the information processing of the local repulsive stimulus, the transient Ca²⁺ increase propagated the local information about the stimulus to the non-stimulation sites (NS-sites), leading to the generation of a new pattern and the start of coordinated migration of the plasmodium.