The plasmodium of Physarum polycephalum is a unicellular and multinuclear giant amoeba. Recent studies revealed that the plasmodium has a kind of computational abilities and it can perform spatial optimization such as shortest path search in a maze and optimization of a network between multiple attractant. However, most of such studies observed the plasmodium in a closed space and the behavior of the organism after the full search of the space. There is thus a very few number of studies on the behavior of the plasmodium in an open space, though we suppose that we can find more enhanced biological characteristics of the biological entities by observing the behaviors of them in an open and unknown environment.
In this study, we developed an experimental system that has an unlimitedly extendable space and observed the long-range motility of the plasmodium, to study how the organism explores the open space. As a result, we found that the migration velocity of the plasmodium conforms to a power-law distribution. Furthermore, we performed a simulation to test the efficiency of the plasmodium-type exploratory behavior, and demonstrated that this type of the exploration is highly effective.