Abstract
A sensitive multi-electrode was developed to observe the spatio-temporal evolution of extracellular electric potential around plasmodia of starved Physarum polycephalum. As the starvation proceeded, oscillation of the electric potential in all places was observed, with a large reduction in the frequency and a great increase in the amplitude. This was followed by morphological change about one hour later. In spite of the great change in the oscillation, however, there was a specific relationship between the frequency and amplitude: (amplitude) × (frequency)2 = constant.
Under anaerobic conditions, the oscillation was greatly suppressed and the morphological changes were completely suppressed. This strongly suggested that some activity related to respiration was very important to the proliferation of the starved plasmodia. In addition, in the presence of the proton pump in-hibitor diethylstilbestrol (DES), the spatial uniformity and the amplitude change of the electric potential oscillation were greatly reduced, although the development of the frequency of the electric potential was very similar to that in its absence. DES also inhibited the morphological change of starved plasmodium. The correlation between the oscillation phenomena and the mor-phological change is discussed.
