Density, Starvation, and Swimming Rate in Didinium Populations

The response of Didinium nasutum to simultaneous changes in density and starvation was measured in the laboratory. As feeding rate cannot be used as a response in starvation experiments, the related activity of swimming rate was used. At low starvation rates of 1/2-1 h, Didinium respond to an increase in density by decreasing the swimming rate. At low densities of one to three individuals per 100 μl, Didinium respond to starvation of up to 30 h with a slight decrease in the swimming rate. At all combinations of density higher than three/100 μl and starvation times equal to or greater than 5 h, Didinium respond with a higher swimming rate than that found in well fed individuals. This behavior is interpreted to be one favoring increased dispersal from the site of an exhausted food supply. It is concluded that Didinium at higher densities have increased efficiency of energy utilization over that of individuals at lower densities.