Fig. 3

Environmental water immediately affects and can restore feeding behavior specifically. a. A schematic illustration of the experimental design for behavioral assays in various environmental waters. Planarians grown in 0.005% ASW for at least 2 weeks were transferred to assay fields containing each type of environmental water and briefly subjected to behavioral assays. b. The percent time spent in the target quadrant during 90 s in the photo-orientation assay is shown as a box-and-whisker plot with mean (circles). c. Speed of movement (mm/sec) during photo-orientation assay. There were no significant differences (NS) in either the photo-orientation behavior or the motor activity among planarians bred in the different environmental waters (Kruskal-Wallis test). d. The concentration of ions in the environmental water determines planarians’ sensitivity to the presence of food. The food intake was analyzed using colored food pellets containing different proportions of liver homogenate (33.3, 40, and 62.5%). Planarians cultured long-term with a low concentration of ions (0.005% ASW) showed restoration of the feeding behavior immediately after transfer into Kanatani water, tap water, or 0.05% ASW. The feeding index increased in a food-proportion-dependent manner. *, p < 0.05; **, p < 0.01; ***, p < 0.005 (Wilcoxon test)