Fig. 1

Breeding water affects food intake and population size. a. Typical living animals that had been cultured in five kinds of breeding water and had then ingested liver homogenate tagged with a pink powder. Ingested food was visualized using a Texas Red fluorescence filter set. No fluorescence signals were detected in the unfed planarians. The strong fluorescence signals were detected in the planarians grown in Kanatani water, tap water, or 0.05% ASW, while weak signals were detected in planarians grown in 0.005% ASW or 0% ASW/pure water. Anterior is to the left. Bar, 1 mm. All animals are shown from the dorsal side. b. The feeding index determined by the ratio between the fluorescence area and the whole body area is shown as a box-and-whisker plot with mean (open circles). The feeding index of planarians grown in Kanatani water, tap water, or 0.05% ASW showed high score and there were no significant differences (NS by Kruskal-Wallis test) among them. By contrast, a low concentration (0.005% ASW) or absence (0% ASW/pure water) of ions in the breeding water reduced the score of the feeding index. **, p < 0.01 (Wilcoxon test). c. Population growth curve of planarians cultured in breeding waters for 6 weeks. The curves are shown as a trend line of three independent batches with 95% confidence interval (gray). The horizontal dashed line indicates the doubling of the number of individuals present at the start point. The number of individuals at 6 weeks was different, depending on the breeding water. ***, p < 0.005 (ANOVA)