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Fig. 5 | Zoological Letters

Fig. 5

From: Calcium ions in the aquatic environment drive planarians to food

Fig. 5

Calcium ions are required for the feeding behavior. a. Schematic illustration of the experimental design for the behavioral assays in environmental waters in the absence of a particular ion. Planarians grown in 0.005% ASW for at least 2 weeks were transferred to assay fields containing each type of modified Kanatani water and briefly subjected to behavioral assays. b. The feeding index of planarians in Kanatani water in the absence of a particular ion is shown as a box-and-whisker plot with means (circles). The absence of calcium ions in the environmental water reduced food intake, whereas the absence of potassium ions or sodium ions did not affect it. c. The food-localization assay in each type of modified Kanatani water. The cross indicates the position of the colored food pellet. The circle indicates the planarian’s start region. Planarian behavior was quantified using the time spent in the target quadrant. The diameter of the circular field was 9 cm. Heat map view of the averaged behavior of 10 individually assayed animals in a food-localization assay field. Warm colors indicate locations where much time was spent, and cool colors those where little time was spent. Planarians in Kanatani water, Kanatani water without potassium ions, or Kanatani water without sodium ions showed a preference for moving to and remaining in the region with the food, whereas planarians in Kanatani water without calcium ions did not show such food-localization behavior. t = 300 s. d. Time spent in the target quadrant during assay of planarians in Kanatani water without a particular ion is shown as a box-and-whisker plot with mean (circles). e. Speed of movement of planarians during the assay. The absence of calcium ions in the environmental water impaired the motor activity. f. The food-localization index is the adjusted value of the spent time in the target quadrant calculated by assuming all individuals had the same speed. The adjustment was performed using the median value of the speed (0.38 mm/sec) of the planarians in Kanatani water without calcium ions. g. The food-localization assay in Kanatani water containing 10 mM EGTA. Planarians in Kanatani water (Ctrl) showed a preference for moving to and staying in the region with the food, whereas planarians in Kanatani water containing EGTA did not show such food-localization behavior. t = 300 s. h. The food-localization index is the adjusted value of the spent time in the target quadrant calculated by assuming all individuals had the same speed of movement. The adjustment was performed using the median value of the speed (0.51 mm/sec) of the planarians in Kanatani water containing EGTA. i. The feeding index of planarians in Kanatani water containing EGTA is shown as a box-and-whisker plot with means (circles). The chelation of calcium ions by EGTA in the Kanatani water reduced the food intake. *, p < 0.05; **, p < 0.01; ***, p < 0.005; NS, not significant (Wilcoxon test)

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