waves. (a) Time course of fluorescence intensity changes. Shown are 1 min (left panel) and 5 min (middle panel) post-recording. ROIs 1–5 were set at regular intervals for analysis, as shown in b. The wave fronts traveled from the upper right to the lower left, as shown in the right panel (in min). The scale bar represents 100 μm. See also Additional file 4: Movie S4. (b) Intensity changes in the 5 ROIs defined in a. The arrowheads indicate sudden increases in intensity, i.e., wave fronts. (c) Time course of fluorescence intensity changes at the cellular level. The intensely highlighted structures are probably mitochondria. The yellow arrow indicates the direction of travel. The pink arrowheads indicate the wave-front cells. Ca2+ signals are elevated a few cells at a time. The scale bar represents 10 μm. See also Additional file 5: Movie S5. (d) The same visual field as c, in which 6 ROIs are defined to examine the intensity changes in e. The scale bar represents 10 μm. (e) Fluorescence intensity changes in the 6 ROIs defined in d. The wave fronts are indicated by arrowheads. (f) Scatter plot of the propagation distances and velocities of Ca2+ waves. Each dot represents a single wave, and the different colors represent different individuals. The Pearson correlation coefficient r and its associated p-value are shown.