Fig. 3

Correlated variation of gastric pouch and siphonoglyph numbers in D. lineata. a Frequency of individuals as a function of the number of orange stripes corresponding to first, second, and directive gastric pouches. b Representative examples (upper panel) and frequency of monoglyphic (I), diglyphic (II), and triglyphic (III) individuals. Black dashed arcs indicate siphonoglyphs. Numbers at the bottom of each panel denote the number of individuals, n = 114. The star mark indicates intermittent white pigmentation unrelated to the siphonoglyph position. Scale bars, 500 μm. c Scatter plot of the stripe number as a function of the siphonoglyph number with the Pearson correlation coefficient \( r=\frac{N\left(\Sigma xy\right)-\left(\Sigma x\right)\left(\Sigma y\right)}{\sqrt{\left[N\Sigma {x}^2-{\left(\Sigma x\right)}^2\right]\left[N\Sigma {y}^2-{\left(\Sigma y\right)}^2\right]}} \), where x, y, and Σ denote the number of siphonoglyphs, that of stripes, and the summation for the observed individuals, respectively. Data sets are identical among a–c