Fig. 2

The process of tentacle branch formation. a–h Images of the same tentacle with branches forming as it grows. The main tentacle that extends from the medusa umbrella is numbered as ⓪. Newly formed branches are numbered in the order of their formation (the first branch = Branch①, the second branch = Branch②, the third branch = Branch③ …). These numbers are circled in this figure and others. The day when the first branch is observed (① in A) is defined as Day 1. In most cases, the medusa is released on Day 3. An example of a branched radial canal used as a reference to continually track same tentacle is marked by a star (c). The insets in a, e and g are blown-up images of the rectangle regions shown in the respective images. Scale bars: 200 μm. i Summary of tentacle branch formation. New branches are formed one after another at positions proximal to the older branches on the main tentacle (blue) as it elongates and are shown in different colors. j A table showing when branches were formed in 17 cases/tentacles. Each number represents how many numbered branches were observed for the first time on a given day among 17 tentacles