Growth of the cell mass (CM) during the development of Temnopleurus toreumaticus . (A,B) The photographs show epifluorescence images of DAPI-stained larvae 2 days (A) and 7 days (B) after fertilization (dorsal view). (A’) and (B’) show higher magnification images of the CM in white broken squares in (A) and (B). Arrows indicate individual cells. The CM in (B) has started to change its shape by cell migration. Scale bars = 50 μm. (C) Schematic diagram of a four-armed larva indicating measurement made during the period from 2 to 15 days after fertilization before adult rudiment formation. The distance between the tip of the post-oral arm and the posterior end of the larval body was defined as the ‘larval body length’ and the maximum diameter of the CM was defined as the ‘size of the CM’. (D,E) Changes in mean larval body length (D) and mean size of the CM (E) (± the standard error of the mean).