Fig. 3

Early larval development in Schizocardium californicum. a-d, f-g Light DIC micrographs of live specimens. Optical sections through the middle of the embryo (a, c-d, f) or surface views (b, g). e, h-o Maximum intensity projections of confocal stacks. Larvae are labeled with four markers: phalloidin (green), anti-acetylated tubulin (red) and anti-serotonin (yellow) antibodies, and DAPI (blue) unless otherwise indicated. All panels are anterior to the top. Lateral views are ventral to the left. a, b Hatched gastrula stage embryos at the time of pore canal formation, 33 hpf. c-e Developing tornaria larva at the time of protocoel formation, 2 dpf. f-o Early tornaria after mouth formation, 3 dpf. i Close-up lateral view of the apical organ_. j Close-up view of the squamous epithelium of the dorsal ectoderm. o Close-up dorsal view of the apical organ. a, archenteron; ao, apical organ; at, apical tuft; cb, serotonergic cell body; cc, cells of the presumptive circumoral ciliary band; dv, dorsal view; lv, lateral view; m, mouth; of, oral field; p, protocoel; pd, protocoel duct (pore canal); pof, postoral field; post, postoral loop of the circumoral ciliary band; pp, protocoel pore (hydropore); pre, preoral loop of the circumoral ciliary band; prf, preoral field; st, stomodeum; vv, ventral view. Scale bars: 50 μm