Fig. 5

Multiday, multi-angle SPIM of hand2:EGFP zebrafish embryos from 18 to 82 hpf (n = 6). A Maximum intensity projection (MAX) of embryo expressing the LPM-marking drl:mCherry (24 hpf onwards restricted to cardiovascular lineages) (magenta) and hand2:EGFP (greyscale) at 48 hpf. Boxes depict selected regions in C–G. Bhand2:EGFP-positive populations within 48 hpf embryo, lateral view left and dorsal view right. C–E 3D-rendered hand2:EGFP embryo, focused on pericardium formation. C Rostral view, visualizing formation of pharyngeal arches (asterisks) and primary heart tube. D Ventral view, illustrating left and right flanks of the forming pericardium meeting at the midline (32 hpf, arrowheads). E Single plane, highlighting how the pericardial cavity forms within anterior LPM (arrows). hand2:EGFP labels coelomic epithelium, contributing to ventral and dorsal pericardium. F, G Single-plane cross-sections showing the migration of hand2-positive cells over yolk (G) and yolk extension (H), forming parietal peritoneum. Yellow arrows point out dorsal-ventral directed migration path. White arrows indicate inwards-migrating EGFP-expressing cells, contributing to coelomic epithelium maturing into visceral peritoneum. H Schematics of how hand2-expressing cells laterally migrate over the yolk forming parietal peritoneum, and migrating medially to wrap around endodermal-derived organs forming the visceral peritoneum. Red blood cells (rbc), heart tube (ht), pharyngeal arches (pa), and yolk (y). Scale bars A, B 500 μm and C–G 25 μm.