Fig. 1

Branchial aortic arch and ventral aorta development. Aortic arches 3–6 first appear in an anterior-to-posterior sequence as angioblast islands (indicated as numbers 3 through 6) in the lateral pharyngeal mesoderm; sprouts emerge from these islands and travel ventromedially and dorsally (A–L; see also Movie 1). By 48 hpf (M), ventral sprouts merge to form bilateral ventral aortae (VA), which fuse into a single midline vessel by 72 hpf (N). Dorsally (O; 72 hpf), branchial aortic arches turn medially beneath the primary head sinus (PHS). Aortic arches 3 and 4 connect independently to the lateral dorsal aortae, whereas aortic arches 5 and 6 merge and extend to the lateral dorsal aortae as a single vessel, the aortic arch 5 extension (AA5X). A–D: tie1 in situ hybridization. E–H and N: 2D confocal projections of TG(flk1:GFP^la116;gata1:dsRed) embryos, labeling endothelial and blood cells green and red, respectively. Panels E–H are representative time points taken from Movie 1. M, O: 2D confocal projections of TG(flk1:GFP^la116) embryos. I–L: wiring diagrams of images in panels E–H; vessels were traced using Photoshop. A–L: lateral views, anterior to the left. M, N: ventral views, anterior to the left. O: dorsal view, anterior to the left.