Development of the superficial system. (A-F) Projections of confocal z-stacks (left in each panel) showing ocular vessels in Tg(kdrl:EGFP) live embryos at different developmental time points, which are depicted in each panel. On the right side of each panel are the same conofocal images combined with bright field images showing position of vessels relative to eye tissues. (A) Arrowhead points at an initial sprout that will form the DRV. (B) Arrowheads point at two vessels, one or both will form the DRV. These vessels have connected and the tip cell (arrow) grows towards the CrDI. (C) The DRV and NRV have formed. One of the two initial vessels that sprouted from the PMBC is being pruned (arrowhead). (D) Sprouts arising from the VRV and NRV/SAV junction send long filopodial extensions towards each other (arrows). The posterior part of the SAV begins to grow ventrally (arrowhead). (E) The posterior SAV continues to grow ventrally, but there is only minor angiogenic activity from the VRV. Arrows point at tip cell of posterior SAV and small filopodial extension from the VRV. (F) The completed superficial system. Arrow points at the hyaloid vein and arrowheads at the SAV. All images are lateral views, anterior to the left, dorsal up. CrDI, cranial division of internal carotid artery; DRV, dorsal retinal vessel; H, hyaloid system; L, lens; NRV, nasal radial vessel; PMBC, Primordial midbrain channel; SAV, superficial annular vessel; VRV, ventral radial vessel. Scale bars are 50 μm.