(A–B) 23 hpf vasculatures, green. SBs, red. Horizontal myoseptum (HM), white dotted line. SeA sprouts, numbered. (A) WT. (B) obd. SeA sprout position (C) and abundance (D) in 23 hpf WT and obd. (E–F) WISH, 28 hpf trunks. Ectopic SeA sprouts, white arrowheads. Riboprobes: flt4 (blue), cdh5 (red). WT (E). obd (F). (G–H) 32 hpf chimeric vasculatures with ECs of donor (green) and host (red) origin. Examples of ectopic SeA sprouts, white arrowheads. (C–D) n = 8 WT, 12 obd. Error bars, s.e.m. ***p < 0.001. (E–F) n = 10/10 WT, 10/10 obd. (A–B, E–H) Anterior, left; dorsal, up. Scale bars, 30 μm. See Figure S1.