(A-H) Lateral images of the PHS fixed at 36 hpf (A-B, E-F) and 42 hpf (C-D, G-H) in lyve1b:EGFP fish that have been fluorescently immunostained with anti-PROX1 (green) and anti-GFP (red). These show a decrease in the number of Prox1-positive PHS ECs in the ccbe1 morpholino-injected (B, D) and sFLT4 mRNA-injected embryos (F, H) compared with control morpholino-injected (A, C) and uninjected embryos (E, G). At 42 hpf, ccbe1 morpholino-injected embryos (D) and sFLT4 mRNA-injected embryos (H) lack the PHS-LP domains present in the control embryos (C, G; large arrow heads). (I-J) Quantitation of the percentage of PHS ECs that are lymphatic progenitors relative to the total number of PHS ECs in control morpholino-injected embryos at 36 hpf (n = 27) and 42 hpf (n = 17) and ccbe1 morpholino-injected embryos at 36 hpf (n = 36) and 42 hpf (n = 12) (I) or in uninjected embryos at 36 hpf (n = 27) and 42 hpf (n = 21) and sFLT4 mRNA-injected embryos at 36 hpf (n = 26) and 42 hpf (n = 17) (J). (K) Quantitation of the total number of PHS ECs in control morpholino-injected embryos at 36 hpf (n = 27) and 42 hpf (n = 17) and ccbe1 morpholino-injected embryos at 36 hpf (n = 36) and 42 hpf (n = 12) or in uninjected embryos at 36 hpf (n = 27) and 42 hpf (n = 21) and sFLT4 mRNA-injected embryos at 36 hpf (n = 26) and 42 hpf (n = 17) 