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Fig. 4 Endoskeletal joints and hemisegment separation do not require Evx1. A–D,G,H: Lateral views of wild-type (WT) or heterozygous siblings (A,C,G,H) and evx1 mutants (B,D). E,F: Cross sections through WT (E) and evx1 mutant (F) lepidotrichia. A,B,G,H: Anal fins. C,D: Dorsal fins. E,F: Caudal fins. A,B: 43 days postfertilization (dpf). C,D: 28 dpf. E,F: Adult. G: 22 dpf. H: 35 dpf. A,B: evx1 expression. C–F: Alcian blue/Alizarin red staining. G,H: gdf5 expression. A,B: evx1 is expressed at intersegmental joints in WT siblings (A), but it is not expressed in equivalent regions in evx1 mutant fins (B). Fin endoskeleton is not affected by the evx1 mutation. C,D: The distal radials of dorsal fins separate from the proximal radials (arrows) in both WT siblings (C) and evx1 mutants (D). E,F: Dermoskeletal hemisegments are separated and not fused in WT (E) and evx1 mutant (F) fins. G,H: gdf5 is expressed during joint formation in the endoskeleton (G) but not in the dermoskeleton (H). Arrow in H indicates a joint clearly visible by differential interference contrast microscopy. Scale bar in panel E = 120 μm in A,B, 160 μm in C,D, 34 μm in E,F, 55 μm in G, 100 μm in H.