Fig. 10. Hyoid cartilage and bone in wild type (WT; A) and partially rescued edn1 mutants (B,C). Left-side views with dorsal to the top and anterior to the left. (B) Walking stick fusion phenotype (similar to that of stu mutant in Fig. 8D) in an edn1 mutant partially rescued by injecting human EDN1 protein. (C) Branchiostegal-opercle transformation phenotype (similar to that of the hoo mutant in Fig. 9B, but here the fan regions are fused) in an edn1 mutant partially rescued adding back a zebrafish edn1⁺ DNA construct. We have never observed either of these bone phenotypes in non-rescued edn1 mutants. The methods of rescue are as described by Miller et al. (Miller et al., 2000). Rescue of the cartilage phenotype is only partial, as indicated by the absence of the joints in the mandibular arch (asterisk in B and C, the arrow indicates the normal joint in A). The cartilages and attached bones were dissected from the heads of fixed and Alcian Green-stained larvae 4 days postfertilization, and are shown as flat mounts. In vivo, the bones project more posteriorly away from the cartilages than shown in the dissected wild-type preparation. bsr, (posterior) branchiostegal ray; ch, ceratohyal cartilage; hs, hyosymplectic cartilage; m, Meckel's cartilage; op, opercle; pq, palatoquadrate cartilage. Scale bar: 50 µm.