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Fig. 4 The absence of the scaphium in the first vertebra in hoxb4a−/−;hoxb5a−/− mutants. (A-H) The anterior vertebrae were examined by micro-CT scan in hoxb4a−/− (A-D, n=4) and hoxb4a−/−;hoxb5a−/− (E-H, n=5) adult fish. Representative images are shown. For hoxb4a−/− and hoxb4a−/−;hoxb5a−/− mutants, fish with the desired genotypes were obtained by multiple intercrosses between each heterozygous fish, and the genotype analysis of the surviving juveniles is shown in Tables S1D,E. The arrowheads indicate the absence of scaphium on the first centrum in hoxb4a−/−;hoxb5a−/−. The asterisk indicates the elongated bone dorsal to the second centrum. Digital dissection of each vertebra in hoxb4a−/−;hoxb5a−/− is shown in Fig. S3. (I,J) Trunk region of wild-type (n=3) and hoxc8a−/− fish (n=5). Adult fish were obtained by several intercrosses between hoxc8a+/− fish, and genotype analysis of the surviving juveniles is shown in Table S1F. The arrowheads indicate the tip of the anterior-most rib. The rib shortening was observed in three of the five hoxc8a mutants. Such rib shortening was not detected in the other Hox mutants isolated in this study. Scale bars: 1 mm in A-H; 2 mm in I,J. For detailed information, micro-CT scan 3D movies are provided in Movies 11,12,13. A summary of the phenotypes of these mutants is shown in Table S2. Digital dissection of each vertebra in hoxb4a−/−;hoxb5a−/− is shown in Fig. S3. ic, intercalarium; lp, lateral process; os, os suspensorium; sc, scaphium; tp4, transverse process of vertebra 4; tri, tripus.