(A, D, G, J, M, P, S) xirp2a myotome marker in situ hybridization at 27 hpf. (B, E, H, K, N, Q, T) entpd5:Kaede expression between 15 dpf and 20 dpf. (C, F, I, L, O, R, U) Alizarin Red bone preparations of adults between 6 months and 1 year of age. (A to L) Triple and double heterozygote embryos for her1, hes6 and her7, have wild type myotome boundaries, arches and chordacentra. (M) The her7;hes6 homozygous mutants have normal myotome segmentation (n = 36). At both embryonic (N (n = 5)) and adult stages (O (n = 6)) her7;hes6 mutants have well-formed centra and neural and hemal arches. (P) her1;hes6 mutants (n=15) and (S) her1;her7;hes6 mutants (n=9) have disordered myotome boundaries. In both cases, neural and hemal arches show fusions (arrow in Q and T) (Q (n = 3), R (n = 1), T (n = 5) and U (n = 6)) and small vertebrae (asterisk in Q and T) and fusion between two vertebrae (cross in R). All animals in lateral view with anterior to the left. Scale bars are 100 µm in A, D, G, J, M, P, S; 300 µm in B, E, H, K, N, Q, T; and 0.6 mm in C, F, I, L, O,R,U).