Fig. 5. Relationship of somites or myotomes and vertebral column in zebrafish. To determine the alignment of the somite series with the vertebral column, future myotome cells in somite 5 (S5) were labeled during the first day of development and then visualized in conjunction with Alizarin Red staining of the vertebral column at 12 d as shown schematically in A. Cells originally labeled in S5 were found in the fifth myotome (M5) at 12 d (arrows in B). M5 was adjacent to vertebra 2 (V2) and vertebra 3 (V3), as shown schematically in A and in a representative fish in B. The resulting relationship between somite and vertebral alignment is shown in a schematized dorsal view in C.