Fig. 2

Somitogenesis period at different axial positions. A: Somitogenesis period in the anterior trunk does not differ significantly from the period in the posterior trunk. Populations of embryos from the same clutch were filmed in parallel, either with or without chorion from lateral or dorsal view, respectively. Normalized mean somite formation times ± SD were scored from either set of movies. Linear fits to both data sets (somites 1-6 for the dorsal view, somites 6-17 for the lateral view) yielded slopes that were not significantly different. Note that the limited number of data points for period estimation for the anteriormost somites results in a large confidence interval. T = 27.6 ± 0.1°C. B: Somitogenesis period increases in the tail. Tail outgrowth of embryos homozygous for the nic^b107 allele was filmed, and somite formation times were analyzed from somite 4 onward. A linear fit to data points in the trunk region (somites 4-17) indicates nonlinear behavior as somitogenesis proceeds into the tail. T = 27.4 ± 0.1°C.