Figure 2. Comparison of model output with an axolotl embryo.

Column A1 shows photographs taken from a single live axolotl embryo, and a stage 17 cross-section from a different embryo. Stages in the figure are labeled with the letter A to denote them as axolotl stage numbers. Column S1 shows a simulation of normal neurulation. For the simulation shown in column S2, the strength of the lamellipodium action L was reduced to 80% of its normal value. Not only are the morphogenetic movements delayed but the tube does not close. When L forces are turned off on one side of the embryo (the side labeled with an I, for inactive, as opposed to the active side A), an asymmetric phenotype results (column S3), and closure fails. See Supplementary Material, for corresponding videos.