Simulations of pholidosis of the carapace with a reaction-diffusion model. Darker colours indicate higher concentrations of activator of the first reaction diffusion-process (A1) or the inhibitor of the second reaction-diffusion process (I2). A, The beginning (t=0) and end (t=250000 iterations) of the simulation with the original parameters of Moustakas-Verho et al. (2014). The diffusion rates of A1 and its inhibitor I1 are 4 and 120, respectively. B, Simulations with lower diffusion rates of the activator and the inhibitor in the first process. The simulation with ⅛ of original diffusion rate parameters was run for 300000 iterations, and formed additional series of placodes but not scute seams. C, Comparison of simulated and real pholidosis patterns.