Branching growth of ribbing patterns and the significance of concealed signals

Extending the analysis of the ribbing patterns of Recent branchiopods, pattern transformation with the progression of growth is discussed. In ribbing patterns of brachiopods, each rib grows wider and higher, and sometimes branches off. It is proposed that median patterns appear as predictable outcomes of a simple space-filling process with stochastic properties, as shown by some investigators. From the analysis by the modified Fly method, it is found that branching points are determined by deterministic long range waves (breather-like solitons) which strongly interact with one another. For these patterns, all possible Interactive Lindenmayer systems with two sided inputs of most neighbouring cells were simulated, and all patterns were classified, compared to solutions with non-linear wave equations. It is concluded that ribbing patterns with deterministic signals are realized by coupling automata between I-L system developing kinks, and cell automata developing solitons. The importance of a morphogenetic control theory involving coupling and long range signals is emphasized.