Regeneration phenomena are ubiquitous in nature and are studied in a variety of experiments. Positional information and feedback-loop hierarchy are theories that have been proposed to explain ordering rules in regeneration; however, some regeneration phenomena violate the rules derived from them. In particular, grafted junction stumps with the same value/hierarchy sometimes lead to one extra segmented portion, termed segmented regeneration. To present a unified description of all insect leg regeneration phenomena, we propose a theoretical mechanism for regeneration without postulating positional information, by using a model that consists of intracellular reaction dynamics of chemical concentrations, cell-to-cell interactions, and an increase in cell number. As a normal developmental process, successive differentiation from pluripotent cells appears, as described by transition from cells with intracellular chaotic dynamics to those with oscillatory or fixed-point dynamics. By assigning chaotic and nonchaotic cell types to corresponding positions instead of positional information, intercalary, segmented, and tarsus regeneration are explained coherently. With this assignment of pluripotency to chaotic dynamics, a unified description of regeneration is obtained with some predictive value for new experiments.
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