Separation of wound healing from regeneration in the cockroach leg.

It has been shown that after a critical point in the moult cycle of a cockroach, wound healing can occur but regeneration of pattern does not take place until the following intermoult period. Leg removal after the critical point is used to separate the processes of wound healing and leg regeneration. This permits the study of patterns of cell division resulting from wound healing to be distinguished from those involved in leg regeneration. During wound healing, cell division occurs in the epidermal cells of approximately the distal half of the trochanter. The cells then return to the resting state until after the next ecdysis. Regeneration starts with cell division occurring in the distal half of the trochanter, and then spreading to include cells of the proximal trochanter and distal coxa. This spread and the following patterns of growth and redifferentiation appear to be the same as for regeneration following leg removal prior to the critical point, with the more distal structures completing early stages of regeneration first. Scanning electron micrographs of the cuticle of the trochanter after the ecdysis following leg removal support the evidence from the patterns of cell division in suggesting that the distal half of the trochanter is dedifferentiated during wound healing.