Pattern of cell proliferation in the early stages of arm regeneration in the feather star Antedon mediterranea

Arm regeneration in the crinoid echinoderm Antedon mediterranea can provide a very useful model for studying regenerative development. This process can be described as an epimorphic process in which new structures develop from migratory actively proliferating cells. Both the repair and the regenerative phases are due to this fundamental mechanism, which is the only way of recruiting cells to form the cicatricial layer and the blastema. In order to identify the source, the proliferation sites and the recruitment times of these cells, cell proliferation was monitored by employing an immunocytochemical system to detect the thymidine analogue bromodeoxyuridine (BrdU) incorporated by S‐phase cells of the regenerating tissues. On the basis of BrdU incorporation the actively proliferating elements can be identified both close and far from the amputation 1) in the populations of migratory cells which are produced at the level of the brachial nerve and the coelomic wall and 2) in the coelomic epithelium itself. These structures are preferential sources of new cells and give a differential contribution during the repair and the regenerative phases in terms of potential of cell proliferation.