Mechanisms of arm regeneration in the feather star Antedon mediterranea: Healing of wound and early stages of development

Crinoids have remarkable regenerative capacities. After traumatic or self‐induced amputation they can replace one or several arms through a complex sequence of morphogenetic events which lead quickly to the complete reconstruction of the lost part. These phenomena are well known in their general aspects and a comprehensive description of arm regeneration was previously provided (Candia Carnevali et al., Recent Trends in Regeneration Research. Plenum Press, New York, '89). However, there is a considerable gap in knowledge of the early regenerative phases which are particularly significant for the following development. The aim of the present work is to describe and interpret the different aspects of these early stages of arm regeneration in Antedon mediterranea. According to our results the regenerative development of Antedon arm seems to consist of an epimorphic process which essentially implies the involvement of proliferating undifferentiated cells. The early stages of this process can be distinguished in a first repair phase, which includes the overall 24 hr post‐amputation period and is characterized mainly by the processes of wound healing and tissue repair, and in a second regenerative phase, which includes the 24–72 hr post‐amputation period and is characterized by the first regenerative events. The different arm components involved in the amputation/regeneration phenomena seem to play different and specific roles in these initial phases.