Regeneration in Echinoderms: repair, regrowth, cloning

Regenerative potential is expressed to a maximum extent in echinoderms. It is a common phenomenon in all the classes, extensively employed to reconstruct external appendages and internal organs often subjected to amputation, self-induced or traumatic, rapidly followed by complete successful re-growth of the lost parts. Regeneration has been studied in adult individuals as well as in larvae. In armed echinoderms, regeneration of arms is obviously frequent: in many cases, the detached body fragments can undergo phenomena of partial or total regeneration independently of the donor animal, and, in a few cases (asteroids), the individual autotomised arms can even regenerate to produce new complete adults, offering superb examples of cloning strategies. In the species examined so far most results throw light on aspects related to wound healing, growth, morphogenesis and differentiation, even though in most cases many crucial questions remain unanswered. The present paper provides an overview of the current understanding of the phenomenon and covers the main biological aspects of regeneration giving an idea of the “state of the art” across the phylum in terms of experimental approaches and representative models.