Regeneration in Echinoderms
Physiology of Regeneration



In the phylum Echinodermata, regeneration is common in all five classes and involves the adult and larval stages. [12] Echinoderms can regenerate external body parts (e.g., arms, spines) and internal organs (e.g., gut, whole visceral mass, vital organs) following self-induced (autotomy) or predator-related mutilations. Echinoderms can also regrow a whole individual from body fragments (asexual reproduction). [4], [5]

Illustration of the mechanisms of regeneration:
Epimorphosis (B), Morphallaxis (C)
Image provided by [13] and adapted for this website.

Regeneration is executed through a combination of epimorphosis and morphallaxis, the two basic mechanisms of regeneration: [4], [5]

- In epimorphosis, new tissues arise from undifferentiated (dedifferentiated/stem cells). These cells are recruited to develop a blastema from which - through cell proliferation - the regenerated structures are derived.

- In morphallaxis, new tissues arise from rearranging/recycling differentiated cells. The regenerated structure is formed through cell proliferation from existing tissues by reversal of differentiation and/or migration.

The following sequence of events illustrate the mechanisms of regeneration:
Recruitment of stem cells and/or dedifferentiated cells -> cell proliferation and migration -> supply of regulatory/trophic factors -> and finally expression (or re-expression) of a specific developmental program.

Regeneration of the muscle system in echinoderms. The mechanism shown below demonstrates a morphologically differentiated coelomic epithelium cell undergoing reversal of differentiation (functionally dedifferentiation). The dediferentiated cell can undergo rediffferentiation to become a coelomic epithelium cell again, or transdifferation, where it can become an entirely different type of cell.
Image provided by [6] and adapted for this website.




jubedoya@davidson.edu