[Regeneration of the digestive system in holothurians].

Five variants of regeneration of the digestive system in holothurians are recognized on the basis of original and published data. They depend on presence of organs remains, ability of cells for de-differentiation, damage type, and ontogenetic stage. Regeneration occurs in all cases by means of differentiated cells, no stem cells participation was recorded in any species studied. It is suggested that the entire diversity of recovering reactions observed for the holothurians gut is not an evolutionary innovation in Holothuroidea but evolved on the basis of already existing mechanisms of regeneration and blastogenesis in the ancient echinodermats. Analysis of khown data indicates that holothurians possess two groups of recovering processes, one of which is close to embryonic development and another to blastogenesis by respective mechanisms. This may indicate probable polyphyletic origin of reparative regeneration in Echinodermata.