[Unusual way of regenerating intestinal epithelium during seasonal intestinal transformation in Stichopus japonicus holothurians (possibility of an "external cambium")].
In Stichopus japonicus during summer months a profound morphofunctional rearrangement of the digestive tract resulting in its renovation is noted. It includes certain destructive-atrophic changes in the wall of the intestinal tube and some reparative processes accompanying them. In some species a spontaneous throwing out of the intestine with its subsequent restoration takes place. The mechanisms of the intestinal tube regeneration after its partial atrophy and after its spontaneous throwing out have much in common between them and with those previously described after an experimental throwing out. It is possible that under natural conditions (as well as under experimental ones) certain forms of wandering cells, migrating from the sublayers and/or from the surrounding structures (mesenterium and others), participate in the regenerative histogenesis of the intestinal epithelium. A suggestion is made that these cells are of coelomesodermal origin and play the role of the external cambium at sharp seasonal rearrangements of the holothurian intestinal tract.