The effects of x‐rays on regeneration in Tubifex Tubifex

Abstract

Abstract Posterior regeneration in Tubifex is inhibited by suitable radiation with x‐rays. Only a small knob is formed at the cut surface by rearrangement of the terminal region of the old body tissues. Location of the cut within the segment and repeated removals of segments within the posterior three‐fourths of the body do not change this result. The worms are as though ‘castrated’ against regeneration. Normal worms regenerate readily under similar conditions and replace lost segments within thirty‐five days. Mesodermal tissues in normal regenerating Tubifex are formed from neoblasts, which arise from peritoneal cells upon the posterior faces of septa near the cut, migrate to this wound surface, and differentiate into new structures. After radiation no neoblasts arise from peritoneal cells and there is no mesodermal regeneration. No changes, other than failure to form neoblasts, can be observed in the peritoneal cells. Migrating neoblasts are destroyed within a few hours by similar radiation. Epithelial tissues are also affected by x‐rays, as shown by absence of mitoses and failure of regeneration in ectodermal and endodermal epithelia. During normal regeneration cells which form these epithelia and certain muscle fibers arise by proliferation from the epidermis and intestinal lining in the regenerating region, as shown by numerous mitoses in these layers. Failure of regeneration in radiated worms is thus related to lack of cells which are present in normal regeneration.