REGENERATIVE ABNORMALITIES IN NOTOPHTHALMUS-VIRIDESCENS INDUCED BY REPEATED AMPUTATIONS

The fidelity of the regenerative response in the adult newt, N. viridescens, was examined following repeated amputations at the level of the distal 1/3 of the humerus. Following amputation (3-4 mo.) all regenerates were scored for gross morphology, reamputated, and stained with methylene blue for skeletal elements. The occurrence of abnormal regeneration with respect both to gross morphology and to skeletal structure increased directly with the number of times the limb stumps were required to initiate dedifferentiation and repair. The initial amputation-regeneration process produced structurally normal replacement limbs in 91% of the cases examined. Reamputations of 4-digit regenerates (3-4 mo. after the previous transection) resulted in structurally abnormal regenerates in 28% of the cases following 2 amputations; 50% of the cases following 3 amputations; 65% of the cases following four amputations; and 81% of the cases following 5 amputations. The relationships between repeated dedifferentiation, proliferation, and redifferentiation and normal limb development are discussed.