The fate of transplanted tails in frog larvae

Frog larvae recieved transplants of autografts, allografts, and xeonografts using Rana brevipoda and Rana japonica. Tail tip autografts heal rapidly, continue to grow but undergo degeneration at metamorphosis. Allografts and xenografts also heal but show signs of rejection by the host's immune system. Onset of rejection depends upon the stage when grafts were performed. If transplants were made during early stages, onset was late; if performed later, onset was early. Because frog larvae will eventually undergo metamorphosis as a result of thyroxine effects, they are excellent experimental models for correlating the immune and endocrine systems with differentiation, growth, and aging.