Atrophy of Anuran Tail Muscle During Metamorphosis.

Abstract

The total atrophy of the larval Anuran's tail constitutes one of the most striking changes evidenced during metamorphosis. The general concept held by many workers has been that the growth of the urostyle so impinges on the arteries supplying the tail that a condition of acidosis results in the latter structure due to inadequate circulation. This acidosis then results in the histolysis of the various tissues with resultant total atrophy. In a recent communication, Helff 1 has shown that the urostyle cannot be concerned since normal atrophy occurs following the removal of the larval urostyle before the latter undergoes growth. At the same time Lindeman 2 was able to show that tail integument underwent normal degeneration during metamorphosis when previously transplanted to the back of tadpoles. The present paper describes the similar transplantation of tail muscle to foreign regions to see whether or not normal atrophy would occur during metamorphosis.

All transplantations were made on large Rana clamitans' tadpoles. Four types of autoplastic muscle transplants were made, viz., tail muscle to the back, back muscle to the tail, tail muscle to another region on the tail, and back muscle to another region on the back. The technique for all these operations was briefly as follows: A small 2 mm. cube of muscle was first removed from the back or tail, as the case might be. A flap of integument was then laid back from the region to receive the transplant, and the transplant either laid on the muscle beneath or partially inserted in an incision made in the muscle. The flap of skin was then replaced and the grafts allowed to heal for 2 or 3 days following which period the larvae were metamorphosed artificially with desiccated thyroid. The engrafted muscle was then examined at 10, 15 and 21 day intervals thereafter, and the normalcy or degree of atrophy recorded.