Independence of Taste Organs with Respect to Their Nerve Fibers Demonstrated in Living Salamanders

Abstract

In these experiments the development of taste organs in embryos and larvae of Amblystoma punctatum has been studied in the living specimen under high magnification with the aid of micro-aquaria. In one series part of the anlagen of the tongue from the endodermal floor of the pharyngeal cavity was transplanted to the side of the body and oriented so that the smooth glistening surface of the en-doderm was exposed to the outside. The donor and recipient in a single experiment were usually similar in age. These grafts were from donors ranging in ages from the tail-bud to the early swimming reaction stages and long before the first appearance of taste organs normally takes place. This series contains donors in which either no cranial nerves had yet formed or no nerve fibers had reached the region from which the graft was taken.

They showed that normal taste organs appeared in the transplants at the normal time (about stage 40 of Harrison series, several days before the mouth is open) and that they increased in number and persisted up to and through metamorphosis as the grafted tongue grew in size. The increase in the number of organs is by a process of budding brought about by mitosis and often a migration of the peripheral supporting cells. This is similar to that described by the author^{1, 2} in the case of accessory lateral-line organs.

These results prove that the taste organs in this form develop in situ and are independent of any specific influence on the part of gustatory nerves to initiate their formation. The results also strongly suggest that the initiation of their development is entirely independent of any reaction on the part of nerve fibers which might grow in from the new environment.