Growth of Heteroplastically Transplanted Eyes and Limbs in Amblystoma.

Abstract

For the purpose of comparing the growth of normal and heteroplastically transplanted organs, eye vesicles (with lens ectoderm) and limb discs were transplanted between Amblystoma punctatum and A. tigrinum. The operations were done in the “tail-bud” stage, and the grafts were placed in the normal position and orientation. To standardize the feeding, both species were daily fed the maximum amount they would eat.

Measurements of normal and transplanted eyes were made with a micrometer ocular at regular intervals. As accurate measurements of the developing limb are impossible, pairs of animals with heteroplastically transplanted limbs were killed from time to time as a comparison.

Measurements made as soon as the outline of the eye became sufficiently visible, before either species had reached the feeding stage, showed that the normal and transplanted eyes were of the same size. This relation is maintained during most of the larval period. As the time of metamorphosis approaches, accurate measurements of the eye can no longer be made, but apparently the normal tigrinum eye now becomes slightly larger than the transplanted eye on the punctatum, and the transplanted punctatum eye becomes larger than its control. In other words, the 2 eyes on the tigrinum, normal and transplanted, become larger than the 2 on the punctatum.

In normal development, the fore-limb of Amblystoma punctatum becomes visible externally about the same time as the gills, while that of A. tigrinum does not appear until just before the animal begins to feed. When the limb disc is transplanted heteroplastically, the transplanted limb and the normal limb of the donor species appear at the same time. During the major portion of larval life the transplanted limb and the normal limb of the donor species maintain the same size. Eventually, in late larval life, the normal limb of the tigrinum becomes somewhat larger than the limb transplanted to the punctatum, and the transplanted punctatum limb becomes larger than its control. The growth relations of the eye and limb after heteroplastic transplantation are therefore the same.