Return of Vision in Larval Eyes Exchanged between Amblystoma Punctatum and the Cave Salamander, Typhlotriton Spelaeus

¹ Department of Anatomy, School of Medicine, Yale University, New Haven, Conn.

Right eyes were exchanged and normally oriented between larvae of 13 Typhlotriton spelaeus and 13 Amblystoma punctatum. At operation the Typhlotriton ranged from 31 mm. to 92 mm. in length, a wide larval age span. The Amblystoma larvae at operation varied from 28 mm. to 34 mm. in length. Reciprocal hosts were usually sacrificed at the same time to compare grafts with normal donor left eyes. Some Amblystoma hosts were approaching metamorphosis when sacrificed. Return of vision was demonstrated in 5 Amblystoma and 4 Typhlotriton transplants including both grafts in 3 reciprocal pairs with good retinas connected with the brain by regenerated optic nerves. Vision failed to return in 3 Typhlotriton and 5 Amblystoma eye grafts because of the lack of optic nerve connections. Some hosts, difficult to test, gave no visual responses although the grafts possessed good retinas with slender optic nerves leading to the brain. By some selective mechanism the optic nerve fibers from the retinas of these two different species of salamanders reach the proper centers of the optic tectum, even though in one of them, the cave salamander, the eye normally undergoes degeneration in the late life of the host.