Journal of Neurophysiology, Vol 41, Issue 1 97-107, Copyright © 1978 by APS
Organization of peripheral nerves and spinal roots of the Atlantic stingray, Dasyatis sabina
R. E. Coggeshall, R. B. Leonard, M. L. Applebaum and W. D. Willis
1. The sizes and numbers of axons in peripheral nerves and spinal roots
were investigated in the stingray, Dasyatis sabina. 2. The axons of the
dorsal and ventral roots do not mingle in peripheral nerves of this animal
as they do in higher vertebrates. Thus, it was usually possible to split
the peripheral nerve into two portions, one containing only dorsal root
axons, the other containing only ventral root axons. This feature was
useful for the analysis of certain aspects of spinal cord organization. 3.
The fact that dorsal and ventral root axons were segregated in peripheral
nerves enabled us to demonstrate, without experimental surgery, that the
central processes of the dorsal root ganglion cells and the proximal
ventral root axons were 10-20% narrower, on the average, than the distal
processes of the same dorsal root ganglion cells or the distal parts of the
same ventral root axons. 4. The stingray is remarkable in having very few
unmyelinated axons in the dorsal roots, ventral roots, or peripheral
nerves. This paucity of unmyelinated axons distinguishes the Atlantic
stingrays from all other vertebrates whose roots and nerves have been
examined for unmyelinated fibers. 5. Similar findings were obtained for one
spotted eagle ray (Aetobatus narinari) and two cow-nose rays (Rhinoptera
bonasus).
