Abstract
Studies on the regenerative capacity of teleosts have given conflicting results. Koppanyi and Weiss 1 reported functional recovery and morphological reconstruction in the severed spinal cord of the adult goldfish. The return of function after spinal section in adults of this fish was further substantiated by Pearcy and Koppanyi. 2 However, Hooker 3 was unable to demonstrate either functional or morphological regeneration in adult goldfish after spinal section. Nicholas 4 failed to demonstrate morphological regeneration following section of the cord in Fundulus embryos, but Hooker 5 was able to show both functional and morphological restitution in the rainbow-fish when the cord had been severed during the first 4 days after “birth”. Tuge and Hanzawa 6 proved both functional and morphological regeneration after spinal section in adult Japanese rice-minnows.
To further test regenerative capacity of the spinal cord in teleosts, the cord was transected in 132 adult rainbow-fish (Lebistes reticu-latus). Females were used because the males are too heavily pig-mented for satisfactory translumination. The transluminated cord was cut with a narrow, thin-bladed knife under a binocular Greenough microscope, either just cephalic to the dorsal fin or at its caudal border.
Those which survived operation more than 24 hours (104 individuals) were observed and tested for reflexes at 24- to 48-hour intervals, for as long as 41 days in some cases.
The completeness of transection was evidenced by paralysis behind the lesion, drooping and loss of active motion in the caudal fin and appearance of the avoiding reaction described by Hooker. 5 To select fish with complete operations but to rule out extensive damage to structures other than the spinal cord, complete paralysis behind the lesion and a bilateral avoiding reflex were required.
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