Regeneration in the African lungfish, Protopterus. I. Gross aspects

Abstract The regeneration of appendages of Protopterus annectens and P. aethiopicus has been studied. Both limbs and tail demonstrate a notable capacity for self‐replacement. The initial direction of growth in the regenerate depended upon the nature of the amputation plane: straight, pointed, or terminally notched cuts elicited new growth along the primary axis, whereas cuts made at an angle resulted in regenerates whose axis was perpendicular to the plane of cut. In these cases, differential growth ultimately compensated and the final form was consistent with the axis of the original appendage. Lateral notches made in the posterior margin of the pectoral limb may effect the growth of a secondary filament. Such bifidism could not be elicited from pelvic limbs or tails. Growth curves showed a lag period of up to three and one‐half weeks, a period of rapid growth lasting one or more months, and then a time of decelerating growth. For each individual fish, these phases were undergone simultaneously, regardless of appendage, direction of cut, or amputation level. Limbs cut proximally, however, showed greater and more rapid growth than those with less material removed. Total replacement was found in all but some pelvic limbs. Regeneration, if in the lag phase, was halted by estivation, but rapid growth commenced shortly after arousal. Comparisons are made with other vertebrates.