REGENERATION IN THE AFRICAN LUNGFISH, PROTOPTERUS. III. REGENERATION DURING FASTING AND ESTIVATION

¹ Department of Biology, Mary Baldwin College, Staunton, Virginia, 24401

1. Limb and tail regeneration of Protopterus annectens and P. aethiopicus was observed under conditions of fasting and induced estivation.

2. Three fish were fasted for 212, 246, and 308 days, respectively. During this period, weight losses of 26-40% were recorded. A regenerating pectoral limb on each fish showed healing and latent phases comparable to well-fed controls, but growth itself was considerably slower and averaged only 50-60% replacement after several hundred days. The contralateral intact pectoral shrunk 7-20% during the same period and axial length shortened by about 8%. After feeding resumed, weight was rapidly regained, the old regenerating limb increased its growth rate, and a new pectoral regenerate grew normally.

3. Fifteen fish were induced to estivate after they had regenerated varying amounts of limb and tail tissue. Estivation sharply limited but did not halt further growth if the regenerate was in the latent or early growth stages, but it did stop growth or even cause shrinkage of more mature regenerates. The pectoral regenerate, first to grow after amputation, was also the first to be inhibited by estivation; the tail was the last to be affected.

4. Short-term estivation experiments revealed that the bulk of the growth took place in the 3-4 weeks preceding dry cocoon formation. It is concluded that deep estivation has an inhibitory effect on regeneration.