The regenerative capacity of the tail in embryonic and post-natal lizards (Lacerta vivipara Jacquin)

Abstract

ABSTRACT The structure and development of the fracture planes in the tail of Lacerta vivipara are briefly described. The histological features of normal tail regeneration in baby and adult lizards are described. Regeneration occurs after autotomy or after amputation through either an intravertébral or an intervertebral plane, and becomes clearly visible after 2 to 3 weeks. The technique, based on the work of Panigel, of rearing embryos of lizards in a form of culture after removal from the mother, and of operating on them is described. In recent experiments over 40 per cent, of the embryos subjected to the operation of tail amputation at stages 30 – 32 in the normal table by Dufaure and Hubert survived to reach near hatching stages (39 – 40). A few hatched after periods of 17 to 24 days in culture at 28° C. Embryos operated on at very late stages generally succeeded in hatching. The effects of tail amputation during embryonic life were studied histologically in fifty-nine individuals. Almost all the embryos operated on at stages younger than 39 failed to regenerate after up to 36 days in culture, and showed appearances suggestive of rapid healing. Most of the embryos operated on at stages 39 – 40, very late in embryonic life, showed early regenerative changes. Others showed failure of regeneration, as in the younger embryos, and in a few specimens the results were doubtful. A possible reason for the lack of regenerative power in embryo lizards, and for its appearance at or shortly before hatching (or in nature, birth) is suggested. There is evidence that regeneration may depend upon the rate of healing and the extent of the wound surface. Substantial keratinization of the scales and stiffening of the sub-epidermal tissues occur towards the end of embryonic life. By preventing premature healing and helping to maintain a large wound surface such changes may provide the necessary conditions for regeneration. From the standpoint of natural selection the lack of regenerative power of the lizard embryo is not surprising, since regeneration would have no survival value until post-natal life.