Tail Regeneration in the Scincid Lizard, Mabuya carinata, related to Breeding Seasons and Thyroid Activity

Abstract

The influence of two different seasons as well as of thyroid hormone on tail regeneration in Mabuya carinata has been evaluated by measuring the rate of growth of the regenerate at various time intervals. The analysis has revealed no apparent seasonal alteration in the final length attained at the end of 60 days. However, the average per day rate of growth indicates some difference between the late non-breeding and the early breeding phases. A better growth rate was noticeable in the non-breeding phase during the first 25 days (blastemic and differentiation phases) while it was better in the early breeding phase during the last 20 days of tail regeneration (late differentiation and growth phases). These observations correlate with the differential physiological and endocrine status characteristic of the two seasons. Hypothyroidic animals showed a 71% retardation of regenerative ability as compared to euthyroidic animals, which was however rectified by thyroxine replacement. Modes of action of thyroxine on lizard tail regeneration are discussed.

Serum T3 and T4 levels during tail regeneration in the gekkonid lizard Hemidactylus flaviviridis

“…In the light of the previously reported alterations in systemic carbohydrate metabolism (Menon et al, 1981), the increased T3 level may also find added correlation. The earlier reported bimodal influence of thyroid hormone(s) in lizard tail regeneration (Ramachandran et al, 1984) in this context gains additional credibility.…”

“…Previous studies from this laboratory on Hemidactylus and Mabuya (e.g. Ramachandran et al, 1984) have highlighted the importance of thyroid hormones in lacertilian tail regeneration. Although the influence of hormones in general on appendage regeneration in vertebrates has been demonstrated by many experimental evaluations, an actual measurement of circulating levels of hormones during regeneration has not been carried out except for the attempt of Liversage and Korneluk (1978) on T4 and T3 in Notophthalmus viridescens.…”