Parachlorophenylalanine retards tail regeneration in the gekkonid lizard Hemidactylus flaviviridis exposed to continuous light.

Parachlorophenylalanine (p-CPA) was used for chemical pinealectomy in a study of tail regeneration in the gekkonid lizard, Hemidactylus flaviviridis. Two doses of p-CPA (200 or 400 micrograms kg-1 body mass) were injected into two groups of lizards (5 days prior to and 30 days after caudal autotomy) exposed to continuous light of 2500 lx intensity during the summer season (March-May). Our observations show that the initiation of regeneration, the daily growth rate, the total length of new growth (regenerate) produced, and the total percentage replacement of the lost (autotomized) tails 30 days after autotomy were all significantly less with 400 micrograms kg-1 and insignificantly less with 200 micrograms kg-1 of p-CPA than in the control group of animals. The results may indicate that the effect of the drug p-CPA, an agent employed for chemical pinealectomy, on tail regeneration in H. flaviviridis is dose-dependent and that p-CPA at the high dose of 400 micrograms kg-1 has a similar retardation effect to that of complete pineal ablation. The role of the pineal in photoperiodic photoreception, and the effect of p-CPA on serotonin-melatonin biosynthesis and the consequent effects on tail regeneration, are discussed.