Tail regeneration in the common house gecko Hemidactylus frenatus: Sexual differences and environmental determinants

Tail regeneration in lizards is a critical adaptive mechanism that enhances survival following autotomy but is shaped by intrinsic biological factors and external environmental conditions. This study examined sexual differences and environmental drivers of tail regeneration dynamics in the common house gecko (Hemidactylus frenatus) under laboratory-controlled conditions. Ten adult males and ten adult females were subjected to induced caudal autotomy and monitored weekly for 20 weeks. Regenerated tails differed structurally from original tails in both morphology and scalation, lacking whorls of erect spiny tubercles and displaying irregularly arranged subcaudal scales, indicating functional replacement rather than morphological restoration. Tail regeneration exhibited a consistent temporal pattern, with rapid early elongation peaking in Week 3 (males: 8.8 ± 1.17 mm week⁻¹; females: 6.8 ± 3.21 mm week⁻¹), followed by progressive deceleration and stabilization after Week 15. Weekly regeneration rates did not differ significantly between sexes (all p > 0.05). However, males achieved greater cumulative regeneration by Week 20 (70.7 ± 9.59%) than females (59.5 ± 11.22%). Significant sex differences in regeneration percentage were detected during Weeks 3, 5, 6, 8, 10, 11, and 12 (p < 0.05), indicating differences in cumulative recovery rather than instantaneous growth rate. Generalized additive models revealed strong environmental effects, with external humidity and both internal and external enclosure temperatures emerging as highly significant predictors of regeneration rate (p ≤ 2.0 × 10⁻¹⁶), particularly during Weeks 2–12. In contrast, snout–vent length and body mass showed inconsistent and largely non-significant effects. These results demonstrate that tail regeneration in H. frenatus is strongly influenced by environmental conditions, with sex influencing cumulative recovery outcomes, and highlight the ecological and systematic implications of regeneration in a widespread gekkonid species.