Reproductive Cycles and Sexual Dimorphism in the Viviparous Skink, Sphenomorphus indicus (Sauria: Scincidae), from Wushe, Central Taiwan

Wen-San Huang (1996) Reproductive cycles and sexual dimorphism in the viviparous skink, Spenomorphus indicus (Sauria: Scincidae), from Wushe, central Taiwan. Zoological Studies 35(1): 55-61. Seasonal variation in the male and female reproductive cycles of the viviparous scincid Sphenomorphus indicus is described in this study. Mean snout vent length (SVL) of adult females (n = 50) (range: 76 to 94, mean = 81.6 mm) was significantly larger than that of the adult males (n = 29) (range: 63 to 85, mean = 73.6 mm). However, the mean values of head length (HL) and head width (HW) showed no significant differences between sexes. Females exhibited a spring vitellogenic period with parturition occurring in June and July. The onset of vitellogenesis coincided with increasing rainfall and showed a negative correlation with the female liver somatic index (FLSI). Females produced 4 to 11 embryos and the clutch size was positively correlated with body size. Males exhibited a spermatogenic cycle with spermatogenesis commencing during late summer and autumn. Peak spermiogenesis occurred during spring at which time testis somatic indices were maximum. Peak spermiogenesis in males coincided with vitellogenesis in females. Testicular regression occurred during summer, with seminiferous tubule diameters at their minimum values. Male seminiferous tubule diameter (MSTD) and testis somatic index (MTSI) had a negative correlation with temperature.