Observation of reproductive cycle of female yellow-margined box turtle (Cuora flavomarginata) using radiography and ultrasonography

This study presents a combination of radiography and ultrasonography to observe the reproductive cycle of 24 captive female yellow-margined box turtles in Taiwan. Radiography was mainly used to monitor clutch size, whereas ultrasonography was applied to detect changes in the follicles throughout the year. The observation of the 24 female turtles was performed from April 2007 to June 2008. Their average carapace length was 16.62 ± 1.66 cm and their average body weight was 812 ± 164.98 g. The mean clutch size was three (87 eggs/29 clutches) and the reproductive frequency was 95.83% (23/24). Double clutches were detected in 79.2%, and 20.8% had single clutches. Ovulation occurred from March through August, and the average follicular diameter was 2.16 ± 0.18 cm. Follicles entered the latent period in October (at 1.54 ± 0.26 cm), and vitellogenesis of the next reproductive cycle began in November. Using radiography, the eggshell could be detected on the ninth day after ovulation. The average period of the single clutch group was 6.9 weeks (range 5.1-8.5 weeks). In the double clutch group, the average period of the first clutch was 5.5 weeks (range 4-7.8 weeks) and that of the second clutch was 5.2 weeks (range 4-7.8 weeks). This study has advanced the understanding of reproductive physiology of yellow-margined box turtle and established a valuable and practical model for comparative study of the reproductive physiology of other chelonians.