Sexual Dimorphism in Body Size and Shape of Beal's Eyed Turtle (Sacalia bealei)

Abstract We studied the sexual dimorphism in body size and shape of Beal's eyed turtle, Sacalia bealei, by measuring 15 morphological characteristics of 68 adult individuals (40 females, 28 males) collected from Fujian Province, China. Females were slightly larger than males in carapace length with a sexual dimorphism index of 0.09. This translated into greater absolute values of females for all the traits we measured except for tail length, preanal tail length, and analia to supracaudal junction length. Comparisons between the sexes of size-corrected morphological traits indicated that females exhibited a longer plastron and higher carapace relative to carapace length, thereby providing a larger internal volume. Females also exhibited relatively wider heads. In males, the plastron was smaller and more indented than in females and the openings between the plastron and the carapace were also more developed. Overall, females were larger in size and displayed a more voluminous shell than did males while males had longer tails and larger spaces available to move the legs, head, and tail.