Age, Body Size, and Sexual Dimorphism in Size and Shape in Salamandrella keyserlingii (Caudata: Hynobiidae)

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Why is it important?

If sexual size dimorphism occurs before maturity in indeterminate growing organisms, whether is females’ larger mean body size caused by a difference in age at maturity, age-specific size, divergent growth prior to maturity, or selection on post-maturational growth? To address these questions, age and body size are determined based on a careful description of a growth trajectory for each sex in salamanders, using 555 independent data points from skeletochronological studies. Females reach maturity at 3–4 years of age, a year later than males that reach maturity at 2–3 years of age. Mean body size is 57.63 mm in males and 61.70 mm in females. Delayed sexual maturity results in sexual size dimorphism, but this dimorphism is highly detected before maturity. Females after maturity continue to grow and result in larger asymptotic size than males. These results suggest that when determining sexual size dimorphism the difference in mean adult-body size results from the difference in age-specific size.