Blackburn, D.G. and V.A. Bernardo (1998). Sexual dimorphism and testosterone responsiveness in hypaxial muscles of the leopard frog, Rana pipiens. Amphibia - Reptilia 19: 269-279.
Abstract: Abdominal hypaxial muscles of male anurans function in vocalization by causing forcible expulsion of pulmonary air through the larynx. The hypaxial muscles were studied in the leopard frog, Rana pipiens, to test whether functions of these muscles in males are reflected in sexual dimorphism and in androgen responsiveness. The combined abdominal oblique muscles and the rectus abdominis showed significant sexual dimorphism in wet mass and dry mass. However, the abdominal oblique muscles were less concentrated in protein content in males than in females. In overwintering males, exogenous testosterone cypionate stimulated a significant increase mass and protein content of the abdominal oblique and rectus abdominis muscles. Castration had no effect on muscle mass or on the response to androgen treatment.