Blackburn, D.G., R.S. Darrell, K.T. Lonergan, R.P. Mancini, and C.A. Sidor (1995). Differential androgen sensitivity of sexually dimorphic forelimb muscles of male leopard frogs, Rana pipiens: test of a model system. Amphibia-Reptilia 16: 351-356.
Abstract: Certain forelimb muscles of anurans exhibit strong sexual dimorphism in mass and fiber composition, offering potential for studies of the effects of hormones on muscle characteristics. Androgen - responsiveness of major forelimb muscles of male leopard frogs, Rana pipiens, was evaluated by quantifying the effects of testosterone cypionate administration and castration on lyophilized muscle mass. The coracoradialis, pectoralis epicoracoideus, and pectoralis sternalis muscles were highly-responsive to testosterone treatment, showing a mean dry mass increase of approximately 50% over control values. However, the pectoralis abdominis muscle was unaffected by testosterone administration, and castration had no effect on any of the muscles. Testosterone sensitivity reflects both the degree of sexual dimorphism and the inferred functional roles of the muscles. Because their forelimb muscles vary markedly in androgen-sensitivity, leopard frogs show considerable promise as a model system for clarifying hormonal regulation of muscle characteristics.