The Herpetological Journal

pp. 219-224
Authors: Mi, Zhi Ping

Abstract: Theory predicts that sexual dimorphism evolves as a consequence of sexual selection. I studied sexual dimorphism in ten forelimb muscles used in the amplexus of Bufo gargarizans (deltoideus, pectoralis, coraco-humeralis longus, coraco-humeralis brevis, sterno-radialis, flexor carpi radialis, extensor carpi radialis, abductor indicus longus, extensor digitorum communis longus and flexor digitorum communis), and three forelimb muscles not involved in amplexus (infraspinatus, latissimus dorsi and triceps branchii). Muscle mass was higher in males for all muscles considered. Males found in amplexus had significantly larger forelimb muscles involved in amplexus than non-amplectant males (exceptions: coraco-humeralis longus and abductor indicus longus), whereas the mass of the three muscles not involved in amplexus did not differ between amplectant and non-amplectant males. My findings suggest that a male-mating advantage depends on the absolute mass of muscles involved in amplexus, in line with the assumption that sexual dimorphism in forelimb muscle mass has evolved under sexual selection.

Keywords: SEXUAL SELECTION, BUFO GARGARIZANS, SEXUAL DIMORPHISM, FORELIMB MUSCLE