The influence of locomotion and habitat use on tendo-muscular units of an anuran clade (Anura, Diphyabatrachia)

Tendons have unique mechanical properties, contributing to the transmission, amplification, and recycling of muscle energy. In this light, anuran tendons are especially interesting due to their highly mechanically demanding locomotor modes. Herein we aim to investigate the relation between tendons and muscles from two perspectives: (1) the tendinous area in relation to the potential force produced by associated muscles, and how this relation varies for different tendons of the anuran body; (2) the tendinous proportion of a tendo-muscle unit in relation to different locomotor modes and habitat uses in a monophyletic unranked anuran clade (Diphyabatrachia) which includes Leptodactylidae and Centrolenidae, two highly diverse frog family groups of the Neotropics. Our data suggest a significant and positive relation between tendon dimensions and potential muscle force for most of the analyzed elements. We also found that species of different locomotion and habitat use show a divergence of tendinous proportions for tendo-muscle units of the pectoral girdle and hindlimb. Notably, jumper-arboreal species differentiate from all others in all tendo-muscle units tested. Finally, the optimization of tendinous proportions showed great phylogenetic correspondence. These results are in agreement with the hypothesis that morphological variation is related to a combination of phylogenetic, functional, and ecological factors.