THE COMPARATIVE MYOLOGY OF THE THIGH AND CRUS IN THE SALAMANDERS AMBYSTOMA-TIGRINUM AND DICAMPTODON-TENEBROSUS

Variation in myology of the hind limb among salamanders has been poorly characterized. Nineteen major hind limb muscles of Ambystoma tigrinum (Ambystomatidae) and Dicamptodon tenebrosus (Dicamptodontidae) were studied to provide baseline descriptive data on hind limb myology in salamanders and to generate hypotheses of hind limb muscle function. Most superficial muscles of the hind limbs span multiple joints, including a unique three-joint muscle, the ischioflexorius, that extends from the pelvic girdle to the plantar fascia. The deeper hind limb muscles span single joints. No myological differences were observed between the hind limbs of A. tigrinum larvae and individuals that had just metamorphosed. Fully adult tiger salamanders that had been housed in terraria for many years had hypertrophied femorofibularis and ischiofemoralis muscles, a condition similar to that reported in Paramesotriton and Taricha, which engage in terrestrial locomotion. In contrast, adults of D. tenebrosus, which are also good walkers, possess a hypertrophied ischioflexorius muscle and a reduced femorofibularis. These regular myological differences, and those described by previous workers for different salamander taxa, may be associated with differences in life-history traits, and in the case of A. tigrinum, with patterns of muscle use.