A comparison between field habits and contractile performance of frog and toad sartorius muscle

Summary

The contractile characteristics of the sartorius muscle isolated from the frog,Rana pipiens, and the toad,Bufo americanus, are compared at 25°C and pH 8.0. Frog sartorius muscles have faster shortening velocities and greater mechanical power at low loads, while toad sartorius muscles develop greater tetanic tension (Fig. 1). During the rising phase of an isometric tetanus, the latent period and time to half-maximum tension are shorter and the rate of tension development is faster in frog sartorius muscles than in toad sartorius muscles (Table 1). There is no difference between the two species during relaxation, i.e., the half-relaxation time after an isometric tetanus is quite similar (Table 1). It is concluded that most of the contractile characteristics of frog and toad sartorius muscles correlate well with the habits, jumping ability, burrowing activities and endurance to fatigue of the two species in the field.