Allometric relations of take‐off speed and power with body mass of anuran amphibians

Abstract

Previous studies have postulated that isometric animals exert similar locomotory capacity (speed, distance) because the amount of energy available for the motion would be the same regardless of body mass (m). To test propriety of this theory, we examined body shape and take‐off potential of two frog species, Rana nigromaculata (powerful jumpers) and Bombina orientalis (slow hoppers). Morphological measurements included thigh muscle mass (indicative of total muscle force), hindlimb length (L, determining acceleration distance), and interilial width (shaping take‐off motion). To gauge locomotory capacity, take‐off speed (v) and take‐off angle (6) were measured from video analyses, and jump distance (R) and take‐off power (P _t) were calculated from equations R=v²sin2θ/g and P_t=mv³/2L (where g is the gravitational constant). Scaling exponents of morphometric variables for both species were 0.96–1.11 for thigh muscle mass, 0.28–0.29 for hindlimb length, and 0.30–0.36 for interilial width. Scaling exponents of locomotory performance for the two species were ‐0.01–0.14 for take‐off speed, 0.24–0.31 for jump distance, and 0.66–0.84 for take‐off power. The results demonstrate that the frogs of this study showed isometric body shape within species, but that take‐off response changed allometrically with body mass, indicating that these data did not fully support the previous proposition. An exception was found in take‐off speed of B. orientalis, in which the speed changed little with body mass (slope = ‐0.01). These findings suggest that the energy availability approach did not properly explain the apparent allometric relations of the take‐off response in these animals and that an alternative model such as a power production approach may be worth addressing

Key words:

• Body mass
• Bombina orientalis
• Rana nigromaculata
• Frogs
• Hindlimb length
• Scaling
• Take‐off speed

Notes

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