EIDIETIS, Laura; Univ. of Michigan: Predicting performance differences from morphology: a comparison of the fast-starts of three anuran tadpoles

Tadpole acceleration during fast-starts is considered critical for surviving predator encounters. A simple model based on morphology predicted inter-specific differences between woodfrog, bullfrog, and American toad tadpoles for maximum translation of the center of mass and maximum rotational acceleration of the head. Parameters were the capacity of muscle to produce force, modeled as proportional to tail muscle mass, resistance to translational acceleration, modeled as proportional to tadpole mass, and rotational inertia of the head, estimated from head dimensions. At a given length, tail muscle mass increased as woodfrog&lttoad&ltbullfrog and tadpole mass increased as woodfrog&ltbullfrog&lttoad, predicting translational acceleration to increase as toad=woodfrog&ltbullfrog. The predicted ranking for maximum translational acceleration was verified during actual fast-starts. At a given length, torque production capacity increased as woodfrog&lt&lttoad&ltbullfrog, and rotational inertia did not differ between species, predicting maximum rotational acceleration of the head to increase as woodfrog&lttoad&ltbullfrog. The actual ranking of maximum rotational acceleration of the head was woodfrog=toad&ltbullfrog. Though the morphologically-based model predicted the measured performance differences between species, the same method failed to accurately predict performance differences between individual tadpoles. One reason for this failure may be that the force predicted by morphological measures is divided between rotational and translational acceleration during an actual fast-start. This division of effort is not constant among fast-start events. Thus, substantial variation between individual performance events is caused by a behavioral decision between turning the head and translating, rather than variation in morphology.