ESPINOZA, N.R.: Effects of developmental temperature on musculoskeletal growth and jumping performance in the treefrog Hyla chrysoscelis.

Several vertebrate species have shown ontogenetic adjustments in the form and material properties of the growing musculoskeletal system to allow the same level of locomotor performance in juveniles and adults. The rate of growth and amount of time the musculoskeletal system has to develop may affect the amount of compensatory change needed to produce the same level of performance; for example, the faster the growth rate and/or the shorter the amount of time for development, the greater the need for these adjustments. To test these predictions, individuals of Hyla chrysoscelis were raised at 28�C and 18�C to evaluate the effects of developmental duration and growth rate on bone and muscle morphology, bone material properties, and jumping performance. Although two-fold differences in developmental duration and larval growth rates were found between frogs raised at 28�C and 18�C, little or no difference was found in hind limb morphology, bone shape, bone mineral content, bone material properties, relative muscle mass or jumping performance at the end of metamorphosis. However, during the first nine weeks of post-metamorphic growth in both groups, absolute jumping performance, relative proportion of hind limb muscle mass, and bone material properties changed with age. These results suggest that an increase in the relative proportion of hind limb muscle mass, as well as an increase in the strength and stiffness of the hind limb skeleton, contribute to the improvement of jumping performance during post-metamorphic growth. Supported by a Howard Hughes Predoctoral Fellowship and NSF (IBN-9701121).