Maternal Investment and Developmental Plasticity: Functional Consequences for Locomotor Performance of Hatchling Frog Larvae

1. We examined the consequences of maternal investment and developmental plasticity for morphology and locomotor performance of early stage larvae of the frog Bombina orientalis. 2. We quantified the stages at which B. orientalis hatch in a natural population in the Republic of Korea. Greater than 95% of embryos hatched with prominent yolk masses and had not yet acquired circulation in the caudal fin (stages 19-21). Stage at hatching did not depend on egg size or the temperature experienced during development. 3. To investigate relationships between egg size, temperature during embryonic development, hatchling morphology and locomotor performance, we reared embryos at either a high or low temperature in the laboratory. Among individuals at the modal stage of hatching in the field (stage 21), egg size had positive effects on both snout-vent length (SVL) and tail length. In contrast, the temperature experienced prior to hatching influenced only tail length, with development at high temperature resulting in shorter tails. These effects of egg size and developmental temperature resulted in a range of hatchling morphologies that in turn influenced maximum sprint speed. Specifically, longer tails but not greater SVLs increased sprint speed. Moreover, development from larger eggs resulted in slower speeds, after controlling for the effects of total length. 4. We also examined morphology-performance relationships after larvae developed for one additional stage (stage 22). Among these individuals, egg size again had positive effects on both SVL and tail length, and a high developmental temperature resulted in shorter tails. But in contrast to individuals at the modal stage of hatching, both longer tails and greater SVLs increased sprint speeds and there were no residual effects of egg size after controlling for total length. 5. These results concur with previously demonstrated relationships between egg size, hatchling morphology and susceptibility to predation in the field (Kaplan 1992). This suggests that locomotor performance may be a functional link between maternal investment in individual offspring and subsequent offspring fitness. Finally, we discuss the rapid ontogenetic changes demonstrated in this study in relation to the causes and consequences of performance variability, as well as the evolution of optimal levels of maternal investment.