Meeting Abstract
Anurans undergo dramatic structural changes during metamorphosis, in which the tail is resorbed, and fore- and hindlimbs emerge. These structural changes cause a shift in locomotor mechanics, from axial to appendicular-based propulsion. Previous studies of species that metamorphose into terrestrial jumpers have shown that tadpoles experience decreased survival against predators when both the limbs and tail are intermediate in development. It is possible that increased limb length is initially detrimental to performance and survival, but that the limbs become the primary source of locomotion during tail resorption, thus increasing survival later in metamorphosis. To test this hypothesis, we conducted selection trials on Xenopus laevis tadpoles using a fish predator. This species differs from those studied previously, in that adults use their limbs for swimming rather than jumping on land. Tadpoles (N=15) were spread equally across three developmental stages: NF56 (with tail and newly budded limbs), NF 63 (functional hindlimbs and tail), and NF 64 (fully functional limbs and minimal tail). Predation trials ended after 50% of tadpoles were eaten. Remaining tadpoles were filmed to assess escape performance and photographed to collect morphological data. Survival increased uniformly across ontogeny as the hindlimbs grew and the tail was resorbed, rather than showing an intermediate stage of low survival when both legs and tail were functional. Thus, survival across stages may be driven by a rapid increase in hindlimb development prior to significant tail resorption. These data suggest that contributions of hindlimbs to escape performance may play a larger role in survival than tail length in this fully aquatic frog species, in which the hindlimbs do not need to function in two distinctly different locomotor modes.
