Meeting Abstract
The startle response is vital to an organism’s survival. Animals must perform startle throughout life history as they undergo changes in their body shape and nervous system. Anurans (frogs and toads) undergo metamorphosis, during which time the limbs develop, the tail is lost, and the trunk stiffens. At intermediate metamorphic stages, they are particularly susceptible to predation. Here we ask how a critical function, startle, is maintained through a switch in its underlying morphology in the African clawed frog (Xenopus laevis). Tadpoles have been shown to perform an axial-based C-start, much like the response observed in fish. We found that X. laevis gradually integrate a limb-based “pushback” response into their startle repertoire starting at developmental stage 58. We hypothesized that there is a critical period during metamorphosis when the C-start performance declines and the pushback has yet to reach peak performance levels. We performed high-speed video recordings of startle trials of 18 animals ranging from stage 57, when only C-starts are performed, to 66, when metamorphosis is complete and startles are limb-based. For pushback, we found that maximum and average velocity (bl/s) increased significantly with metamorphic stage. From these and other parameters, we conclude that pushback performance improves through metamorphosis from stage 58 to stage 66. We could elicit C-start responses up through stage 63, but curvature of the trunk becomes limited from stage 61-63, resulting in a negative impact on performance. These data indicate that there is a period where neither startle strategy is functioning at peak performance, and the animal may be more vulnerable to predation.
