Meeting Abstract

10.3  Sunday, Jan. 4  Scaling of suspension feeding in tadpoles RYERSON, W.G.*; DEBAN, S.M.; University of South Florida, Tampa; University of South Florida, Tampa wryerson@mail.usf.edu

We investigated the scaling of the buccal pumping mechanism in an ontogenetic series of suspension feeding Xenopus laevis tadpoles by examining the morphology, kinematics, fluid flow, and pressure generated in the buccal cavity. Tadpoles were imaged during feeding to obtain kinematics and fluid velocity. Reynolds number was calculated using fluid velocity and morphology data, and pressure was calculated using flow data and a pipe model of the branchial filter basket. Buccal volume and head width exhibited negative allometry, with scaling coefficients of 1.22 +/- 0.20 and 0.36 +/- 0.15, respectively. Scaling of the kinematics did not match scaling patterns of bass or aquatic salamanders. Only scaling of maximum hyoid distance (0.60 +/- 0.74), duration of mouth closing (0.74 +/- 0.51), and duration of hyoid elevation (0.69 +/- 0.55) could not be distinguished from isometry. The only negatively allometric variable was maximum gape distance (0.52 +/- 0.37). No effect of size was found for duration of mouth opening (-0.05 +/- 0.60), duration of hyoid depression (0.40 +/- 0.51), and velocity of hyoid elevation (-0.31 +/- 0.39). Velocity of mouth opening (-0.72 +/- 0.20), velocity of mouth closing (-0.50 +/- 0.35), and velocity of hyoid depression (-0.65 +/- 0.16) decreased with increasing size. Fluid velocity increased with size, and is best predicted by a piston model that includes head width and hyoid depression velocity. Reynolds number increased with size and spanned two flow regimes (laminar, intermediate) ranging from 2 to over 100. Pressure was found to be greatest in the smallest tadpoles and decreased as size increased, ranging from 2 kPA to 80 kPa, suggesting that abiotic factors such as the physical properties of water may set a lower size limit on suspension feeding.