Meeting Abstract

82.6  Sunday, Jan. 6  The effects of altering viscosity on suspension feeding kinematics in Xenopus laevis tadpoles RYERSON, W.G.*; DEBAN, S.M.; University of South Florida; University of South Florida wryerson@mail.usf.edu

Tadpoles of the family Pipidae are unusual among the Anura in that all lack keratinized mouth parts and most are obligate midwater suspension feeders. Two genera in this family, Hymenochirus and Psuedhymenochirus are not suspension feeders, but instead are suction feeding carnivores and begin feeding at a smaller body size than other members of Pipidae, with observations of feeding in Hymenochirus tadpoles at less than 1mm SVL compared to 4 mm SVL for Xenopus. At these small body sizes, the properties of the fluid medium become important factors in the behavior of an organism, especially the relative dominance of viscosity compared to inertia (expressed as Reynolds number, Re). The objective of this study was to test the hypothesis that suspension feeding is not possible in Hymenochirus of 1 mm body length by quantifying the effects of increasing the viscosity of water on the kinematics of suspension feeding in Xenopus laevis tadpoles. Small Xenopus, when faced with a similar Re regime as 1 mm Hymenochirus, increased velocities of mouth and hyobranchial movements significantly compared to feedings by tadpoles of the same size in water, but larger tadpoles decreased velocities. These data fail to reject the hypothesis that 1 mm Hymenochirus tadpoles are too small to suspension feed, but demonstrate strong effects of Re on suspension feeding kinematics.