DEAN, M/N: A born sucker: The pipid frog, Hymenochirus boettgeri as a model suction feeder

Vertebrate feeding systems are diverse and exhibit extreme variation in form and function. Despite this phenotypic breadth, convergent acquisitions of functionally analogous systems are seen across taxa. These can be driven by the medium (air or water) in which the animal lives. As a result, the contrast between aquatic and terrestrial feeding modes is often used to delineate the separation of fishes and tetrapods. As the majority of fishes rely on suction (creation of subambient buccal pressures) for aquatic prey capture, tetrapods that exhibit this mode prove especially valuable for functional morphological analysis of vertebrate response to constraints of the medium. The current study quantitatively and qualitatively analyzes the feeding kinematics of the dwarf African clawed frog Hymenochirus boettgeri, unique among anurans as a suction feeder. High-speed kinematic recordings were used to characterize prey capture events. Hymenochirus boettgeri employs bi-directional inertial suction when feeding on non-living chironomid larvae presented on the substrate. Suction events are preceded by a body lunge toward the food item and followed by recoil of the body with lateral spreading of the forelimbs. The sequence from onset of mouth opening to mouth closure has a mean duration of 50.1 msec, with maximum hyoid depression following mouth closure. Kinematic variables of the capture sequence show no significant differences among individuals and always proceed in a rostrocaudal sequence. Differences exist between individuals for variables describing post-capture recoil. However, these are size-related and may be attributed to constraints imposed by the physical properties of water. Kinematics and morphology are discussed in terms of vertebrate aquatic feeding and ecology of H. boettgeri.