KINEMATICS AND FUNCTIONAL-MORPHOLOGY OF AQUATIC FEEDING IN AUSTRALIANSNAKE-NECKED TURTLES (PLEURODIRA, CHELODINA)

Head kinematics during aquatic feeding of the Australian long-necked t urtle (Chelodina) were studied by means of high speed video recordings . Buccal expansion was assessed by calculation of elliptical cross-sec tional surfaces. Further, displacements of head, carapace, and prey in the earth bound frame, of the prey relative to the center of the gape , and of the head relative to the carapace were determined. Rates of c hange (velocities) of all these variables were calculated. These data are combined with information on the osteology and myology of the head . The robust development of the large hyobranchial apparatus, the mass ive intercornuatus muscle, and the presence of the branchiosquamosus m uscle were related to aquatic feeding skills. Head kinematics are vari able in amplitude and relative timing, but proceed always in a rostroc audal sequence. According to their effect on the prey, two components are distinguished in the process of expansion. The first compensates f or head/body movements (compensatory suction). The second causes disti nct acceleration of water and prey (inertial suction). The latter comp onent is mainly driven by the abduction of the second branchial arch. In spite of largely different structural solutions, optimal feeding co nditions as deduced for suction in feeding fishes are also employed by Chelodina. This further promotes the assumption that hydrodynamics co nstrain evolutive solutions for aquatic feeding. (C) 1997 Wiley-Liss, Inc.