Meeting Abstract
Dorso-ventral oscillations of caudal flukes of cetaceans generate lift-based thrust that allows them to operate with a high propulsive efficiency. Flexibility of the tail flukes is an important element in this system and the ability to rotate the flukes about the ball vertebra allows for changes in angle of attack and smooth bending. There are three sets of tendons that pass through the odontocete peduncle and insert onto the caudal vertebrae. It is unknown to what extent these tendons affect fluke flexibility. The purpose of this study was to investigate direct effects of peduncle tendons on odontocete fluke flexibility, deflection angle and investigate tendon elasticity. One-point bending tests were conducted on isolated harbor porpoise (Phocoena phocoena) flukes that were immobilized at their base. Tension was created by the addition of weight to each tendon. Tensile testing was performed on harbor porpoise and striped dolphin (Stenella coeruleoalba) tendons using an Instron 5848 MicroTester. Histological analyses of collagen fibers were performed on the tendons. Flexibility of the fluke decreased and deflection angle increased as a result of tension applied to tendons indicating the possibility that these tendons play a role in controlling fluke stiffness and thrust production. The stiffness differed among tendons in the peduncle and was overall more compliant than average mammalian tendons. The collagen fibers that make up the three sets of tendons in the cetacean peduncle were found to be longitudinally wavy, suggesting the ability to store elastic energy. In addition, the terminal ends of two tendons branched into the core of the flukes. These results indicated that there is potentially active control of flexibility in odontocete flukes during locomotion.
