Meeting Abstract
The flukes of cetaceans are the principal structure used to power swimming. Dorso-ventral oscillations of the caudal flukes generate lift-based thrust that allows cetaceans to operate with a high propulsive efficiency. This high efficiency has been assumed to partially result from the release of elastic energy stored during the oscillatory cycle from various body components. There are three sets of tendons that pass through the cetacean peduncle and insert onto the posterior caudal vertebrae that may be associated with energy storage. The purpose of this study was to investigate cetacean tendon anatomy and elasticity through dissection, histology, and mechanical tensile testing of the tendons. Tensile testing was performed on the excised tendons with an Instron 5848 MicroTester. Histological analysis of collagen fibers was performed on the tendons. Dissections conducted on various dolphin species revealed two sets of tendons on the dorsal side (epaxial I and II) and one set on the ventral side (hypaxial) of the tail base. The epaxial I and hypaxial tendons inserted serially along the posterior caudal vertebrae. Epaxial II tendons were smaller in diameter and inserted only on the terminal caudal vertebrae. The collagen fibers that make up the three sets of tendons in the cetacean peduncle were found to be longitudinally wavy, suggesting elastic properties. The excised tendons of bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) were shown to act similar to a spring to store elastic energy. The tendons of dolphins in the caudal peduncle were revealed to exhibit spring-like properties that can potentially affect the energetics of swimming.
