Meeting Abstract
Among cetaceans, species with rigid, torpedo-shaped bodies anterior to the caudal region are considered the most active, high-speed swimmers. Interspecific variation is encoded in the axial skeleton, where vertebral morphology varies among species with different modes of locomotion. Here, we categorized ten species of cetaceans based on functional groups determined by swimming modes (rigid-body vs. undulatory) and diving behavior (shallow vs. deep). The goal of this study was to determine trabecular bone mechanical properties among cetacean functional groups and regions of the vertebral column. We hypothesized that the greatest mechanical properties would be in shallow-dwelling, rigid-bodied swimmers and in the caudal regions of the vertebral column. Dephinid and kogid vertebrae were obtained from necropsies and stored fresh and frozen before testing. Vertebrae were dissected from four regions of the vertebral column (thoracic, lumbar, and two caudal) and were cut into 6 mm3 cubes. Bone cubes were compression tested in the rostro-caudal orientation at 2mm/min using an Instron E1000 material tester. Stiffness, yield strength, and toughness were calculated from stress-strain curves. Preliminary data suggest that rigid-bodied, shallow-diving cetaceans had the greatest material properties compared to undulatory, deep-diving animals, while animals with rigid bodies but habitually dive to deep depths were intermediate between the two. These data may indicate that in addition to whole body rigidity, animals that habitually overcome surface drag and wave turbulence have increased skeletal loading during active swimming than those that incorporate prolonged glides during deep dives.
