Meeting Abstract
Trabeculae form the porous architecture found in long bones, and they dynamically change in vivo to support mechanical demands on the body throughout life. Bone mechanical properties of terrestrial mammals reflect the degree of species-specific precociality, and skeletons must be stronger and stiffer in those animals that are mobile soon after birth. Previous studies have shown that secondarily adapted aquatic mammals have vertebral trabecular microarchitecture that differs from their terrestrial counterparts, but we have limited understanding of aquatic bone responses to loading. We are interested in the mechanical behavior of vertebral trabecular bone and the adaptations to for a non-terrestrial environment. We investigate the mechanical properties of trabecular bone in a precocial obligate swimmer, the Florida manatee, Trichechus manatus latirostris, at various regions along the vertebral column and ontogenetic stages. Vertebrae were dissected and machined into rostrocaudal-oriented sections and sampled in compression. We calculated stiffness, ultimate strength, and toughness from stress-strain curves. We found that material properties increased with age; stiffness quadrupled between the perinatal and adult stage while strength doubled. On average, stiffness was significantly greater in the anterior vertebral column, but strength was similar along the column length. Material properties were twice as strong and stiff in manatee calves compared with bovine calves, and stronger compared with adult bovine bone. These data suggest that vertebral trabecular bone must be stronger in a fully aquatic mammal to power undulatory locomotion, and we can begin to better understand how the vertebrate skeleton adapted to support body mechanics in the land to water transition.
