Meeting Abstract
Amplitude and frequency of lateral undulation during swimming varies greatly across shark species. As animals swim through the water, the vertebral column behave as a spring and a break mechanically loading mineralized cartilaginous vertebrae with each tailbeat. Previous research has quantified mechanical properties of shark vertebrae from under the first dorsal fin. To better understand mechanical function in vertebrae of a swimming sharks, we conducted compression tests on centra from five regions along the vertebral column in two species with dramatically different swimming styles: angel (Squatina squatina) and mako (Isurus oxyrinchus) sharks. In each region, we quantified the stiffness (resistance to compression) and maximum strength (largest stress) of the shark centra at three displacement rates: 10%, 1%, and 0.1%. We dissected three adjacent vertebrae from five regions along the column. Vertebral arches were removed with a scalpel and centra were stored in elasmobranch Ringer’s solution before testing. Three adjacent vertebrae were measured at each region and their lengths averaged to determine strain rates at 10% 1% and 0.1%. Vertebrae were tested to 1kN on an Instron. In these species, we found that stiffness did not vary across region, but stiffness was greater at the slowest strain rate. We also found that the total average stiffness is higher in angel sharks. These values highlight the viscoelastic nature of the mineralized cartilaginous material found in shark vertebrae, and also that mechanical properties vary widely in animals utilizing different swimming strategies.
