Meeting Abstract
The mechanical behavior of mineralized cartilaginous shark vertebrae varies among body regions and species and these variations may be partially influenced by vertebral mineral architecture. We quantify mineral arrangements (radiating lamellae number and angles, and number of nodes) and calculate bone mineral densities (BMD) of vertebrae belonging to two orders of sharks (Carcharhiniformes and Lamniformes). Previous work has shown that shark vertebrae from the posterior column are the toughest and stiffest; therefore we hypothesized that the posterior region of lamniform species will have the most radiating lamellae with the smallest angles and the greatest node density. We also expected that carcharhiniform sharks will have larger BMD values due to the block-like calcification within their vertebral bodies. We dissected vertebrae from six species of sharks (three per order) along the anterior, mid, and posterior body regions. After measuring length and diameter with calipers, we scanned each vertebra using a BrukerSkyScan 1173 µCT scanner. We then obtained BMD values with Bruker CTAn software and measured the morphological variables using ImageJ. Our preliminary data show that the posterior region of lamniform sharks had a greater number of lamellae with overall smaller angles, and increased node density. The posterior region of all individuals showed significantly higher BMD values, though carcharhiniform species had greater mineralization overall when compared to lamniform individuals. We hypothesize that increased mineral density and morphological architecture may aid in thrust production and energy storage, as lateral body displacement is concentrated in the posterior region during swimming.
