Meeting Abstract

130.1  Monday, Jan. 7  Extracellular matrix dominates the mechanical properties of shark vertebral columns in bending PORTER, ME*; DIAZ, C; LONG, JH; Vassar College; University of Akron; Vassar College meporter@vassar.edu

In contrast to the acellular bone in fishes, cells are present in the calcified cartilage of the skeletons of sharks. In the vertebral column (VC), chondrocytes are arrayed in the centra and fibroblasts are present in the intervertebral ligaments. These cells build the surrounding extracellar matrix (ECM). We hypothesized that these cells also structurally contribute to the mechanical properties of the VC. To test this hypothesis, we lysed cells by freezing the tissues. We compared mechanical properties in dynamic bending before and after by freezing from phylogenetically distant, conspecific, shark species, Squalus acanthias and Mustelus canis. We hypothesized the mechanical properties of the fluid-filled intervertebral joints will be impacted by cell lyses resulting in an overall change in the vertebral column properties. We used a customized rig on dynamic testing machine (MTS Tytron 250) to translate single axis movement into bending. In an environmental chamber filled with Elasmobranch ringers, we tested fresh segments of ten centra over a range of frequencies and curvatures, similar to those experienced by these species during swimming. Segments were frozen at -18ºC for six months, defrosted to room temperature (22ºC) under hydration and tested over the same range of curvatures and frequencies. We found that freezing the specimen does reduce both work, W (J), and structural stiffness, K (Nm-1), of frozen vertebral columns. This work was supported by NSF IOS-0922605.