Meeting Abstract
Jaw suspension type in sharks is characterized by the amount of support they provide to the jaws. We predict that those that provide relatively more support should be stiffer in response to biological load. The jaw and hyoid arches of sharks have mineralized blocks of cartilage surrounding an inner core of hyaline cartilage. Greater mineralization of the hyomandibula confers greater stiffness a previous study. Here we perform mechanical property tests on the jaw and hyoid cartilages of several shark species to characterize the response to load. The hyomandibula, ceratohyal, palatoquadrate, and Meckel’s cartilages of several species that vary by jaw suspension and morphology were removed and tested individually in a material testing system. Axial and transverse length changes in the cartilages were measured under compression using sonometric crystals, which measure distance via ultrasound. Strain, Young’s Modulus, and Poisson’s ratio were then calculated using the distance changes and load. Young’s modulus was higher in those species with greater mineralization of the jaw and hyoid elements. Poisson’s ratio varied widely and was smaller in those species with greater mineralization. Those species with higher Young’s modulus and smaller Poisson’s ratio use suction or crushing modes of feeding, while those with lower moduli are bite feeders. Strain in the hyoid arch elements was higher in those species with relatively shorter elements and those with relatively smaller cross-sectional areas, while strain was similar in the jaw cartilage. A complicated relationship exists between jaw suspension type and mechanical property. It appears that tessellated cartilage allows similar levels of strain among the jaw suspension types while mineralization levels vary among the jaw suspension types.
