Abstract
Zebra sharks are durophagous sharks, which consume the hard-shell bearing prey, such as mollusks and crustaceans. Besides, zebra sharks also feed on bony fish. In feeding on these two types of prey, zebra sharks undergo the teeth reorientation through a unique mechanism for puncturing and grinding. To understand the design strategy of high wear resistance in the durophagous fish, zebra shark teeth were investigated by chemical composition analysis, microstructure characterization, and mechanical property evaluation. The needle-like shortfin mako shark teeth, which were used for puncturing fish prey, were also studied and compared with zebra shark teeth. The results revealed that both sharks were constructed with similar chemical composition; thus, they showed the similar mechanical properties, with the hardness and reduced modulus comparable to that of the conch shell in enameloid. Without the superior mechanical properties, zebra sharks utilize dentition and teeth reorientation to prevent the damage from grinding and wearing during feeding shellfish. The difference between sharks is the orientation and distribution of enameloid bundles, which is be related to the external loading condition during feeding. Zebra shark teeth showed the mixture of the characteristics from puncturing and grinding due to its tunable feeding mechanism. Shark teeth have evolved unique structures as well as optimized properties to adapt their living environment and fulfill functionalities.