RAMSAY , Jason B; WILGA, Cheryl D; University of Rhode Island; University of Rhode Island: Dual Function Shark Teeth

Whitespotted bamboo sharks, Chiloscyllium plagiosum, readily feed on hard and soft prey. However, C. plagiosum does not possess dental morphology that is typically associated with prey crushing. Instead, they possess broad faced, cusped teeth commonly associated with piscivory. Investigation of tooth morphology in C. plagiosum has revealed a novel dual function of the teeth during feeding. The teeth are versatile and can easily grasp soft-bodied prey like fish and squid as well as crush hard prey, such as crustaceans. This is the first time that such morphology for alternate durophagous and piscivorous strategies has been described in any fish species. The spike-like cusps and inward pointed teeth are ideal for capturing soft-bodied prey by piercing into the soft flesh thereby preventing escape. Alternatively, when the cusps come into contact with a hard surface, they fold inward towards the oral cavity allowing the broad flat face of the tooth to be used as a crushing surface. This dental innovation permits bamboo sharks to effectively feed on a wide variety of prey types. Biomechanical modeling reveals that rotation of the tooth during feeding behavior is not actively controlled; rather it is a passive mechanism that is influenced by the type of prey (hard or soft-bodied) being consumed. The position of the jaw joint is vertically offset to the occlusal plane similar to the nutcracker mechanism for grinding in herbivorous mammals. This allows all of the functional teeth to impact a hard surface, such as a crab carapace, and rotate into the flattened orientation nearly simultaneously. Possession of these novel mechanisms are advantageous to individual survival by allowing the utilization of a wide array of prey types, enhancing feeding performance, decreasing the effects of competition and increasing the number of potential prey resources.