Meeting Abstract
Sharks exhibit a wide array of feeding mechanisms, behaviors, and ecologies, among which the cookie cutter sharks (Isistius spp.) are rather unique. Their semi-circular, scoop-shaped lower jaw bears teeth fused into a saw blade, which is used to excise circular flesh plugs from large fishes and marine mammals via longitudinal rotation of the body. To identify the extent to which these unique anatomical attributes facilitate their unique feeding niche, Finite Element (FE) models of the jaws of the large tooth cookie cutter shark Isistius plutodus and spiny dogfish Squalus acanthias were developed from CT scans; the spiny dogfish represents a generalized shark feeding mechanism for comparison. Models for both species were then virtually manipulated to represent all possible character states, resulting in 7 models per species (jaws, jaws + fused/unfused functional teeth, jaws + fused/unfused replacement teeth, jaws + fused/unfused functional teeth + fused/unfused replacement teeth). FE simulations were run to determine jaw performance during normal biting (i.e., forces applied perpendicular to the jaw surface) and rotational biting (i.e., forces applied parallel to the jaw surface), and jaw stress and strain energy were determined. Preliminary analyses for the cookie cutter shark indicate that jaw stress and strain energy are 1) lower during rotational biting than during normal biting, and 2) lower when fused functional and replacement teeth are present, suggesting structural adaptation for the unique feeding niche occupied by this shark.
