Abstract
The shape of shark teeth varies among species, but traditional testing protocols have revealed no predictive relationship between shark tooth morphology and performance. We developed a dynamic testing device to quantify cutting performance of teeth. We mimicked head-shaking behaviour in feeding large sharks by attaching teeth to the blade of a reciprocating power saw fixed in a custom-built frame. We tested three tooth types at biologically relevant speeds and found differences in tooth cutting ability and wear. Teeth from the bluntnose sixgill (Hexanchus griseus) showed poor cutting ability compared with tiger (Galeocerdo cuvier), sandbar (Carcharhinus plumbeus) and silky (C. falciformis) sharks, but they also showed no wear with repeated use. Some shark teeth are very sharp at the expense of quickly dulling, while others are less sharp but dull more slowly. This demonstrates that dynamic testing is vital to understanding the performance of shark teeth.
Highlights
Conventional wisdom suggests that mammals have the greatest diversity in tooth morphology, but another vertebrate group rivals them—sharks
There are few theoretical predictions about cutting performance that can be drawn from morphology alone [2]
With dynamic testing, there are differences in performance among shark teeth with different morphologies
Summary
Conventional wisdom suggests that mammals have the greatest diversity in tooth morphology, but another vertebrate group rivals them—sharks. Though some teeth are simple triangles (e.g. silky shark teeth, Carcharhinus falciformis), many are spear shaped (e.g. mako shark teeth, Isurus oxyrinchus), deeply notched (e.g. tiger shark teeth, Galeocerdo cuvier) or multi-cusped. The relationship between tooth morphology and function is not readily discernable. Despite their variation, teeth from several species of shark performed well in tests of puncture and unidirectional draw force of individual teeth through prey tissue [1]. Perhaps the variation in tooth shape across large sharks reflects selection for dynamic tooth–prey tissue interactions, which is not discernable through morphological study and static testing regimes
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