Pronounced variations in the cutting performance and durability of the teeth of different species of shark have been measured by researchers – using a novel testing device designed to replicate sharks’ behaviour in the wild.
The US scientists attached multiple shark teeth to a fixed reciprocating power-saw blade and set it to mimick the head-shaking behaviour seen in large sharks when feeding. Performance was recorded on high-speed video as the device cut through chunks of fresh fish.
The report, published in Royal Society Open Science, showed that teeth from the bluntnose sixgill shark, a coldwater species, turned out to be poor at cutting compared with those of tiger, sandbar and silky sharks. However, the sixgill’s teeth could be used repeatedly without showing signs of wear.
As with man-made blades, the sharpest teeth among the other species dulled after only a few interactions, while less-sharp teeth dulled more slowly. As sharks are continuously replacing their teeth, this would not necessarily be a problem for them.
The researchers chose teeth of three main types that would also represent those of other species, from the triangles with small serrations of silky and sandbar sharks to the deeply notched triangles with large serrations of tigers and the elongated, multi-cusped teeth of sixgills.
The report surmised that adult sixgill sharks, with the least effective bite, tended to take their prey whole and use their teeth to restrain rather than cut it. As a coldwater species, sixgills might replace their teeth at a slower rate than the other sharks, and the researchers predicted a relationship between rapid dulling and more frequent replacement.
The research team – Katherine Corn, Stacy Farina, Jeffrey Brash and Adam Summers – believed that their sharpness-testing device could be used to produce a comprehensive database of effectiveness in future.
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