Friday, 23 September 2016

How do shark teeth bite? Reciprocating saw, glue provide answers




Date: September 8, 2016
Source: University of Washington

Sharks have a big reputation for their teeth. The ocean predators use their buzz saw mouths to efficiently dismantle prey, ranging from marine mammals and sea turtles to seabirds and -- as Hollywood likes to remind us -- an occasional human.

There are more than 400 species of sharks in the world and each has a unique tooth shape. Some are simple triangles, while others are deeply notched or spear-shaped. But despite this variety, scientists haven't detected a difference in how different shark teeth cut and poke tissue.

A recent University of Washington study sought to understand why shark teeth are shaped differently and what biological advantages various shapes have by testing their performance under realistic conditions. The results appeared in August in the journal Royal Society Open Science.

"When you have all these different tooth shapes, there should be some functional reason. That issue was fundamentally troubling to me," said senior author Adam Summers, a UW professor of biology and of aquatic and fishery sciences. "It seemed likely what we were missing is that sharks move when they eat."

Sharks shake their heads rapidly when they bite their prey, so evaluating how teeth perform while in a side-to-side motion was critical to the study tests, which took place during a summer marine biology course at the UW's Friday Harbor Laboratories on San Juan Island.
Summers and his collaborators affixed three different types of shark teeth to the blade of a reciprocating power saw, then cut through thick slices of Alaska chum salmon at a speed that mimicked the velocity of head-shaking as a shark devours its prey.

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