Tails You Lose : A shark whose attack relies on ' extreme yoga ' :

When a thresher shark attacks, it doesn't lunge in teeth first. When it approaches a school of fish, it lowers its head, flexes its body and flicks its whiplike tail over its head. The smack of the tail stuns some fish, which the shark gobbles up.

This hunting technique piques the interest of Marianne Porter, a biologist at Florida Atlantic University. '' You've got this shark doing extreme yoga,'' she said. '' What does its backbone look like to make that happen ? ''

She and her colleagues tried to answer this question in a paper published in the journal Royal Society Open Science.

Dr. Porter's team worked with the National Oceanic and Atmospheric Administration to get thresher specimens, which aren't easy to obtain because the sharks are rare and stick to the open ocean.

They examined mineralised structures within the cartilage skeletons. Using CT scans, the researchers compiled 3-D models.

Inside the shark's vertebrae, researchers found an arrangement of mineralized plates that spread out '' like spokes on a bike wheel,'' said Jamie Knaub, a doctoral candidate at Florida Atlantic University.

The scientists found variations of the plate structures '' that we think will biomechanically act more stable in the main body of the shark, and then towards the tail, it's a lot more flexible,'' Ms. Knaub said.

The vertebrae themselves also varied, with longer individual vertebrae in the trunk and shorter vertebrae in the tail to increase flexibility there. [Kate Golemeiewski]


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