Believe It: Some Deep-Sea Sharks Can Float

posted: 06/22/15
by: Discovery News
A bluntnose sixgill shark, sometimes called the king of the deep.
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The bluntnose sixgill shark (Hexanchus griseus) is sometimes called "the king of the deep".

The first-ever camera mounted on a deep-sea shark found that at least two species of sharks that live at great depths are positively buoyant: they float up.

Most sharks sink if they stop swimming and can rise only gradually by swimming forward.

"We didn't expect to find evidence of positive buoyancy, and ran two sets of experiments to confirm our initial observations of this phenomenon. This finding was a total surprise," said Carl Meyer, assistant researcher at University of Hawai'i Maui's Hawai'i Institute of Marine Biology (HIMB) and co-author of the study, said in a press release.

The sharks in the study -- sixgill (pictured) and prickly sharks -- live at greater depths during the day than at night. The researchers say they might have evolved buoyancy in order to rise through the water column without having to use cold muscles.

Or there could be other reasons.

"We want to better understand why these sharks are positively buoyant," said Meyer. "Does this trait perhaps give them a 'stealth' advantage during hunting, allowing them to glide motionless upward to capture prey above them in the water? Or does it help them with nightly migrations to shallower areas?"

This post originally appeared on Discovery News

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