By Deborah Netburn
5:51 PM EDT, June 20, 2013
The hairy-chested Yeti crab, which survives in an environment of no light, little oxygen, extreme temperatures and tremendous pressure, may not be able to survive a warming ocean, scientists say.
The alien-like crab -- nicknamed the "Hoff" in honor of David Hasselhoff's similarly hairy torso -- was discovered in 2009, living on the perimeter of hydrothermal vents thousands of feet beneath the Indian and Arctic oceans.
The area around the hydrothermal vents is beyond extreme. The vents heat the water to temperatures of 716 degrees Fahrenheit and spew plumes of noxious chemicals, creating an acidic environment with high levels of heavy metals and hydrogen sulfide. Light does not penetrate at these depths, and oxygen is scarce.
Rather than hunt for food in this harsh environment, the Hoff crab grows its own. It farms sulfur-oxidizing bacteria on the hairs of its chest and harvests it using a comb-like structure in its mouth.
The crab, and the bacteria that it grows for food, occupies a narrow zone around the vents. The crab needs to be close enough to the vent to allow its bacteria to access the streams of hydrogen sulfide, but also far enough away to keep the crab from burning to a crisp.
Scientists have occasionally seen crabs with burnt shells and burnt muscle tissue, said Alex Rogers, a researcher at Oxford University who studies the crabs. He also said that the crabs have been observed fighting one another as they jockey to find the sweetest spot around the vents.
In a paper published this week in Proceedings of the Royal Society B, a team led by scientists at Oxford University reports that the crabs are not an ancient species left undisturbed at the bottom of the ocean for hundreds of millions of years (as some had thought) but, rather, that they evolved 40 million years ago -- relatively recently on the evolutionary scale.
(Turtles, for example, first showed up 210 million years ago.)
Rogers, an author in the study, said this discovery, made by sequencing the crab's DNA, supports the theory that the animal population around the hydrothermal vents is highly sensitive to the levels of oxygen in the deep ocean.
As the ocean warms, it interferes with the ability of oxygen-rich surface waters of the ocean to mix with deep ocean waters, he said.
Fifty-five million years ago, during a period of intense global warming, a previous population of animals that lived around the hydrothermal vents went extinct, likely because of reduced oxygen levels in the deep sea, Rogers said. The extinction may have eventually paved the way for new species, like the Hoff crab, to thrive at the vents when the ocean waters cooled again.
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