for National Geographic News
Perhaps the most heat-tolerant complex organisms on Earth, Pompeii worms (Alvinella pompejana) thrive along hydrothermal vents found deep in the Pacific Ocean.
Wrapped in fleecelike mantles of bacteria, the worms live in papery tubes, which they burrow into the sides of deep-sea geysers. The hydrothermal vents spew a toxic brew of boiling water, sulfur, and metal compounds.
Scientists say the water temperature at the base of the tubes is 176 degrees Fahrenheit (80 degrees Celsius). Only single-celled bacteria are known to survive hotter temperatures.
"How the worm tolerates these temperatures is still unknown," said Craig Cary, a marine biologist at the University of Delaware in Lewes, who is leading his sixth trip to the East Pacific Rise, an underwater volcanic mountain chain about 1,200 miles (2,000 kilometers) west of Costa Rica, to study the creatures.
A team of French scientists first discovered the Pompeii worm at hydrothermal vents in the Galapagos Islands in the early 1980s.
Since then, scientists have labored to understand how the four-inch-long (ten-centimeter-long) worms thrive in their extreme environment.
Not only do they survive the scalding temperatures and toxic chemicals spewed by hydrothermal vents, but the worms also live in total darkness and under the crushing pressure of the deep ocean.
In 1998 Cary and colleagues published findings on the temperature of the Pompeii worm's tube in the science journal Nature.
Water at the tube bottom is a scalding 176 degrees Fahrenheit (80 degrees Celsius), while the worm's head, which sticks out of the tube, rests in water at a tepid 72 degrees Fahrenheit (22 degrees Celsius).
Prior to the discovery, few, if any, scientists believed complex organisms could survive such extreme environmental temperatures, Cary noted. He cautioned, however, that he and his colleagues only measured the temperature inside the tube, not the worm itself.
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