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February 17, 2001

The Worm that Boasts Earth's Hottest Lifestyle
Marine scientist finds that a hydrothermal vent worm thrives in near-boiling waters
by Mike Matz


Scientists have discovered that the Pompeii worm, an inhabitant of hydrothermal vent ecosystems, can withstand hotter temperatures than any other creature on earth can -- except for certain one-celled organisms.

Scientists recently granted a hairy little worm found in the deep sea the distinction of being the most heat-tolerant complex organism on earth. The research team of University of Delaware marine scientist Craig Cary discovered that the Pompeii worm (Alvinella pompejana) thrives in waters as hot as 80° C (176°F), easily beating out the Sahara Desert ant Cataglyphis long considered to be the world's most extreme creature. Only certain simple one-celled organisms can survive higher temperatures.

The worm inhabits ocean-floor formations known as hydrothermal vents, which are geysers found along underwater volcanic mountain ranges formed by shifting plates in the earth's crust. The chimney-like vents release jets of "super-heated" water -- more than 300° C (570° F) -- that is rich in sulfur and metal compounds.

Despite the absence of sunlight as an energy source, hydrothermal vents are oases of biological diversity in the otherwise barren deep-sea-floor environment, teeming with bizarre-looking creatures that have evolved ways to live off the chemicals the chimneys spew. Most of these species are found nowhere else on earth, such as an eight-foot long red tubeworm without a digestive system and a shrimp with a unique organ that may detect heat and guide it to nutrients.

According to Dr. Cary, the ten-centimeter-long (4 inches) Pompeii worm makes its home in papery tubes that it burrows into the sides of the chimneys. Hot water from inside the vent flushes through these tubes and flows into much colder deep-sea water from outside. This results in a dramatic drop in water temperature over just a few inches, from over 80° C (176° F) in the tube's inner regions to about 14° C (57° F) at the tube's outer entrance. Amazingly, the worms simultaneously inhabit both extremes, with their heads positioned at the cooler openings and their tails withstanding the inner heat.

The creatures more than just tolerate this environment. "The worm likes it in there," said Dr. Cary.

 


Marine scientist Craig Cary led the team that probed into the Pompeii worm's hot lifestyle.

Dr. Cary's team made the finding while studying the worm in hydrothermal vents along the East Pacific Rise, an ocean-floor rift in the waters west of Mexico. Venturing more than a mile below the surface in the ALVIN deep-submergence vehicle, Cary's team operated a six-inch-long titanium probe inside the worm's tubular abode to analyze water temperatures.

It's still unclear how the worm accomplishes its feat of heat-tolerance, said Cary. But Cary suspects that the explanation has to do with one of the worm's most striking physical features -- the hairy shawl that covers its back. Analysis of this fleecy fuzz has revealed that it's actually made entirely of bacterial colonies that feed on the sugars secreted by the worm.

According to Cary, the hair, which can be up to a centimeter thick, may act as a protective thermal blanket for the worm. He believes the bacteria in the hair contain special proteins known as eurythermal enzymes that can withstand a broad temperature range.
Cary's colleagues are conducting biochemical studies on bacteria samples collected from the worm to identify these enzymes and determine how they resist heat. Unfortunately, scientists have yet to successfully bring the worm itself back alive because, as Dr. Cary says, "They do not decompress well at all."

These remarkable proteins may offer enormous benefits to the production of pharmaceuticals, paper, detergents, textiles, and other products-which is why many industries are closely following the protein research.

Stunning discoveries like that of the Pompeii worm are not uncommon in hydrothermal vents these days. That's because these ecosystems are relatively new to science -- first spotted just a few decades ago -- and biologists frequently find never-seen-before species there.

"Almost on every dive something very new and interesting exciting comes up," said Dr. Cary. "In biological systems, that's fairly rare."

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