In 1998, University of Delaware marine biologist Craig Cary and his colleagues made international headlines when they confirmed that the Pompeii worm, which lives at hydrothermal vents, is the Earth's most heat-tolerant animal.

The Pompeii worm (Alvinella pompejana) — a fuzzy gray, critter about as long as a hand, sporting tentacle-like, scarlet gills on its head — can survive a bath as hot as 176°F.

While some bacteria can live at even higher temperatures, Dr. Cary says the Pompeii worm ranks as the most heat-tolerant among higher-order life forms. It beat out the Sahara Desert ant, which formerly held the record at 131°F.

"For most of us, a hot shower is around 100°F, says Dr. Cary. "How the Pompeii worm survives the nearly boiling water emanating from the vents is a mystery."

The worm also displays a remarkably broad temperature gradient along its hairy body.

"The Pompeii worm makes paper-like tube colonies attached to hydrothermal vent chimneys," says Dr. Cary. "While the very hottest water shoots out the top of the chimneys, these structures are so porous that hot water also seeps out the chimney sides and through the worm's tube home."

By inserting a temperature probe called "the Mosquito," from the submersible Alvin into the worm's tube, Dr. Cary found that the worm's rear end sits in water as hot as 176°F, while its gilll-covered head, which often pokes out of the worm's tube home, rests in much cooler water, only about 72°F.

As chief scientist for the Extreme 2003 expedition, Dr. Cary says the research team's chief objective will be to learn more about the Pompeii worm's incredible heat tolerance by studying its unique biology and the bacterial colony that lives right on its back.

"The gray fleece, or "hair," that you see on the worm's back is actually bacteria," he notes. "Tiny glands in the worm's skin secrete a mucous that the bacteria appear to live and feed on."

These bacteria are of particular interest to science and industry because the microbes may harbor enzymes capable of operating in hot, corrosive, high-pressure environments. Such enzymes can help dislodge oil inside wells, convert cornstarch to sugar, process food and drugs, and support a number of other industrial processes by speeding up chemical reactions.

"Every time we visit the vents, we find something new," says Dr. Cary. "By studying "extremophiles" like the Pompeii worm, we can better understand this amazing ecosystem and the human benefits it may yield." His research is funded by a grant from the National Science Foundation.