"We proved that the tubeworm larvae can live long enough for the underwater highways that run deep in the ocean to take them from one vent to another," said Donal Manahan, professor of biological sciences and dean of research in the USC College of Letters, Arts and Sciences.

Manahan studies life in extreme conditions, although he does not view them as extreme. "Most of planet Earth's biosphere is seawater about the same temperature as your refrigerator," he said.

Three-quarters of the earth's surface is ocean where life can exist thousands of feet deep, added Manahan. In contrast, life on land exists only in a thin layer extending a few hundred feet above terra firma. "So more than 99 percent of the places where life can exist is in the ocean, and it's the part we know the least about."

Writing in the May 3 journal Nature, the scientists described taking the Alvin, a miniature submarine from Woods Hole Oceanographic Institute, to gather giant tubeworms hundreds of miles off the coast of Costa Rica.

They dissected the worms and, by artificial insemination, produced tiny tubeworm embryos or larvae. The researchers kept the larvae inside an apparatus that maintained a continual flow of 35-degree (F) seawater at the same water pressure as the deep vents.

"That's about two tons per square inch," said Manahan. "When you are raising babies, you normally keep them warm, feed them a lot and are careful not to crush them. To rear these deep-sea babies, we kept them refrigerator cold, didn't feed them at all and crushed them with 250 atmospheres of pressure."

The scientists also measured horizontal and vertical flow of currents in the vicinity of the vents. They determined that the giant tubeworm larvae were neutrally buoyant, and they calculated their metabolic rate. They were able to document some of the giant tubeworms' life cycle, about which little had been known.

In the late 1970s, scientists discovered there were vents thousands of feet deep in the ocean along the ridges formed by the earth's major tectonic plates. The vents belch geysers of hot water containing sulfur and other minerals and were surrounded by hundreds of brand-new species of animals, bacteria and some life forms that didn't fall into any of those categories.

"These vents are like an oasis driven by geothermal energy," said Manahan. "Microbes take sulfur and use it to fix carbon dioxide in a process called chemosynthesis. This is similar to photosynthesis -- but instead of sunlight, the key to the process is heat and sulfur."

The star of this unique ecosystem is the giant tubeworm, a 3- to 6-foot worm whose colonies are often seen waving in television science programs. The tubeworm has no eyes, mouth or intestine and is sustained by chemosynthetic microbes living inside it.

The question Manahan and his colleagues set out to solve was how giant tubeworms, and presumably other vent life forms, colonize new vent sites. The vents are ephemeral, with old vents shutting down and new ones springing up 50 or more miles away.

Other researchers who participated in the project were Adam G. Marsh, a postdoctoral fellow in Manahan's lab in the USC College of Letters, Arts and Science's dept. of biological sciences; Lauren S. Mullineaux, a scientist from Woods Hole Oceanographic Institution, Woods Hole, Mass.; and Craig M. Young, a biologist at the Harbor Branch Oceanographic Institution, Fort Pierce, Fla.

The research was supported by a grant from the National Science Foundation. In addition to his USC duties, Manahan is also the director of the National Science Foundation's Biology Training Program in Antarctica. - By Bob Calverley

(Editor's Note: A colony of giant tubeworms 8,000 feet deep in the Pacific Ocean can be viewed at this URL.)

[Contact: Bob Calverley]

04-May-2001