When Washington State University biologist Raymond Lee set out to study the most heat-tolerant animals on Earth, he headed, oddly, for the open ocean off the coast of Washington.
There, with the help of a remote-operated submarine, he found his quarry: inch-long worms clinging to the sides of hydrothermal vents on the ocean floor more than a mile below the surface.
The vents are holes in the Earth’s crust where molten minerals seep out of the planet’s interior, raising the seawater to near-scalding temperatures and creating a habitat that is home to some of the oddest, and hardiest, organisms known.
Lee’s special interest is extreme environments, and how animals and plants have adapted to them. He was intrigued by the vent worms, because they were reported to live at higher temperatures than any other animal—60°C (140°F)—and to tolerate brief exposure to 80°C (176°F). That was based on readings from a thermometer researchers had inserted via remote control into a worm’s tube-like covering.
“As evolutionary physiologists, we’re interested in all the different ways that animals have engineered to cope with their environment,” says Lee. “Extreme organisms like these have pushed the limits” of what’s possible, he says.
In the case of the vent worms, Lee thought their reported tolerance of temperatures of 60°C or higher pushed too far. Most of the enzymes and other proteins critical to life stop functioning normally between 45° and 55°. Lee decided to test the worms himself, by bringing them into the lab—a task just as challenging in its way as manipulating a tiny probe via robot at the bottom of the sea.
That challenge was half the fun. Lee loves to build things. In his lab, power tools outnumber microscopes. He sketched a rough blueprint for a chamber that would let him keep vent worms at the intense pressure they’re adapted to. His ideal chamber even had windows so he could film the worms’ reactions to various temperatures. John Rutherford, a machinist at the College of Science’s Instrument Shop, refined the plan.
“They’re very patient,” says Lee of the shop staff. “They had a scratchy little drawing. John would call me up and say, ‘Did you mean this? Can you come down here?’ Eventually we got it all figured out.”
They came up with chambers about the size of a two-pound coffee can, made of thick Plexiglas inside a heavy aluminum sleeve with portholes cut into it. With his colleague Peter Girguis of Harvard, Lee had a remote-controlled sub pull worms off their vent and bring them to the surface. The worms survived that trip, and Lee immediately placed them into a chamber and pumped up the pressure. They did fine there for several weeks—as long as the temperature didn’t go above 50°C (122°F). The worms became sluggish at 52°C; at 60°C, the temperature previously reported to be their normal environment, they died within minutes.
Lee then asked whether the worms would stay in hot water if they had a cooler choice. He went back to his lab/shop and made a longer chamber that let him heat one end and chill the other. With a thermal gradient in the chamber, the worms were free to seek their preferred temperature. They hung out at 50°C most of the time, occasionally probing the 55°C (131°F) zone but withdrawing after a few minutes. It was a dramatic demonstration that vent worms really do “like it hot”—hotter than any other aquatic multicellular animal—but not as hot as previously reported.
Now, with a new grant from the National Science Foundation, Lee is studying the physiological processes that enable vent worms to cope with such high temperatures; and he and Girguis are designing an infrared instrument that will let them read the temperature of a vent worm in its natural habitat just by pointing it at the creature.
Lee says solving the practical problems of studying vent animals, either in the sea or in the lab, lays the groundwork for the techniques we’ll need to study creatures from other worlds.
“Vent organisms may be as difficult to deal with as something from another planet,” he says. “It’s all remotely operated. If we find something on Mars, it will be the same situation, just a longer distance.”