Worms' hot ends set thermal record

Science News, Feb 21, 1998 by Mari N. Jensen

If The Guinness Book of World Records had an entry for animals living at high temperatures, tube-dwelling worms near hydrothermal vents on the seafloor would win. The Pompeii worm keeps a cool head in that hot clime, however. While in its tube, the worm's rump may be immersed in water as hot as 81 [degrees] C, while its head is in water of a moderate 22 [degrees] C.

This worm lives at higher temperatures and routinely experiences a wider temperature range than any other multicellular organism known, report scientists in the Feb. 5 Nature. The previous record holder, an ant that lives in the Sahara Desert, forages in air temperatures of 55 [degrees] C.

Scientists thought that organisms whose cells contain membrane-bound structures like nuclei and mitochondria cannot tolerate rapid, extreme temperature changes or temperatures greater than 55 [degrees] C. "Membranes can adapt, but they take time," says study coauthor S. Craig Cary of the University of Delaware in Lewes. "If you change the temperatures too abruptly, the membranes will fall apart or freeze."

Nevertheless, the Pompeii worms weather extreme temperature shifts with impunity, since they often leave their hot tubes to forage outside in the 10 [degrees] C water. "The neat thing is the range of temperatures," says Verena Tunnicliffe of the University of Victoria in British Columbia.

The water inside the worm's tube would be thermally and chemically lethal for many animals, Cary says. It contains sulfides and heavy metals, such as lead, cadmium, cobalt, zinc, and copper. He believes that symbiotic bacteria living on the worm's back may detoxify the environment. If so, he says, enzymes from the bacteria may have practical uses, such as cleaning up toxic waste sites.

"There are many different possible applications of enzymes that can operate over broad temperature ranges," Cary says. "If you can find bacteria that have novel pathways to deal with metals, that might be an approach for bioremediation."