Heavy Metal-Eating "Superworms" Unearthed in U.K.

James Owen
for National Geographic News
October 7, 2008

Newly evolved "superworms" that feast on toxic waste could help cleanse polluted industrial land, a new study says.

These hardcore heavy metal fans, unearthed at disused mining sites in England and Wales, devour lead, zinc, arsenic, and copper.

The earthworms excrete a slightly different version of the metals, making them easier for plants to suck up. Harvesting the plants would leave cleaner soil behind.

"These worms seem to be able to tolerate incredibly high concentrations of heavy metals, and the metals seem to be driving their evolution," said lead researcher Mark Hodson of the University of Reading in England.

"If you took an earthworm from the back of your garden and put it in these soils, it would die," Hodson said.

DNA analysis of lead-tolerant worms living at Cwmystwyth, Wales, show they belong to a newly evolved species that has yet to be named, he said.

Two other superworms, including an arsenic-munching population from southwest England, are also likely new to science, Hodson said.

"It's a good bet they are also different species, but we haven't categorically proved that," he said.

The findings were announced in September at the British Association Festival of Science in Liverpool.

Micro Processors

Hodson's team's investigation used x-rays to zap worms with intense light, allowing them to track metal particles a thousand times smaller than a grain of salt.

The findings suggest the arsenic-tolerant population produces a special protein that "wraps up the metal and keeps it inert and safe so it doesn't interact with the earthworms," Hodson said.

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