Newspaper article The Christian Science Monitor

Scientists Explain Earthworms' Leaf-Busting Guts

Newspaper article The Christian Science Monitor

Scientists Explain Earthworms' Leaf-Busting Guts

Article excerpt

Earthworms are known for their indiscriminate digestive tracts, so perhaps it comes as no surprise that they can digest some plant toxins without difficulty.

Researchers have identified unique chemical compounds in the digestive tracts of 14 earthworm species. These compounds counteract the defensive toxins produced by plants, allowing earthworms to consume them safely. A new study, led by Imperial College metabolomics expert Jake Bundy, appeared Tuesday in Nature Communications.

"Earthworms are so easy to find and study, yet there are still new and surprising things to discover," Dr. Bundy says. "It makes me wonder how many other unique biochemical mechanisms there are out there that we don't know about, just because we haven't looked."

As sedentary organisms, plants rely on creative measures to deter hungry herbivores. Many plants produce defensive chemicals called polyphenols. By binding gut enzymes, polyphenols inhibit the digestion of plant matter. Dead plants retain these chemicals even as they fall to the soil, discouraging would-be decomposers in the process.

"Plant defense chemicals definitely have a negative effect," Bundy says. "Humans and other vertebrates have evolved their own, separate way of dealing with plant polyphenols: we produce specialized chemicals in our saliva that bind to the polyphenols so tightly that they then pass through our gut without interacting."

Earthworms have evolved a different solution altogether. Their guts produce drilodefensins, which disrupt the chemical properties of polyphenols. These compounds are classified as surfactants, which act a lot like detergents - a large amount of purified drilodefensins could clean your dishes.

In fact, Bundy and colleagues found that commercial detergent also protected against polyphenols. But you can't simply swap out an earthworm's drilodefensins with Tide and expect the worm to thrive, because it would inhibit other enzyme activity. Bundy suggests that earthworm enzymes and drilodefensins evolved in tandem to be compatible.

With three types of imaging mass spectrometry (IMS), Bundy and colleagues were able to observe cross-sections of their worms at an extremely fine scale. …

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