Now researchers at Imperial College London have figured out how the worms manage to digest dead plants despite toxic chemicals that deter most other herbivores. Plants make polyphenols, which act as antioxidants and give the plants their color. They also usually block digestion.
The scientists identified molecules in the earthworm’s gut that counteract the plant’s natural defenses. The molecules, named drilodefensins, allow an earthworm to eat up to one-third its body weight in a single day. The more polyphenols detected in an earthworm’s diet, the more drilodefensins it produces in its gut, the researchers found.
As earthworms burrow into the ground, they eat soil with their mouths, located in their first segment. They extract nutrients from decomposed organic matter, transporting nutrients and minerals from below to the surface through their waste — and their tunnels aerate the ground.
“Without drilodefensins, fallen leaves would remain on the surface of the ground for a very long time, building up to a thick layer,” Jake Bundy from the Department of Surgery and Cancer at Imperial, said in a press release. “Our countryside would be unrecognizable, and the whole system of carbon cycling would be disrupted.”
So much munching requires a lot of the earthworm’s digesting molecule. Manuel Liebeke from Imperial College London estimates that for every person on Earth there are at least 1 kg (2.2 lbs) of drilodefensins present in the planet’s earthworms. Even with such a quantity of the molecules, they are still in such high demand that earthworms recycle the molecules to keep on digesting.
The researchers identified the key to the worms’ digestion by using modern visualization techniques based on mass spectrometry. Manuel Liebeke from Imperial College London explained that the technology has allowed scientists to zero in on animals’ biology like never before.
Read more at Discovery News
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