Without earthworms, our planet would be one giant composting experiment gone awry. And without an immensely abundant type of molecule whose critical function scientists have only just uncovered, earthworms would not be able to digest a lot of plant matter.

Those molecules now finally have a name: drilodefensins. Recycling all of the dead leaves and other bits of unappetizing plant matter is an enormous task, and earthworms are some of the only organisms on the job because digesting plants isn't easy. Using incredibly powerful microscopes that can pinpoint the location of particular molecules, researchers determined that drilodefensins in earthworms' guts are key to performing that job successfully, according to their report in the journal Nature Communications.

"Without drilodefensins, fallen leaves would remain on the surface of the ground for a very long time, building up to a thick layer. Our countryside would be unrecognisable, and the whole system of carbon cycling would be disrupted," study co-leader Jake Bundy, from the Department of Surgery and Cancer at Imperial College London, said in a statement.

Many leaves and other plant parts are chock-full of toxic chemicals to deter animals from eating them. This would be a problem for earthworms, too, if it weren't for drilodefensins. These molecules neutralize harmful compounds found in leaves – known as polyphenols – so that earthworms can safely digest them.

The study authors estimate that for every single person on Earth, there is at least one full kilogram of drilodefensins. But these molecules are so crucial that this still isn't enough that earthworms don't have to be careful about their consumption of them. They actually recycle these invaluable molecules in their bodies so that they can use them repeatedly.

Without a molecular microscope, the researchers may never have realized that earthworms have drilodefensins stowed away in their guts – or why.

"Using these molecular microscopes is changing how we understand complex biochemistry of living beings; we are now able to locate every molecule in, for example, an earthworm to a specific location," study co-author Dave Spurgeon of the Centre for Ecology and Hydrology said in a statement. "Knowing the location of a molecule can help us to figure out what it actually does."

Photo: Gilles San Martin | Flickr