Drilodefensins are the secret weapon of earthworms. Most plants produce toxins designed by evolution to discourage herbivores from consuming plant leaves. And these toxins remain effective even after the leaves fall. So, how do the humble earthworms turn over 35 billion tons of leaf litter and dead grass every year? They munch on fallen leaves and dead roots, and enrich the soil by returning concentrated nutrients and carbon.
Earthworms produce drilodefensins to counter plant toxins
Scientists at the Imperial College London have discovered that earthworms produce drilodefensins to counteract the plant’s natural defenses. Plants produce polyphenols that have health benefits to humans, but are toxic to most herbivores. They block digestion by preventing enzymatic activity. To counter these toxins, earthworms produce large amounts of drilodefensins. These molecules allow the “gardener’s best friend” to consume plant materials up to one-third of its body weight in a single day.
Lead researcher Dr Jake Bundy said earthworms produce more drilodefensins if the plant materials contain more polyphenols. The world would be entirely different without drilodefensins. He said for every person living on Earth, there is at least 1 kilogram of drilodefensins in all the earthworms that populate our planet.
But demand for these molecules is so high that despite the huge quantity of drilodefensins, earthworms have to recycle the molecules over and over again to keep on digesting. Findings of the study were published in the journal Nature Communications. Researchers used mass spectroscopy-based visualization techniques to identify the key to the earthworms’ digestive system.
Drilodefensins are unique to the ‘nature’s plows’
Researchers discovered that these molecules are unique to earthworms. They found drilodefensins in the gut of 14 different earthworm species. But other closely related invertebrates like leeches lacked drilodefensins. Dr Dave Spurgeon, a co-author of the study, said these worms have a “metabolic coping mechanism” to counter plant toxins.
Dr Jake Bundy said fallen leaves would remain on the ground for a very long time, building up a thick layer if earthworms didn’t produce drilodefensins.