Scientists have discovered how earthworms can digest plant material, such as fallen leaves, that would defeat most other herbivores. Earthworms are responsible for returning the carbon locked inside dead plant material back into the ground. They drag fallen leaves and other plant material down from the surface and eat them, enriching the soil, and they do this in spite of toxic¹ chemicals produced by plants to deter² herbivores.

 

The scientists, led by Dr Jake Bundy and Dr Manuel Liebeke from Imperial College London, have identified molecules³ in the earthworm gut⁴ that counteract⁵ the plant's natural defences and enable digestion⁶. Their work is published today (4 August 2015) in Nature Communications and includes support from the Centre for Ecology and Hydrology, the University of Oxford⁷, and Cardiff University.

 

The molecules, which have been named drilodefensins, are so abundant that Dr Liebeke estimates that for every person on earth there is at least 1kg of drilodefensins present within the earthworms that populate the world's soils. Their abundance is not, however, an excess - drilodefensins are so precious that earthworms recycle the molecules in order to harness their effects again.

 

A world without drilodefensins would be a very different world, according to the researchers. Dr Bundy, from the Department of Surgery and Cancer at Imperial, said: "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."

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