Metal munching earthworms

Worm poo could hold the key to cleaning up toxic metals in contaminated soils. Diamond’s intense X-rays were used to probe tiny granules of calcium carbonate (the main component of snail shell) excreted by earthworms that had been living in lead contaminated soil. Although tiny to us, the granules scaled up would be like a human excreting a spikey football!

 

The group are also interested in the mineral form of the calcium carbonate granules. Sometimes the calcium carbonate is amorphous, meaning that its ions are not organised in a regular repeating pattern as within a crystal (gel is an amorphous solid). The interesting structural properties of amorphous materials are appealing to material and biomedical scientists who would look to make micron-scale devices out of the unique material.

There is also a general interest in increasing our knowledge on how and why the calcium carbonate granules form, which has been a mystery since the humble earthworm caught the attention of Charles Darwin and he described the granules in 1881 when he published his book Formation of Vegetable Mould Through the Action of Worms with Observations on their Habits. It sold 6,000 copies in its first year, selling faster than On the Origin of Species by Means of Natural Selection when it was first published. Spending four decades studying the worm's brain power and senses, after much serenading and tobacco chewing (during his studies, Darwin tested the worms’ reactions to the noise and vibrations of a piano and to his breath whilst chewing tobacco) Darwin concluded, “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.” More information about how metals are partitioned within the granules, such as that gathered from Professor Hodson’s group’s data, could lead to a better understanding of how the granules form, filling in the gaps in our knowledge of an animal deemed so important by Darwin.