Can of Worms

For its achievements in the area of ecological balance, it would well deserve the title “Worldworm”. The English refer to this king of the earth as the earthworm, in German it is “Regenwurm” – for its active (“rege”) behavior. The most widely known representatives include the dew worm and the compost worm; they are related to at least 7,000 species within the subclass of Oligochaeta.For such a small organism, the earthworm, which is blind and deaf and which possesses neither spine nor limbs nor teeth, is capable of extraordinary feats. It lifts 60 times its body weight. The dew worm, at 30 centimeters, is one of the longest worms in its family, and it lives for up to six years. To make it clear from the start: it will only reach this ripe old age if it does not fall victim to a spade that will cut it in half. The belief that earthworms will survive such trauma is an urban myth. It is only possible under certain circumstances. More on that later.

Charles Darwin’s book on worms

It begs the question: why did 141 researchers from 57 countries embark on creating a world atlas of worms and decide to publish it in the American scientific journal “Science_®”? Well, even the father of evolutionary theory, Charles Darwin (1809 –1882), devoted an entire book to the earthworm in 1881 – his last. “The Formation of Vegetable Mould through the Action of Worms” ended up being almost as successful as his work on evolutionary theory. The British naturalist recognized the importance of the earthworm for the fertility of the soil. Many of his colleagues deemed him to be crazy; at the time, earthworms were considered a garden pest that would gnaw on plant roots. Today we know the more worms populate the soil, the higher the soil fertility.To quote Darwin: “It may be doubted if there are any other animals which have played such an important part in the history of the world as these lowly organized creatures.” More than 140 years later, worm scientists bemoan the fact that research into the exceptional role of the earthworm is still incomplete, and in October 2019, they wrote in “Science®”: “Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution and the threats affecting them.”

Global research

In order to change that, scientists have compiled an atlas of earthworm societies from 6928 locations in 57 countries; they searched for patterns with respect to diversity, number and biomass of earthworms. A surprising discovery: “Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide”, write the researchers.At the same time, the earthworm works comprehensively on preserving our ecological balance. This soil engineer not only breaks up the soil, it literally plows through the earth, loosens and aerates it and mixes mineral and organic substances. With its mouth-like front section, it attaches itself to a rotting leaf via suction and then transports the leaf underground – its tunnel, or living-tube, can reach up to two and a half meters deep and be up to 20 meters long. However, before the toothless worm can enjoy it, the leaf must be predigested by bacteria and fungi. Every day, the worm devours close to half its body weight in food, and during a single night, it pulls up to 20 leaves into its living-tube.

Waste disposal and delivery service

The earthworm simultaneously assumes the duties of waste disposal and delivery service. With its help, dead material is converted into nutrients. The digested remains, excreted by the worm on the surface at night, are of particular importance to the ecological balance: earthworm humus features a balanced nutrient ratio; its combination of enzymes, humic acids and minerals is unique. The resident microorganisms improve the soil in a substantial manner – this is why the purchase of earthworms is a common practice among gardeners.Its tunnel systems also assist the penetration of rain water and increase the water-storing capacity of the soil. In this way, the earthworm effectively prevents floods. In addition, the tunnels facilitate the growth of plant roots into the deeper layers of the earth with their unique nutrients. Speaking of delivery service: for some animals, the earthworm is a yummy treat. Blackbirds and robins, for example, savor it.And now for the earthworm myth. The belief that one earthworm, when cut in half, will give rise to two new worms is widely held. Not so: only the front portion, which includes the essential organs, continues to live – under the condition that the intestine is still long enough. In that case, the hind end may regrow. So – please be careful while gardening and avoid hitting a superworm!

Surprising facts

• 
  Earthworms are hermaphrodites; each one of them possesses testes as well as ovaries. During mating, each partner acts as the male.

• Little powerhouses: earthworms can lift 50 to 60 times their own body weight, making them one of the strongest animals in the world in relation to their body size.

• While the earthworm burrows through the soil, it presses its short clawlike bristle pairs into the ground to prevent sliding.

• In the 16th century, the German “Regenwurm” was known as “reger Wurm” (active worm) because it was always working and eating. This is the origin of its modern German name.

• The worm does not like the rain. The vibration caused by the droplets hitting the ground lures it from the soil – where deadly UV-radiation and hungry birds await it.

• One square meter of soil is typically inhabited by 100 earthworms. The animals enjoy moist, loose soil.