Tens of thousands of species of earthworms are likely to be wriggling in the world’s soil, yet to be discovered by scientists – which will probably take more than 100 years to do.

Earthworms play a critical role in recycling organic nutrients in ecosystems. Researchers fear that without identifying all these species, they could be lost before we know they exist.

More than 5700 species and subspecies of earthworms have already been described by scientists. But at the University of Montpellier in France wondered if this could be an underestimate when he noticed the diversity of earthworms while he was working in the Amazon rainforest.

To learn more, Decaëns and his team conducted sampling surveys in French Guiana, often flying by helicopter to remote areas of the rainforest. They spent up to two weeks collecting every worm they could find in 1-hectare plots, discovering many species that were new to science.

“We have only recorded 55 described species in French Guiana,” says Decaëns. “Whereas there are probably at least 2000 species there.” The scientists did similar sampling in France, which together suggested that the diversity of earthworms is must greater than previously thought.

In another part of the experiment, they worked with a statistician to estimate the number of earthworm species worldwide that haven’t yet been discovered, according to existing records and the rate at which new species are described.

“On a global scale, we estimate that at least 30,000 species of earthworm exist on the planet,” says Decaëns. Based on the number of worm taxonomists globally and the rate at which they classify specimens, it will take 120 years before they are all identified, he says.

“It is harder to conserve a group of species, such as earthworms, if we don’t know the basics of how many species there may be and where those species are,” says team member at the University of Helsinki in Finland.

at the Biological Recording Company in the UK says the research highlights how little we know about earthworms. “It is baffling how we’ve become so behind with understanding such an ecologically important group of animals.”

Worms that create intricate, tangled blobs with their bodies can disentangle in milliseconds when threatened. This speedy unscrambling is possible because each worm wriggles in a special corkscrew motion.

California blackworms (Lumbriculus variegatus) tangle their bodies into knotted “worm blobs” to preserve moisture during droughts. In the wild, these balls can contain up to 50,000 worms. It takes the animals a few minutes to form a blob, but when at the Georgia Institute of Technology shined ultraviolet (UV) light on one of these twisted-up worm balls in the lab he was shocked to see the worms disentangle in just a few tens of milliseconds.

He and his colleagues wanted to understand how the worms were extricating themselves from the blob a hundred times more quickly than they formed it. They used ultrasound to look inside blobs of about 20 worms and determine the details of their structure, such as how many times each worm coiled around another. To do this, they encased the blob in gelatine so the worms would wriggle less. Next, they put the blob in a shallow container of water, scared the worms with electric shocks or UV light and then filmed the rapid disentangling, with researchers manually tracking the trajectory of each animal’s head.

The team also collaborated with mathematicians who specialise in the theory of knots. These researchers used data from the observations to construct a mathematical model and run computer simulations, which revealed that the key difference between the worms’ slow entangling and rapid disentangling was the direction in which each animal performed a type of helical wriggle.

Repeating a corkscrew motion in one direction for a while and then abruptly switching directions leads to tangling, but quickly alternating between corkscrewing left and right efficiently disentangles the blob, says at Stanford University in California.

“I would have thought that, mathematically, disentangling isn’t really a solvable problem because it’s so complex, but then Harry and colleagues showed us these videos and it was like, if worms can solve this problem, so can we,” he says.

This new understanding of how blackworms morph from a tight blob to being more dispersed may help researchers eventually achieve the “dream of creating a material that can do stuff by itself” says at the University of Amsterdam in the Netherlands. In the future, materials made from tangled soft filaments could become looser and more bendable, or harder and more compact, if those filaments could be made to wriggle like the worms, he says.