A creeping threat Slimy flatworms are spreading in Switzerland

The invasive flatworm species is increasingly spreading in Switzerland and poses a serious threat to native species. Without natural enemies, the slimy invaders from overseas are multiplying rapidly.

With their smooth body and slimy appearance, flatworms do not arouse much sympathy. Their nickname "killer worm" does not exactly contribute to the popularity of these slippery creatures.

These worms belong to the invasive alien species, also known as neozoa.

Dangerous representatives of this species have already been discovered in the cantons of Thurgau, Basel-Stadt and most recently in Olten, as reported by "20 Minuten".

Experts are sounding the alarm and calling on the public to help fight them.

Flatworms eat native species

Europe itself is home to 28 species of flatworm. However, the real threat is posed by three invasive species from Australia and New Zealand ("Caenoplana variegata"), South America ("Obama nungara") and Japan ("Diversibipalium multilineatum").

The carnivorous worms have almost no natural enemies, prefer to feed on earthworms, snails and arthropods and "liquefy their prey with an enzyme slurry", as the NZZ reports.

And: as the three flatworms can reproduce almost unhindered, they significantly reduce both the population and the food sources of native species. However, these are essential for the ecosystem and soil quality.

While the three invasive flatworm species reproduce almost uncontrollably, they decimate the populations of native species and deprive them of food.

The cantonal authorities are working hard to prevent the uncontrolled proliferation of these invasive species and stop them spreading into the forests.

Five millimeter eggs

Flatworms mainly travel through imported potted plants, garden plants and packaged soil. The robust worms can also overwinter: Hidden in the soil, they survive the winter without any problems.

During the day, they seek out dark, damp hiding places, such as under flower pots, mats or foil. Their peculiar eggs, about five millimeters in size, are often conspicuous. Freshly laid, they are reddish, but turn black after a few hours.

Adult flatworms can be recognized by their smooth, flat body, in contrast to earthworms, which have grooves.

Freeze the worm as a sample, but do not cut it up

Suspected cases should be reported immediately to the relevant cantonal neobiota office, stating purchase and location information, according to a leaflet from the canton of Zurich. Neobiota refers to species that have become established in an area where they were not previously native as a result of human influence.

At least one worm should be frozen as a sample, while the remaining worms and eggs should be collected and killed.

The eggs can be crushed and the worms placed in a soapy water bath. Important: Never cut the worms as this will cause them to multiply. They can regenerate and continue to live as two separate parts.

To prevent this, plants should be checked thoroughly for flatworms before purchase. The undersides of pots, insides and the root area should also be checked regularly.

Around 50 invasive neozoa are currently known in Switzerland and the surrounding countries, out of a total of over 1000 alien species. Neozoa are animal species that were not originally native to an area and have entered this area with the direct or indirect help of humans and now live there in the wild.

In Switzerland, these include the Asian hornet, the Asian tiger mosquito, the quagga mussel and the longhorned beetle.

Compared to other invasive alien species, flatworms have been kept relatively well under control so far.

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