Invasion of the predatory flatworms

A predatory worm has already spread widely in France. (Image: Pierre Gros)

“Aliens” with an appetite for earthworms and the like: Flatworms that have been introduced are currently spreading in Europe’s gardens, researchers report. The bizarre creatures from South America eat animals living on the ground and thereby threaten the local ecosystems. France in particular is already affected by the invasion, the study documents with the participation of garden owners.

Animal and plant species were once restricted to certain regions of the world due to geographic obstacles such as the seas and mountains. However, as is well known, humans ensure globalization: through trade and transport, living things get from one continent to another or to remote islands. In some cases, they end up in “paradise”: they encounter ideal living conditions, have no enemies and can therefore multiply greatly. There are numerous examples of such invasive species that are currently threatening the original ecosystems in many areas of the world.

Already widespread

The research team led by Jean-Lou Justine’s National Museum of Natural History in Paris is now focusing on intruders that garden owners in Europe could now encounter more and more frequently in the future: flatworms – so-called land planarians. Already in 2018 they reported finds from representatives of these beings from New Guinea and Asia that had been brought in to Europe. The range of these invaders was limited. The new intruder, on the other hand, has already established itself widely, at least in France, according to the study. It is the Obama nungara worm, which is up to seven centimeters long.

The invasive cold worm eats a snail. (Image: Pierre Gros)

The predatory inhabitant of the earth’s surface has already been sighted in several European countries, including Spain, Portugal, Great Britain, Italy and Belgium. However, the extent of O. nungara occurrence has not been systematically examined in any of these countries. In France, Justine and his colleagues have now recorded the occurrence using a hands-on project: garden owners from all over France have reported finds of the worms.

Threat to ecosystems

The results show that O. nungara already exists in 72 of the country’s 96 departments – an area that makes up 75 percent of the area of ​​France. In some gardens, the slimy fellows apparently abound. The species is particularly common along the Atlantic coast and the Mediterranean coast, according to the data. Worm finds have also been reported from Alsace near the German border. One can only speculate about the actual extent of the spread of O. nungara in Europe.

Studies of the animals showed that they originally come from Argentina. According to the researchers, they were probably spread through potted plants. Justine and his colleagues say it is still unclear exactly how the intruders will affect ecosystems. But their feeding behavior suggests bad things: They are targeting snails, earthworms and other soil-living organisms and could therefore threaten the biodiversity and the ecological balance considerably. According to the authors, in the case of O. nungara we are now dealing with the most threatening representative of all invasive flatworms occurring in Europe.

Source: PeerJ, technical article: PeerJ, doi: 10.7717 / peerj.8385

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