Over the past 20 years, metropolitan areas across France have been invaded by several species of hammerhead flatworms, according to a new study. The predatory worms are native to Asia and could pose a threat to French wildlife.
Giant hammerhead flatworms grow up to 40 centimetres in length and feed on earthworms and other invertebrates that contribute to soil health. “As active predators, [the worms] constitute a danger to native fauna wherever they are introduced,” warns a report published in the open-access journal PeerJ on Tuesday.
The report was co-authored by Jean-Lou Justine, a professor at the National Museum of Natural History in Paris, and Pierre Gros, an amateur naturalist. After requesting information about flatworms in France, the team received over 100 reports of flatworm sightings between 1999 and 2017.
“We have scientific proof from citizen scientists that they are infesting gardens year after year after year,” Justine told The Washington Post. Many of the worms were spotted in the south of France, where the climate is mild enough for them to survive.
Researchers said they were surprised that the worms, identified as land planarians belonging to the genera Bipalium and Diversibipalium, went undetected until now.
“We were amazed,” the authors write in their study, “that these long and brightly coloured worms could escape the attention of scientists and authorities in a European developed country for such a long time.”
“It is France! It is supposed to be a developed country,” Justine told The Washington Post. “We have a lot of scientists, we have universities everywhere.”
In a study five years earlier, Justine “dismissed the worms as nothing more than exotic greenhouse pests,” reports The Washington Post. “That was completely erroneous,” he said.
Entomologist Archie Murchie, from the UK’s Agri-Food and Biosciences Institute, told The Washington Post: “The species are cryptic and soil-dwelling so can be easily overlooked, which often explains their inadvertent shipment round the world.” Murchie, who was not involved in the research, warned that these types of worms will continue to spread “with increased global trade.”
Researchers noted that flatworms are found in many French territories across the globe, including Polynesia, Montserrat and the island of La Reunion.
The authors called for the implementation of control strategies to help limit the worms’ negative impacts on other species and on farmland.
“Invasive flatworms can have a major impact on other soil fauna,” Murchie said. “The authors are rightly cautious about the potential impact of the hammerhead flatworms.”
The giant flatworms reproduce asexually and are able to regenerate – parts of the worms that are amputated can regrow into whole worms – which contributes to their success as an invasive species, reports Live Science.
“Another reason is the absence of predators,” Justine told Live Science. “Land flatworms produce chemicals that give them an unpleasant taste,” and thereby avoid being eaten by predators.
Although reports suggest the species could be invasive, it remains unclear exactly how the worms are affecting French ecosystems, reports The Washington Post. Justine and Gros said further ecological research is necessary to assess what kind of impact the worms might have on local biodiversity.
Photo: Bart Everson / Flickr