An international team of researchers led by Dr. Jean-Lou Justine of the Muséum National d’Histoire Naturelle, Paris, has identified at least five species of invasive hammerhead flatworms living in metropolitan France, a few European countries, and overseas French territories in three continents.
Hammerhead flatworms of the genera Bipalium and Diversibipalium (bipaliines) are giants among land flatworms, reaching length of 3.3 feet (1 m).
These worms are easily distinguished from other land flatworms by the characteristic hammer shape of their head.
Bipaliines have their origin in warm parts of Asia and are invasive species, now widespread worldwide.
They are predators of soil animals, including earthworms, and are a possible threat to the biodiversity of native animals and to soil ecology.
In a paper published in the journal PeerJ, on the basis of a four year survey based on citizen science, which yielded observations from 1999 to 2017 and a total of 111 records, Dr. Justine and co-authors provided information about five species of bipaliine worms present in metropolitan France and French overseas territories in the Caribbean, South America, Africa and Oceania.
“Three species of bipaliines are reported from metropolitan France: Bipalium kewense, Diversibipalium multilineatum, and an unnamed Diversibipalium ‘black’ species,” the researchers said.
“We also report the presence of Bipalium kewense from overseas territories, such as French Polynesia (Oceania), French Guiana (South America), the Caribbean French islands of Martinique, Guadeloupe, Saint Martin and Saint Barthélemy, and Montserrat (Central America), and La Réunion island (off South-East Africa).”
“For Bipalium vagum, observations include French Guiana, Guadeloupe, Martinique, Saint Barthélemy, Saint Martin, Montserrat, La Réunion, and Florida (United States).”
“A probable new species, Diversibipalium sp. ‘blue,’ is reported from Mayotte Island (off South–East Africa).”
“In metropolitan south-west France, a small area located in the Department of Pyrénées-Atlantiques was found to be a hot-spot of bipaliine biodiversity and abundance for more than two decades, probably because of the local mild weather.”
These species of bipaliine worms show no genetic variation, according to molecular studies, based on the cytochrome oxidase type 1 sequences.
The species are clonal (genetically identical) and reproduce asexually. Bipalium kewense had a single haplotype, found in five continents.
“Our findings strongly suggest that the species present in metropolitan France and overseas territories should be considered invasive alien species,” Dr. Justine and colleagues said.
“Our numerous records in the open in metropolitan France raise questions: as scientists, we were amazed that these long and brightly colored worms could escape the attention of researchers and authorities in a European developed country for such a long time; improved awareness about land planarians is certainly necessary.”
J. Justine et al. 2018. Giant worms chez moi! Hammerhead flatworms (Platyhelminthes, Geoplanidae, Bipalium spp., Diversibipalium spp.) in metropolitan France and overseas French territories. PeerJ 6: e4672; doi: 10.7717/peerj.4672