While the return of the wolf or the reintroduction of the Pyrenees ibex could suggest a resurgence of wildlife, works about less emblematic organisms remind us that a biodiversity crisis is unfolding before us, in France too.
Two researchers have just published a species revision of the genus Mercuria, a tiny genus of snail living in the fresh waters of coastal zones, of which most species are endemic to France – meaning that they live nowhere else on earth. The researchers first studied the samples present in museum collections – including the Muséum national d'Histoire naturelle, in Paris – and also collected new specimens at sites where the different species have been reported from the mid-19th to the late 20th century: on the Atlantic coast, from La Négresse lake close to Biarritz, Teich in the Arcachon Bay, Belle-Île-en-mer Island and the Somme estuary; and on the Mediterranean coast, from La Foux de Draguignan, the Napoule ponds, Grasse, Nice and Bonifacio in Corsica. Across all of these sites, they noticed a striking absence of the tiny Mercuria, some of which were nonetheless present in the 1970s.
Historical collection sites of species of the genus Mercuria.
White dots symbolize sites of recent collection; red crosses, the sites where the species are now extinct.
Their article, published in the scientific journal Zoosystema, implicates progressive habitat destruction, such as in Bonifacio, and also the pollution of natural environments, as on the shore of La Négresse lake in Biarritz, as the causes for this decline
Of the seven species collected in the past, only one has been found during recent prospections; the other six are extinct or greatly endangered of extinction.
Boeters H. D. & Falkner G. 2017. — The genus Mercuria Boeters, 1971 in France (Gastropoda: Caenogastropoda: Hydrobiidae). West-European Hydrobiidae, Part 13. Zoosystema 39 (2): 227-261.