A revision of the genus Belgrandia, with the description of a new species from France (Caenogastropoda : Hydrobiidae)

A new species of the hydrobiid genus Belgrandia Bourguignat, 1869, B. gfras t, nov. sp., from the nature reserve Petite Camargue Alsacienne in France i s described, in order to define the new species, it was necessary to invest igate the syntype series or topotypes of the known nominal species. This re vision is based on morphometric analyses of the shells and demonstrates tha t the number of diagnosable species is much higher than 20th century revisi ons have suggested. On the other hand, several nominal species attributed t o Belgrandia turned out to belong to Bythinella Moquin-Tandon, 1856. I reco gnize 16 species and one subspecies -this figure does not include Italian t axa, which are the subject of a revision by Italian colleagues -as belongin g to Belgrandia. The range of this genus covers the Iberian Peninsula, Fran ce, Italy, Croatia, and Greece. The highest diversity is found in southern France, with nine species. Morphologically, the new species is characterized by the combination of a p ointed apex, convex whorls, a single varix on the body whorl, which is most ly close to the aperture but may lie up to half a whorl behind it, and a ra tio of shell height to shelf width of 1.78 (mean). Anatomically diagnostic features are the wide visceral oviduct and the penis, with a wide, rounded muscular lobe on the left side in the distal half. Occasionally, there is a second, smaller lobe on the right side of the penis. The generic allocatio n is justified through the shell varix and the distal female genitalia with two receptacula seminis and a bursa copulatrix originating from the renal oviduct, which describes a loop of 270 degrees. All specimens investigated anatomically had peritrich ciliates of the genus Trichodina Ehrenberg, 1830 , in their mantle cavities. The new species is only known from a single locality. It lives in constantl y cool water (11.3-12.3 degreesC), which has high concentrations of calcium and magnesium. However, the concentrations of nitrate, chloride and potass ium are also considerable. The sources of this contamination are probably t he nearby settlements and agriculture.