Biodiversity and distribution of freshwater molluscs in superficial waters of Ouergha watershed (Morocco)

The primary goal of this work was to establish the specific biodiversity of freshwater molluscs in aquatic environments of Ouergha watershed. This faunal inventory fills the gaps in inventories malacological of Morocco especially the malacofauna of high altitudes. The missions surveys conducted between 2002 and 2005 show that the species found in the catchment area belong mostly to the class of gastropods. Indeed, among the 40 surface freshwater molluscs known in Morocco, 20 species have been recorded including two potential taxa : Planorbis Planorbis and Gyraulus laevis. The species inventoried are divided into 10 families: two families of Prosobranchia, six families of Pulmonata and two family of Bivalvia. The subclass Pulmonata has the most species (10 species) followed by Prosobranchia (5 species ) and Bivalvia (4 species). The presence of Lymnaea maroccana, endemic species of Morocco, was confirmed in ponds of Annasser. Biotic and abiotic factors are the most controlling the distribution of aquatic in the study area. Those factors are speed of water current, nature of the substrate and abundance of aquatic plants.