High amphipoda species richness in the Nert groundwater system (southern France)

Two types of habitats in the alluvial sediments of the Nert stream (a tribu tary of the Salat, in the Garonne drainage basin) were investigated. In the hyporheic habitat, six stygobite amphipod species (Salentinella gineti, S. petiti, Parasalentinella rouchi, Niphargus pachypus, N. gineti, and Ingolf iella thibaudi) were caught, during a 13 month sampling campaign and within an area of 30 m(2) (sampled at 0.6 m and 1.0 m depth). With the aid of two piezometres, located in the alluvial plain (15-20 m removed from the strea m), the previous six species were found again over a six month sampling per iod, and another stygobite amphipod, Niphargus robustus was caught, too. Th e quantitative micro-spatial distributions of the amphipods are presented, anal the origin of this unusually large local biodiversity is discussed.