The family Niphargidae are amphipod crustaceans which are common in western Eurasia, mainly in subterranean freshwaters habitats. The genus Niphargus is the largest genus of the family Niphargidae with more than 300 species. An individual species often has a very small range and lives at a narrow water temperature range, but the genus includes both species of cold and relatively warm places. While they are extremely variable in their appearance, they are always troglobites, so they are white or colourless, lack eyes, and are rather small, between 2mm and 35mm in size. Many species are able to survive for more than 200 days without food.
A basic step in exploring the fauna of a river cave is to catch some of them with trap, small boxes with some cheese. Speleologists are dependent on biologists specialized on this family to determine the actual species, which is quite difficult.