How many species of Cladocera are there?

An estimation of the number of taxa within families, genera and local faunas of Cladocera reveals that only c. 129 species (17% of all known species) may be considered as sufficiently well described (valid species), and c. 146 as rather well described (fair species) but needing further study using modern methods of investigation. The status of all other species is vague. The families Chydoridae, Daphniidae and Sididae and genera Diaphanosoma, Daphnia, (including Daphniopsis), Megafenestra, Scapholeberis, Eurycercus, Chydorus, Ephemeroporus and Pleuroxus have been comparatively studied best. The largest number of valid species is known from Europe, North America, Australia and South America, and the smallest number from Africa. Presence of large number of vague species of Cladocera negatively affects faunistic, zoogeographic, and ecological studies of continental waters.