The phylogenetic relationships of "predatory water-fleas" (Cladocera : Onychopoda, Haplopoda) inferred from 12S rDNA

Within the Cladocera, the water-fleas, four major taxa can be distinguished : Anomopoda, Ctenopoda, Haplopoda, and Onychopoda. Haplopoda and Onychopoda are called "predatory water-fleas." The Haplopoda is monotypic; its only r epresentative, Leptodora kindtii is common in palearctic and nearctic fresh water bodies. The Onychopoda show a remarkable geographic distribution. Mos t of the described species are restricted to the Caspian Sea, the Aral Sea, and peripheral areas of the Black Sea, including the Sea of Azov--all remn ants of the Eastern Paratethys. The remaining onychopods are either freshwa ter inhabitants or marine animals, widespread in the world oceans. We prese nt molecular evidence for a sister group relationship between Haplopoda and Onychopoda within the Cladocera. The Onychopoda and its three families are monophyletic. We suggest an independent invasion into the Ponto-Caspian ba sin at least three times, twice originating in the palearctic freshwater bo dies and once starting from the world oceans. (C) 2001 Academic Press.