L. Forró szerk.: Miscellanea Zoologica Hungarica 9. 1994 (Budapest, 1994)

Csányi, B.: The macrozoobenthon community of the Danube between Rajka and Budapest

range of the investigated area. These taxa live in the Mosoni Danube too, but are absent from the upper main Danube arm. Hypania invalida, the only pontocaspic polychaet worm of Hungary, is relatively common between Rajka and Budapest. New records of the aquatic bug, Aphelocheirus aestivalis, are given in this report from the upper stretch (Ásványráró and Gönyü) having characteristic rapid currents. Although the number of benthic, taxa, living in the profundal region of the Danube, is much Table 2. Macrozoobenthon taxa found in dredge samples of the profundal (1987-1993) (for explanation of numbers of sampling sites see Fig. 1) No.Taxa Sampling sites Cnidaria 1 2 3 4 5 6 7 8 9 Total 1 Hydra sp. 0 0 0 0 0 0 0 0 1 1 Mollusca 2 Dreissena polymorpfta Pallas 0 0 0 0 0 0 0 1 0 1 3 Esperiana esperi Férussac 0 0 0 0 0 0 0 0 1 1 4 Pisidium s p. 0 0 0 0 0 0 1 0 1 2 5 Potamopyrgus antipodarum Gray 0 0 0 0 0 0 0 0 1 1 6 Sphaerium corneum L. 0 0 1 0 0 0 0 0 1 2 7 Theodoxus fluviatilis L. 0 0 0 0 0 0 0 1 1 2 8 Viviparus acerosus Bourguignat 0 0 0 0 0 0 0 0 1 1 Annelida 9 Aelosoma sp. 0 0 0 0 0 0 0 0 1 1 10 Criodrilus lacuum Hoffmeister 0 0 0 0 0 0 0 1 0 1 11 Oligochaeta sp. 0 1 1 1 1 0 0 0 1 5 Crustacea (Malacostraca) 11 Corophium curxnspinum Sars 1 1 0 0 0 0 0 0 0 2 12 Dikerogammarus villosus Sovinski 1 1 0 1 1 1 1 1 1 8 13 Limnomysis benedeni Czerniavsky 0 0 0 0 0 0 0 1 0 1 14 Obesogammarus obesus Sars 0 0 0 0 0 0 1 0 0 1 Insecta 15 Cricotopus sp. 1 1 0 1 1 1 1 1 1 8 16 Heptagenia sulphurea Müller 0 0 0 0 0 0 1 0 0 1 17 Hydropsyche angustipennis Curtis 0 0 0 0 0 0 0 1 1 2 18 Hydropsyche contubernalis McL. 1 1 0 1 1 0 1 0 1 6 19 Hydropsyche sp. 0 0 0 0 0 0 0 0 1 1 Total number of taxa 4 5 2 4 4 2 6 7 14 48 lower than in the littoral zone, the richness of the community has considerably increased downstream (Table 2). 14 taxa were found in the lowest cross section at Budapest, many of them are absent from the upstream stretch. The most common taxa are the amphipod Dikerogammarus villosus, the chironomid Cricotopus sp., Hydropsyche contubernalis and the Oligochaeta sp. Only two common mollusc taxa (Pisidium sp., Sphaerium corneum) were present in the dredge samples above Budapest, but 6 were detected at the last two sampling sites of the city. The three snail species (Esperiana esperi, Potamopyrgus antipodarum, Theodoxus fluviatilis) living in the main current were not described from the profundal region earlier. Further investigations, with special dredging methodology in the zones near the littoral will most probably provide numerous new data on the distribution of many benthic taxa.