L. Forró - É. Murai szerk.: Miscellanea Zoologica Hungarica 6. 1991 (Budapest, 1991)

Nesemann, H.: Zoogeography and composition of leech fauna of Danubian lowland rivers in the Kisalföld compared with some molluscs (Hirudinea, Gastropoda)

MATERIALS AND METHODS From 1987 to 1991 the fauna of leeches, Prosobranchiate snails and Unionacean mussels was investigated in alluvial floodplains of the rivers in the Kisalföld. Qualitative samples were collected by hand from many localities and from different kinds of water bodies. The leeches were preserved in 70 % alcohol. The material has been given to the Hungarian Natural History Museum for documentation. Where no other data are presented, the specimens are from the author's collections. RESULTS The leech species found in seven rivers are listed in Table 1. The highest number was observed in the River Danube itself. Data of the partial biocoenosis were presented for the Austrian reaches, where fourteen species occur (NESEMANN 1989, 1990b). Downstream the Moson reach in Hungary the River Danube contains a leech fauna, which is completely different from that of the upper river. This is caused by the general change of environmental characteristics where the rivers leave the mountains and enter the plain. The morphology of the investigated rivers in the northwestern parts (Austrian Danube, Lajta) is strongly influenced by the mountains. Here the reaches are fast flowing and have strong bed load and gravelly or stony bottoms. In contrast the southeastern rivers (Hungarian Danube, March, Thaya, Rábca, Rába, Zala) have a low velocity of flow with loamy or sandy bottoms. The natural fall of the Danube changes at once from 40 cm per km to 7 cm per km downstream Gönyü. The main distribution patterns of many freshwater species are in accordance with these conditions. Hirudinea Fam. Glossiphoniidae Glossiphonia paludosa (Caren , 1824) (Fig. 16) Localities: Danube at Budapest (H), Szabadság-híd, km 1645.3, 15. Oct. 1988, leg. FORRÓ & NESEMANN; Ráckevei Duna near Szigethalom (H), 8. Jan. 1991, leg. FORRÓ & NESEMANN; Soroksári Duna near Dunaharaszti (H), 20. Jan. 1989, leg. FORRÓ <& NESEMANN; Danube at Szalkszentmárton (H), km 1577.5, 31. Jan. 1991, leg. WIMMER & NESEMANN; Danube at Dunaföldvár (H), km 1560.8, 31. Jan. 1991, leg. WIMMER & NESEMANN; Szentendre Duna between Tahitótfalu and Leányfalu (H), 7. Oct. 1989, leg. PUKY & NESEMANN; Danube at Vác (H), km 1680.4, 7. Oct. 1989, leg. PUKY & NESEMANN; Danube near Szob (H), km 1706.6, 7. Oct 1989, leg. PUKY & NESEMANN; Danube and Cuhai-Bakony-Ér near Gönyü (H), km 1789.8,3. Apr. 1990; Danube downstream Gönyü (H), km 1783,1, Danube near Ásványráró (H), Dunaág, Felsősziget, km 1817, 23. Oct. 1990; Danube, oberer Tiergartenarm near Hainburg (A), 25. Apr. 1989; Danube near Mannswörth (A), in a dead-water reach, km 1917, 10. Feb. 1988; Danube-Kühwörther Wasser near Mühleiten (A), in a dead-water reach, Nov. 1990; Danube in the Lobau-area (A), Ölhafen, km 1920, Oct. 1990; Rába at Győr (H), 28. Jul. 1990; Lajta at Mosonmagyaróvár (H), 3. Apr. 1990; Leitha-Komitatskanal (Lajta bal parti csatorna) near Nickelsdorf