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)

(A), Feb. 1989; March (Morava) near Markthof (A), 24. Mar. 1990; March near Stillfried (A), 29. Jul. 1990; March downstream Marchegg (A), 20. May 1990; March near Grub (A), 3. Jun. 1990; March at Marchegg (A), 20. May 1990; March, in a secondary branch near Schlosshof (A), from three samples, Feb. and Apr. 1990; March, in the main stream near Schlosshof (A), 22. Apr. 1990; March near Angern (A), 5. Aug. 1990; Thaya (Dyje), in a secondary branch near Rabensburg (A, CS), Aug. 1990. The species is spread widely all over Central and Eastern Europe. It is common in some parts around the Mediterranean Sea. G. paludosa has a disjunct range of distribution in the northern and western parts of the settled area. Its occurrence is restricted only to some parts of plains and lowlands with a special warmer climate. The distribution has its centres in the Danube- and Po River basins (CHIAUDANI & MARCHETTI 1984). The species is a typical member of the Potamon biocoenosis. It is very common in the lower reaches of slow-flowing rivers of the Hungarian Great Plain, wherein it prefers gravel bottoms on sandy loam. G. paludosa has not occurred in the Danube upstream Vienna, it has not been found in the Upper Austrian and German reaches yet (NESEMANN 1991a). Its distribution in the Danube was proved to be very dissimilar by the author. In the upper reach of the settled area, where the conditions are similar to a torrential stream caused by strong gravity, G. paludosa is restricted to anabranches and dead-water reaches. Downstream the mouth of the River March, the nature of the Danube is gradually changing to a lowland river and the natural bed load is being reduced (Gönyü). Upstream until the Moson reach (Ásványráró), G. paludosa occurs frequently in the main stream and is present in high abundances throughout the whole Hungarian Danube. Glossiphonia concolor (Apathy, 1888) (Fig. 17) Localities: Soroksári Duna near Dunaharaszti (H), Type-locality, 20. Jan. 1989, leg. FORRÓ & NESEMANN; Danube-Krumpenwasser near Stockerau (A), km 1948, 17. Mar. 1989; Danube-Lusthauswasser, a dead-water reach (Prater) near Vienna (A), 1988-1990; Danube, in a dead-water reach near Orth (A), 9. Oct. 1987; Danube-Kühwörther Wasser near Mühleiten (A), from several samples 1989-1990; Danube near Mannswörth (A), in a dead-water reach, 10. Feb. 1988; Zala SE Fenékpuszta (H), 20. Jun. 1990, leg. FORRÓ & NESEMANN; Zala in the Kis-Balaton reach (H), 21. Jun. 1990, leg. FORRÓ & NESEMANN; Lajta at Mosonmagyaróvár (H), 3. Apr. 1990; Leithakanal (Rét-árok) near DeutschJahrndorf (A), May 1989; Leitha SW Pachfurth (A), dead-water reaches in the Auwinkel-area, 2. Jun. 1990, leg. MANN & NESEMANN; Leitha near Rohrau (A), in a secondary branch, 27. May 1990; Leitha near Pachfurth (A), Aug. 1990; Leitha between Seibersdorf and Bruck (A), from several localities, 1988-1990; March (Morava) N Grub (A), in a dead-water pond, 4. Jun. 1990, March near Schlosshof (A), in a dead-water reach, 22. Apr. 1990. The complete range of distribution is not known, because G. concolor in former times was often confused with Glossiphonia complanata or considered under this name. According to LUKIN (1976), NESEMANN (1990a) and other authors, the species occurs in most parts of Europe with a concentration in the southern parts of the European part of the Soviet Union, the Danube Basin and some lowlands in the northern and eastern parts of Central Europe. The distribution patterns are generally very similar to that of G. paludosa, but the ecological preferences are quite different. G. concolor occurs in large numbers in old bran-