L. Forró szerk.: Miscellanea Zoologica Hungarica 10. 1995 (Budapest, 1995)

Nesemann, H., Pöckl, M.; Wittmann, K. J.: Distribution of epigean Malacostraca in the middle and upper Danube (Hungary, Austria, Germany)

Materials and methods A great number of malacostracans were examined from our own samples as well as from the crustacean collection of the Hungarian Natural History Museum, Budapest. The museum material was collected and determined for example by E. Dudich, I. Loksa, E. Unger, and A. Kesselyák. For each species, only those materials are listed that were examined and checked by the present authors. Our material is deposited in the Hungarian Natural History Museum and a smaller part in the Museum of Natural History in Vienna. The crustaceans were picked up by hand or qualitatively sampled with a pond net. All samples were preserved in a solution of 70% ethanol. The species were determined by comparison with museum specimens and by using published keys, such as listed by Pöckl (1988). The excellent key by Carausu et al. (1955) was especially useful. Results Family Janiridae Jaera istri Vieulle, 1979 Material: Danube at Harta, 05. 09. 1991; Danube at Dunaújváros, 05. 09. 1991; Szentendrei Duna at Leányfalu, 04. 09. 1991, leg. Ofenböck, T. & H. Nesemann; Mosoni Duna at Dunaszeg, 23. 10. 1990; Danube between Komeuburg and Hainburg, from samples at rkm 1883, 1886, 1887, 1888, 1896, 1910, 1915, 1940, 02. and 03. 1991; Danube at Zwentendorf, 20. 04. 1991, leg. Nesmann, H.; Danube, from numerous samples between Altenwörth and Krems, 07. 1985 - 07. 1990, leg. Pöckl, M.; Danube at Engelhartszell, on the Jochstein rocks, 14. 11. 1989, leg. Zerz, J. & H. Nesemann; Danube at Winzer, 07. Ol 1991; Danube at Aicha, 07. 07. 1991; Danube at Barbing, 01. 07. 1990; Lake Balaton at Révfülöp, 14. 08. 1991, leg. Nesemann, H. J. istri is one of the three Ponto-Caspian species of the genus Jaera and was described as late as 1979 by Vieulle from the locus typicus Kladovo near the Kazan-pass reach of the Danube. It is distributed along the river from Romania to Bavaria. The older literature is referring to Jaera sarsi Valkanov, 1938 and to Jaera caspica Kesselyák, 1938. In contrast to these species, which live in brackish waters, J. istri is well adapted to freshwater. The distribution of this group of /űera-species in the large Ponto-Caspian rivers (Danube, Bug, Dniepr, Dniestr, Don, Volga, Ural), in the Caspian Sea and the offshore lakes of the Black Sea was regarded as relictary and typical for the ancient Paratethys (Vieulle 1979). In the Middle and Upper Danube, only J. istri was found. This primarily lithophilous species prefers high flow velocities and does not invade tributaries. It was suggested that J. istri is endemic for the Danube, however, it was also recorded from Lake Balaton near Révfülöp by H. Nesemann. Kothé (1968) collected specimens for the first time in the Bavarian Danube, and determined the material as /. sarsi. He thought to deal with an isolated population, because this species was previously unknown in Upper Austria. Our results show that J. istri is distributed throughout the whole section of the upper Danube at least as far upstream as Barbing near Regensburg. Family Asellidae Asellus aquaticus (Linnaeus, 1758) Material: Danube, deadwater reach Rosskopfarm near Stopfenreuth (rkm 1889), 09. 05. 1987; Danube, deadwater reach near Schönau (rkm 1909), 10. 05. 1987; Danube, in a secondary branch "Giessgang" near Tulln (rkm 1963),| 11. 07. 1986; Danube near Erlau (rkm 2214), 23. 09. 1993, leg. Wittmann, K. J.