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)

expansion, in 1989-90 the western limit of D. villosus and C. ischnus was located a few km upstream from Krems. S. ambuláns and A. leptodactylus did not expand beyond the basin of Vienna in western direction. Here L. benedeni had its western limit in 1982-83. O. obesus and O. limosus are restricted to the Great Hungarian Plain in the Eastern part of Hungary. Records of J. istri and C. curvispinum in early investigations in Hungary and in Germany show, that these Ponto-Caspian elements did not largely extend their Danubian range (unlike in other riverine systems) in the present century. N. hrabei, S. ambuláns and A. leptodactylus show a stable distribution pattern (Nesemann 1991). Since the beginning of the present century, some Malacostraca have significantly extended their range in upstream direction. This fact, however, did not basically change the biological zonation of the Danube River. The precise informations about the distribution of these species given in the 1930s, chiefly by Dudich (1927) and by museum material for the Hungarian Danube, extended in the 50s and 60s for the Austrian and German Danube by Vornatscher (1965) and Kothe (1968), respectively, are most suitable for a comparison with the current situation. The following species have extended their previously wide distribution for several 100 km: O. obesus in the Hungarian section of the Danube, L. benedeni, C. ischnus, and D. villosus in Austria and Germany (Weish & Türkay 1975, Wittmann 1995). In addition D. haemobaphes, D. villosus, and C. ischnus are currently invading even the Rhine (Bij de Vaate & Klink 1995). D. haemobaphes (before 1987), and later also D. villosus (1992), and L. benedeni (1993) explosively invaded the Bavarian Danube (compare Kothé 1968, Foeckler 1987, Wittmann 1995). Also the American crayfish, O. limosus, significantly extended its previously very limited distributional range and is rapidly expanding lately in the Danube. In the Danube at Linz, three ships were examined for the presence of Malacostraca (Wittmann 1995). This material was now examined also for gammarids and so we can give the following species list: inside ships: D. villosus, D. haemobaphes, and C. curvispinum. Outside attached to hulls we found the same three species plus L. benedeni. So there is no doubt that navigation is among the crucial factors for dispersion of Malacostraca. The decapod Atyaephyra desmaresti (Millet, 1831) was recently found in the Main-Danube-Canal, but records from the Danube itself are still lacking (Wittmann 1995). The record by Pretzmann & Pauler (1981) for backwaters in the Lobau near Vienna was questioned by Wittmann (1995). Among the mysid species, Paramysis intermedia (Czerniavsky 1882) was introduced by fishery biologists into Lake Balaton and other Hungarian waters in about 1955 (Prof. M. Bácescu, pers. comm.). So we may expect this species also in the middle Danube, but so far we have no positive records. In the lower Danube, we found it together with L. benedeni and Paramysis locust ris tanaitica (Marti nov 1924) on several locations between the delta and as far upstream as the confluence with river Iskar (leg. B. Csányi, 01. 12. 1991). Acknowledgements We wish to thank Dr. László Forró, Budapest, for his permission to examine the crustacean collection of the Hungarian Natural History Museum and for accomodation during our stays in Budapest; Prof. Dr. Ragnar Kinzelbach, Darmstadt, Dr. Michael Türkay and Andreas Allspach, Frankfurt, for help in providing literature and informations about synonymy.