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)

This species is highly tolerant to organic pollution. It is very common in all adjacent waters of the Danube and is distributed widely throughout the whole river basin. Family Gammaridae Gammarus pulex (Linnaeus, 1758) This amphipod is common in the Rhine river basin and the uppermost Danube in Germany. According to Dudich (1947), it does not occur in the Carpathian Basin. It is known from Upper Austrian streams as far eastwards as the Traun River. Several specimens of G. pulex were collected by B. Csányi for the first time in the Austrian part of the Danube, 17. 12. 1991, right bank, directly at the confluence with river Enns. Gammarus fos sarum Koch, 1835 Material: Danube near Orth, 20. 04. 1988, 19. 06. 1989; Danube in Vienna, 19. 04. 1988; Danube upstream of Krems, from numerous collections, 11. 12. 1986 - 17. 12. 1987, leg. Pöckl, M.; Danube at Winzer, 07. 07. 1991, leg. Nesemann, H. G. fossarum is a widely distributed amphipod, especially in the highlands of Central, Eastern and Southeastern Europe. The distribution area includes the Pyrenees, the Alps, the mountaneous and hilly regions of Central Europe, the Danubian valley, the Balkan Peninsula and Asia Minor (Karaman & Pinkster 1977a). G. fossarum usually inhabits springs and the upper reaches of small streams and rivers. It tolerates high current and low temperatures. When Gammarus pulex (Linnaeus, 1758) is absent - most probably in most parts of Austria - G. fossarum inhabits the middle and lower reaches of streams and rivers where current velocity is low. There, it coexists and possibly competes with G. roeseli Gervais, 1835 (Pöckl 1992, Pöckl & Humpesch 1990). Examples for these types of potamon rivers are the Lajta and Zala, where G. fossarum was collected frequently but in low numbers only. In the Danube River, G. fossarum was found sporadically, possibly due to passive drift from the préalpine rivers. As the upper Danube typically has a rhithron character, this species may locally find acceptable conditions as far downstreams as Budapest. Gammarus roeseli Gervais, 1835 Material: Danube at Dunaföldvár, 05. 08. 1991, leg. Ofenböck, T. & H. Nesemann; Danube at the confluence of the river Fischa near Fischamend, 28. 04. 1991, leg. Nesemann, H.; Danube upstream of Vienna, 25. 08. 1987; Danube near Altenwörth, 24. 07. 1986; Danube upstream of Krems, 12. 12. 1986; Danube at the confluence of the river Enns (near rkm 2112), 29. 09. 1993; Danube near Ottensheim (Alte Donau, rkm 2145), 24. 04. 1992, leg. K. J. Wittmann; Danube at the Jochenstein rocks near Engelhartszell, 14. 11. 1989, leg. Zerz, J. & H. Nesemann; Danube at Passau, 28. 08. 1991; Danube at Winzer, 7. 07. 1991; Danube at Aicha, 7. 07. 1991; Lajta near the confluence with the Mosoni Duna at Mosonmagyaróvár, 6. 09. 1991, leg. Ofenböck, T. & H. Nesemann; Rába at Győr, 28. 07. 1990, leg. Nesemann, H.; Main-Danube-Canal near Forchheim (rkm 26), 9. 09. 1994, leg. K. J. Wittmann. The distribution area of G. roeseli includes Asia Minor, the Peloponesos, the western Balkan Peninsula, the Hungarian Great Plain, the Danubian valley and the plains and lower mountains of Central and Western Europe. It was suggested that its evolutionary centre was in Southeastern Europe or Asia Minor (Karaman & Pinkster 1977b). Its penetration in other parts of Europe seems to be a very recent one, or at least postglacial. The present distribution pattern shows rather clearly the network of large and medium sized river valleys as routes of its range extension northwestwards and in particular that of the Danubian system.