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)

MISCELLANEA ZOOLOGICA HUNGARICA Tomus 10. 1995 p. 49-68 Distribution of epigean Malacostraca in the middle and upper Danube (Hungary, Austria, Germany) by H. Nesemann, M. Pöckl and K. J. Wittmann (Received June 23, 1995) Abstract: The Danube between Harta (rkm 1549) and Kehlheim (rkm 2410) was sampled qualitatively in 1985-1995 at all seasons. Eighteen epigean species of Malacostraca (Janiridae, Asellidae, Gammaridac, Talitridac, Corophiidae, Mysidae, Astacidae, Cambaridae) were recorded. The malacostracan fauna shows a distinct longitudinal zonation in the River Danube. At least nine species are of Ponto-Caspian origin. The actual distribution patterns were analyzed with respect to former studies. At least six species were strongly expansive during the last few decades. Navigation appears to be among the crucial factors for this dispersion. Keywords: Danube, Malacostraca, zoogeography, distribution, immigration Introduction During the first half of the present century, investigations on the higher crustaceans (Malacostraca) were mainly restricted to the lower and middle course of Danube River. The scientific interest on the upper Danube arose as late as in the 1950s and culminated in a book edited by Liepolt (1965-1967) and in the foundation of the international I.A.D.-working group of the Societas Internationalis Limnologiae. Recently, important summarizing lists concerning the fauna of the Austrian Danube were published by Moog et al. (1994), Moog et al. (1995). For the majority of taxonomic groups in the animal kingdom, including the Malacostraca, the knowledge about distribution in large rivers is still incomplete. The faunistic research of the Danube is very important because of the immense diversity of species which live in this river which is the second largest in Europe. The aim of the present study goes beyond local faunistic interest, by describing in detail the actual distribution pattern of selected species of the subclass Malacostraca, and how it has been achieved historically. Special attention is directed to the biological zonation of the Danube River and to the question, how and when the present Zoogeographie situtation may have established. The dramatic spreading of some species in recent years is included in this context. An der Lan (1967) correctly arrived at the following conclusion: "Das Studium der Donau-Organismen führt zwangsläufig zu einer tiergeographischen Betrachtungsweise und einer daraus resultierenden Gesamtschau der Geschichte unserer europäischen Süsswasserfauna". The highly significant biological zonation of the Danube (Nesemann 1991) and the Rhine (Kinzelbach 1985, 1990) is marked by distribution limits, which are essentially the result of the geological development in the past (Pécsi 1959).