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The study of aquatic Oligochaeta in freshwaters in Serbia contributes to the oligochaete fauna inventory of the Balkans. Based on our results and literature review, 97 species (45 genera from 8 families) are listed in the running waters of Serbia. From the list of 61 species recorded during our investigation, 12 were noted for the first time. The ecological analysis of Oligochaeta communities showed the largest participation of potamal and rhithral species. As regards current preferences, rheolimnophilous species predominated, and with respect to feeding type, collectors prevailed. Most of the species are tolerant to moderate and high organic load. According to microhabitat preferences, three types of rivers stood out, as follows: (1) pelophilous (dominance of L. hoffmeisteri); (2) psammophilous (dominance of S. heringianus); (3) phytophilous (dominance of N. bretscheri). Analyses of the relation to different types of waterbodies showed regularity in the distribution of oligochaetes, with a higher species richness in main watercourses (types 1 and 2), and a lower species richness in tributaries (types 3, 4 and 6). According to the dominant taxa, the running waters of Serbia can be classified into four groups which are characterized by the prevalence of naidids (naidins and tubificins), enchytraeids and lumbriculids. Our results show that community composition is a good indicator of the horizontal distribution of Oligochaeta. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 451-03-68/2020-14/200007]

The aim of this work is to discuss the distribution of Oligochaeta (Annelida) in the Danube River using the collections made by the Joint Danube Survey 2007 (JDS2) on more than 2800 km of the river. The basic faunistical features of the oligochaete assemblages were analysed with regard to three main sectors of the Danube (upper, middle and lower reaches, the last with the Danube Delta). A total of 52 oligochaete taxa have been recorded. Most of the observed species are typical of the potamon-type rivers in the region, and are well adapted to moderate-to-high organic load. The highest taxa richness and frequency of occurrence were observed among the Tubificidae family. Naididae, Propappidae, Enchytraeidae and Haplotaxidae had also low frequency. The upper reach of the Danube showed the lowest species richness, while the middle reach is characterised by its highest species richness. Construction of dams and regulation of the riverbed have resulted in an increase of limno(rheo)philic taxa which prefer slow-flowing and lentic zones.

The aim of this study was to use the data on the distribution of aquatic macroinvertebrates obtained from 14 sites within a 413 km long stretch of the Danube River in Serbia to show the relevance of the bordering zone between the Middle and Lower Danube. A total of 68 macroinvertebrate taxa were observed. Molluscs were the major component with regard to species richness and relative abundance. Lithoglyphus naticoides (C. Pfeiffer, 1828) was the most abundant species and Unio tumidus (Retzius, 1788) was the most frequent species. Product-moment correlation coefficients or Pearson r coefficient was used to analyse the relation between the sites based on macroinvertebrate distribution. The data obtained by product-moment correlation served as input for cluster analyses. According to a cluster analyses Danube River in Serbia could be separated in the free-flowing sector, the stretch with a backwater effect and the area of the Iron Gate.

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