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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.

In this study, we investigated the level of sanitary pollution and organic contamination of the Velika Morava River, the largest river in central Serbia. Samples of water for microbiological analysis were collected at 5 sites, monthly, from April 2010 to February 2011. Sanitary analysis, i.e. enumeration of total and fecal coliforms and intestinal enterococci, indicated moderate to critical fecal contamination, while organic load assessment (oligotroph to heterotroph ratio, index of phosphatase activity) revealed the category of moderately polluted water. We also investigated seasonal variations of these groups of bacteria and the factors that could contribute to these differences. Our results showed that the micro- biological quality of the water in the Velika Morava River during different seasons is affected by numerous factors such as unequal loading of wastewaters, solar irradiation, and relations of flow/dilution and rainfall/runoff. [Acknowledgments. This study was financially supported by the Ministry of Education and Science of the Republic of Serbia: projects No 173025, No 177045 and No 043002.]

We report the discovery of Bothrioneurum vejdovskyanum Štolc, 1886 (Annelida: Oligochaeta: Tubificidae: Rhyacodrilinae) in Serbian freshwaters. Fifteen specimens were found in the middle course of the River Ibar (southern Serbia), at a locality where the macrolithal type of substrate and strong currents prevail. These organisms were found together with Stylodrilus heringianus (Claparede, 1862). They were among the most abundant Oligochaeta species. The species are described and its biology and distribution are discussed. The present record contributes to the knowledge on the general distribution of this rare species, particularly in the Balkans (southeastern Europe). [Acknowledgments. This work was supported by the Ministry of Education and Science of the Republic of Serbia, Projects No. ON 173025 and III 43002]