| Abstrakt: |
This article is the second communication in a series devoted to the study of the microturbellarian fauna (Plathelminthes, Rhabditophora) of Boguchansky Reservoir, in the lower reaches of the Angara River, Eastern Siberia. This communication provides data on the taxonomy, structure of the male copulatory organ, and zoogeography of species from the families Provorticidae Beklemischev, 1927; Macrostomidae Benden, 1870; and Microstomidae Luther, 1907. The fauna of these worms in the Angara River and Lake Baikal are still poorly studied. Three species from these families were recorded and described more than 90 years ago from the Angara River before our study; however, the original descriptions were accompanied by highly schematic and non-informative sketches, which, on the whole, do not allow us to conduct exact species identifications and comparisons. During the study of the lower part of the Angara River, we found representatives of three other species: Macrostomum johni Young, 1972, Microstomum rogozini Timoshkin et Krivorotkin (in press), and Baicalellia nasonovi Timoshkin et Krivorotkin, sp. n. The stylets of M. johni from the Angara River and Lake Baikal are almost identical in structure and size to those of specimens of the type series from Great Britain. M.rogozini is one of the most common species of Microstomidae that inhabit the coastal zone of Lake Baikal. The stylet structure of the Baicalellia species resembles that of Baicalelliabaicali Nasonov, 1930 and Baicalellianigrofasciata Nasonov, 1930; however, their available descriptions do not make it possible to compare them reliably with the species that we found. Therefore, we propose to consider both these names as nomen nudum and attribute the discovered individuals to B. nasonovi, a species new to science. Despite the significant geographic isolation, the stylets of the Baikal and Boguchansky specimens are identical in structure and size. Similarly to kalyptorhynchian species (see Communication 1), the discovery of provorticids and microstomids of Baikal origins in such a remote section of the Angara River considerably expands their ranges and demonstrates their capacities to colonize water bodies hydrographically connected to Lake Baikal. Illustrated descriptions of the Boguchansky and Baikal specimens of M. johni, M.rogozini, and B.nasonovi and comparisons with the most similar species and zoogeographic information are given. In addition, a complete checklist of the Angara River microturbellarian fauna, which currently includes 35 species from nine families, is presented. [ABSTRACT FROM AUTHOR] |
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