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Phoxinus phoxinus is a species widely distributed throughout Palaearctic and is a good model for investigation of parasite communities. Species composition and structure of parasite communities in the minnow from the streams if different types, namely Yenisei river near Krasnoyarsk City and its left affluent Kacha River, were examined. Indices of Shannon, Simpson, and Berger-Parker were used to describe the component parasite communities. Twenty five parasite species of seven classes were revealed, and ectoparasite were found to be dominating among them. The host-specific parasite species Paratrichodina phoxini (Infusoria), Dactylogyrus borealis (Monogenea), Parahemiurus merus and Diplostomum phoxini (Digenea) constitute the peculiarity of the parasite fauna in minnow. Parasite community of minnow in the Kacha river is the most various one. It is caused by the following factors — favorable temperature conditions, composition of ichthyofauna, and a high density of fish population in the Kacha river. Metacercaria of Diplostomum phoxini, the specific parasites of minnow's brain, are dominating in both streams.

The morphogenesis of the Staphylocystis furcata (Stieda, 1862) cysticercoids has been studied in the experimentally infected beetles Geotrupes stercorosus and their structural and ontogenetic features have been described. At the initial stage of its development metacestode of S. furcata forms lacuna primitiva. The primordium of scolex invaginates early into the posterior part of the larva, and then the scolex develops in the cyst cavity. There is only an anterior obturator valve developing in the cyst. Posterior obturator valve is absent, that results in the cyst remaining unlocked and the cercomer does not separate from the cyst. There is no lacuna primitiva in the cercomer. The tegument of metacestode gets covered with a solid fibrous layer at the final stage of morphogenesis. It makes the cyst partly or completely pressed in the anterior part of the cercomer when it grows. The similarity between S. furcata cysticercoids and morphologically related cysticercoids Hymenolepididae has been analysed.

Analysis of original long-term investigation (1980—2006) and literary data on the helminthofauna of reptiles in the Republic of Belarus is carried out. Seven species of reptiles were examined on Southern Belarus, 32 species of helminthes were found with total infestation 72.7%. It is established that the helminthofauna of reptiles in the Republic of Belarus includes 33 species (18 trematodes, two cestodes, 12 nematodes, and one acanthocephalan). The largest number of helminth species (26) was recorded in the common water snake Natrix natrix, and the least number of species (four) was recorded in the turtle Emys orbicularis and snake Coronella austriaca.

Distribution of Aspidogaster conchicola Baer, 1827 in the organisms of its hosts Colletopterum spp. from the Chivyrkuiski Gulf of Lake Baikal was investigated. The number of A. conchicola in the organism of Colletopterum spp. was found to decrease along the row pericardial cavity—mantle cavity—gills—kidney. The pericardial cavity of Colletopterum spp. is the most favorable habitat for A. conchicola with 72% of the helminthes parasitizing in it. In the pericardial cavity the largest number (61%) of A. conchicola was found in its posterior part.

The complete taxonomic composition (158 species of freshwater Myxosporea inhabiting European Part of Palaearctic is presented. Their distribution by faunistic complexes and groups is established. Analysis of similarity between myxosporean faunas by zoogeog-raphical areas and districts is carried out. Historical background of the distribution and formation of the freshwater myxosporean fauna is discussed.

Hitherto data on the morphology of Tetraonchidae and their eggs obtained with scanning electron microscopy (SEM) were absent in the literature. In the present paper results of SEM study of two genera of Tetraonchidae, Tetraonchus and Salmonchus, are given. Fine morphological traits of eggs, larvae, and definitive individuals of Tetraonchidae, as well as patterns of their attachment to host gill, were established for the first time. A deep penetration of the worms into the branchial epithelium of the host was shown.

Cellular components of the Planorbarius purpura hemolymph are represented by three phyla of haemocytes (prohemocytes, eosinophilis microgranulocytes, and basophilis granulocytes) and vesicular cells. As a result of the invasions of P. purpura with the trematode Echinoparyphium aconiatum, changes of the linear dimensions of granular hemocytes and their nuclei took place. Moreover, an increase of the hemocytes' number per 1 mm³ of hemolymph and change of the percentages of different hemocyte types were recorded. Under the influence of zinc ions, linear dimensions of prohemocytes and their nuclei (at 10 MPCns of the toxicant) were changed. In granular hemocytes and abnormalities of all histometrical and hematological parameters were observed. All cytometrical, karyometrical, and hematological alterations were expressed more clearly in infested mollusks than in non-infested ones, and occurred usually under lower concentrations of zinc ions.

A complicated multicellular gland is situated in tarsi of all the legs, occupying one third to half of the segment. Glandular cells form a single-layer sack; inner surface of the sack (gland cavity) is enveloped by a multilayer membrane. Cuticular rods connecting muscles with the claw pass inside this cavity. Glandular cells are characterized by the presence of numerous apical microvilli associated with accumulations of mitochondria, and secretory vacuoles enclosed in cellular membranes. The basal part of each cell contains lipid vacuoles and glycogen granules. The possibility of the track contact pheromone's production by the tarsal gland is discussed.

Distribution of fleas by their rodents hosts was investigated by field experiments using the method of individual labeling both the parasites and the hosts. The experimental site was situated in sand landscapes of the northwestern Precaspian region. Pattern of the contacts between rodents leading to the exchange of their ectoparasites was established. Average distance of the rodent migration from the site of its previous record was 54 m, while the distance of flea transfer for the same period was 142 m. The probability of host exchange by a flea under under its periodic attacks on host amounted to the value 0.500—0.889. The parameters of flea spreading in the northwestern Precaspian region and in the sand landscapes between Volga and Ural were shown to be similar. The ability of the flea Xenopsylla conformis to parasitizing on social vole without a significant decrease of its abundance was revealed.

Summary is absent.

Summary is absent.