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Zoogeographical analysis of the subfamily Amblyomminae (Ixodidae) is given. Distribution of genera and of tribes throughout zoogeographical regions of the world are considered. Composition of subgenera in the Palearctic and their related connections with faunas of other zoogeographical regions have been examined.

The attachment of ixodid tick Ixodes ricinus larvae to white mice and histopathology of host tissue in the attachment site were investigated by means of electronic microscopy. It was demonstrated the presence of cement substance around the mouthparts of tick during the first and the second days of feeding period and the absence of it at the last day of this period. The cement substance consists only of the cement cone (the external cement), situated on the surface of host epidermis. The tick mouthparts in the host dermis were surrounded by zone of modified collagene fibers. Examination of feeding site showed the intensive neutrophil migration and the formation of feeding cavity in 2 days after attachment of tick. At the same time the erythrocytes and active fibroblasts were found in the feeding cavity.

Examined specimens of horseflies flew out of 3 start points disposed on the water surface of the lake, about 250—300 m from the coast line (I start point), 90 m (II start point), 20 m (III start point). This position of start points minimised the number of topographic landmarks for the horseflies and gave the possibility for a visual monitoring of flight trajectories. In favorable weather circumstances for the flight (17—22°C, wind 0—1 m/sec, cloud 0—5%) the majority of horseflies demonstrated the flight trajectories to the most close points of the coast. The lesser favorable weather circumstances (16—17°C, wind 3—5 m/sec, cloud 60—100%) decreased the number of horseflies flying to far points of the coast line; unfavorable weather circumstances (16—17°C, wind 5—8 m/sec, cloud 80—100%) almost completely suppressed the flight activity on I start point and decreased it on II and III start points.

In a sample of 80 fish-eating birds collected on Hooker Island (Franz Josef Land — FJL) and Kharlov Island (East Murman coast of Barents Sea) 5 dilepidid, 4 hymenolepidid and 3 tetrabothriid species were recovered. 14 kittiwakes, 10 arctic terns, 8 glaucous gulls and 6 murres were examined on Hooker Island, 9 herring gulls, 4 guillemots and 29 kittiwakes — on Kharlov Island. All Arctic terns but one were free from cestodes. The infected bird harboured 2 immature specimens of Nadejdolepis sp. only. Two guillemots were infected with Alcataenia campylacantha and 4 murres — with A. armillaris (the latter species once occured also in a kittiwake from Kharlov Island — new host record). Herring gull harboured 5 cestode species, out of them Paricterotaenia porosa and Wardium cirrosa were found only in this host. Kittiwake demonstrates the reachest cestode fauna comprising 7 species. Two of them, Nadejdolepis nutidulans and Tetrabothrius immerinus, were recovered only from this host and only on Kharlov Island. The rest 5 species are more widespread: Alcataenia larina occured in kittiwake on Kharlov Island as well as on FJL; Anomotaenia (?) micracantha and Microsomacanthus ductilis occured in herring gull on Kharlov Island and in kittiwake and glaucous gull on FJL; Tetrabothrius erostris occured in herring gull and kittiwake on Kharlov Island and in kittiwake and glaucous gull on FJL; T. morschtini occured in kittiwake and glaucous gull on FJL. The latter species is registered for the first time since its description from glaucous gull of Kanin Peninsula (Muravijova, 1968). As for T. cylindraceus which was indicated for Barents Sea gulls by Markov (1941) and Bielopolskaya (1952) as a common parasite, it was absent in our material. On Kharlov Island (1991 expedition) all herring gulls investigated and 76% of kittiwakes were parasitized by cestodes. On FJL all kittiwakes studied in 1991 and all glaucous gulls (1992 expedition) harboured them; out of 4 kittiwakes studied in 1992 only 3 were infected. Alcataenia larina dominates in kittiwake on Kharlov Island (65.5%); the total prevalence of Tetrabothrius spp. is 34.5%. On FJL the picture is inverse: the prevalence of T. erostris in 1991 exceeded the same of A. larina more than twice (90% and 40% respectivly). Similarly, 87.5% of glaucous gulls investigated on FJL were infected with T. erostris, 25% — with T. morschtini and only 12.5% — with dilepidids (Anomotaenia micracantha). The life cycle of tetrabothriids includes fish as intermediate host. The demonstrated predominance of this group on FJL indicates the more restricted diet of gulls in high latitudes.

A histomorphological study of glands of cercariae of Trematodes belonging to different Heterophyata и Plagiorchiata: Cryptocotyle lingua Lüne 1899, Metorchis sp., Plagiorchis sp., Cercaria nigrospora Wergun 1957, Prostogonimus sp., Pleurogenoides medians, Pleurogenes sp. 1, Pleurogenes sp. 2, Lecithodendriidae gen. sp., has been carried out. In all cercariae, penetration glands, subtegumental glands of different types (mucoid, cover-forming and cystogenic), and in many cases, oral succer glands were found. In the Plagiorchiata cercariae, mucoid glands play the major role as compared to cover-forming glands, the latter being totally absent in the higher Plagiorchiata (fam. Pleurogenetidae). On the contrary, in the Heterophyata cercariae, mucoid glands are less developed than cover-forming glands. For the penetration glands, there is a tendency towards oligomerization and differentiation.

The results of the study of parasites of the mollusc Dreissena polymorpha (about 3000 specimens examined) in the Upper, Middle and Lower Volga in 1991—1992 are given. In the mantle, in pericardial cavity and other internal organs the parasites were recovered as follows: Aspidogaster limacoides (Aspidogasterea), Phyllodistomum angulatum and Bucephalus polymorphus (Trematoda), Caspiobdella fadelevi and Helobdella stagnalis (Hirudinea), and also eggs of aquatic mite of the genus Unionicola (Arachnida). The distribution of parasites and quantity characteristics of infection of molluscs in different parts of the Volga basin are given. The helmints were recovered in adult molluscs only with the size 18—26 mm (mean 24.5 ± 1.8). Priority infection of mollusc females is noted. The role of D. polymorpha and carpio bentos eater fishes in the life cycle of A. limacoides is discussed. The analysis of published dats on the parasite fauna in D. polymorpha in different points of its areal is given. In relation to the intervention and distribution of the mollusc D. polymorpha (Zebra mussel) in water basins of North America the possibility of parasite transmitting by D. polymorpha and the possibility of infection by local parasites are discussed.

The ultrastucture of the digestive tract of the digenetic trematode A. amphoraeformis was investigates. The foregut consists of a mouth, prepharynx, small muscular pharynx and long oesophagus. The whole region is lined by an extension of body tegument. The lining of long caeca is represented by cellular gastrodermis. The junction between foregut epithelium and gastrodermis is marked by septate desmosome. Glands open into the lumen of prepharynx via microtubular-supported ducts. Tegument of prepharynx and oesophagus contains specific secretory inclusions which are formed in subjacent tegumental cell bodies. The surface of apical plasma membrane of prepharynx epithelium is greatly increased by numerous extensions, infoldings and deep invaginations. Surface extenisons of various configuration are also noted in oesophagus. Gastrodermal cells display highly developed rough endoplasmic reticulum, sparse mitochondria, numerous electron-dense secretory granules and autophagic vacuoles, which are also rather numerous. The desintegration of whole gastrodermal cells was observed. Sparse short narrow lamellae cover the apical surface of gasrtodermal cells. Small plate-like invaginations of basal plasma membrane and junctional complexes with parenchymal cells are the few.

The fauna of parasitic protozoans of the bream (Abramis brama) from different reachs of the Rybinskoye water reservoir was investigated. 350 fish specimens have been examined by the method of total dissection. The greater number of parasites and diversity (33 species) were observed in the Volzhski reach: infusoria — 16 species, myxosporidia 12, flagellata — 4, dermocystidia — 1. In the breams of Sheksninski reach 18 species of parasites were recovered: infusoria — 8, myxosporidia — 8, flagellata — 1, dermocystidia — 1. Parasite protozoans from the Molozhski reach were represented by 14 species: myxosporidia — 8, infusoria—5, flagellata — 1. Statistic analysis of the morphological variability of spores of the myxosporidians from gills (Myxobolus muelleri and M. exiguus) has displayed the decrease of spore size in the row Molozhski — Volzhski — Sheksninski reachs. Some parasitic protozoans could be used as indicators of local fish herds.

The attempt to overcome the natural resistence of white rats Wistar to Leishmania infantum infection was made by the mean of the immunodepressant Tricort-40, the corticosteroid of prolonged activity. In the serie of experiments with the mercy scheme of immunosupression the inoculation of the amastigotes L. infantum taken out of the donors, the golden hamsters Mesocricetus auratus, caused the progressive infection with intensive affection on target organs (the spleen, liver, bone marrow). The stem of L. infantum been passed through the immunosupressed rats has preserved its pathogenity to the golden hamsters.

The results of the investigation of the distribution of the synathropic mosquito Culex pipiens in dwelling buildings in Nehryungri in 1992—1993 are reported. It has been recovered that this mosquito species inhabits all stone buildings and therefore it is a very important problem for city people in the region of investigation.

For the first time in the fauna of Russia and surrounding states 4 species of mites of the subgenus Graphiurobia (Myobiidae, Radfordia) were registered, one of them, R. (G.) myomimusi sp. n. was described as the new species. All the registered mite species are the parasites of rodents of the family Gliridae (= Myosidae) (Rodentia). The short diagnosis of all the development stages of the subgenus Graphiurobia, and the description of R. (G.) myomimusi sp. n., collected on Myomimus personatus Ognev in Western Kopet-Dag (Turkmenia), and the description of the unknown before deutonymphes, tritonymphes and males of R. (G.) dyromys Fain et Lukoschus, 1973, are given. The key for identification of all the species of the subgenus is worked out.

Summary is absent.

Summary is absent.