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The ixodid ticks are the vectors of several hundreds of agents of transmission diseases of vertebrates and human. This agents are represented by viruses, rikketsiae, bacteriae, protozoans and fillariae. For the majority of these agents the ticks are not only vectors, but also are intermediate or final hosts. In the system agent-tick the antagonistic relationships dominate, and therefore the agent is actually a parasite of its vector. A wide spectrum of parasitic relationships form the high pathogenity and lethality of an agent for its vector to the fast and complete elimination of a microorganism in a tick could be observed within the system in question. Somewhat balanced type of relationships occurs most often, thus pathogen agent causes a minimal damage to the tick-vectors and could stay in their organism and hold a capability of the transmission to the vertebrate hosts and within the population of ticks.

A total of 740 adult Ixodes persulcatus ticks were collected from the vegetation by flagging in Russian foci where Borrelia afzelii and B.garinii circulate, and 156 I. dammini² ticks were collected in north-western USA regions in foci with B. burgdorferi s. str. circulation. Smears prepared from the internal organs of ticks were stained according to Romanovsky-Giemsa and analyzed under a microscope at a X 1125 magnification. All borreliae in 250 microscopic fields were counted, and concentration of microbial bodies per 100 microscopic fields was determined. The general level of infection by Borrelia in both vectors was similar: 26.2 X 3.2 in I. persulcatus and 26.3 ±7 in I. dammini. However, the proportions of ticks with generalized infections differ considerably (12.9 ± 4.8 in I. persulcatus compared with 2.4 ± 4.8 in I. dammini; significance of difference t = 3.1). We did not reveal any definite increase in the proportion of ticks with borreliae in the salivary glands among ticks with high concetrations of microbial bodies in the gut. In 25 I. persulcatus ticks with generalized infections, series of actual numbers of borreliae (per 100 microscopic fields) found in the gut and salivary glands did not correlate with one another (r = -0.23). These results confirm our previous conclusion (Korenberg, 1994) that frequencies of generalized infection in main vectors of different ixodid tick-borne borrelioses are also different, which is probably due to peculiarities of relationships between spirochetes of each species and corresponding tick vectors. These factors can be responsible for differences in the ways of horizontal and vertical transmission of pathogens belonging to the group under study. This study was supported in part by FIRCA Grant 00 097. ² There is the viewpoint (Oliver e. a., 1993, J. Med. Entomol. Vol. 30, N 1. P. 54-63) that I. dammini Spielman, Clifford, Piesman et Corwin, 1979 is the junior synonym of I. scapularis Say, 1821 (the footnote of the editor).

The detailed maps of the distribution of sittings and feedings of the 12 tabanid species among 22 zones of a cow's body are given. The material on the observations of individually marked tabanids attacking a single cow in conditions of the Pskov region in 1984-1990 (Konstantinov, 1992) has been used in present paper. It is established, that the distribution of sittings and feedings onto the cow's body has a species-specific character. The 12 species were arranged into 5 groups based on characters of the topographical similarity of their distributions. The distribution of feedings has the less range than the distribution of sittings within each species. The distribution of sittings and feedings within each species coincide averagely by 60%. The effectiveness of tabanid's sittings is different within different zones of the cow's body.

Quill mites of the family Syringophilidae have been studied for the first time on birds of Kyrghizia. In result of this study three new species have been discovered and one new genus has been established. The genus Mironovia gen. n. belongs to the genus group characterized by the narrow stylophore (Kethley, 1970). It is similar to the genus Colinophilus Kethley, 1973 but distinguished by the less number of chambers in longitudinal (medial) branches of the peritremes, by the absence of hypostomal teeth and by only two pairs of paragenital setae (pg) in both sexes. The type species Mironovia phasiani sp. n. was founded in quills of primary feathers of the Common Pheasant Phasianus colchicus (Galliformes: Phasianidae). Two other new species were founded in quills of primary feathers of the Common Sturling Sturnus vulgaris (Passeriformes: Sturnidae). Female Syringophilopsis sturni sp. n. differs from other species of this genus by elongated trapezoid-shaped propodosomal plate, by 5-7 chambers in lateral and 10-13 chambers in longitudinal branches of peritremes, by less number of tines (8-10) in multiserrate setae a' and c" of tarsi. Female Syringophilodus presentalis sp. n. is distinguished from other species of the genus by the prominent front border of propodosomal plate, by hypostomal lips with two well-developed projections, by M-shaped peritremes with 2-3 chambers in lateral branches and 10-12 chambers in longitudinal branches.

Observations were made through examination of thin blood films which were prepared at appropriate intervals from citrated fresh blood of infected birds. The comparative discription of gametogenesis, zygote and ookinete formation of Haemoproteus lanii and H. minutus under the light microscope is given. The most informative signs, which can be used for haemoproteid systematics, were determined and compared with such signs of H. balmorali, H. belopolskyi, H. dolniki, H. fringillae, H. majoris, H. pallidus, H. tartakovskyi (Валькюнас, Ежова, 1993, 1994). Among them the microgamete length, zygote structure, morphological peculiarities of developing ookinete as well as the rate of ookinete formation can be pointed out first of all. Microgametes of H. minutus and H. pallidus are nearly twice shorter than the microgametes of other species. A large clear vacuole is formed in zygote of H. balmorali and H. fringillae only. The majority of diagnostic feature have the developing ookinetes. Three types of initial stages in ookinete formation were distinguished. The first type is characteristic of Haemoproteus balmorali, H. belopolskyi, H. dolniki, H. lanii, H. majoris and H. tartakovskyi. Ookinete formation in these species starts with the appearance of thin long digital growth. In the course of development this growth increases in size and gives the beginning to the apical end of ookinete. The second type is characteristic of H. fringillae. In this species a short blunt growth appears in the middle part of the parasite. The growth stretches itself and the forming ookinete is put into the shape of a pear. The third type is observed in H. minutus and H. pallidus. Ookinete formation in these species occurs without the development of any expressed growths. One side of the zygote becomes prolonged, thus giving the beginning of ookinete. The ookinetes of H. minutus and H. pallidus are nearly twice shorter than the ookinetes of other species. There were clear differences between haemoproteid species on the rate of ookinete formation. The ookinetes of H. balmorali, H. belopolskyi, H. fringillae, H. majoris are formed significantly more slowly than H. lanii, H. minutus and H. pallidus ones, and significantly more rapidly than H. dolniki and H. tartakovskyi ones. The peculiarities of gametogenesis, zygote and ookinete formation under the stable conditions in vitro can be used as usefull additional sings for determination of haemoproteid species.

Peculiarities of the cell differentiation in different parts of strobile of the cestode Triaenophorus nodulosus was studied with an autoradiography and electron microscopy. Some parameters of the cell cycle are determined. Two morphological types of epithelium and genital ducts are recovered. A suggestion about an existence of two subpopulation of the semistem elements is proposed.

An electron microskope study of the embryonal shells in the proboscis worm Arhythmorhynchus petrochenkoi on different stages of an embryogenesis was carried out. It is shown that the formation is performed on the surface of internal embryonal shell of the germ. The eight stages of genesis are recognized. General peculiarities in the structure of embryonal shells of proboscis worms of the class Palaeacanthocephala are discussed.

A dynamics, some peculiarities of a reproduction of daughter generation partenits of Hemiuridae gen. sp., and particular processes of formation and function of the special sporocyst germinal mass reproductive organ were studied. Essential distinctions of these structures in different-aged partenits is recovered. The role of germinal masses in reproductive processes of the daughter sporocysts of Hemiuridae gen. sp. is discussed.

The reproductive structure of the nematode Camallanus truncatus in the population of the perch Perca fluviatilis in dependence upon host's size and seasons was studied. It is recovered, that only the bigger sized host groups influence the formation of reproductive-functional structure of the C. truncatus hemipopulation.

The morphology and ultrastructure of two new species of the aseptate gregarines Lankesteria cyrtocephala sp. n. and Lankesteria levinei sp. n. are described. The problem of the using of some ultrastructural features in taxonomic diagnoses in discussed. Lankesteria cyrtocephala sp.n. Diagnosis. Trophozoites drop-like, ca. 188 µm long and 50 µm wide, with rounded posterior end and with simple, assymetric, clear, rounded mucron, bearing good developed smooth area and apical papilla. Epicytar folds on the cross-section finger-like, monomorphic; glycocalix is well developed. Number of apical arcs and apical filaments - 3-4; apical filaments are rounded on the cross-section. Paraglycogene grains ca. 1.2 µm with radial zones of heightened electronic density. The sphaerical nucleus ca. 13-21 µm lies in an anterior third of the body and contains 1 excentric rounded karyosome. The other stages unknown. In Dendrodoa grossularia, intestine and stomach; White Sea. Lankesteria levinei sp. n. Diagnosis. Trophozoites drop-like, ca. 140 µm long and 45 µm wide, able a little to change the degree of the lengthening, with a rounded posterior end and with simple, clear, rounded mucron, bearing apical papilla. The smooth area on the mucron poorly developed. Epicytar folds on the cross-section finger-like, monomorphic; glycocalix is well developed. Number of apical arcs 3-4, apical filaments - 3; apical filaments elongated on the cross-section. Paraglycogene grains ca. 0.9-1.3 µm, with ring-shaped zones of heightened electronic density. The sphaerical nucleus ca. 18-48 µm lies in the middle of the body and contains 1 excentric rounded karyosome. The other stages unknown. In Ascidia callosa, intestine and stomach; White Sea.

It has been demonstrated that A. paradoxus has two generations during a year in S. lucioperca of the age 0+ and three ones in older fishes (1+-9+). The lower parasite abundance on S. lucioperca gills was observed in the summer under the highest water temperature. The important role of S. lucioperca males for the enhancement and distribution of the parasites among young fishes of the next generation have been demonstrated. Unimportant average prevelence of A. paradoxus among fish males became quite significant during the period of the sexual activity of males: abundance index and coefficient of aggregation (according Ackundoff) became much higher in males than in females during a spawning period. It is concluded that heavily infected males are the main source of the young fish invasion during the fish-nest and fry guardian periods.

A new species of chigger mite Microtrombicula argentatus sp. n. is described. It is most similar to M. gratiosa Schluger et Kudryashova, 1969, and it differs from this species by the shape of dorsal scutum. In M. argentatus the posterior margin of the scutum is widely ovoid, while M. gratiosa has clearly drawn out shape of it with caves on both sides. The new species has the dorsal setae measurements D-41, NDV-72, while in M. gratiosa these measurements 34 and 80 respectively.The holotype and paratypes are deposited in the Biological Institute. The Kyrghizian National Academy of Sciences (Bishkek, Kyrghizian Republic).