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It is recovered, that full engorged females of Ixodes persulcatus lay average of 25 250 eggs per 1 ha during the season in the test area. It produces 13 750 larvae. The abundance of hungry larvae is reduced up to 12 500 during the winter period. 11 643 larvae become engorged. The total abundance of hungry nymphs counts: 10 933 in autumn, and 9895 in spring. The total abundance of hungry adults, half of which is represented by females, makes 1774 in autumn, and 1084 in spring. About 10 females found their hosts and became successfully engorged.

The authors confirm the fact of disperiosn of oribate mites by birds, that was earlier noticed in acarological references. More than 400 individuals of 53 virds species belonging to different ecological groups have been examined. About 50 species alive oribates were collected in bird feathers: Liochthonius sellnicki, Brachychthonius sp., Hypochthonius rufulus, Nothrus palustris, Malaconothrus egregius, Camisia segnis, Camisia sp., Hermanniella granulata, Trhypochthonius tectorum, Oribatula tibialis, Zigoribatula exilis, Scheloribates laevigatus, Sch. latipes, Suctobelba trigona, Suctobelbella sp., Fosseremaeus laciniatus, Tectocepheus velatus, T. knullei, Nanhermannia coronata, Achpteria coleoptrata, Parachipteria punctata, Damaeus riparius, Eremaeus oblongus, Diapterobates notatus, D. humeralis, Carabodes areolatus, C. marginatus, Sphaerozetes tricuspidatus, Ceratozetes parvulus, C. cisalpinus, Mycobates sp., Punctoribates punctum, Trichoribates trimaculatus, Galumna sp., Oribella paoli, Chamobates laciniatus, Neoribates roubali, Neoliodes farinosus, Oppiella nova, 0. unicarinata, O. fallax, Oppia ornata, Steganacarus striculum, Steganacarus applicatus, Tropacarus carinatus, Protoribates capucinus, Scutovertex minutus, Autognetha willmanni, A. longilamellata, Belba sp., Metabelba pulverulenta, Gustavia microcephala, Fuscozetes fuscipes и Pergalumna nervosa. Carabodes marginatus were met most often, on 8 species of birds, Tectocepheus velatus, on 12 species, Oppiella unicarinata — at 7 species. Some oribate species constantly occur in bird feathers.

A representative of the family Apionacaridae is recorded from the passerine birds Passeriformes for the first time. Fringillosphaera bochkovi gen. n., sp. n. is described from the chaffinch Fringilla coelebs (Fringillidae). The new genus obtains main diagnostic characters as follows. Vertical setae vi absent. Prodorsal shield free from scapular sheilds and epimerites Ia. Humeral sheilds present. Epimerites I convergent, connected by sclerotized plate. Lateral setae f2 and pseudanal setae ps3 absent. Coxal fields I—IV sclerotized. In male: legs IV present, genital apparatus at level of trochanters IV, genital arch with divergent branches. Epiandrium absent. Coxal setae 3a absent. Morphological peculiarities, host associations and phylogenetic relationships of the family Apionacaridae are briefly discussed. It is suggested that this family represents and ancient and relic phylogenetic branch, which had split rather early from the common ancestor of the superfamily Analgoidea in the period of formation of the Neognathae birds.

he structure of pseudosetae, spinelets, and spines of combs (ctenidia) was studied by means of light and SE microscopy in 80% of genera and subgenera of the World fauna. It is found out that peculiarities of ctenidiae in the prothorax and in tergites of the abdomen are characteristics of families and infraorders of fleas. Some characters of ctenidiae found in certain flea genera are reductions and apparently caused by habitation in some extremal conditions. An absence of ctenidiae in the unfraorder Pulicomorpha is compensated by more developed posterior margin of prothorax and general abbreviation of all thoracal segments. Reasons of ctenidiae absence, which is observed in certain genera of the infraorders Ceratophyllomorpha, Pygiopsyllomorpha and Hystricopsillomorpha associated with the same hosts, is not clear. It is confirmed, that distance between ctenidiae in different flea species associated with the same species host species, however it is recovered, that this distance correlates with the diameter of most thin hair of host. In some flea species the distance between ctenidia spices in females is larger, than in males. It is found, that sexual dimorphism by this character may not be expressed in certain species of closely related species group of fleas. It is suggested that ctenidiae were present even in the common ancestor of fleas. The hypothesis on origin of spines and pseudosetae from setae of the posterior walls of toracal and abdominal segments in the common ancestor of fleas is proposed.

The reproduction in the first parthenogenetic generation — mother sporocyst (MS) in two species of echinostomes (E. caproni, E. paraensei) is investigated. A group of densely packed cells, which noticeably differ from others, occupies the posterior part of the miracidium. They are characterized by large sizes and a large bubble-shaped nucleus with heterogeneous nucleolus and strong dispersed chromatin. The use of histological and electron microscopic methods has shown that with observed similarity these cells are classified in two tyoes and have a completely different origin. First of all, large secretory cells stand out. In E. caproni miracidia their number averages 6.8 ±0.2 and linear sizes is 10—12 µm. Secretory cells possess a large bubble-shaped nucleus. The caryoplasm looks optically empty because of strong dispersion of chromatin. A large nucleolus occupies a bit eccentric position. Eosinophilic cytoplasm contains poorly noticeable at light-optical level accumulations of small granules. The second group of cells is represented by typical germinal cells (GC). The number of GC does not exceed six. Their polymorphy is well above that of secretory cells. The sizes of GC vary from 5.4 to 9 µm. The largest cells (8.1—9 µm) occupy the front position and usually are located between secretory cells. Intensively basophilic cytoplasm surrounds bubble-shaped nucleus with a large nucleolus like border with uniforming thickness. The heterochromatin is evenly distributed over the caryoplasm. Its content of nuclei is more than that in nuclei of secretory cells. That is why they do not look optically empty. So, it is "mature" germinal cells. Four or five cells are located directly behind "mature" cells. Their sizes are gradually decrease towards the posterior of the miracidium (the diameter of the smallest cells reaches 5.4 µm). Nuclei with a centrally located nucleolus are characterized by larger amount and more condensation of the heterochromatin than those in "mature" cells. Meanwhile, they concern to nuclei of bubble-shaped type. In general, all cells of second type represent the primary germinal cells distinguished by the stage of their differentiation. Also, 2—3 undifferentiated cells occupy the most posterior part of the miracidium. Their sizes average 5.55 ±0.18 µm. The nucleus contains a lot of densely packed heterochromatin. On parasitic phase of MS development undifferentiated cells give rise to secondary GC. Electron microscopic data in details confirm the situation described above. The essentially similar results were received during the investigation of E. paraensei miracidia. The differences are observed in parametrical characteristics of germinal material and in small variability of the extent of germinal material development. With E. paraensei, germinal material may be represented by not only GC and undifferentiated cells, but one germ as well. So, our investigation has shown that germinal material of echinostomes represents typical germinal mass. The germinal material condition does not change on parasitic phase of E. caproni MS development during the first day of post infection (PI). The activization of germinal material coincides in the time with the beginning of schizocoel formation in 2 Days PI. On the 3rd day of PI, the proliferation of undifferentiated cells begins and the first germs are free to float in enormous schizocoel. After 8 days of PI, MS release the first rediae. During the following 2—3 days the other rediae formed by primary GC left MS. The release of rediae derived from secondary GC was observed later. So, E. caproni MS give rise to 12—16 rediae which is much less than the number of GC formed in MS. The earlier release of the first E. paraensei rediae by MS is predetermined by the difference in the structure of germinal mass in E. paraensei miracidia. Therefore, Echinostomatidae is intermediate between two groups of trematodes. The first group has MS that completely realize reproductive function in the time of miracidial formation; but the second group includes higher trematodes characterized by the transfer of reproductive time on a parasitic phase of MS development. The question concerning to so-called "pedogenetic larvae of trematodes" is discussed.

The inluence of different concentrations of the copper sulfate (0.2, 1, 1.8 mg/l) on the Lymnaea stagnalis heart rate in a control and in the case of the trematode infection was examined. Concentrations which cause the decrease and the increase of heart rate were estimated. Pathological reactions in infected individuals are more expressed and appear earlier.

The age dynamics in oxygen consumption of the cercariae Himasthla elongata, Cryptocotyle lingua and Cercaria parvicaudata (Renicola sp.) was studied using modified Winkler's method. It was detected that under stable temperature and water salinity conditions the rate of oxygen uptake depends directly on cercariae size. The highest intensity of energetic metabolism was recorded in the first few hours of cercariae life when their movement activity was maximal. The following reduction of oxygen consumption passed unequally in three cercariae species studied. Large, long-lived H. elongata cercariae after relatively short period of active swimming turn to crawling on the bottom. The rate of oxygen uptake in such cercariae was two times less than in free-swimming ones and remained approximately invariable up to the cercariae death. The smaller sized, short-lived Renicola sp. cercariae swim actively in the water and during this time the level of their energetic metabolism remains more or less stable. It decreased drastically after cercariae sinking to the bottom, after that they perished very soon. Also relatively smalk C. lingua cercariae alternate the active and passive phases of swimming. Thanks to that they consume the energetic resources economically and prolong their longevity. During free-swimming period the rate of oxygen uptake of C. lingua cercariae remains more or less stable. As in the case of Renicola sp. cercariae, it decreased drastically after the cercariae sinking to the bottom. Apparently such cercariae lose their ability to infect the second intermediate host (fish). The study was supported by RFBR (project N 99-04-49788) and INTAS (project N 10224).

A new subspecies of entomopathogenic nematode, Steinernema feltiae protense subsp. n., isolated from Yakutia grasslands is described. These nematodes demonstrate a high invasion activity to insect-hosts at 6°C, maximum infestation of insect-hosts was registered at 13—21°C.

In the present study authors claim that the adult orthonectids can not move through host tissues by themselves. In various species of these enigmatic parasites there are at least two different mechanisms of emission of males and females from the host body. Intoshia linei, the orthonectid from Lineus ruber (Heteronemertini), and Intoshia variabili, the parasite of a flatworm Macrorhynchus crocea, realize the first way of emission. The Plasmodium of these species forms tube-like outgrowths, which pierce the host tissues reaching the host body surface. The cytoplasm structure of these outgrowths differs from the cytoplasm of the central mass of Plasmodium. Small mitochondria with electron dense matrix, lipid granules and vesicular bodies being common in the central part are absent in these outgrowths. Plasmodial outgrowths reach the host body surface and adult orthonectids move inside them using their cilia and stopping from time to time. The plasmodial outgrowths penetrate the ciliated epithelium, then males and females leave the host. Duration of emission may vary in different species from 6 to 13 days. The second mechanism of emission is common for the orthonectid parasites of mollusks. Our observations of Rhopalura philinae from the gastropod Philine scabra lead to the conclusion that males and females leave their host practically simultaneously. When the Plasmodium attains the terminal stage of its development most of the host entrails are already displaced by plasmodial mass. It causes breaks in host body walls and hence to emission of sexual individuals. During this process, which lasts about 24 hours, the mollusk dies. The same mechanism was observed in Rhopalura littoralis — parasite of the gastropod Onoba aculeus. Our investigations of emission ways reveal that the plasmodium of orthonectids has a potency of directing growth and can form certain structures. The process of forming the plasmodial outgrowths is coordinated in time and space. These outgrowths have certain directions inside the host body and the maturation of sexual individuals is clear related with the development of plasmodium outgrowth system. Our results suggest that forming of plasmodial outgrowths is an element of development of the united and highly integrated system. It is necessary to emphasize the capability of plasmodium to accomplish such morphogenetic transformations. This fact argues that plasmodium is a part of parasite organism and not host cells modified, like some experts supposed.

The diversity of parasite fauna of the Atlantic salmon parr from the Teno River and its tributaries recovered in 1993—1995 is discribed. 35 parasite species were found, the majority of them are represented by the parasites with a direct cycle of development. High prevalence of infection with Chloromyxum januaricus wes detected.

Three new species of the family Trilosporidae (Myxosporidia) from fishes of the northern Pacific are described: Trilospora sphaerica sp. n., Unicapsula pacifica sp. n., U. schulmani sp. n.

The zebra mussel Dreissena bugensis (Andrusov), a representative of mollusc fauna in the Dnieper-Bug estuary, have been found for the first time in the Rybinsk reservoir (the Volga reach, Shumorovka River). In pericardial and mantle cavities and inner organs of molluscs the following parsites have been found: Aspidogaster limacoides, Caspiobdella fadejevi, Helobdella stagnalis, eggs of the water mites of the genus Unionicola, and representatives of nonspecific saprotrophic fungi of the genus Acremonium. It is shown that composition of parasites and free-living organisms in D. bugensis is similar to that in D. polymorpha.