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The age structure of Ixodes persulcatus natural populations from St. Petersburg and its outskirts was evaluated on the fat reserves in midgut and fat body.

It was demonstrated that the flea Xenopsylla vexabilis, the main vector of plague agent in the "natural plague foci" of Hawaii in first half of XX century, is a specific parasite of small white-toothed rat Berylmys berdmorei, inhabiting tropical forests and grasslands of Indo-China, including Vietnam. In Vietnam settlements X. vexabilis was not recorded. This flea was found in the fields bordering natural landscapes and agricultural areas as a parasite of the greater bandicoot rat Bandicota indica and savile's bandicoot rat B. savilei and on a rat Rattus koratensis. It was speculated that the bandicoots might play important role in the introduction of the flea to the Pacific islands where X. vexabilis changed bandicoot hosts to the synanthropic rats. The new data do not support the coevolution conception of the plague agents' association Rattus exulans—Xenopsylla vexabilis—Yersinia pestis.

Ticks belong to the major groups of parasitic arthropods vectored the dangerous animal and human infections. Among ticks inhabiting Central Caucasus, Dermacentor spp. shows the high abundance and diversity, as well as wide host ranges among domestic and wild animals. Studies of ixodids of North Caucasus started by Belavin, Nikolsky (1937), up to 1980-thies the host ranges, seasonal variability in the host attacks activities of common species the genus Dermacentor were already revealed. At the end of XX century the favorite environment conditions led to population increase of Dermacentor spp. and consequently to the epizootic and epidemic situation of their vectored diseases. The goal of our survey was to estimate the recent distribution, host-parasite relationships, seasonal activities and sanitary significance of the ticks belonging to the genus Dermacentor in all administrative areas the Stavropol Territory, based on original materials collected during 2000—2012. The fauna of Dermacentor Koch, 1844 in Central Pre-Caucasian region was represented by following species: D. marginatus (Sulzer, 1776); D. reticulatus (Fabricius, 1794) (= D.pictus Hermann, 1894); D. niveus Neumann, 1897 (= D. daghestanicus Olenev, 1929) (table 1); the shares of D. marginatus was 14.8%, D. reticulatus — 2.8%, D. niveus 0.01%. of the total ixodid number. Dermacentor margipatus inhabits grasslands of plains and mountains; it is wide spread in the steppes and forest-steppe landscapes. After the winter diapause D. marginatus activated in March and April, in some years in mid-February during thaws, with two peaks of activities in spring and autumn. Spring peak is from a third decade of April to the second ten days of May; the autumn activation is from the third decade of August till mid-October. The main hosts are cattle, sheep and goats, horses, domestic carnivores. The number of the D. marginatus attacks on humans was 4.1%. The share of this species taken from the humans, was up to 10%. Dermacentor reticulatus is much less representative species than Dermaceptor marginatus, inhabiting the wet meadows and shrubs in the forest-steppe and foothill provinces of the Stavropol Territory. Activation of D. reticulatus was detected in the first decade of March and April. Early activation after winter diapause is to be explained by the species tolerance to low positive temperatures, comparing to other tick species. The main hosts are wild big mammals, because of scarcity of domestic animals passing the ticks habitats in early spring. To reveal the optimum environmental conditions for the tick's activation, the meteorological parameters for 7 years (2000—2006) were compared with the abundance of D. marginatus. These ticks were activated at the average temperature of +2.07°C and the average amount of rainfall of 47.2 mm. The number of ticks reached its peak on hosts at the monthly average air temperature of +7.8°C, and the average amount of rainfall of 56.2 mm. Autumn activation was recorded at the average air temperature of +15.3°C, and the average amount of rainfall of 58.2 mm.

So far the information on parasites of introduced Amur Sleeper in waterbodies of the Ural and Siberia was relatively scarce. The first data on the Amur Sleeper parasite fauna were collected in waterbodies of forest-steppe zone of the Western Siberia (Novosibirsk region, Russia). Specimens were fished from dammed tributary area of Upper Ob River and two waterbodies belonging to the closed water system of the Barabinsk Lowland. Nine parasite species were found as well as some taxa which were not identified to species level. Tylodelphys sp. was recorded for the first time in Palearctic fishes. Spironucleus sp. and larva of mite Parasitengona gen. sp. were detected for the first time in Amur Sleeper and odontobutid fishes. Metacercariae of Tylodelphys sp. (0.901—1.116 X 0.261— 0.307 mm) were located in a body cavity of Amur Sleeper. The generic attribution of revealed parasites was confirmed by molecular data (ITS1+5.8S+ITS2 site of rDNA). The host-specific parasite of Amur Sleeper, cestode Nippotaenia mogurndae, was detected. Fishes from the waterbodies of the Barabinsk Lowland and from tributary of Upper Ob River have no common parasite species.

Textual, tabular and computer-aided keys to species of the genus Paraphelenchus are given. Pathogenicity and ecology, bionomics and nematode associations with fungi are reviewed. Diagnostic characters of species are listed and discussed.

Histological assay of the amebocyte-producing organ (APO) in susceptible and resistant strains of Biomphalaria glabrata snails was done. The APO was studied in intact and Echinostoma caproni infected snails. Dimensions of APO nodules proportions and number of the cells in it were measured in control and during the infection. APO locates between the mantle and pericardium epitheliums and includes 3 nodules on average in non-infested resistant and susceptible snails. In E. caproni infested snails, the number and dimensions of nodules are increased. The maximum level of APO growth was recorded at 4th day after infestation in susceptible snails, and at 5th day after infestation in resistant mollusks. Lager dimensions of APO were recorded in resistant mollusks. It consists of 9 nodules on average, which include 550 ± 15.7 cells on the whole. After 14 days post infection, APOs of the both molluskan strains revert to the initial parameters. We suppose that APO produces prohaemocytes, which differentiate into granulocytes and hyalinocytes inside the blood vessels.

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