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The seasonal dynamics of the Monojoubertia microphylla micropopulations in different sex and age groups of the chaffinch Fringilla coelebs (Passeriformes: Fringillidae) have been studied during the nest and migration periods in the North-West of Russia. Three bird groups were determined within the chaffinch population during the study: adult males, adult females, immature chaffinches. Total number of bird specimens examined — 353. In all chaffinch groups, the mean mite numbers and age structure of mite micropopulations were similar during the spring migration. The number of mites gradually increased from April to May. During the nest and autumn migration periods the seasonal dinamics of M. microphylla micropopulations were quite different on adult males and females of the chaffinch, because of different roles of male and female in the process of infestation the young bird generation. On the adult chaffinch males, the mite number continued to increase during the breeding period (June) and began to decrease significantly in July because of the postbreeding plumage moult. The mite number slowly decreased in the end of summer and the autumn migration. On the adult chaffinch females, the mite number decreased abruptly during the nest period. During this period, the chaffinch female sits together with nestlings for a long time, and the great number of its mites (about 60% of mite micropopulation) moves from the female onto the nestlings. The mite micropopulation migrated onto nestling is represented mainly by males, females (about 25% each) and tritonymphs (38%). Total mite number on the chaffinch females continued to decrease in July under the influece of postbreeding moult and slightly increased up to the autumn migration only. On the young chaffinches, the number of M. microphylla quickly increased during the second part of summer. It is the result of the great quota of mite instars being ready for the reproduction (imago, tritonymphs) within the micropopulation migrated from the chaffinch female onto the nestlings. The decrease of the M. microphylla micropopulation on the young birds was observed in the autumn only. In the end autumn migration (October), the mean numbers of mites on all chaffinch groups became approximately similar, but did not reach the mean rate observed in the begining of the spring migration. During both migration periods, the imago and all preimaginal instars of M. microphylla were active, the diapause was not observed. In the begining of spring migration and the end of autumn migration the main part of the mite micropopulations was represented by females, while in all other periods of chaffinch's stay in the North-West of Russia the immature instars predominated.

Morphological and karyotypical features of a new blackfly species Cnetha akopi sp. n. from Armenia are described. Comparative analysis of the new species and four closely related endemic species from Caucasus is performed. Photographic maps of polythene chromosomes are provided.

A new checklist of mosquitoes (Culicidae) recorded in the Asian part of Russia includes 79 species. The checklist is provided with taxonomic comments and compared with ones compiled by previous authors. In a comparison to the checklist of Kukharchuk (1980) including 73 species, 10 species are added into the present checklist and 6 species mentioned by this author are excluded, as far they were not actually found in Asian part of Russia. The names of 9 species are chanched according to the International Code of Zoological Nomenclature (1966). In the checklist of Stojanovich and Scott (1995) including 64 species, 5 species were included erroneously and 21 species were missed. The classification and valid species names are listed according to the Catalog of the Mosquitoes of the World (Knight, Stone, 1977) and its supplements (Knight, 1978; Ward, 1984, 1992; Gaffigan, Ward, 1985), except 5 species. These species (Aedes implicatus, Ae. esoensis, Ae. rossicus, Ae. albescens, Ae. subdiversus) are considered in the comments to the checklist.

The random amplified polymorphic DNA (RAPD) technique was applied for the studies of genetic heterogeny between several natural populations of trematodes belonging to the Microphallida family. Initially, the metacercariae from the daughter sporocysts infestating Littorina saxatilis and Littorina littorea periwinkles were used. Comparison of the banding patterns obtained for the different metacercariae within one sporocyst gave an unpredicted results. For two of three studied species (M. pygmaeus and M. pseudopygmaeus), the consederable differences in RAPD patterning was detected. According to the classical point of view, the process of cercariae (metacercariae in case of the "pygmaeus" group of microphallides) formation does not include DNA recombination. Because of that, all metacercariae within one single sporocyst should be genetically identical. However, data obtained clearly shows that at least in some cases it is not so. We can hardly believe that such result could be a methodological artifact, for not single difference in a RAPD patterns was recorded between the metacercariae within sporocysts of M. piriformes. Moreover, even the 100 fold dilution of the total DNA used for PCR amplification does not change the banding patterns. Hence, our results can not be explained by slight fluctuations in the DNA concentrations between the samples. The most evident conclusion is that we came across yet strange, but real phenomenon — some degree of genetic difference within the progeny of each of the sporocysts — metacercariae. However, the detailed study is needed to understand and interpret these observations correctly. Amplification of the total DNA extracted from the whole sporocysts (containing metacercariae) never showed any differences in RAPD patterns between the parasites been derived from one infestated snail (local parasite hemipopulation). That allowed us to compare different parasite populations referring the RAPD pattern of one sporocyst from a snail to as a representative of one local hemipopulation. Analysis of the RAPD-loci frequencies showed a considerable genetic differences between the subpopulations of M. piriformes, infestating different paraxenic intermediate hosts — L. saxatilis and L. obtusata. This phenomenon was statistically significant for 2 localities of 3 studied. No heterogeny within populations was recorded for M. pygmaeus. Both M. piriformes and M. pygmaeus are characterized by the genetic differentiation in the microgeographic scale (within the Chupa bay of the White sea, the longest distance between the analyzed localities is 20 km). According to the frequencies of the RAPD-loci, parasites from the sheltered locality differ significantly from the parasites of other two localities exposed to the open sea. For both species the degree of genetic similarity between the populations correlates positively with the distance between the localities. We can suppose that the population structure of microphallids depended mainly upon the population structures of their intermediate hosts, definitive hosts and geographical structure of the areal. However, taking into consideration the low motility of snails, we believe that the distribution, migration and species composition of the definitive hosts play the key role in the genetic structuring of M. pygmaeus and M. piriformes hemipopulations. As an addition, the RAPD analysis of the parasite populations from the Barents Sea (East cost of Murman peninsula) and North Sea (Western cost of Sweden) revealed no significant genetic differences between the worms from those places and from the White Sea. However in case of this macrogeographic comparison, insufficient number of samples does not allow us to draw any final conclusions.

A morphofunctional aspect of pathogenesis in various mollusc—trematode combinations is very different. To evaluate the level of antagonism between the host and parasite, it is reasonable to use a summarized parameter of general physiological state of infected individuals. The somatic growth of the host could be used for that purpose. Analysis of original and reference data has shown, that the gastropod growth responce to the trematode infection depends on the longevity of molluscs. The growth acceleration (gigantism) in infected individuals is common for snails with the intermediate longevity (3—4 yr), such as Hydrobia, Onobia and Bithynia (Prosobranchia: Rissoacea). As an exception, the gigantism is observed in the short-living species, which do not change the growth rate when they are parasitized: Biomphalaria, Bulinus, Helisoma and Lymnaea (Pulmonata: Basomatho-phora). Earlier, it was assumed that the single trend manifested in the infected long-living species (6—27 yr), such as Littorina (Prosobranchia: Littorinacea) and Cerithidea (Prosobranchia: Cerithiacea), in the decrease of the growth rate. The only case of the growth acceleration within the long-living molluscs was detected in the Littorina littorea from the White Sea infected with low pathogenic partenits of Cryptocotyle lingua (Heterophyidae). Based on the groups of snails with different longevity and being phylogenetically distant from each other, we can presume that the growth response to the infection correlates with the morphological peculiarities of hosts. The morphofunctional distinction in the systems formed by trematodes and molluscs of different taxa are expressed in the parthenit localization in the host body and in the degree of digestive gland and/or gonad destriction. From the viewpoint of general physiological status of the host organism, the results of disfunctions in these organs are not similar. The destruction of digestive system ("energy power station" of organisms) is more fatal for infected individuals than a parasitic castration. Therefore, the localization of parasites in the mollusc gonad can be recognized as a parasitic adaptation to decrease the probability of a premature host's death and respectively to prevent the elimination of parasites. Phylogenetically distant gastropods with different life cycles use a diverse reproduction strategy, which implies a different proportion of gonad and digestive gland volume. Thus, snail species from different taxa are not similar in relation to the life space, which could be "granted" to the parasite without any risk to reduce a viability of the host. The space lack forces the parthenits parasitizing in the molluscs with the longer life span to occupy the digestive gland tissues, that increases their pathogenicity and decreases the host's growth rate.

The ultrastructure of the epithelium in Notentera ivanovi (Turbellaria, Fecampiida) has been studied. Notentera ivanovi lacks the digestive system but has a pad of the epidermal cells on the dorsal side of the body, which seems to be similar to the digestive epidermis on LM. Both the ventral and dorsal epithelium are cellular, ciliated and not insunk (fig. 1, a). The ultrastructure of the ventral and dorsal epithelium is similar in essential features. The cells bear abundant microvilli, cilia and are very rich in mitochondria, but the cytoplasm does not contain lysosomes and shows no other indications of phago- or pinocytosis. The basal membrane of epithelial cells forms deep invaginations (fig. 1, б), partly with dilations (fig. 1, a; 2, a) containing the lamellated material (3, в). In the basal part of the cells the numerous Golgi apparatus and rare cysternae of the smooth endoplasmic reticulum were observed (fig. 2, a, 6). The epithelium consists of several types of cells, which differ in the structure of secretory granules. The most abundant type of cells contains the granules with the rough-fibrillated content (fig. 1, a; 2, б; 3, a). The cells of this type cover most part of the body. In some cells the content of such granules becomes condensed and electron-dense granules appear (fig. 3, a, б). Another type of cells contains the giant granules with the rough-fibrillated content (fig. 3, г). Third type of the secret is the granules with the finely fibrillated content which is ejected by exocytosis. The cells of the second and third types form a separate areas of the epithelium of the dorsal side of the body but occasionally were observed in the ventral epithelium too. The epithelium of N. ivanovi differs from that in Kronborgia by the abundance and diversity of secretory contents. The role of the epithelium in the digestion remains conjectural. It seems to be mainly the suckering tissue transporting the low molecular nutrients.

There are about 250 coccidian species associated with fishes. They belong to 8 genera (Calyptospora, Cryptosporidium, Crystallospora, Eimeria, Epieimeria, Goussia, Isospora, Octosporella) and 3 families (Calyptosporidae, Cryptosporidiidae, Eimeriidae). Two genera are represented by great number of species associated with fishes: Eimeria — 157 and Goussia — 69 species. Most diverse fauna of coccidians was found in fishes of the class Actinopterigii; fishes of the class Elasmobranchii have significantly less number of coccidians. These parasites have never been recorded on the class Holocephali. Coccidian have been recorded in 55 orders of fishes. Within the Actinopterigii, the richest coccidian fauna is recorded from Cypriniformes and Perciformes. Accumulated data on host associations proves that coccidian species have mainly a restricted hosts specificity.

The mites of genus Neharpyrhynchus Fain, 1972 (Acari: Harpirhynchidae) are recorded from Rissia for first time. Two species, N. hippolae sp. n. from Hippolais icterina (Passeriformes: Sylviidae) and N. plumaris (Fritsch) from Fringilla coelebs (Passeroformes: Fringillidae) from N. W. Russia was found. N. hippolae sp. n., female holotype (all measurements in mkm, abbreviations — see Fain e. a., 1999): L 517, W 382, LS 179, WS 325, PA 27, thicker than PI 49 and PE 24, pts smooth, vi, ve и sci are subequal, about 94, 15 247; propodosomal shield not divided; anterior region of pronotum with rounded verrucosites; venter without scales; legs I—II with 2 free segments and strongly developed lobes at their bases; legs III—IV with one segment, bears 4 and 5 setae respectively (in paratypes number of these setae is variable, A—5). Male: L 227—254, W 210—219, LS 129—134, WS 170—183, pts are smooth, ve 78—87, sci 83—90, sce 89—95, h 90—110; penis 49—56 long; legs III with 2 free segments, basal segment bears seta, apical segment with 5—6 setae; legs IV with one free segment, it bears 4—-5 setae. The new species is closely related to N. pilirostris (Berlese et Trouessart, 1889) and distinguished by characters as follows. N. hippolae sp. n. (female): the setae PI about 2 times are longer than PA and PE; the apical segment of legs III—IV bears 4—5 setae. N. pilirostris: setae PA, PI и PE are subequal; the apical segment of legs III—IV bears 4 setae only. N. plumaris differs from closely related species N. novoplumaris Moss e. a., 1968 by characters as follows. In female of N. plumaris, the setae PA are subequal to PE and 1.6—4.8 times shorter than PI. In N. novoplumaris, the setae PA shorter than PI and PE.

Summary is absent.

Summary is absent.