Pathogens in Ixodes persulcatus and Ixodes ricinus ticks (Acari, Ixodidae) in Karelia (Russia).

Ixodid ticks (Acarina, Ixodidae) are vectors of dangerous human infections. The main tick species that determine the epidemiological situation for tick-borne diseases in northern Europe are Ixodes ricinus and Ixodes persulcatus. In recent years, significant changes in the number and distribution of these species have been observed, accompanied by an expansion of the sympatric range. This work summarizes the data of long-term studies carried out in Karelia since 2007 on the infection of I. persulcatus and I. ricinus ticks with various pathogens, including new viruses with unclear pathogenic potential. As a result, tick-borne encephalitis virus (TBEV, Siberian genotype), Alongshan virus, several representatives of the family Phenuiviridae, Borrelia afzelii, Borrelia garinii, Ehrlichia muris, Candidatus Rickettsia tarasevichiae and Candidatus Lariskella arthropodarum were identified. Data were obtained on the geographical and temporal variability of tick infection rates with these main pathogens. The average infection rates of I. persulcatus with TBEV and Borrelia burgdorferi sensu lato were 4.4% and 23.4% and those of I. ricinus were 1.1% and 11.9%, respectively. We did not find a correlation between the infection rate of ticks with TBEV, B. burgdorferi s.l. and Ehrlichia muris/chaffeensis with the sex of the vector. In general, the peculiarities of the epidemiological situation in Karelia are determined by the wide distribution and high abundance of I. persulcatus ticks and by their relatively high infection rate with TBEV and B. burgdorferi s.l. in most of the territory, including the periphery of the range.

Morphology and phylogeny of Henneguya oviperda infecting oocytes of Esox lucius, with description of parasite-induced histopathology.

Henneguya oviperda (Cohn, 1895) (Myxozoa: Myxobolidae) is a parasite infecting oocytes of the northern pike Esox lucius Linnaeus, 1758 (Actinopterygii: Esocidae). Infected oocytes are surrounded by all oocyte layers, some of them thinner and less visible than intact oocytes. A mature plasmodium of H. oviperda fills the entire internal space of the oocytes at the secondary growth phase, rendering the nucleus and organelles of the latter undetectable. Apart from the observed degradation of internal structures, alterations in the envelopes of the infected oocytes, and the deformation of the intact oocytes adjacent to them, no other developmental anomalies have been found in the reproductive products of female northern pike. Mature spores of H. oviperda have oval bodies with polar capsules of almost equal size and caudal projections that are on average equal to the spore body length. Phylogenetic analysis comparing 18S rDNA sequences placed H. oviperda into a clade of esocid-infecting species of the genus Henneguya and also supported H. psorospermica as a sister species.

Irregularity of the Linear Growth of the Margaritifera margaritifera (Bivalvia: Margaritiferidae) Population of the Nemina River, Karelia.

The dependence of shell growth in length and height during ontogeny has been studied in the pearl mussel Margaritifera margaritifera inhabiting the Nemina River (basin of Lake Onega, Karelia). It has been shown that the population is heterogenous based on the height-to-length ratio. It has been found that during ontogeny M. margaritifera from the studied population undergoes a constant change in the relative growth of the shell leading to either lengthening or rounding of the shell.

[NUMBER DISTRIBUTION AND POPULATION STRUCTURE OF PROTEOCEPHALUS LONGICOLLIS (ZEDER, 1800) (CESTODA: PROTEOCEPHALIDEA), A PARASITE OF SMELT AND COREGONIDS].

The spatial structure and seasonal aspects in the number distribution of the cestode Proteocephalus longicollis population, maintained by trophic connections of specialized plankton-feeders (the vendace Coregonus albula L. and the smelt Osmerus eperlanus L.) in the Lake Onego were studied. Differences in the distribution of number of cestode population in host population, size-age structure, and pre-reproductive/reproductive stages ratio of the studied parasites were revealed. It was demonstrated that the spatial structure of P. longicollis was shaped by the specific characteristics of vendace and smelt populations in the Lake Onego. These species possess partially overlapping ecological niches and differences in the use of food resources, significantly determining the infection dynamics of the examined fish species.

[MORPHOLOGICAL VARIABILITY OF PROTEOCEPHALUS PERCAE (MÜLLER 1780) PARASITIZING COREGONID FISHES].

Morphological variability of Proteocephalus percae from native host--perch Perca fluviatilis and two species of coregonids (whitefish Coregonus lavaretus and Arctic cisco C. autumnalis) from fish farms of Karelia were studied. Parasite groups from 3 host species differed by morphometric parameters. Morphological structure of P. percae from native host included three morphs, those numbers were almost equal. Parasite groups of whitefish and Arctic cisco differed from that of perch in morphological structure and dominance of different morphs. Changes of the P. percae morphological structure was related to differences in ecological niches of three hosts of parasite. This reflects the initial stages of microevolution. The results obtained allow us to estimate an adaptive response of parasitic worms to new host species settling to pond.

[Ecological and Biochemical Aspects of Parasite-Host Interactions in Transformed Aquatic Bodies: A Case Study of the Cestode Triaenophorus nodulosus and Its Host, the Northern Pike Esox lucius].

The lysosomal enzyme activities of the cestode Triaenophorus nodulosus and its host, the pike, in-aquatic bodies with different degrees of technogenic transformation (Northern Karelia, Russia) have been studied. As has been shown, iron-ore waste causes an increase in the acid phosphatase, nuclease, and beta-galactosidase activities of the host and a decrease in its beta-glucosidase and cathepsin D activities. As a rule, the changes in the same cestode enzyme activities are the opposite. With a decrease in the technogenic load, most of the studied characteristics display the trend of approaching the corresponding values observed in a clean lake. It is assumed that the host plays a leading role in the biochemical adaptation of the parasite and its host to mineral environmental pollution.

[Helminth fauna of the bank vole myodes glareolus (Schreber, 1780) in the Kizhi Archipelago].

The present study was aimed to examine the specific features of the helminth fauna in insular populations of the bank vole (Myodes glareolus) in the north of the species range. The material was collected in and nearby the Kizhi Archipelago (Lake Onega, 62°1' N 35°12' E) during August 1997, 2005-2007, 2012 and 2013. Small mammals were trapped on 23 islands (varying from 2 to 15,000 ha) and on the mainland. Helminthological met- hods were applied to examine 301 specimens of M glareolus. Fourteen helminth species were found: trematodes--Skrjabinoplagiorchis vigisi; cestodes--Paranoplocephala omphalodes, P. gracilis, Catenotaenia henttoneni, Taenia mustelae, Cladotaenia globife- ra, Spirometra erinacei; nematodes--Trichocephalus muris, Aonchotheca murissylvatici, Hepaticola hepatica, Heligmosomum mixtum, Heligmosomoides glareoli, Longistriata minuta, Syphacia petrusewiczi. The parasites S. vigisi, S. erinaci, H. hepatica and T. muris were identified in the bank vole in Karelia for the first time. Significant differences were detected between the helminth faunas of local insular populations of the bank vole. A distinctive feature of all small islands was that samples from them lacked the widespread pa- rasitic nematode Heligmosomum mixtum. The studies have confirmed the general trends observed in the parasite fauna of most isolated populations of small mammals: a poorer species diversity and high infestation rates with certain species of parasites. The Kizhi Archipelago is characterized by the specific high abundance of regionally rare parasite species (H hepatica, A. murissylvatici), and by the absence of common parasites (H. mixtum, H. glareoli).

[PARASITES OF THE COMMON ROACH (RUTILUS RUTILUS L.) UNDER THE IMPACT OF INDUSTRIAL POLLUTION OF A LAKE].

The consequences of man-induced transformation of Lake Kostomukshskoe (tailings dump) related to increased mineralization and entry of highly dispersed dredge material not typical for northern lakes were studied using roach parasites as the example. It was found that the roach parasite fauna has been losing rare and scant parasite species of different taxonomic groups, mainly helminthes with an indirect life cycle. Common and dominant species of myxosporidians, monogeneans, trematodes of genera Diplostomum and Tylodelphys have been preserved. The chances of survival are higher for those parasites with direct life cycle. Also the parasite species whose larvae can actively penetrate the host have been survived. The species Ligula intestinalis, Philometra rishta, Pseudocapillaria tomentosa had reported very rare. Fish are infected with these parasites by feeding of Copepoda and oligochaetes.

[Concerning the problem of the northern limit of Ixodes persulcatus (Acari: Ixodidae) distribution in Karelia].

The influence of changes in climate conditions on the abundance and formation of the northern limit of Ixodes persulcatus distribution in Karelia has been studied. It has been demonstrated that the territory in which the heat provision is sufficient for the development of ixodid ticks significantly increased during 2000-2007. Thus, it favored an increase in the abundance and enhanced distribution of I. persulcatus.

[Specific features of the numbers and structure of the population of Proteocephalus longicollis (Zeder 1800) (Cestoda: Proteocephalidea)--a mass parasite of whitefish Coregonus lavaretus L. under conditions of technogenic pollution of the water body].

The numbers, age structure, and morphological variation of the cestode Proteocephalus longicollis from whitefish of a natural water body (Kamennoe Lake) and those of Kostomuksha Lake polluted with wastes of the mining industry (Northern Karelia) have been studied. In the polluted water body, a high infestation of whitefish and domination of larval stages in the structure of the parasite population have been established. It is shown that under conditions of pollution, only one of the variations ofscolex signs dominates in the structure of phenotypic diversity. The size indices of cestodes are reliably smaller as compared with cestodes from the natural water body. The data obtained indicate that technogenic pollution determines a decrease in the intrapopulation diversity of P. longiocollis, and a decrease in the values of morphometric characters indicates inhibition of the morphophysiological state of individuals.

[Trematodes fauna of waterfowl birds in Karelia].

Trematode fauna of waterfowl birds of Karelia comprises 23 species; 8 of them are described from the region for the first time. Descriptions and figures of Urogonimus macrostomus, Neoeucotyle zakharovi, Hypoderaeum conoideum, Echinostoma robustum, Orchipedum tracheicola, Prostogonimus cuneatus P. ovatus, and P. rarus are given.

[Peculiarities of the biology and parasite fauna of juvenile Atlantic salmon (Salmo salar L.) in the Pista River (White Sea Basin), according to the Gyrodactylus salaris infestation].

Juvenile salmon Salmo salar m. sebago Girard from the Pista River system (the White Sea Basin) was investigated. The data on species composition and occurrence peculiarities of Gyrodactylus salaris Malmberg, 1957 are given. This monogenean is the alien species for the river system and it is recorded for the first time. It is shown that the distribution of the parasite abundance is can be described as the negative binomial distribution; variations of its parameters (k and p) were also characterized. Parasitological data obtained, as well as the data describing the characteristics of growth and age structure of juvenile salmon population, suggest the potential influence of G. salaris infection on the degree of survival of fishes in the lake-river system examined.

[Population biology of cestode genus Triaenophorus in natural and man-made water bodies].

A comparative study of the frequencies of occurrence and distribution of the abundances of pike parasites, tapeworms of the genus Triaenophorus, was carried out in natural lakes and water bodies contaminated by the Kostomuksha mining and concentration mill (Northern Karelia). We demonstrate that the wide presence of T. crassus and T. nodulosus in natural northern lakes is due to the diversity of aquatic organisms and the structure of trophic relations. The abundance of both species is modeled by the negative binomial distribution. Relations in the host-parasite system are stable. Estimates of the parameter k of the negative binomial distribution reflect the changes in the interactions in the host-parasite system. T. nodulosus has survived in the man-made water body storing the highly mineralized recirculated water from the mill. Disturbance-related distinctions were detected in the parameters of the T. nodulosus abundance distribution in the host population. In the Okunevoye Lake, where the water discharged from the tailings dump is more diluted, the infection rates in pike did not differ from those in undisturbed water bodies.

[Peculiarities of the parasitofauna of Atlantic salmon parr (Salmo salar L.), brown trout (Salmo truttae L.), and char (Salvelinus alpinus L.) in the Utsjoki River system (Northern Finland)].

Data on the parasite diversity in Salmonidae fish parr from different parts of the Utsjoki River obtained during 1993-1995 and 2006-2007 are presented. Three fish species, Salmo salar L., S. truttae L., and Salvelinus alpinus L., were examined on the presence of helminthes. Twenty species of salmon parasites were found, the majority of which are the parasites with complicated life cycles. Infusorians C apriniana piscium, myxosporidia Chloromyxum januaricus and Myxobolus neurobius, metacercaria of the genera Diplostomum and Apatemon, and the nematode Raphidascaris acus larvae were the most numerous in salmon parasite fauna. Brown trout had the most number of specific parasite species, whereas char was infested by protozoan parasites only.

[Microevolutionary aspects of morphological variability and specificity of cestodes by the example of Proteocephalus longicollis (Zeder, 1800) (Proteocephalidae), a parasite of Coregonids].

Morphological variability of the cestode Proteocephalus longicollis from the smelt Osmerus eperlanus L., which was spontaneously introduced into the Syamozero Lake, has been studied. It was established that P. longicollis became an abundant element of the smelt parasite fauna during last 20 years, thereby showing the absence of host specificity. It was revealed that morphological polymorphism of P. longicollis from smelt combines features of ecological forms characteristic for aboriginal host species, namely whitefish Coregonus lavaretus L. and vendace Coregonus albula L. Cestodes from smelt are more similar to ecological forms from whitefish by the characteristics of variability. It is concluded that colonization of a host species, which is new for a given water body, is accompanied by the forming of a new group of host, which contributes to the maintenance of the parasite number and to its population stability under changing conditions of freshwater ecosystems.

[Trematode fauna patterns of the freshwater fish on the border of the geographical range].

The trematode fauna of the fishes inhabiting Lake Ladoga are represented by forty-six species; nine species of which are found here on the northern boudary of their geographic range. The depauperization of the trematode fauna compared to the southern pools is a result both of the decreasing impact of the Pont-Caspian group and of the introduction of the boreal piedmont species complex. The increase in the biological productivity of Lake Ladoga for the last 50-year period leads to enrichment of the species biodiversity. The same process increases the invasion extensiveness by trematodes, which use fish as an intermediate host. The Diplostomida, the presence of which is crucial for the young fish survival rate, dominate among the trematodes.

[Abundance of larvae and nymphs of the taiga tick Ixodes persuicatus (Acari: Ixodidae) on small mammals in the cut-over lands of the middle taiga subzone of Karelia].

Data of long-term investigations (1998-2004) on the abundance of the taiga tick larvae and nymphs in the cut-over lands of different age in the middle taiga subzone of Karelia (62 degrees 04'S; 33 degrees 55'W) are presented. The investigation was carried out on three model cut-over lands of different age: 1) "young" cut-over land; age of cut-over in the beginning of investigation is 7 years; Betula-Deschampsia cespitosa-Agrostis tenuis; 2) "middle" cut-over land; age of cut-over is 12 years; Salix-Deschampsia cespitosa-Agrostis tenuis; 3) "old" cut-over land; age of cut-over 25 years; Alnus incana-Rubus idaeus-grass. The number of ticks was estimated by using common parasitological indices: prevalence, abundance, and index of feeding intensity (the tick abundance multiply by the number of small mammals per hundred traps-nights). In the beginning of investigation the "young" cut-over land was a typical meadow association. The lowest tick abundance was recorded here. That was a result of unfavorable abiotic conditions and low number of small mammals in the beginning of summer. "Middle" cut-over land is characterized by the highest number of the tick larvae, which is the evidence for high number of the hosts of tick imago. "Old" cut-over land has the optimum conditions for development of taiga ticks. High abundance of the ticks (larvae and nymphs) was recorded during the whole period of investigations. The number of preimaginal ticks is shown to be much higher in cut-over lands as compared with that in mixed and coniferous forests, due to the higher number of small mammals.

[Dynamics of the helminth fauna in the common shrew (Sorex araneus L.) from cut-over lands of different age in Karelia].

Species diversity of helminths in the common shrew from three cut-over lands of different age in Karelia was studied. It was shown, that change of the plant cover in cut-over lands have no a significant effect on the species diversity of helminth communities in Sorex araneus, but the abundance of individual parasite species changes considerably. Changes of the S. araneus infestation with helminths were the greatest in a new cut-over land. Structure of the helminth community comprises four categories of parasites (dominants--4 species, subdominants--8, rare species--13, very rare species--10) and depends on the time passed since the felling. A redistribution of the species constituting the core of the helminth fauna was to be observed. It was shown, that being an integrated indicator of the status of terrestrial ecosystems, parasites clearly indicate changes not in the structure, but in the abundance and domination of individual species of terrestrial invertebrates and vertebrates in cut-over lands.

[Population dynamics of glochidia of the freshwater pearl mussel Margaritifera margaritifera L., parasitizing on juvenile Salmonidae fishes in northern water reservoirs].

This paper presents data on the population dynamics of glochidia of the freshwater pearl mussel Margaritifera margaritifera L. (1758) (a declining species of European fauna), parasitizing on juvenile Salmonidae fishes in rivers of northern Europe. It was found that the number of glochidia parasitizing on gills of juvenile salmon and trout in explored water reservoirs are stimulated by negative binomial distribution. Estimation of the distribution parameter allows us to obtain statistically valid data on the population number of pearl mussel and to judge the stable character of interactions in the host-parasite system (balance of host specimens that are resistant and nonresistant to infection).

[Long-term changes in the parasite fauna of the bream Abramis brama L. in eutrophicated lake].

Data on the dynamics of parasite fauna if the bream Abramis brama for 50-year period are presented. The relation between trophic status of the reservoir, preferred type of the bream feeding, and the abundance of its parasites is shown. It was established, that the number of parasites developing in plankton organisms increases during the period of intensive eutrophication. Recent data on the parasite fauna of bream indicate preferred feeding of the host on benthic invertebrates, that is favourable to its growth. Permanent tendency to the increase of the bream invasion by the Diplostomum metacercaria could be a reliable parasitological indicator of the water body eutrophication.