E. P. Ieshko

Long-Term Population Dynamics of Ixodid Ticks and Development of Tick-Borne Encephalitis Foci under Conditions of the Middle Taiga Subzone

Long-term (1995–2003) population dynamics of ixodid ticks and their main hosts (small mammals) and conditions providing for the formation of tick-borne encephalitis (TBE) foci were studies in the middle taiga subzone (Karelia). The results show that the bank vole (Clethrionomys glareolus Schr.) is the main host for the larvae and nymphs of Ixodes persulcatus Schulze, 1930 and for the larvae, nymphs, and adult individuals of I. trianguliceps Birula, 1895. The proportion of ticks feeding on this species (relative to their total number) reaches 63.3% (64.0% of I. persulcatus and 61.1% of I. trianguliceps). Activity of a TBE focus is determined primarily by the abundance of bank voles of older age groups.

The European whitefish, Coregonus lavaretus (L.), under conditions of technogenic pollution in the Kostomuksha tailing pond

The population structure and biological parameters of the European whitefish, Coregonus lavaretus (L.), have been analyzed in a technogenically polluted water body. The biochemical state of the whitefish and the fauna and morphology of helminths parasitizing them have been assessed. It is shown that the species composition of the fish, plankton, benthos, and parasite faunas of this water body are depleted and the morphological parameters of common fish parasites are altered. It is noted that, in addition to adaptive rearrangements in biochemical metabolism, the whitefish from the transformed water body are characterized by a reduction in the level of protein synthesis in muscles and the rate of aerobic energy metabolism in the liver and muscles.

Comparative analysis of the growth of Margaritifera margaritifera (Bivalvia) from different populations of Karelia and Kola Peninsula

Comparative analysis of individual linear growth of Margaritifera margaritifera populations from the Syuskyuyanioki, Nemina, Vuokinioki, Keret (Karelia), and Varzuga (Kola Peninsula) rivers has been performed. Data on the lengths of consecutive annual growth rings on the external shell surface have been obtained. The comparative analysis has been made of two coefficients of the united growth equation, one of which determines the initial growth rate; the other determines growth inhibition. Growth parameters are assumed to vary greatly within each population and differ significantly between different specimens. The values of the coefficients decrease with increasing geographical latitude of the habitat. It is shown that the population in the Syuskyuyanioki River is comparable with respect to the growth constant with the southernmost populations of rivers in Northern Spain.

The ecology of the freshwater form of the Atlantic salmon Salmo salar L., the brown trout Salmo trutta L., and the freshwater pearl mussel Margaritifera margaritifera L. in Syuskyuyanyoki River (Basin of Lake Ladoga)

The locations and the area of the spawning–growing grounds have been assessed in the Syuskyuyanyoki River (the basin of Lake Ladoga), as has the population density of the juveniles of the freshwater form of the Atlantic salmon and the brown trout. The Atlantic salmon spawns at present on the rapids downstream of the hydroelectric power plant because of the insurmountable dam; the population density of this species has decreased dramatically. Only the landlocked form of the brown trout was found; the anadromous form was not. The brown trout has resettled along the major part of the river. We suggest that there are two subpopulations of the freshwater pearl mussel that differ with regard to the host for their larvae. The intensity of invasion of the juveniles of salmonids by the larvae of the freshwater pearl mussel and the survivability of glochidia did not depend on the host species. The growth rate of the mollusks and the age–size structure of the freshwater pearl mussel population have been assessed.

The freshwater pearl mussel Margaritifera margaritifera L.: Metamorphosis, growth, and development dynamics of encysted glochidia

The growth and morphogenesis of glochidia of the freshwater pearl mussel Margaritifera margaritifera on the gills of the Atlantic salmon Salmo salar in the Syuskyuyanyoki River (Karelia) are studied. Comparative analysis of histological features of glochidia depending on the age of the cyst is made, and the results of studies of the relationship and the influence of seasonal changes in water temperature on growth and morphogenesis of glochidia, which is essential for adaptation of living organisms and ensuring the sustainability of the participants of the parasite–host relationship, are presented.

Comparative characteristics of the lipid status of gills of juvenile Atlantic salmon infected with glochidia of the freshwater pearl mussel living in rivers of the European North

A comparative study of the lipid status of gills of juvenile Atlantic salmon infested with glochidia of the freshwater pearl mussel inhabiting the Vuokinyoki (White Sea basin) and Syuskyuyanyoki (basin of Lake Ladoga) rivers in the fall is carried out. The most infested gills of juvenile salmon and the lower water temperature (1.3°C) in the Vuokinyoki River reveal higher cholesterol levels and cholesterol/phospholipids ratios, which are due to the influence of infection factors; thereby they slow down biochemical processes. It is noted that variations in the lipid composition in juvenile salmon the gills of which are infected with glochidia reflect the development of adaptive responses that maintain homeostasis of juveniles under invasion.

Irregularity of the linear growth of the Margaritifera margaritifera (Bivalvia: Margaritiferidae) population of the Syskyanjoki River, Karelia

The interdependence of shell growth in length and height during ontogeny has been studied in the pearl mussel Margaritifera margaritifera, inhabiting the Syskyanjoki River (basin of Lake Ladoga, Karelia). It was shown that by the height-to-length ratio of the shell the population is heterogeneous. The question of whether this is due to the heterogeneity of genetic variability or due to variations in the environmental conditions remains unclear. It was found that during the ontogeny of the M. margaritifera from the population there is a constant change in the relative growth of the shell, leading to lengthening or rounding of the shell. Conventionally, all mussels can be divided into two groups, different by the periods of change in the relative growth. A comparison of the results with the data obtained previously for pearl mussels of the Varzuga River (basin of the White Sea, Murmansk oblast) was performed.

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 β-galactosidase activities of the host and a decrease in its β-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.

Characteristics of parasitic infection in the least cisco, Coregonus sardinella valenciennes, 1848, in the Ural tributaries of the lower Ob

Data on the parasite fauna of the least cisco, Coregonus sardinella Valenciennes, 1848 in Ural tributaries of the Ob downstream of the city of Salekhard have been obtained for the first time. The formation patterns of the parasite fauna in this species and the rate (prevalence and intensity) of infection by Ichthyocotylurus erraticus (Odening, 1969), a parasite specific to coregonids, have been revealed. Infection of the least cisco with six parasite species (out of the 12 species found) occurs as the fish feed on zooplankton and benthic organisms. The dominant parasites are trematode larvae of the genera Ichthyocotylurus and, in some years, Diplostomum; this composition of dominants is evidence that the least cisco fattens up mainly in shallow areas. All sexually mature fish of this species were found to be infected by I. erraticus, but the average intensity of infection was rather low: the abundance index of the parasite did not exceed 40 ind. per fish. Analysis of the distribution of I. erraticus metacercariae in the least cisco shows that the relationship in the host-parasite system is stable and the parasite has no pathogenic effect on individuals of older age classes.

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.