Growth Biorhythms of the Freshwater Pearl Mussel Margaritifera margaritifera (Bivalvia,Margaritiferidae), Nemina River Population (Karelia)

Biology Bulletin - Individual linear growth was studied in 23 specimens of the freshwater pearl mussel Margaritifera margaritifera by measuring successive annual growth rings on the shell surface....     

Formation of parasite fauna in the bullhead (Cottus gobio L.) (Pisces: Cottidae)

The formation of parasite fauna in the bullhead Cottus gobio L. in different water bodies was examined. The largest number of parasite species including specific parasites was observed in the Onega and Ladoga lakes. It is suggested that the host and their parasites migrated namely from these water bodies to other part of the range of the bullhead.     

Comparative analysis of the growth of <Emphasis Type="Italic">Margaritifera margaritifera</Emphasis> (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.     

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.     

Biorhythms of <Emphasis Type="Italic">Margaritifera margaritifera</Emphasis> (Bivalvia,Margaritiferidae) Freshwater Pearl Mussel Growth: Population of Syuskyuyanioki River (Karelia)

It was demonstrated that individual linear growth of the Margaritifera margaritifera freshwater bivalve mollusk in Syuskyuyanioki River is accompanied by natural biorhythms. The periods of biorhythms, as well as growth retardation coefficients, vary widely and differ in different individuals. The periods of biorhythms in individual ontogenesis are approximately constant. Mean values of the growth retardation coefficients and periods do not depend on the biotope and are 0.114 ± 0.003 year^–1 and 3.88 ± 0.06 years, respectively. The possibility of thermodynamic nature of biorhythms is discussed.     

Irregularity of the linear growth of the <Emphasis Type="Italic">Margaritifera margaritifera</Emphasis> (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.     

Abundance of larvae and nymphs of the taiga tick <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> Schulze (Acarina,Ixodidae) on small mammals in deforested areas in the middle taiga subzone of Karelia

The data on long-term studies (1998–2004) of the population density of preimaginal stages of the taiga tick Ixodes persulcatus Schulze, 1930 collected from small mammals in deforested areas (foresting during 7, 12, and 25 years after forest cutting) in the middle taiga zone of Karelia are given. The lowest population density of I. persulcatus was observed in the most recently deforested area. The territory where forestation lasted for 25 years after deforestation was the most favorable biotope for the taiga tick development. Deforested areas, in comparison with secondary forests, are characterized by significantly higher population density of preimaginal stages of ixodid ticks; this phenomenon is determined first of all by the high population density of small mammals.     

The helminth fauna of the shrew genus Sorex (Insectivora: Soricidae) in the Kandalksha nature reserve

The helminth fauna of shrews (Sores araneus, S. caecutiens, S. minutus, S. minutissimus) from the Karelian coast and islands of the Kandalaksha nature reserve was studied. 18 helminth species belonging to 3 taxonomic groups, Trematoda (3), Cestoda (8), and Nematoda (7) were found. The main body of the helminth fauna of shrews is represented by the nematodes species Longistriata codrus, L. didas, and the cestode species Ditestolepis diaphana. Inhabiting of shrews in the insular localities leads to the decrease of the species diversity and the abundance of their helminths. The distribution ranges of the shrew parasites have been outlined more accurately.     

Seasonal dynamic of the infestation of young landlocked salmon (Salmo salar morpha sebago, Girard) by the monogenean species Gyrodactylus salaris

Seasonal dymanic of the infestation of young landlocked salmon (Salmo salar morpha sebago, Girard) by the monogenean species Gyrodactylus salaris Malberg, 1957 was studied in the river Lizhma, Karelia. It is established, that the temperature optimal for the development and reproduction of the parasite is about 3-8 degrees C. It is stated, that the abundance of G. salaris in the river Lizhma do not reach so high values, as it was observed in the regions outside the natural area of the parasite.