Data concerning the occurrence and abundance of the taiga tick Ixodes persulcatus in eastern Finland (North Karelia and Kainuu regions) are presented. Sampling was carried out in May 2008 and June 2009, around the University of Joensuu Mekrijärvi Research Station and the City of Kuhmo. In 2008 and 2009, the abundance of adult taiga ticks in the first study area was 0.17 and 0.13 ticks per flag-km, respectively. Only a single I. persulcatus specimenwas found in the second study area (abundance was 0.02 specimens per flag-km). All ticks (635 specimens) collected from cats and dogs in south-eastern Finlandwere identified as Ixodes ricinus.

The freshwater pearl mussel Margaritifera margaritifera is a unionid species distributed across Northwestern Russia, Fennoscandia, Western and Southwestern Europe, and the Atlantic Coast of North America. In this study, we reconstructed the post-glacial expansion routes of this species based on FST genetic distances and the fact that M. margaritifera distribution is directly connected with salmonid expansion. The freshwater-pearl-mussel populations from North America and Northeastern Europe were the closest groups, judging by FST distances, supporting the concept of the North Atlantic Salmo salar colonization of the Barents and White Sea basins. We also documented that unique haplotypes in the populations of the Baltic and White Sea basins may have originated in isolated glacial refugia in Eastern and Northeastern Europe. The Iberian clade was the most distant group of populations, which is consistent with the previously observed role of the Iberian Peninsula as a glacial refugium. The high genetic diversity in the populations of Northern and Eastern Karelia was facilitated by migrants utilizing complex periglacial hydrological networks and by admixture in the contact zone where the migration flows met. We confirm that this region should be considered as a major center of genetic diversity within the European part of the species’ range.

Data are presented on the distribution and state of populations of a rare species, the European freshwater pearl mussel, in the rivers of Karelia. Populations of Atlantic salmon in the rivers surveyed, and pearl mussel glochidial infection in salmon juveniles were analyzed. It is demonstrated that timber floating, hydropower engineering, pearl harvesting and deforestation have resulted in extinction of the pearl mussel in several rivers. Decline in juvenile salmon abundance has negative influence on the pearl mussel recruitment. However, our data prove that Karelia, both the White Sea and the Baltic Sea catchments, still possesses viable populations of the pearl mussel.

Diplostomum is a taxonomically problematic genus of trematodes, with many members harmful at the metacercarial stage to fish in aquaculture. We found metacercariae in the eye vitreous humor of the rudd, Scardinius erythrophthalmus; the bleak, Alburnus alburnus; and the roach, Rutilus rutilus, in Karelia (Russia) and identified them as Diplostomum numericum based on a combination of morphological and ecological data. Previously, D. numericum was thought to be conspecific with Diplostomum gavium. However, our phylogenetic analysis based on the sequences of the cox1 mitochondrial DNA gene did not support this hypothesis. We demonstrated the conspecificity of D. numericum with the larval trematode Diplostomum sp. Lineage 3 of Blasco-Costa et al. (2014) from the eye vitreous humor of European salmonid and cyprinid fishes. Therefore, we resurrected the species D. numericum and identified Diplostomum sp. Lineage 3 of Blasco-Costa et al. (2014) as D. numericum. Finally, we hypothesized that D. numericum was, in fact, conspecific with Diplostomum colymbi and that the latter was distinct from D. gavium sensu stricto.

This paper presents data on the population dynamics of glochidia of the freshwater pearl mussel Margaritifera margaritiferaL. (1758) (a declining species of European fauna), parasitizing on juvenile...