Narrow-clawed crayfish in Finland: Aphanomyces astaci resistance and genetic relationship to other selected European and Asian populations

The narrow-clawed crayfish (Pontastacus leptodactylus) is an alien species in Finland with only a few populations reported from the southeastern region during the last century. We discovered a productive population in the lake Jängynjärvi, which is upstream from the previously reported wild narrow-clawed crayfish population in that region. Preliminary studies indicated that this population is not infected with Aphanomyces astaci. We collected narrow-clawed crayfish samples from the lake Jängynjärvi population for both infection challenge and genetic studies, in order to investigate possible A. astaci resistance among this Finnish population and to evaluate their phylogenetic position that would enable us to speculate different scenarios of distribution pathways or origin of the population. The infection studies indicated that the narrow-clawed crayfish in this population were more resistant against A. astaci infection (B haplogroup A. astaci) compared to the noble crayfish (Astacus astacus) from the lake Rytky in North Savo, while all crayfish of both species in the B haplogroup A. astaci challenged groups died within 58 days post-infection. Results of the phylogenetic reconstruction indicate that the lake Jängynjärvi narrow-clawed crayfish are closely related to narrow-clawed crayfish from the lake Bolshoye near Krasnoye, located on the White Sea island of Solovestky and also populations from Tyumen region, both in Russia. This could confirm previous speculations about introduction of the narrow-clawed crayfish from Russia into Finland or could indicate previous hydrological connection.