Vannella russkaya sp. nov. (Amoebozoa, Discosea) - a new marine amoeba from a terrestrial habitat.

A new amoeba species, Vannella russkaya sp. nov., is described based on morphological (light and transmission electron microscopy) and molecular (SSU rRNA and Cox1) analyses. The strain was isolated from soil near a brackish stream, Solonik (Novgorod Region, Russia), and was cultivated under marine conditions. Phylogenetic analysis placed the new species within a clade comprising predominantly marine Vannella, with the closest affinity to V. salarenaria, which was also found in soil and cultivated under marine conditions. The studied strain exhibits a broad tolerance to salinity from 5‰ to 50‰, with trophic forms observed. Notably, it does not form cysts under the tested salinities. These features suggest adaptation to saline-influenced terrestrial environments rather than strictly aquatic habitats. The phylogenetic relationship with marine taxa, combined with isolation from soil, suggests an ecological shift across habitat boundaries. This highlights the significance of transitional environments, such as brackish soil, as reservoirs of previously unrecognized protist diversity, demonstrating that saline-influenced terrestrial habitats can harbor lineages typically regarded as marine, thereby extending the known ecological range of the genus Vannella.