Eltonia chernetsovi gen. et sp. nov. (Heterolobosea, Eutetramitea) from an ecologically diverse clade comprising closely related soil and seawater species

A novel amoeboid protist, Eltonia chernetsovi gen. nov., sp. nov., was isolated from saline mud collected in the Elton Lake area, Russia (ca. 200–500‰) and characterized morphologically and molecularly. Only amoeboid cells and cysts were found. In amoebae, eruptive cytoplasmic flow and hyaline bulging are evident during non-directional movement. Cysts are spherical with a smooth wall. The nucleus has a large eccentric nucleolus. Experimental analysis of salinity tolerance shows that the strain, initially observed and cultivated in seawater with a salinity of 40‰, may survive freshwater conditions in an encysted form, but does not reproduce in freshwater conditions below 5‰ or in hypersaline conditions at 70‰ or higher. Amoebae demonstrate a short period of reproduction at a temperature of 37 °C; however, they rapidly encyst afterwards. Phylogenetic analyses of the SSU rRNA gene and ITS region place the new strain in a clade with two undescribed species from agricultural soil habitats, suggesting a broad range of biotopes where representatives of this clade may occasionally occur. We establish a new genus for this clade, which branches within Eutetramitea (Heterolobosea) and is related to the marine Oramoeba fumarolia, cf. Stachyamoeba sp. ATCC 50324, and the soil species Vrihiamoeba italica.