Vannella pentlandii n. sp., (Amoebozoa, Discosea, Vannellida) a small, cyst-forming soil amoeba

We describe a new species of cyst-producing soil amoeba Vannella pentlandii from course pasture in the Pentland Hills, Scotland. Analysis of the 18S rDNA gene reveals that it belongs to the sub-group within the genus, presently composed of V. placida, V. epipetala and V. fimicola (the PEF group). This group share features such as longitudinal folds/ridges on the lamella (the anterior hyaline region of the trophozoite), stubby floating forms and cyst production. While each PEF species contain cyst producing strains, not all strains within these species do so. V. fimicola produces cysts on stalks leading to its former classification as a slime mould, however no such stalks were evident in the V. pentlandii, instead groups of cysts become piled on top of each other forming clumps. The encysting amoebae crawl toward each other, pushing some off the surface to form these mounds. The V. pentlandii trophozoites are of typical size for the genus but the cysts at 6.9 μm in diameter, are the smallest so far described in genus Vannella. Other cyst producing species are found in various branches within the Vannella phylogenetic tree, probably meaning that this ability was ancestral but lost in many branches (particularly in marine species), and perhaps re-gained in others.