The diversity of heterolobosean amoebae, important members of soil, marine and freshwater microeukaryote communities in the temperate zones, is greatly under-explored in high latitudes. To address this imbalance, we studied the diversity of this group of free-living amoebae in the Arctic and the Antarctic using culture dependent methods. Eighteen strain representatives of three heterolobosean genera, Allovahlkampfia Walochnik et Mulec, 2009 (1 strain), Vahlkampfia Chatton et Lalung-Bonnaier, 1912 (2) and Naegleria Alexeieff, 1912 (15) were isolated from 179 samples of wet soil and fresh water with sediments collected in 6 localities. The Allovahkampfia strain is the first representative of the genus from the Antarctic; 14 strains (7 from the Arctic, 7 from the Antarctic) of the highly represented genus Naegleria complete the 'polar' cluster of five Naegleria species previously known from the Arctic and Sub-Antarctic regions, whereas one strain enriches the 'dobsoni' cluster of Naegleria strains of diverse origin. Present isolations of Naegleria polarisDe Jonckheere, 2006 from Svalbard, in the Arctic and Vega Island, in the Antarctic and N. neopolarisDe Jonckheere, 2006 from Svalbard and Greenland in the Arctic, and James Ross Island, the Antarctic demonstrate their bipolar distribution, which in free-living amoebae has so far only been known for Vermistella Morand et Anderson, 2007.
Morphological and molecular characterizations of three newly isolated tubulinean strains and re-examination of five strains formerly considered representatives of Saccamoeba and one strain formerly considered as Trichamoeba resulted in (a) the determination of strain BA02, isolated from a dripping rock ledge in Skansbukta (Billefjorden, Svalbard), as a new representative of Ptolemeba bulliensis Brown et al., 2014; (b) identification of strain ATCC(?) 50249?, deposited in the American Type Culture Collection as Trichamoeba, as the same species (P. bulliensis); (c) characterization of the new strain POHL into the Saccamoeba clade as a member closely related to S. lacustris; and (d) changing the generic residence of three strains formerly considered as representatives of Saccamoeba (strain PV67 to the P. bulliensis clade, and W187G and DP7 into the sister group of Ptolemeba noxubium Brown et al., 2014) whereas two other strains (MSED6, NTSHR) retain their original Saccamoeba clade position. Within the individual clades, the ultrastructure (especially the inner architecture of mitochondria) is congruent and thus of superior taxonomic value to that of light microscopic (morphometric) features.
A new amoebozoan species, Vermistella arctica n. sp., is described from marine habitats in the central part of Svalbard archipelago. This is the first report on Arctic amoebae belonging to the genus Vermistella Moran and Anderson, 2007, the type species of which was described from the opposite pole of the planet. Psychrophily proved in the new strains qualifies the genus Vermistella as a bipolar taxon. Molecular phylogenetic analyses based on 18S rDNA and actin sequences did not show any affinity of the genus Vermistella to Stygamoeba regulata ATCC(®) 50892(™) strain. A close phylogenetic relationship was found between Vermistella spp. and a sequence originating from an environmental sample from Cariaco basin, the largest marine permanently anoxic system in the world. Possible mechanisms of bipolar distribution are discussed. This article is protected by copyright. All rights reserved.