A Description of Seven Antarctic Marine Gymnamoebae Including a New Subspecies, Two New Species and a New Genus: Neoparamoeba aestuarina antarctica n. subsp., Platyamoeba oblongata n. sp., Platyamoeba contorta n. sp. and Vermistella antarctica n. gen. n. sp.

. Seven marine gymnamoebae were isolated from different environments of seawater, slush (pack ice meltwater), and sediment in the Ross Sea area of Antarctica. All amoebae were isolated and maintained at temperatures below 4°C. Growth, rate of locomotion, and general morphology were observed at an environmentally appropriate temperature (1°C) and at room temperature (∼25°C). Molecular (srDNA sequences) and microscopical techniques were used to identify the gymnamoebae and establish their phylogenetic affinities. Three isolates (S‐131‐2, SL‐200, and W4‐3) were assigned to a psychrophilic subspecies of Neoparamoeba aestuarina , N. aestuarina antarctica n. subsp., one isolate (S‐205) was assigned to a new species of Platyamoeba , P. oblongata n. sp., two isolates (W51C#4 & W51C#5) were also assigned to a new species of Platyamoeba, P. contorta n. sp., and one isolate (S‐241) was a novel psychrophilic gymnamoeba Vermistella antarctica n. gen. n. sp. Molecular and morphological results revealed that V. antarctica was not related to any described family of gymnamoebae. Strains S‐205, W51C#4, and W51C#5 were capable of locomotion at room temperature, while strains SL‐200, S‐131‐2, W4‐3, and S‐241 exhibited locomotion only below ∼10°C. Our results imply that the Antarctic environment is host both to cosmopolitan gymnamoebae that have acquired adaptations for existence at low environmental temperature and to apparently novel psychrophilic amoebae described here for the first time.