Morphology and molecular phylogeny of Trimyema koreanum n. sp., a ciliate from the hypersaline water of a solar saltern.

A new ciliate, Trimyema koreanum n. sp., isolated from hypersaline water (salinity of 293 per thousand) from a solar saltern in Korea, was investigated using live observation, protargol impregnation, and gene sequencing. Trimyema koreanum is about 30 x 13 microm in vivo, has usually 23 longitudinal ciliary rows forming two distinct ciliary girdles visible both in vivo and in protargol impregnation. A third indistinct ciliary girdle as well as a girdle of mucocysts is distinguishable only in impregnated cells. We suggest T. koreanum as a new species, differing from the most similar species, T. marinum, by the presence of two distinct ciliary girdles (T. marinum usually has six ciliary girdles clearly visible in living cells and three anterior spirals that encircle the cell completely). Although the number of known 18S rRNA sequences in the genus Trimyema was limited, the Trimyema group including T. koreanum forms a strong clade. The phylogenetic position confirms that the isolate belongs to the genus Trimyema and is different from previously sequenced species. Trimyema koreanum is able to consume both prokaryotes and small eukaryotes (specifically, the alga Dunaliella sp.).