The heterotrophic dinoflagellate Gyrodinium moestrupii n. sp. is described based on live cells and cells prepared for light, scanning electron, and transmission electron microscopy. In addition, sequences of the small subunit (SSU), internal transcribed spacers (ITS1 and ITS2), 5.8S, and the large subunit (LSU) of the rDNA were analyzed. The cells have a slender, fusiform body, taper to a sharp point at both apices, and are widest in the middle. The conical episome and hyposome are equal in size. A distinct elliptical bisected apical groove (AG) is present. Gyrodinium moestrupii has longitudinal surface striations (LSS) containing 14 and 23 lines in the episome and hyposome, respectively, whereas Gyrodinium dominans, morphologically the most similar species, has 14 and 18 lines, respectively. In addition, the episome and hyposome of G. moestrupii show distinct twists to the right and left, respectively, unlike those of Gyrodinium gutrula or G. dominans, which are not markedly twisted. The cingulum is displaced by 0.3-0.4 × cell length. Length and width of cells starved for 2 d were 23.9-38.2 and 12.0-18.6 μm, respectively, whereas those of cells satiated with Alexandrium minutum were 30.1-61.4 and 20.7-35.6 μm, respectively. The cells contain a pusule system, trichocysts, a lamellar-like structure, and a fibrous bundle, but lack chloroplasts. The SSU rDNA sequence differed by 0.2-3.9% from those of the three most closely related sequenced species for which data are currently available: G. cf. gutrula (FN669511), G. dominans (FN669510), and Gyrodinium rubrum (AB120003). The LSU rDNA was 3.2-13.9% different from G. dominans (AY571370), Gyrodinium spirale (AY571371), and G. rubrum (AY571369). The phylogenetic trees demonstrated that this novel species belongs within the Gyrodinium clade. Based on the morphological and molecular data, we propose to name it G. moestrupii n. sp.
© 2012 The Author(s) Journal of Eukaryotic Microbiology © 2012 International Society of Protistologists.