Roombia truncata Okamoto et al. 2009

Lee, Won Je, 2015, Small Free-Living Heterotrophic Flagellates from Marine Sediments of Gippsland Basin, South-Eastern Australia, Acta Protozoologica 54 (1), pp. 53-76 : 63

Roombia truncata Okamoto et al. 2009 ( Figs 1h , 3g –h )

Observation: Cells are oblong, 11 to 16 µm long, laterally flattened, and rigid. There are no surface struc- tures on both faces of the cell. Two flagella arise near the anterior-lateral side of the cell separately by a small protrusion. Both flagella are of similar length and not acronematic. The anterior flagellum beats backwardly in a small excursion and the posterior flagellum is usu- ally held down. The nucleus is located in the centre of the cell. The cells appear to move by skidding. When the cells rest, the anterior flagellum lies along the mar- gin of the cell. Rarely observed.

Remarks: This species was reported from a marine habitat in Nova Scotia, Canada by Okamoto et al. (2009). It is similar to Platychilomonas , but is distinguished by the flagellar orientation and the lack of the gullet, and because this species lacks rows of extrusomes. It can be distinguished from other small flagellates by the moving behaviour and the cell ap- pearance such as flatness and lack of surface structure. This species was also observed at marine sediments in subtropical Australia and Korea (Lee unpublished data).

Figures

Fig. 1. a – Chilomastix cuspidata, b – Rhynchopus amitus, c – Spironema multiciliatum, d – Psammosa unguis nov. comb., e – Apusomonas sp., f – Rhynchobodo formica, g – Mantamonas plastica, h – Roombia truncata, i – Thaumatomastix setifera, j – Ancyromonas impluvium nov. spec., k – Helkesimastix faecicola, l – Kurnaimonas celerisnov. spec., m – Sinistermonas sinistrorsus nov. spec., n – Kiitoksia kaloista, o – Protist ‘1’. Scale bar: 10 µm for all figures.

Fig. 3. a–b –Rhynchobodo formica; c –Massisteria marina, general appearance of cell showing pseudopodia and flagella (arrow); d–f – Cercomonas sp.; d – note two acronematic flagella; e – general appearance; f – note flagellar orientation; g–h – Roombia truncata, note cell attached to the substrate by the tip of the posterior flagellum and note extrusomes; i – Protaspa obliqua, note anterior protrusion;j–k – Thaumatomastix setifera, note spines around the body; j – general appearance of cell; k – ventral face showing a deep groove and pseudopodia; l–m – Ancyromonas sigmoides of different cells; l – note slightly thick anterior flagellum with acronematic tip and broad rostrum; m – note thick anterior flagellum and acute rostrum; n–p – Ancyromonas impluvium nov. spec., showing general appearance of cell and note flagellar insertion.All micrographs are DIC images with the exceptions of (d) and (p) which are phase contrast images. Scale bar: 5 µm for all figures.