Apusomonadida Karpov et Mylnikov, 1989

Lee, Won Je, 2019, Small Free-Living Heterotrophic Flagellates from Marine Intertidal Sediments of the Sydney Region, Australia, Acta Protozoologica 58 (4), pp. 167-189 : 180

Apusomonadida Karpov et Mylnikov, 1989 Apusomonas proboscidea Aléxéieff, 1924

Figs 2r , 3a

Description: Cells are 4–12 µm long and dorso-ventrally flattened with a V-shaped structure on the ventral side of the cell. Cell outline is roundish to slightly ovate. The mastigophore emerges from a cavity about two thirds of the cell length from the anterior end, is highly flexible and may be withdrawn into the sheath when the cell is stressed – the mastigophore may become wrinkled. The anterior flagellum is partly in a sleeve, which arises at the distal end of the mastigophore. The length of the flagellum plus the mastigophore is longer than the cell. On the dorsal side, there is no structure. The cells glide closely to the substrate. Rarely observed. Description based on records of 4 cells.

Remarks: Apusomonas proboscidea has been usually found from freshwater sites and soils (e.g. Vickerman et al. 1974; Karpov and Zhukov 1980, 1986) with the ranges of cell length from 9 to 14 µm. This species has a junior synonym, Rostromonas applanta Karpov et Zhukov, 1980 . This is the first observation for the species in marine habitats. Apusomonas proboscidea is similar to Apusomonas australiensis Ekelund et Patterson, 1997 reported from a cultivated garden soil with cell length from 6 to 10 µm ( Ekelund and Patterson 1997), but is distinguished by having a V-shaped structure on the ventral side of the cell and by the lack of the conspicuous pointed bulge that is a diagnostic character of A. australiensis ( Ekelund and Patterson 1997) .

Figures

Fig. 2. (a)–(b) Mastigamoeba psammobia, (a) general appearance of cell, note cytoplasms drawn from the posterior end, (b) general appearance of different cell and note pseudopodia. (c) Hexamita inflata, general appearance, note the nucleus. (d) Trepomonas agilis, general appearance of cell. (e) Chilomastix cuspidata, showing general appearance. (f) Stephanopogon sp., showing general appearance. (g) Saepicula pulchra, showing general appearance of cell. (h)–(j) Goniomonas amphinema. (h) Form I, (i) Form II, (j) Form III, note flagellar ar- rangement. (k) Roombia truncata, note attached cell to the substrate by the tip of the posterior flagellum, note extrusomes, surface striations and deep gullet. (l) Telonema subtilis, showing general appearance. (m) Harpagon descissus, general appearance of cell. (n)–(o) Spironema multiciliatum, (n) general appearance of cell, (o) note the kinetics. (p) Psammosa unguis, general appearance of cell. (q) Bicosoeca conica, general appearance of cell. (r) Apusomonas proboscidea, genera appearance of cell, note the V-shaped structure on dorsal face. All micrographs are DIC images except for (b), which is phase contrast images. Scale bar in (r) = 10 μm for all figures.

Fig. 3. Apusomonadida, Cercomonadida, Protaspidae, Thaumatomonadidae and Protista incertae sedis. (a) Apusomonas proboscidea, (b) Cercomonas parva, (c) Cercomonas sp.1, (d) Cercomonas sp.2, (e) Protaspa flexibilis sp. nov., (f) Thaumatomastix sp., (g) Eoramonas jungensis sp. nov., (h) Gweamonas unicus, (i) Phyllomitus undulans (from Lee 2002a), (j) Protist 1, (k) Protist 2. Scale bar = 10 μm for all figures.