Rhynchopus amitus Skuja 1948

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 : 60

Rhynchopus amitus Skuja 1948 ( Figs 1b , 2p–q )

Observation: Cells are 11 to 18 µm long, sac shaped, but markedly and actively flexible and contractile. There is a fine apical papilla, which has slightly thickened mar- gin and is an ingestion organelle. A conspicuous flagel- lar pocket, about 2 µm deep, opens immediately below the papilla and is directed anterio-laterally. Most cells have very short flagella, which do not emerge from the pocket, but a few cells observed had two thickened flag- ella, 0.5 to 1 times the cell length. These flagella are directed posteriorly and usually inactive. The posterior half of the cell often contains large food vacuoles. The cells move by gliding. Rarely observed.

Remarks: This species was described from a freshwater site in northern Europe by Skuja (1948) and a marine site in Australia ( Al-Qassab et al. 2002). Rhynchopus conscinodiscivorus was reported from a marine habitat by Schnepf (1994), but was regarded as a junior synonym of R. amitus by Al-Qassab et al. (2002). Al-Qassab et al. (2002) suggested that Menoidium astasia reported from a hypersaline habitat (Marion Bay, South Australia) is a senior synonym of R. amitus because it is flexible and has two long flagella or no flagella at times. Rhynchopus is difficult to distinguish from Diplonema , but trophic cells in Diplonema have emergent flagella of a ‘normal’ thickness. Rhynchopus only has emergent flagella in a ‘dispersal phase’ and these flagella are considerably thickened by paraxonemal rods (Simpson 1997). Further studies are needed to establish the identities of the genera, Diplonema and Rhynchopus .

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. 2. a – Chilomastix cuspidata, showing general appearance of cell; b – Goniomonas amphinema, showing general appearance of cell; c – G. pacifica, note two flagella diverging; d – Percolomonas similis, note ventral groove; e – Bodo platyrhynchus; f – Neobodo curvifilus; g – N. saliens; h–i – Hemistasia phaeocysticola, note a papillum (arrow); j – Bordnamonas tropicana, showing general appearance and mouth (arrow); k – Rhynchomonas nasuta; l–o – Rhynchobodo simius; l – tubular ingestion organelle (arrow); m, o – showing groove; n – general appearance of cell; p–q – Rhynchopus amitus; r–s – Spironema multiciliatum; t – Amastigomonas debruynei, general appearance of cell; u – Amastigomonas mutabilis, note anterior flagellum projecting from sleeve and recurrent flagellum; v – Apusomonas sp.; w – Psammosa unguis nov. comb., general appearance of cell; x–y – Mantamonas plastica; x – note anterior flagellum (arrow) and y – ventral depression.All micrographs are DIC images. Scale bar: 5 µm for all figures.