Description of Platyophrya sphagni
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Shape highly variable, depending on condition of cell, basically reniform to bursiform, anterior end more narrowly rounded than posterior, flattened laterally up to 2:1, transverse view thus ellipsoid. Specimens swimming for some time, for instance when samples were shaken repeatedly, usually become more slender, distinctly fusiform and slightly sigmoidal. Distinctly contractile and highly metabolic, fully contracted specimens about 30 um long and bursiform. Metaboly very conspicuous, but usually recognizable only under coverslip pressure and especially when burrowing for food in bacterial flocs. Such specimens lack a definite shape and behave like a naked amoeba. Nuclear apparatus in centre of cell, macronucleus globular in vivo 9-13 um across and studded with very small granules (bacteria?), nucleoli small and pale; micronucleus lenticular, in vivo about 4 x 2.5 um, in small indentation of macronucleus. Contractile vacuole distinctly subterminal near ventral side, excretory pore on right side beneath kineties 7 and 8, which are shortened, i.e. abut to pore. Cortex very flexible, about 1 um thick, bright, slightly orange-coloured by mucocysts. Mucocysts arranged in loose rows between somatic kineties, globular, 0.5-0.7 um across, very compact and thus distinctly bright, extend to up to 10 um long rods in silver carbonate impregnated cells. Cytoplasm colourless, but specimens appear bright green due to symbiotic algae. Food vacuoles 4-5 um across, usually containing U-shaped, colourless bacteria and/or ellipsoidal, reddish bacteria, both found in the slimy bacterial masses usually inhabited by P. sphagni; rarely, large diatoms are ingested. Swims rather fast, but usually P. sphagni burrows within smile bacterial masses showing great metaboly, as described above. Symbiotic algae ellipsoidal and highly variable in number, provide cell with conspicuous green colour. Chlorplast cylindrical with longitudinal furrow and 1-2 globular, acentral pyrenoids. Resting cysts globular, 34-38 um across (n = 4), green by symbiotic algae, have some brownish inclusions, possibly digested zoochlorellae. Cyst wall about 0.5 um thick, colourless, without recognizable ornamentation. (ref. ID; 2307) [Somatic and oral infraciliature] As described by Kawakami (1991) and in other members of genus, differing mainly in morphometric details. Ciliary rows slightly spirally arranged, composed of dikinetids throughout, both basal bodies of dikinetids ciliated at right side, anterior cilium lacking in most dikinetids of left side. Left side distinctly more loosely ciliated than right. Oral opening slightly subapical, minute (about 4 x 3 um) and thus difficult to recognize in live specimens. Paroral membrane C-shaped, cilia only 3 um long, stick together forming distinct membrane. Anteriormost adoral organelle frequently smaller than others, as in Japanese population (Kawakami, 1991), cilia of adoral organelles about 5 um long and directed backwards when inactive. Postoral pseudomembrane distinct, composed of 2 closely spaced rows each comprising 13-16 ciliated dikinetids. Silver line system also as in congeners (Foissner 1993), i.e. reticulate with distinct median silverline between each two ciliary rows on both sides of the cell. Frequently, granules occur in silverlines, very likely indicating mucocysts sites. (ref. ID; 2307) Measurements; Extended specimens in vivo about 60 x 28 um, size, especially length little altered by preparation procedures, specimens impregnated with protargol or the dry silver nitrate method shrunken 10% on average. Wilhelm Foissner and M.Kreutz; Redescription of Platyophrya sphagni (Penard 1922) Foissner 1993 (Protozoa, Ciliophora). Linzer biol.Beitr. 28/2:745-756, 1996
