Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe Author Prokina, Kristina I. Author Zagumyonnyi, Dmitry G. Author Tikhonenkov, Denis V. text Acta Protozoologica 2018 57 4 243 266 http://dx.doi.org/10.4467/16890027ap.18.018.10094 journal article 10.4467/16890027AP.18.018.10094 1689-0027 12637411 Raphidiophrys intermedia Penard, 1904 ( Fig. 5E–H ) Description: Oval, rare triangular plate scales are 4.54–10.0×2.22–5.0 µm. Length to width ratio is 1.94– 3.84. Edges of scales are bent inside and form marginal rim 0.36–0.63 µm in diameter. Radial ribs extend from edges to the center, visible on the outer surface of the scales. Distances between ribs on marginal rim are 0.26–0.43 µm. Fig. 5. Morphology of observed scales of Raphidiophrys and Pterocystis genera (A–D, I–L – TEM; E–H, M–P – SEM): A–B – R. capitata (from sand of Lake Maklok); C–D – R. ovalis (from Sphagnum of Sphagnum bog Klukvennoye-1); E–H – R. intermedia (from plant debris and silt of Lake Maklok); I–L – P. foliacea (from sand of Usman’ River); M–P – P. pulchra (from plant debris and silt Lake Chistoye). E, I, M – scales of the single cell; A, B, C, D, F–H, J–L, N–P – spine and plate scales. Abbreviations: l.w – lateral wing; m.d – medial depression of plate scale; s.p – subapical protrusion; st – stalk. Other abbreviations as in Figs 2, 4. Scale bars: E, I – 10 µm; A, C – 5 µm; M – 3 µm; B, D, F–H, J–L, N–P – 1 µm. Fig. 6. Morphology of observed scales of Raineriophrys genera (A–C, E, F, I–L – TEM; D, G, H – SEM): A–D – R. echinata (A–C – from peat of Sphagnum bog Klukvennoye-2; D – from Sphagnum of Sphagnum bog Klukvennoye-3), E–H – R. erinaceoides (E, F – from water column of Lake Vosmerka; G, H – from plant debris and silt of Lake Cherepashye), I–L – R. fortesca (I – Vosmerka, J–L – Cherepashye). E, I – scales of the single cell; A–D, F–H, J–L – spine and plate scales. Abbreviations as in Fig. 2, 5. Scale bars: A, E, I – 10 µm; B–D, F – 5 µm; G, H, J–L – 1 µm. Distribution: Freshwaters of USA ( Wujek 2005 ), Australia (Croome 1987), Canada , Chile , New Zealand ( Nicholls and Dürrschmidt 1985 ), Sweden , Netherlands ( Siemensma and Roijackers 1988b ). It was found in Russia in freshwaters of European part (Leonov 2009, 2010a; Leonov and Mylnikov 2012 ; Prokina et al. 2017c ). Raphidiophrys ovalis (Dürrschmidt in Nicholls et Dürrschmidt, 1985 ) Siemensma et Roijackers, 1988 [bas.: Raphidiophrys orbicularis ssp. ovalis Dürrschmidt in Nicholls et Dürrschmidt, 1985 ; syn.: Raphidiophrys intermedia sensu Siemensma, 1981 ] ( Fig. 5C–D ) Fig. 7. Morphology of observed scales of unidentified species (TEM): A–C – Heterophrys -like organism (A – from plant debris and silt of Usman’ River; B, C – from plant debris and silt of Lake Krugloye; A – whole cell; B, C – spicules), D–F – unidentified Centrohelea sp. (from water column of Lake Vosmerka; D – scales of the single cell; E, F – plate scales). Abbreviations: sp – spicules. Other abbreviation as in Fig. 1. Scale bars: A, D – 10 µm; B, C, E, F – 1 µm. Description: Oval plate scales are 7.21×5.14 µm, with slightly narrowing elongated ends. Length to width ratio is 1.4. Dense marginal rim is 0.12–0.15 µm in diameter. Radial ribs extend from edges to the center, visible on the outer surface of the scales. Distances between ribs on marginal rim are 0.11–0.20 µm. Remarks: Morphology of observed scale corresponds to previous descriptions, except the smaller size of scales, observed by Nicholls and Dürrschmidt (1985) : 2.0–6.3×2.2–4.8 µm. Distribution: Freshwaters of Europe ( Siemensma and Roijackers 1988b ), N. America ( Wujek 2005 ), Chile , New Zealand , Japan ([as R. orbicularis ssp. ovalis ] Nicholls and Dürrschmidt 1985 ). It was found in Russia in freshwaters of Voronezh Region ( Leonov 2010a ). ****Pterista Shishkin et Zlatogursky, 2018 ***** Pterocystidae Cavalier-Smith et von der Heyden, 2007