taxonID	type	description	language	source
32645169EC1CFF88FF51FA46F264FB98.taxon	description	Description: Spine scale consists of a straight cylindrical shaft and a circular flattened base. Shaft is 3.88 – 5.98 µm in length, 0.12 – 0.21 µm in diameter, base is 0.63 – 0.93 µm in diameter. Tip of shaft divided into 4 rounded furcae (Fig. 2 D) or hooks (Fig. 2 C) 0.10 – 0.16 µm in length. Oval plate scales are 1.98 – 2.47 × 1.42 – 1.68 µm, with medial thickening (0.75 – 1.51 × 0.12 – 0.19 µm) and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF88FF51FA46F264FB98.taxon	discussion	Remarks: A. amura was previously found only in the Far East and Orenburg Region, Russia (Zlatogursky et al. 2017). The presence of two types of spine scales was noted for this species: long spine scales (1.3 – 6.2 µm) with rounded hooks on tips; short spine scales (1.0 – 3.4 µm) with 3 – 5 pointed furcae. We observed only long spine scales with round hooks or round furcae. Morphology of plate scales agreed well with the original description.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF88FCADFBE9F59FF917.taxon	description	Description: Straight or slightly curved spine scales consist of a hollow shaft and circular base. Shaft is 5.0 – 10.78 µm in length and 0.29 – 0.34 µm in diameter, base is 0.96 – 1.21 µm in diameter. Tip of shaft divided on 4 – 6 furcae (0.43 – 0.65 µm in length). Oval plate scales are 3.18 – 3.78 × 1.59 – 2.15 µm, with concave lateral sides, medial thickening (0.55 – 0.72 µm in length) and dense margins. Some plate scales have numerous small granules (Fig. 2 I), others are ornamented with about 50 short (0.15 – 0.27 µm) radial slits (Fig. 1 H).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF88FCADFBE9F59FF917.taxon	discussion	Remarks: This species was previously noted only once from the freshwater pool in the greenhouse of the botanical garden of St. Petersburg State University, St. Petersburg, Russia (Zlatogursky 2015). Morphology of observed scales completely corresponds with the original description.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF8CFCADF97EF575FE89.taxon	description	Description: Spine scales consist of hollow cylindrical shaft and circular base. Shaft is 2.36 – 7.97 µm in length, 0.16 – 0.22 µm in diameter, base is 0.68 – 0.97 µm in diameter. Tip of shaft divided on 3 short rounded furcae (0.15 – 0.20 µm in length). Oval plate scales are 2.42 – 3.18 × 1.51 – 2.04 µm, with radial, branched ribs (Fig. 2 M) 0.34 – 0.67 µm in length, and medial thickening (0.59 – 0.68 µm in length).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF8CFCADF97EF575FE89.taxon	discussion	Remarks: A. elenazhivotovae was previously noted only once from the waterlogged habitat of Yaroslavl Region, Russia (Leonov 2010 b). Scales with 2 furcae were also observed but the possibility of a third hidden furca is not excluded. Morphology of observed scales corresponds to the original description, except with slightly larger sizes. Leonov noted spine scales length 3.2 – 6.0 µm, size of plate scales 2.5 – 2.8 × 1.6 – 1.8 µm. Plate scales of this species are similar to plate scales of A. quadrifurca Nicholls, 1983, however, the last one has 4 pointed furcae on the tips of the spine scales. Acanthocystis mikrjukovii Leonov, 2010 (Fig. 2 N – Q)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF8CFCADF97EF575FE89.taxon	description	Description: Spine scales consist of a hollow cylindrical shaft and circular base. Shaft is 2.50 – 6.84 µm in length, 0.18 – 0.27 µm in diameter, base is 0.66 – 0.93 µm in diameter. Tip of shaft divided on 3 furcae (0.28 – 0.47 µm in length), each furca with 1 tooth on inner side (Fig. 2 O, P). Pear-shaped plate scales are 2.01 – 2.74 × 1.51 – 2.48 µm, with medial thickening (0.43 – 0.72 µm in length), and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC1CFF8CFCADF97EF575FE89.taxon	discussion	Remarks: This species was previously noted only once from the same locality (sphagnum bog Klukven- noye- 1) (Leonov 2010 b). Morphology of observed scales corresponds to the original description except for the smaller diameter of the base of spine scales. Observed scales are similar to A. takahashii Dürrschmidt, 1987 a, but spine scales of the last species contain membrane between the furcae and 1 – 4 teeth on the inner side of furcae. In addition, plate scales of A. takahashii can be not only pear-shaped but also oval (Dürrschmidt 1987 a).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	description	Description: Diameter of protoplast of living cells is 28 – 30 µm. Spine scales of two types (long and short), both consist of a hollow cylindrical shaft and circular base. Shaft is 0.20 – 0.30 µm in diameter, tip divided on 4 – 6 furcae. Long spine scales are 4.13 – 10.95 µm in length, base is 0.89 – 1.22 µm in diameter, furcae diverge on 0.42 – 0.67 µm. Short spine scales are 1.97 – 3.52 µm in length, base is 0.62 – 0.93 µm in diameter, furcae diverge on 0.60 – 1.35 µm and connected by a membrane, forming a cup-shaped structure. Oval plate scales are 2.28 – 3.08 × 1.41 – 2.04 µm, with concave lateral sides, medial thickening (0.50 – 0.86 µm in length), radial slits (0.17 – 0.26 µm in length), and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	discussion	Remarks: Morphology of observed scales corresponds with previous descriptions, however, some authors noted larger plate scales (3.8 × 2.1 µm) (Leonov 2010 a, Leonov and Mylnikov 2012, Kosolapova and Mylnikov 2015) and larger spine scales (up to 15 µm) (Leonov 2010 a). Also, up to 8 furcae on short spine scales were described previously (Dürrschmidt 1987 a, Leonov 2010 a). This species is similar to A. pectinata Penard, 1889, A. polymorpha Dürrschmidt, 1985, A. siemensmae Gerasimova et Plotnikov, 2016, and A. valdiviense Dürrschmidt, 1987, but differs by the morphology of cup-shaped tips of short spine scales and presence of radial slits on plate scales (Mikrjukov 2002).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	distribution	Distribution: Freshwaters of Europe (Cavalier-Smith and von der Heyden 2007), Asia (Kosolapova and Mylnikov 2015), N. America ([as A. pectinata] Nicholls 1983), S. America (Dürrschmidt 1987 a, Prokina and Mylnikov 2019), Australia ([as A. pectinata] Croome 1986), New Zealand, Malaysia, Sri Lanka ([as A. pectinata] Dürrschmidt 1987 a). It was found in Russia in freshwaters of European part (Leonov 2009, 2010 a, Leonov and Mylnikov 2012), in saline inland waters of Orenburg Region (Gerasimova and Plotnikov 2015). Acanthocystis pectinata Penard, 1889 emend. Siemensma et Roijackers, 1988 [syn.: Acanthocystis pectinata Penard, 1889 emend. Nicholls, 1983 ssp. ceylanica Dürrschmidt, 1987] (Figs 1 B, 3 E – I)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	description	Description: Diameter of protoplast of living cells is 27 – 29 µm. Hollow cylindrical shaft of spine scales is 0.20 – 0.25 µm in diameter. Long spine scales are 3.8 – 10.3 µm in length, base is 0.76 – 1.15 µm in diameter, furcae diverge on 0.30 – 0.35 µm. Short spine scales are 1.3 – 3.2 µm in length, base is 0.48 – 0.82 µm in diameter, furcae diverge on 0.77 – 1.20 µm. Plate scales are 1.92 – 3.38 × 1.26 – 1.92 µm.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	discussion	Remarks: Spine scales are similar to A. nichollsi. Plate scales differ from A. nichollsi by lacking the radial slits and presence of numerous granules, medial thickening (0.49 – 0.58 µm in length) and dense margins. This species differs from A. polymorpha, A. siemensmae, A. valdiviense by the morphology of cup-shaped tips of short spine scales (Mikrjukov 2002). Morphology of observed scales corresponds to most known descriptions, except a different number of furcae in some papers: 2 – 3 in Siemensma and Roijackers (1988 a), Leonov and Plotnikov (2009), Plotnikov and Ermolenko (2015), Prokina and Mylnikov (2019); 7 – 8 in Leonov (2010 a), Prokina et al. (2017 c). Many authors noted a larger length of long spine scales – up to 15 µm (Leonov and Plotnikov 2009, Leonov 2010 a, Leonov and Mylnikov 2012, Plotnikov and Gerasimova 2017).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 a, Mikrjukov 1993 b), Africa (Prokina et al. 2017 b), S. America (Prokina and Mylnikov 2019), Sri Lanka ([as A. pectinata ssp. ceylanica] Dürrschmidt 1987 a). It was found in Russia in freshwaters of European part (Mikrjukov 1993 a, Leonov and Plotnikov 2009, Leonov 2010 a, Leonov and Mylnikov 2012, Plotnikov and Ermolenko 2015, Prokina et al. 2017 c), in saline inland waters of Orenburg Region (Plotnikov and Ermolenko 2015, Plotnikov and Gerasimova 2017). Acanthocystis penardi Wailes, 1925 [syn.: Acanthocystis spinifera Greef, 1869 sensu Penard, 1904; Acanthocystis heterospina Nicholls, 1983; Acanthocystis dresscheri Siemensma et Roijackers, 1988] (Fig. 3 J – M)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	description	Description: Spine scales consist of a hollow cylindrical shaft and circular base. Shaft is 3.84 – 17.29 µm in length, 0.25 – 0.41 µm in diameter, base is 0.89 – 1.89 µm in diameter. Tip of shaft divided on 4 – 7 furcae, diameter of the widened part is 0.33 – 0.62 µm. Plate scales are 2.71 – 4.75 × 1.88 – 2.78 µm, with concave lateral sides, numerous granules and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	discussion	Remarks: Morphology of observed scales is similar to previous descriptions, but many authors noted up to 12 furcae on spine scales (Nicholls 1983; Mikrjukov 1993 a, b; Leonov 2009; Leonov and Plotnikov 2009; Prokina et al. 2017 b, c). Some authors have described the larger size of spine scales: length of the shaft up to 33 µm (Mikrjukov 1993 b, Leonov 2009), the diameter of the shaft up to 0.8 µm (Mikrjukov 1993 b), the diameter of base up to 3.3 µm (Mikrjukov 1993 b, Leonov 2009, Leonov and Plotnikov 2009). This species is similar to A. mylnikovi Leonov, 2010, A. taurica Mikrjukov, 1997, and A. dresscheri. A. mylnikovi differs by size and number of furcae as well as the presence of two type of spine scales. All spine scales of A. taurica are almost equal in length, 4 µm (Mikrjukov 2002). A. dresscheri differs by the presence of medial thickening on plate scales (Siemensma and Roijackers 1988 a), however, K. A. Mikrjukov con- siders A. dresscheri a junior synonym of A. penardi (Mikrjukov 2002). Morphology of scales in A. penardi is also similar to A. spinosa (see below).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	distribution	Distribution: Freshwaters of Europe (Mikrjukov 1993 b), Asia (Kosolapova and Mylnikov 2015), Africa (Prokina et al. 2017 b), N. America (Nicholls 1983), S. America (Dürrschmidt 1987 a, Prokina and Mylnikov 2019), Malaysia (Dürrschmidt 1987 a). It was found in Russia in freshwaters of European part (Mikrjukov 1993 a, Leonov 2009, Leonov and Plotnikov 2009, Leonov and Mylnikov 2012, Prokina et al. 2017 c). Acanthocystis spinosa Cavalier-Smith et von der Heyden, 2007 (Fig. 3 N – P)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	description	Description: Spine scales consist of a hollow cylindrical shaft and circular base. Shaft is 2.88 – 8.14 µm in length, 0.16 – 0.24 µm in diameter, base is 0.59 – 0.68 µm in diameter. Distal part of shaft slightly tapers up to 0.12 – 0.18 µm in diameter and divided on 2 – 3 short pointed furcae. Shafts of some spine scales are slightly curved in basal part, flattened and twisted. Oval plate scales are 2.19 – 3.17 × 1.65 – 2.14 µm, with short medial thickening (0.62 – 0.87 µm) and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC18FF80FF50FE96F759FE7E.taxon	discussion	Remarks: Morphology of observed scales almost completely corresponds with the original description of this species from freshwaters of the UK (Cavalier-Smith and von der Heyden 2007), except the larger size of scales in the original description. Those authors no- ticed very large plate scales (11 – 13 µm in length – not typical for scales of Acanthocystis) as well as spine scales up to 17 µm in the text. But on figures (Fig. 1 a, p. 1187, and Fig. 4 i – 4 k, p. 1193) they show different dimensions. Fig. 4 k by Cavalier-Smith and von der Heyden (2007) shows length of plate scales about 12 µm (according to the scale bar), which corresponds to the description in the text. But in Fig. 4 i we can cal- culate the length of plate scales as about 3.0 – 3.5 µm. Also, as we see in the photograph of a living cell (Fig. 1 a), the length of plate scales cannot be 1 / 2 of the diameter of the cell (25 µm), otherwise they would be very clearly visible. Sizes of spine scales in Fig. 4 j and 4 k are four times different. The diameter of shaft of spine scales is about 0.8 µm, and diameter of base of spine scales is about 2.5 – 3.8 µm in Fig. 4 k. But in Fig. 4 j diameter of shaft of spine scales is about 0.2 µm, and diameter of base of spine scales is about 0.7 µm. Thus, we can assume that length of the scale bar on the fig. 4 k is indicated incorrectly and there is a misprint in the text description. If so, sizes of observed scales completely correspond with the original description. Spine scales with 2 – 3 furcae and slightly tapered distal end of the shaft occur in Acanthocystis spinifera sensu Siemensma et Roijackers, 1988. Plate scales of A. spinosa differ by larger oval plate scales without concave lateral sides and with medial thickening. Also, the shaft of spine scales in Acanthocystis spinifera sensu Siemensma et Roijackers, 1988 is located on the base eccentrically.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF80FF51FDC6F4B2FAF8.taxon	description	Description: Spine scales consist of a hollow cylindrical shaft and circular base. Shaft is 2.25 – 11.52 µm in length and 0.15 – 0.26 µm in diameter, base is 0.56 – 1.08 µm in diameter. Distal part of shaft divided on 3 pointed furcae (0.12 – 0.23 µm in length). Oval plate scales are 1.68 – 3.21 × 0.64 – 2.43 µm, with concave lateral sides, medial thickening (0.55 – 1.34 µm in length), numerous granules and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF80FF51FDC6F4B2FAF8.taxon	discussion	Remarks: Morphology of observed scales is similar to previous descriptions. Some authors also observed pear-shaped plate scales (Leonov 2010 a, Prokina et al. 2017 c). Croome (1983) and Nicholls (1986) described smaller diameter of the shaft (0.10 – 0.15 µm). Many re- searchers noted smooth plate scales without granules.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF80FF51FDC6F4B2FAF8.taxon	distribution	Distribution: Freshwaters of N. America (Nicholls 1983), S. America (Dürrschmidt 1985), Australia (Croome 1986), Crimean Peninsula (Mikrjukov 1999). It was found in Russia in freshwaters of European part (Leonov and Plotnikov 2009, Leonov 2010 a, Plotnikov and Ermolenko 2015, Prokina et al. 2017 c), in saline inland waters of Orenburg Region (Plotnikov and Gerasimova 2017), in the Black Sea (Leonov 2010 a).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	description	Description: Diameter of protoplast of living cell is 29 µm. Two types of spine scales, both consist of a hollow cylindrical shaft and circular base, distal part of shaft divided into 2 furcae, without membrane between tips of furcae. Long spine scales: shaft is 13.06 – 16.50 µm in length, 0.35 – 0.44 µm in diameter, base is 2.06 – 2.43 µm in diameter; furcae pointed, 0.53 – 0.89 µm in length, distance between tips of furcae – 0.59 – 0.82 µm. Short spine scales: shaft is 6.21 – 8.85 µm in length, 0.35 – 0.40 µm in diameter, base is 1.74 – 2.09 µm in diameter; long furcae (2.71 – 3.69 µm) slightly tapers to round tips, distance between tips of furcae 3.22 – 5.27 µm. Oval plate scales are 3.74 – 4.50 × 1.98 – 2.54 µm, with large rare granules, medial thickening (1.46 – 2.33 × 0.22 – 0.23 µm) and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	discussion	Remarks: Morphology of observed scales corresponds to previous descriptions. Some authors noted smaller spine scales of both type: length of shaft – 1.8 – 11.5 µm, diameter of base – 0.37 – 1.6 µm (Dürrschmidt 1985, Croome et al. 1987, Leonov and Plotnikov 2009, Plotnikov and Ermolenko 2015, Plotnikov and Gerasimova 2017), as well as larger length of shaft – up to 65 µm, diameter of shaft – up to 0.7 µm (Nicholls 1983, Croome 1986, Prokina et al. 2017 c).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	distribution	Distribution: Freshwaters of Asia (Biyu 2000, Charubhun and Charubhun 2000, Takamura et al. 2000), N. America (Nicholls 1983), S. America (Dürrschmidt 1985), Australia (Croome 1986); marine waters of Europe (Vørs 1992, Mikrjukov 1999, Leonov 2010 a), Antarctica (Croome et al. 1987). It was found in Russia in freshwaters of European part (Mikrjukov 1993 a, Leonov and Plotnikov 2009, Leonov 2010 a, Plotnikov and Ermolenko 2015, Prokina et al. 2017 c), in saline inland waters of Orenburg and Volgograd Regions (Gerasimova and Plotnikov 2015, Plotnikov and Gerasimova 2017). **** Raphidocystidae Zlatogursky in Zlatogursky et al., 2018 Raphidocystis symmetrica (Penard, 1904) Zlatogursky in Zlatogursky et al., 2018 [bas.: Raphidiophrys symmetrica Penard, 1904; syn.: Polyplacocystis symmetrica (Penard, 1904) Mikrjukov, 1996] (Figs 1 D, 4 H – K)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	description	Description: Oval plate scales are 6.02 – 8.68 × 2.06 – 3.09 µm. Length to width ratio is 1.85 – 3.41. Dense marginal rim is 0.21 – 0.34 µm in diameter. Inner space of scale with reticular texture (Fig. 4 K). Longitudinal rib (0.08 – 0.14 µm in length) divided scale into two halves.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	discussion	Remarks: Scales of this species are similar to plate scales of R. ambigua and R. tubifera. R. ambigua differs by the presence of narrowed elongate types of plate scales; R. tubifera differs by the presence of funnel-shaped spine scales.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 b), N. America (Nicholls and Dürrschmidt 1985), Greenland (Ikävalko et al. 1996). It was found in Russia in freshwaters of Voronezh Region (Leonov and 2010 a). *** Pterocystida Cavalier-Smith et von der Heyden, 2007 emend. Shishkin et Zlatogursky, 2018 **** Raphidista Shishkin et Zlatogursky, 2018 ***** Choanocystidae Cavalier-Smith et von der Heyden, 2007 Choanocystis aculeata (Hertwig et Lesser, 1874) Siemensma et Roijackers, 1988 [bas.: Acanthocystis aculeata Hertwig et Lesser, 1874; syn.: A. serrata Nicholls, 1983] (Figs 1 E, 4 L – O)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	description	Description: Diameter of protoplast of living cells is 38 – 40 µm. Spine scales consist of a hollow cylindrical shaft, which asymmetrically sitting on circular flattened base. Shaft is 4.92 – 13.72 µm in length, diameter of proximal part is 0.47 – 0.63 µm, diameter of distal part is 0.25 – 0.29 µm. Proximal part (1 / 3 of the entire length) with round finger-like outgrowths (0.11 – 0.45 µm in length, 0.05 – 0.39 µm in diameter). Tip divided on 4 – 7 teeth. Base is 1.69 – 2.47 µm in diameter, with a small excavation. Dumbbell-shaped plate scales are 4.36 – 5.47 µm in length, width of expanded part is 2.57 – 3.05 µm, width of narrowed central part is 0.88 – 1.73 µm.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	discussion	Remarks: Observations of the scales are in the agreement with previous descriptions. Some authors observed additionally very long plate scales (up to 12.9 µm) (Dürrschmidt 1985, Siemensma and Roijackers 1988 a). Nicholls (1983) described longer outgrowths (up to 0.7 µm); Croome (1986) observed the absence of outgrowths on spine scales of some cells.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 a, Mikrjukov 1993 b), Asia (Wujek and Saha 2006), N. America ([as A. serrata] Nicholls 1983, Wujek 2003), S. America (Dürrschmidt 1985), Australia (Croome 1986), fresh and marine waters of Crimea (Mikrjukov 1999). It was found in Russia in freshwaters of European part (Mikrjukov 1993 a). ***** Raphidiophryidae Febvre-Chevalier et Febvre, 1984 emend. Shishkin et Zlatogursky, 2018 Raphidiophrys capitata Siemensma et Roijackers, 1988 [syn.: Raphidiophrys elegans sensu Nicholls et Dürrschmidt, 1985] (Figs 1 F, 5 A – B)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	description	Description: Diameter of protoplast of living cells is 48 – 54 µm. Elongate oval plate scales are 8.36 – 12.24 × 3.38 – 4.32 µm, with narrowing elongated ends. Length to width ratio is 2.05 – 4.02. Edges of scales are bent inside and form marginal rim 0.25 – 0.37 µm in diameter. Radial ribs with variable length extend from edges to the center. Distances between ribs on marginal rim are 0.16 – 0.30 µm.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	discussion	Remarks: Morphology of observed scales corresponds to previous descriptions, except larger length to width ratio (3.0 – 5.4) in the original description (Siemensma and Roijackers 1988 b).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC14FF86FF51FA47F360FB77.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 b), N. and S. America ([as R. elegans] Nicholls and Dürrschmidt 1985, Wujek 2003). These are the first observations in Russia.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC12FF84FCADFADDF5DDFA5B.taxon	description	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.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC12FF84FCADFADDF5DDFA5B.taxon	distribution	Distribution: Freshwaters of USA (Wujek 2005), Australia (Croome 1987), Canada, Chile, New Zealand (Nicholls and Dürrschmidt 1985), Sweden, Netherlands (Siemensma and Roijackers 1988 b). It was found in Russia in freshwaters of European part (Leonov 2009, 2010 a; Leonov and Mylnikov 2012; Prokina et al. 2017 c). 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. 5 C – D)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC12FF84FCADFADDF5DDFA5B.taxon	description	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.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC12FF84FCADFADDF5DDFA5B.taxon	discussion	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.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC12FF84FCADFADDF5DDFA5B.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 b), 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 2010 a). **** Pterista Shishkin et Zlatogursky, 2018 ***** Pterocystidae Cavalier-Smith et von der Heyden, 2007	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC10FF85FCADFA29F321FEF4.taxon	description	Description: Spine scales leaf-shaped, consist of a hollow cylindrical shaft, lateral and basal wings. Wings connect to each other perpendicularly, forming subapical protrusion. Shaft is 2.49 – 6.02 µm in length, 0.15 – 0.20 µm in diameter. Lateral wings are 2.11 – 2.58 µm in width, slightly narrowed to truncated tips (0.24 – 0.46 µm in width). Oval plate scales are 3.67 – 4.39 × 1.92 – 2.63 µm, with medial thickening and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC10FF85FCADFA29F321FEF4.taxon	discussion	Remarks: Morphology of observed scales corresponds to previous descriptions, however, many authors described smaller plate scales (2.5 – 3.1 × 1.4 – 2.0 µm) (Dürrschmidt 1985, 1987 b; Gaponova 2008; Plotnikov and Gerasimova, 2017; Prokina and Mylnikov 2019).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC10FF85FCADFA29F321FEF4.taxon	distribution	Distribution: Freshwaters of Europe (Gaponova 2008), Asia (Wujek and Saha 2006), Australia (Croome 1987), Africa (Wujek and Ogundipe 2002), S. America (Dürrschmidt 1985, 1987 b; Prokina and Mylnikov 2019), Japan, New Zealand, Sri Lanka (Dürrschmidt 1987 b). It was found in Russia in freshwaters of Orenburg Region (Ermolenko and Plotnikov 2013), in saline inland waters of Volgograd Region (Plotnikov and Gerasimova 2017), in the Black Sea (unpubl. data).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	description	Description: Spine scales with a complex structure: hollow curved shaft (1.71 – 3.14 µm in length, 0.16 – 0.20 µm in diameter) is located on heart-shaped flattened base plate (0.56 – 0.89 µm in diameter). Lateral wings connected to each other in basal part, forming a hollow broad stalk (0.48 – 0.71 µm in diameter). Lateral wings expand into a funnel-shaped structure (diameter of the widened part is 1.32 – 1.75 µm) in a middle part. Distal part of wings conically tapered, forming a pointed tip. Inner side of wings with radial ribs extended from shaft to margins, and from basal part of the funnel to the base. Oval or ovoid plate scales are 1.32 – 2.25 × 0.89 – 1.33 µm, with medial depression (0.62 – 1.03 × 0.18 – 0.41 µm).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	discussion	Remarks: Morphology of observed scales corresponds to previous descriptions, except Dürrschmidt (1985) noted larger size of plate scales (3.0 – 3.3 × 1.7 – 2.0 µm) and spine scales (3.0 – 4.0 × 3.1 – 3.8 µm). Spine scales of this species differ from spine scales of P. plumosa by not extending beyond the lateral wings shaft.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	distribution	Distribution: Freshwaters of USA (Wujek 2005), Chile, New Zealand (Dürrschmidt 1985, 1987 b). This is the first record in Russia. Raineriophrys echinata (Rainer, 1968) Mikrjukov, 2001 [bas.: Acanthocystis echinata Rainer, 1968; syn.: Echinocystis echinata (Rainer, 1968) Mikrjukov, 1997; Pterocystis echinata (Rainer, 1968) Siemensma et Roijackers, 1988] (Fig. 6 A – D)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	description	Description: Spine scales consist of a hollow curved shaft, asymmetrically sitting on a circular flattened base. Shaft is 9.19 – 23.66 µm in length, 0.29 – 0.60 µm in diameter, base is 1.19 – 1.92 µm in diameter. Narrow lateral wings (0.11 – 0.56 µm in width) with pointed teeth. Oval plate scales are 4.95 – 5.18 × 2.11 – 2.43 µm, with medial thickening almost equal the length of scale, 0.35 – 0.42 µm in diameter.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	discussion	Remarks: Morphology of observed scales corresponds to previous descriptions, however, many authors noted larger size of plate scales (4.7 – 8.0 × 2.2 – 3.4 µm) (Siemensma and Roijackers 1988 a; Leonov 2009, 2010 a; Leonov and Plotnikov 2009; Leonov and Mylnikov 2012).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 a). It was found in Russia in freshwaters of European part (Leonov 2009, 2010 a; Leonov and Plotnikov 2009; Leonov and Mylnikov 2012; Prokina et al. 2017 c). Raineriohrys erinaceoides (Petersen et Hansen, 1960) Mikrjukov, 2001 [bas.: Acanthocystis erinaceoides Petersen et Hansen, 1960; syn.: Echinocystis erinaceoides (Petersen et Hansen, 1960) Mikrjukov, 1997; Pterocystis erinaceoides (Petersen et Hansen, 1960) Siemensma, 1991; Raineria erinaceoides (Petersen et Hansen, 1960) Mikrjukov, 1999] (Fig. 6 E – H)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	description	Description: Spine scales consist of a hollow cylindrical shaft, lateral and basal wings. Shaft is 5.02 – 8.75 µm in length, 0.29 – 0.46 µm in diameter, conically tapers to pointed tip. Lateral wings are 2.53 – 5.22 µm in length, narrow from the base to distal end. Basal part of lateral wings connected to basal wing, forming subapical protrusion (1.41 – 2.26 µm in diameter). Oval plate scales are 4.71 – 5.24 × 2.27 – 2.81 µm, with medial thickening (3.06 – 3.77 × 0.26 – 0.44 µm) and dense margins.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	distribution	Distribution: Freshwaters of Europe (Mikrjukov 1993 b, Gaponova 2008), Asia (Kosolapova and Mylnikov 2015), Africa (Wujek and Ogundipe 2002), N. America (Nicholls 1983, Wujek 2006), S. America (Dürrschmidt 1985, 1987 b; Prokina and Mylnikov 2019), Australia (Croome 1986), Sri Lanka (Dürrschmidt 1987 b), Crimean Penninsula (Mikrjukov 1999); marine waters of Europe (Vørs 1992, Mikrjukov 2001). It was found in Russia in freshwaters of European part (Mikrjukov 1993 a, Leonov 2010 a, Leonov and Plotnikov 2009, Ermolenko and Plotnikov 2013, Plotnikov and Ermolenko 2015), in saline inland waters of Orenburg Region (Plotnikov and Gerasimova 2017). Raineriophrys fortesca (Nicholls, 1983) Mikrjukov, 1999 [bas.: Acanthocystis fortesca Nicholls, 1983; syn.: Acanthocystis pantopodeoides Nicholls, 1983; Acanthocystis cuneiformis Dürrschmidt, 1985; Pterocystis fortesca (Nicholls, 1983) Siemensma et Roijackers, 1988] (Fig. 6 I – L)	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	description	Description: Spine scales consist of a hollow cylindrical shaft, lateral and basal wings. Shaft is 4.73 – 11.06 µm in length, 0.18 – 0.27 µm in diameter, distal end divided on 2 – 5 teeth. Lateral wings are 1.80 – 2.64 µm in length, 1.57 – 2.02 µm in diameter, proximal part connected to basal wings, forming subapical protrusion, triangular in outline. Margins of wings bend out- wards. Inner side of basal wing with radial ribs. Oval plate scales are 2.75 – 2.88 × 1.76 – 1.88 µm, darkened by protoplast.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	discussion	Remarks: Morphology of observed scales corresponds to previous descriptions, however, some authors noted larger length of spine scales (13 – 24 µm) (Nicholls 1983, Dürrschmidt 1985, Mikrjukov 1993 a) and smaller size of plate scales (1.6 – 2.9 × 1.0 – 1.9 µm) (Mikrjukov 1993 a, Plotnikov and Ermolenko 2015).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC11FF9AFCB4FE5CF5F0FCD1.taxon	distribution	Distribution: Freshwaters of Europe (Siemensma and Roijackers 1988 a), N. America ([as A. fortesca and A. pantopodeoides] Nicholls 1983, Wujek 2003, 2005), S. America ([as A. cuneiformis] Dürrschmidt 1985), Australia ([as A. pantopodeoides] Croome 1986); marine waters of Europe (Vørs 1992). It was found in Russia in freshwaters of European part (Mikrjukov 1993 a, Plotnikov and Ermolenko 2015), White Sea (Leonov 2010 a).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC0EFF9AFCADFC5DF37FF893.taxon	description	Description: Organic spindle-shaped spicules are 2.75 – 7.57 µm in length, 0.05 – 0.09 µm in width. Spicules are slightly flattened and twisted along longitudinal axis, ends taper to pointed tips. Basal part of spicules submerged into mucopolysaccharide capsule, few axopodia are visible (Fig. 7 A).	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
32645169EC0EFF9AFCADFC5DF37FF893.taxon	discussion	Remarks: Organisms with organic spindle-shaped spicules were previously found in both fresh and marine waters and identified as species of Heterophrys, Marophrys, and Sphaerastrum (Mikrjukov 2002, Cavalier-Smith and von der Heyden 2007). However, re- cent studies have revealed a close similarity between spicule-bearing Heterophrys - like organisms and scalebearing species by both molecular (18 S rDNA sequenc- es of Polyplacocystis species is similar to sequence of Heterophrys - like organism) and morphological data (presence of intermediate forms possessing characteristic Raphidiophrys glabra plate scales and spicules at the same time) (Zlatogursky 2016, Zlatogursky et al. 2018). Based on these observations, Zlatogursky with coauthors (Zlatogursky et al. 2018) have suggested dimorphism of the life cycle in centrohelids with the presence of scales-bearing and spicules-bearing stages. So, Heterophrys - like organism can be a stage of the life cycle of some other centrohelid species.	en	Prokina, Kristina I., Zagumyonnyi, Dmitry G., Tikhonenkov, Denis V. (2018): Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe. Acta Protozoologica 57 (4): 243-266, DOI: 10.4467/16890027AP.18.018.10094, URL: http://dx.doi.org/10.4467/16890027ap.18.018.10094
