Pterocystis pulchra ( Dürrschmidt, 1985 ) Siemensma, 1991

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), pp. 243-266 : 258-259

Pterocystis pulchra ( Dürrschmidt, 1985) Siemensma, 1991 [bas.: Acanthocystis pulchra Dürrschmidt, 1985 ] ( Fig. 5M–P)

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).

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.

Distribution: Freshwaters of USA ( Wujek 2005), Chile, New Zealand ( Dürrschmidt 1985, 1987b). 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. 6A–D )

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.

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 1988a; Leonov 2009, 2010a; Leonov and Plotnikov 2009; Leonov and Mylnikov 2012).

Distribution: Freshwaters of Europe ( Siemensma and Roijackers 1988a). It was found in Russia in freshwaters of European part (Leonov 2009, 2010a; Leonov and Plotnikov 2009; Leonov and Mylnikov 2012; Prokina et al. 2017c).

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. 6E–H )

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.

Distribution: Freshwaters of Europe ( Mikrjukov 1993b, Gaponova 2008), Asia ( Kosolapova and Mylnikov 2015), Africa ( Wujek and Ogundipe 2002), N. America ( Nicholls 1983, Wujek 2006), S. America ( Dürrschmidt 1985, 1987b; Prokina and Mylnikov 2019), Australia ( Croome 1986), Sri Lanka ( Dürrschmidt 1987b), Crimean Penninsula ( Mikrjukov 1999); marine waters of Europe ( Vørs 1992, Mikrjukov 2001). It was found in Russia in freshwaters of European part ( Mikrjukov 1993a, Leonov 2010a, 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. 6I–L )

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.

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 1993a) and smaller size of plate scales (1.6–2.9×1.0–1.9 µm) ( Mikrjukov 1993 a, Plotnikov and Ermolenko 2015).

Distribution: Freshwaters of Europe ( Siemensma and Roijackers 1988a), 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 2010a).

Figures

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.