Acanthocystis trifurca Nicholls, 1983

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 : 253

Acanthocystis trifurca Nicholls, 1983 [syn.: Acanthocystis myriospina Penard, 1890 sensu Dürrschmidt, 1985 ] ( Fig. 4A–D)

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.

Remarks: Morphology of observed scales is similar to previous descriptions. Some authors also observed pear-shaped plate scales ( Leonov 2010a, Prokina et al. 2017c). 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.

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. 2017c), in saline inland waters of Orenburg Region ( Plotnikov and Gerasimova 2017), in the Black Sea ( Leonov 2010a).