Acanthocystis elenazhivotovae Leonov, 2010

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 : 245-247

Acanthocystis elenazhivotovae Leonov, 2010 ( Fig. 2J–M)

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. 2M) 0.34–0.67 µm in length, and medial thickening (0.59–0.68 µm in length).

Remarks: A. elenazhivotovae was previously noted only once from the waterlogged habitat of Yaroslavl Region, Russia ( Leonov 2010b). 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. 2N–Q)

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. 2O, 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.

Remarks: This species was previously noted only once from the same locality (sphagnum bog Klukven- noye-1) ( Leonov 2010b). 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, 1987a , 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 1987a).