Pterocystis jongsooparkii Zagumyonnyi, Prokina et Tikhonenkov, 2020
Diagnosis: The diameter of living cells is 8.2-10.6 μm. Axopodia are two times longer than the cell diameter. Skeletal elements are represented by spine- and plate-scales. Spine-scales consist of a shaft and trapezoidal base (1.44-2.23 μm in the wide proximal part) formed by lateral and basal wings. The lateral wings are 1.60-2.43 μm in length. They gradually taper towards the shaft and abruptly terminate at the middle part of the shaft, forming “shoulders”. The shaft is not tapered, straight, and smooth in the distal part, 3.12-4.60 μm in length, 0.13-0.27 μm in diameter. There are five small rounded marginal teeth at the apex of the shaft. The proximal half of the shaft is connected with basal and lateral wings and curved, forming a scoop-like structure. The inner surface of the lateral wings contains about 10-15 parallel transverse slits. The sides of the lateral wings are bent out, and form a marginal rim 0.07-0.12 μm in diameter. Plate-scales are oval, 2.18-2.98 × 1.19-1.61 μm, with a medial thickening 1.31-2.21 × 0.25-0.39 μm. Marginal rim varies from almost not pronounced (0.04 μm in diameter) to rather wide (0.11 μm in diameter). The length to width ratio of the plate-scales is 1.63-2.13. Cysts formation is not recorded.
Ecology: Marine. Interstitial water within the sand on stony littoral of Jeodo island shore, the Sea of Japan, South Korea.
Remarks: Pterocystis jongsooparkii possesses some significant morphological peculiarities. Among the species of Pterocystis and Raineriophrys, the studied heliozoan is most similar to Pterocystis anapoda Siemensma et Roijackers, 1988 by the trapezoidal base of spine scales. However, P. anapoda is characterized by spine scales that are two times longer, 6.5–14.7 μm (Siemensma and Roijackers, 1988a; Prokina and Philippov, 2019). Distal tips of spine scales of P. anapoda are truncated, without any teeth, while our strain has five small rounded marginal teeth. Scales of P. jongsooparkii are also similar to those of Raineriophrys fortesca (Nicholls, 1983; Mikrjukov, 1999). Both species are characterized by the presence of marginal teeth on the non-tapering distal tip of the shaft, and they are similar in terms of the presence of the radial slits on the inner lateral wings as well as in the shape and size of plate scales. However, spine scales of R. fortesca are usually longer (up to 24.0 μm). Their lateral wings are triangular or circular in shape; the radial ribs are present on the basal wings.