Aspidisca polystyla Stein, 1859

Choi, Ji Hye & Jung, Atef Omar and Jae-Ho, 2023, New record of three Aspidisca species (Protozoa, Ciliophora) from South Korea, Journal of Species Research 12 (1), pp. 90-94 : 93-94

3. Aspidisca polystyla Stein, 1859 ( Fig. 3 )

Material examined. Marine water (salinity 40.0‰, temperature 11.1℃) collected from Anin Beach , Gangdong-myeon , Gangneung-si, Gangwon-do, Korea (37° 44 ʹ 3 ʺ N, 128°59 ʹ 25 ʺ E) on February 28, 2022 .

Diagnosis. Size 31 - 38 × 26 - 28 μm in vivo and 28 - 37 × 22 - 29 μm after protargol impregnation (n = 8); body shape broadly rotund; cortex rigid, without the peristomial spur and projections along left margin; AZM1 about 2 μm long invariably with 4 membranelles, AZM2 about 10 μm long after protargol impregnation and with 11 - 14 membranelles; 7 frontoventral cirri in “ polystyla -arrangement”; 5 transverse cirri, ( Fig. 3A, C, D ), transverse cirrus 1 (leftmost) splits into 2 or 3 parts, cirri 2, 3, and 5 usually split into 2 parts, transverse cirrus 4 consists of one or two parts; 4 dorsal kineties with 8 - 9, 8 - 10, 8 - 12, and 9 - 10 dikinetids in dorsal kineties 1 - 4, respectively ( Fig. 3B, E ); cytoplasm colorless; 1 horseshoe-shaped macronucleus, micronucleus not observed.

Distribution. Italy, Baltic Sea, South Korea.

Remarks. Within the genus Aspidisca , A. polystyla seems to possess the highest number of transverse cirri. Stein (1859) reported that A. polystyla has 10 - 12 transverse cirri. Other investigations suggest that it has up to 15 transverse cirri (Plough, 1915; Tuffrau, 1964). However, Kahl (1932) reported that A. polystyla has 5 - 6 transverse cirri but it looks like it has higher number of transverse cirri because each transverse cirrus splits into two or more parts. According to our observations on the protargol-impregnated specimens of the Korean population ( Fig. 3D ), A. polystyla has only five transverse cirri, although it looks like it has eleven or more in vivo ( Fig. 3C ), suggesting that the split occurs only in the cilia while the bases of cirri are ordinary. Other members of genus Aspidisca , which have seven frontoventral cirri in “ polystyla -arrangement” and without the peristomial spur ( A. major (Madsen, 1931) Kahl, 1932 , A. steini ), can be easily separated from A. polystyla . Aspidisca major differs from A. polystyla by the larger body size (60 - 90 μm vs. 31 - 38 × 26 - 28 μm) ( Kahl, 1932), the ordinary (vs. separated) transverse, and the two (vs. 1) macronuclear nodules ( Wu and Curds, 1979). Also, the Chinese population of A. steini is most similar to A. polystyla , but A. steini differs from A. polystyla by the transverse cirri (the leftmost cirri separated into two parts vs. almost all cirri separated into 1 - 3 parts) ( Wu and Curds, 1979; Song and Wilber, 1997).

Voucher slides. Three slides with protargol-impregnat- ed specimens were deposited at the National Marine Biodiversity Institute of Korean (MABIK PR00044191, PR00044192, and PR00044193).

Figures

Fig. 3. Aspidisca polystyla in life (A-C) and after protargol impregnation (D, E). A, B, Ventral (A) and dorsal (B) view, showing the body shape, the transverse cirri (arrowheads), and the dorsal ridges (arrows). C, Ventral view showing the transverse cirri, each of which separated into two or three parts (arrowheads). D, E, Ventral (D) and dorsal (E) view, showing the anterior and posterior portion of adoral zone of membranelles and the five transverse cirri. Note the split occurs in the cilia of cirri while the bases are ordinary. AZM1, adoral zone of membranelles 1; AZM2, adoral zone of membranelles 2; DK1-4, dorsal kineties; FVC, frontoventral cirri; TC, transverse cirri. Scale bars=10 μm.