Aspidisca hexeris Quennerstedt, 1869

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 : 91-93

2. Aspidisca hexeris Quennerstedt, 1869 ( Fig. 2 )

Material examined. Brackish water (salinity 12.8‰, temperature 33.5℃) collected from Yongdumbeong , Sinyang-ri , Chuja-myeon, Jeju-si, Jeju-do, Korea (33°57 ʹ 38.90 ʺ N, 126°17 ʹ 7.30 ʺ E) on August 19, 2021 .

Diagnosis. Size 32 - 33 × 26 - 29 μm in vivo and 23 - 30 × 21 - 25 μm after protargol impregnation (n = 7); body shape broadly oval; cortex rigid with a single peristomial spur and 4 projections along left margin ( Fig. 2A - C ); AZM1 about 7 μm long with 7 - 8 membranelles, AZM2 about 10 μm long after protargol impregnation and with 10 - 12 membranelles; 7 frontoventral cirri in “ polystyla -arrangement”; 5 transverse cirri, each transverse cirrus not separated except the leftmost one, which splits into 2 parts; 4 dorsal kineties with 8 - 9, 8 - 10, 8 - 12, 9 - 10 dikinetids in dorsal kineties 1 - 4, respectively; cytoplasm colorless; 1 macronucleus horseshoe-shaped, micronucleus not observed ( Fig. 2D, E ).

Distribution. China, South Korea.

Remarks. The Korean population of Aspidisca hexeris is similar to the Chinese population in all features except the body size (23 - 30 × 21 - 25 μm vs. 34 - 43 × 25 - 36 μm after protargol impregnation) ( Jiang et al., 2013). Aspidisca hexeris is unique among the genus Aspidisca in having one conspicuous peristomial spur and four small projections along the left margin. Although Wu and Curds (1979) mentioned that the number of projections is highly variable among populations and Jiang et al. (2013) argued that the number of projections is an intraspecific difference, nonetheless, all specimens observed in this study have invariably four projections. Considering the presence of a peristomial spur and the “ polystyla -arrangement” of frontoventral cirri, A. leptaspis and A. magna Kahl, 1932 are very similar to A. hexeris . However, A. leptaspis has eight (vs. 7) frontoventral cirri and has more membranelles in the AZM2 (14 - 21 vs. 10 - 12) ( Li et al., 2010). Aspidisca magna is larger than A. hexeris (50 - 160 × 40 - 115 in vivo vs. 32 - 33 × 26 - 29), has more frontoventral cirri (7 - 9 vs. invariably 7), and also has more membranelles in the AZM2 (15 - 18 vs. 10 - 12) ( Li et al., 2010; Huang et al., 2011; Jiang et al., 2013). Furthermore, both A. dentata and A. hexeris possess the peristomial spur, however, they differ mainly in the absence (vs. presence) of the projections along the left margin.

Voucher slides. Three slides with protargol-impregnat- ed specimens were deposited at the National Marine Biodiversity Institute of Korean (MABIK PR00044187, PR00044188, and PR00044189).

Figures

Fig. 2. Aspidisca hexeris in life (A, B) and after protargol impregnation (C-E). A, B, Ventral (A) and dorsal (B) view, showing the body shape, the peristomial spur (arrow), and the four small projections (arrowheads) along the left margin. C, Ventral view showing the projections (arrowheads) and the peristomial spur (arrow) along the left margin. D, E, Ventral (D) and dorsal (E) view, showing the anterior and posterior portion of adoral zone of membranelles, the frontoventral cirri, the five transverse cirri, and the projections along left margin of body. AZM1, adoral zone of membranells 1; AZM2, adoral zone of membranelles 2; DK1-4, dorsal kineties; FVC, frontoventral cirri; TC, transverse cirri. Scale bars=10 μm.