Frontonia atra (Ehrenberg, 1833) Bütschli, 1889

Jung, Atef Omar and Jae-Ho, 2021, New record of 21 ciliate species (Protozoa, Ciliophora) from South Korea, Journal of Species Research 10 (3), pp. 301-320 : 315-316

19. Frontonia atra (Ehrenberg, 1833) Bütschli, 1889

( Fig. 18 )

Material examined. Freshwater sample collected from Gyeongpo Gasiyeon Weblands, Gangneung, Korea (37°47 ʹ 26.9 ʺ N, 128°53 ʹ 47.4 ʺ E) Freshwater on 23 July 2020 .

Diagnosis. Size in vivo about 150 × 95 μm (n = 5); body ovate to teardrop-shaped, broadly rounded anteriorly and pointed posterior; cytoplasm full of dark pigments possibly depending on food inside food vacuoles; a single contractile vacuole posterior to mid-body; extrusomes numerous and about 10 μm long in vivo, stain darkly after protargol impregnation; macronucleus globular to ellipsoidal near body center; oral apparatus in anterior half of body composed of undulating membrane on right side of oral apparatus and 3 very close peniculae with 5, 4, 4 ciliary rows at left side, a suture extends from oral opening to posterior body end; about 90 ciliary rows.

Distribution. Europe and Korea.

Remarks. The Korean population of Frontonia atra agrees very well with the previously described populations. Regarding the teardrop shape, F. atra is similar to F. acuminata (Ehrenberg, 1833) Bütschli, 1889 and F. terricola Foissner, 1987 . However, it differs from both species in having larger body size (150 × 95 μm vs. 115 × 75 and 82 × 43 μm) and a higher number of somatic kineties (~90 vs. 55-60 and ~68) ( Kahl, 1932; Dragesco and Njine, 1971; Dragesco and Dragesco-Kernéis, 1986; Foissner et al., 1994). Further, both F. cana Reuter, 1961 and F. nigricans Penard, 1922 have similar coloration in the cytoplasm, and F. nigricans could be a synonym of F. atra because of the tapered posterior end ( Reuter, 1961; Foissner et al., 1994).

Voucher slides. Two slides with protargol-impregnated opening, with a characteristic notch dividing it into 2 parts, the posterior of which is semicircular.

Distribution. Europe, Japan, USA, and Korea.

Remarks. Histobalantium natans viridis is well-known species recently redescribed in a comprehensive study by Foissner et al. (2009) from Biwa Lake in Japan. The Korean population of H. natans viridis matches very well the Japanese population in most features. On the other hand, the European population described by Dragesco and Iftode (1972) differs from both the Korean and Japanese (Asian) populations in the structure of membranelles 1 (2 rows of basal bodies vs. 3 rows and with triangular segment anteriorly) ( Dragesco and Iftode, 1972; Foissner et al., 2009).

Voucher slides. One slide with protargol-impregnated specimens was deposited at the Nakdonggang National Institute of Biological Resources (NNIBRPR20137).

specimens were deposited at the Nakdonggang National Institute of Biological Resources (NNIBRPR20135, NNIBRPR20136).

Figures

Fig. 18. Photomicrographs of Frontonia atra from life (A, B), after protargol impregnation (C), and silver carbonate impregnation (D). A, B. Ventral (A) and lateral (B) view showing the body shape, the location of nuclear apparatus. Note the tapered posterior end. C, D. Ventral (C) and ventrolateral(D) view showing the location of the oral apparatus and ciliature. MA, macronucleus; OO, oral opening. Scale bars=50 μm.