Pleuronema setigerum Calkins, 1902

Jung, Jae-Ho, 2021, Taxonomy of four scuticociliates (Protozoa: Ciliophora) from coastal waters of South Korea, Journal of Species Research 10 (2), pp. 184-190 : 187-188

3. Pleuronema setigerum Calkins, 1902 ( Fig. 3 )

Material examined. Coastal water sample (25.4‰, 21.0℃) collected from Yeosu-si, Jeollanam-do, Republic of Korea (34°2′50″N, 127°17′33″E) on 10 July 2019 ; coastal water sample (34.4‰, 14.4℃) collected from Gang- neung-si, Gangwon-do , Republic of Korea (37°47′55″N, 128°54′59″E) on 16 November 2020 .

Diagnosis (n = 8). Cell size 38.1-55.2 × 15.6-33.6 μm (45.5 × 21.0 μm on average) in protargol preparations, outline oval, dorsoventrally flattened; 1 globular macronucleus, 9.1-15.0 × 6.9-13.3 μm (10.7 × 8.7 μm on average) in size; 1-4 micronuclei attached to macronucleus, elliptical to circular; 5 or 6 preoral kineties (note that 1 out of 8 specimens showed 6 preoral kineties and 1 postoral kinety might have resulted from a fragmentation of somatic kinety 1), 20-23 somatic kineties, prolonged caudal cilia; buccal area occupying 58.3-83.8% (73.9% on average) of body length; paroral membrane conspicuous, hook or ‘6’-shaped; M1 three-rowed, M1:M2a length ratio about 33%; posterior end of M2a ring-like arrangement; M2b V-shaped; M3 three-rowed.

Distribution. USA ( Calkins, 1902; Borror, 1963), Europe ( Kahl, 1931), China ( Pan et al., 2010; Pan et al., 2015b), and Korea (this study).

Remarks. More than 20 species have been reported in the genus Pleuronema ( Wang et al., 2009; Pan et al., 2016). Of the congeners, P. setigerum can be characterized by the ring-like bosal body arrangement at the posterior end of M2a ( Pan et al., 2010). Pleuronema setigerum highly resembles P. paucisaetosum Pan et al., 2015 by the number of somatic kineties, oral apparatus, and macronucleus ( Pan et al., 2015a). According to Pan et al. (2015a), P. setigerum differs from P. paucisaetosum by the structure of M2a (ring-like vs. hook-like posterior end; zigzag vs. onerowed basal body pattern in middle portion).

Voucher slides. Five slides with protargol-impregnated specimens were deposited at the National Marine Biodiversity Institute of Korea (GUC002230-2231, 2251-2252, Yeosu population) and the National Institute of Biological Resources, Korea (NIBRPR0000110225, Gangneung population).

Figures

Fig. 3. Pleuronema setigerum after protargol impregnation. A, C, D. Ventral views showing infraciliature and nuclear apparatus, arrows denote micronuclei. B. Dorsal view showing somatic kineties and nuclear apparatus, arrow denotes a micronucleus. CC, caudal cilia; Ma, macronucleus; M1, 3, membranelles 1, 3; M2a, anterior part of membranelle 2; M2b, posterior part of membranelle 2; PM, paroral membrane; PK; preoral kineties; SK, somatic kineties. Scale bar=30μm.