Euplotes raikovi Agamaliev, 1966

Yeo, Jeong Hyeon & Jung, Pablo Quintela-Alonso and Jae-Ho, 2023, New record of five Euplotes species (Protozoa, Ciliophora) collected from South Korea, Journal of Species Research 12 (3), pp. 203-211 : 207-208

5. Euplotes raikovi Agamaliev, 1966 ( Fig. 5 )

Material examined. Marine water (salinity 34‰, temperature 26℃) collected from Jongdal harbor, Gujwa-eup, Jeju-si, Jeju-do, Korea (33°29′48″N, 126°54′42″E) on August 19, 2020 .

Diagnosis. Body size about 35.2-48.0 × 20.0-28.7 μm (on average 40.5 × 24.6 μm) after protargol impregnation, shape oval, 6 dorsal and 3 ventral ridges; macronucleus C-shaped with a single spherical micronucleus attached to it; 27-31 adoral membranelles; 7 frontoventral [note that the reduced, non-ciliated, frontoventral cirrus (basal plaque) is not counted], 5 transverse, 2 caudal cirri and 1 marginal cirrus; 7 or 8 dorsal kineties, of which the middle one is composed of about 9-11 dikinetids; dorsal argyrome pattern of double- patella type.

Distribution. Cosmopolitan.

Remarks. The Korean population of E. raikovi highly resembles the type population ( Agamaliev, 1966) except for the number of dorsal kineties (7 or 8 vs. 6 or 7). Short time after the original description, Agamaliev (1967) reported a population with 8 frontoventral cirri (vs. 7 in the type), but Jiang et al. (2010a) considered it as a different form because the basal plaque is very stable among populations ( Washburn and Borror, 1972; Miceli et al., 1981; Jiang et al., 2010a). Additionally, Jiang et al. (2010a) reported 8 kineties. Considering the basal plaque and saline habitat, E. raikovi is similar to E. elegans Kahl, 1932 , E. orientalis Jiang et al., 2010a , E. pseudoraikovi Alekperov, 2005 , and E. strelkovi Agamaliev, 1967 . Originally, E. raikovi had 8 frontoventral cirri, one of which disappeared and remained as a trace, leaving 7 frontoventral cirri. Only two species within the genus Euplotes have 7 frontoventral cirri, i.e., E. raikovi and E. oropensis (Fernández-Leboráns and Castro de Zaldumbide, 1986) , however, they can be distinguished by the dorsal argyrome pattern, double- patella in E. raikovi vs. double- eurystomus in E. oropensis .

Voucher slides. One slide with protargol-impregnated specimens (NNIBRPR25663) and one slide with wet silver nitrate-impregnated specimens (NNIBRPR25664) were deposited at the Nakdonggang National Institute of Biological Resources.

A KEY TO THE SPECIES OF KOREAN EUPLOTES

Figures

Fig. 5. Euplotes raikovi in vivo (A) and after protargol (B, C) and “wet” silver nitrate impregnation (D). A-C. Ventral (A, B) and dorsal (C) views of specimens showing the infraciliature and ventral and dorsal ridges. D. Silverline system on dorsal side of double-patella type. AZM, adoral zone of membranelles; DK, dorsal kineties; FVC, frontoventral cirrus; MC, marginal cirri. Scale bars: 30 μm.