Strongylidium koreanum, Chae & Park & Min, 2023

Chae, Kyu-Seok, Park, Kyung-Min & Min, Gi-Sik, 2023, Strongylidium koreanum n. sp. (Protozoa: Ciliophora), a new soil species from South Korea, Zootaxa 5227 (2), pp. 194-204 : 196

publication ID	https://doi.org/ 10.11646/zootaxa.5227.2.2
publication LSID	lsid:zoobank.org:pub:51A480AD-6FD5-4FDC-9EC9-24441DB568AD
DOI	https://doi.org/10.5281/zenodo.10555187
persistent identifier	https://treatment.plazi.org/id/7A2387FA-D060-FFFF-FF45-FF74E0080C5B
treatment provided by	Plazi
scientific name	Strongylidium koreanum
status	sp. nov.

Treatment

Strongylidium koreanum n. sp.

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ; Table 1)

Diagnosis. Size 125–150 × 35–55 µm in vivo and 105 × 32 µm on average in protargol preparations. Body elliptical in outline, anterior end broader than the posterior end. Two macronuclear nodules and two to three micronuclei in the left cell. Cortical granules absent. Adoral zone with 26 membranelles on average. Three frontal cirri. Single buccal, fronto-ventral cirrus, and postoral ventral cirrus. Right and left ventral rows with 21 and 35 cirri on average, respectively; 37 cirri in right marginal row and 29 cirri in left marginal row. Right and left marginal rows with 37 and 29 cirri, respectively. Three bipolar dorsal kineties and three caudal cirri.

Type locality. Soil from Jeju Island, South Korea, 33°24′15.4′′ N, 126°20′59.7′′ E GoogleMaps .

Material examined. A holotype slide ( NIBRPR0000110849 ) and one paratype slide ( NIBRPR0000110850 ) with protargol-impregnated specimens (including some dividers) were deposited at the National Institute of Biological Resources ( NIBR) , South Korea. Each specimen is marked with circles or bars at the bottom of the slides. And, two non-type slides were deposited at Inha University (accession numbers: INHC314 and INHC315 ) .

Etymology. Named after the country where the species was discovered: South Korea.

Gene sequence. The 18S rRNA gene sequence of S. koreanum n. sp. has been deposited in GenBank under accession number MW344121 View Materials .

Zoobank registration.

Present work: urn:lsid:zoobank.org:pub:629C287E-594A-4AFA-8030-C1568850ADAE

Strongylidium koreanum n. sp.: urn:lsid:zoobank.org:act:56366467-DC77-4CC1-8DA9-D98DF1D918D8

Description of interphasic specimens. Body size was 125–150 × 35–55 µm in vivo (n = 5), on average 105 × 32 µm in protargol preparations ( Table 1). Slender body shape with tapered posterior end; grayish at low magnification, flexible ( Figs. 1A, C, D View FIGURE 1 , 2A–C View FIGURE 2 , 3A–C View FIGURE 3 ). Two macronuclear nodules, ellipsoidal, 8–18 × 5–10 µm in size in stained cells, arranged in left half of cell. Two to three micronuclei, spherical, 2–4 × 2–4 µm in protargol preparations, adjacent to the macronuclear nodules ( Figs. 1D View FIGURE 1 , 2F View FIGURE 2 , 3C View FIGURE 3 ). Contractile vacuole as approximately 10 µm in diameter when fully extended, slightly above the left mid-body ( Figs. 1B View FIGURE 1 , 2B View FIGURE 2 ), collecting canals not recognizable. Locomotion without peculiarities, usually moderately fast, creeping on the bottom of the Petri dish.

Frontal and transverse cirri approximately 13 µm long in vivo; remaining cirri approximately 8.5 µm long. Three enlarged frontal cirri, fronto-ventral cirrus (III/2) below right frontal cirrus; one buccal cirrus; one postoral ventral cirrus, behind the proximal end of the adoral zone of membranelles; two ventral cirral rows, left ventral row with (=pseudorow; see Morphogenesis section) 27–42 cirri, commences approximately near right frontal cirrus, right ventral row with 15–28 cirri, starts slightly above mid-body. One left marginal row with 23–36 cirri commences above the level of the buccal vertex and extends the posterior cell end; one right marginal row with 30–46 cirri begins at the level of the right frontal cirrus, extends along the right cell margin, and terminates at a level similar to that of the left marginal row ( Figs. 1A–C View FIGURE 1 , 3A, B View FIGURE 3 ). Dorsal cilia approximately 3 µm long in vivo ( Fig. 2G View FIGURE 2 ), each with one caudal cirrus at distal terminus.

The oral zone is composed of 23–32 membranelles, occupying approximately the anterior fourth of the ventral side in the stained specimens. Paroral slightly curved inwards and endoral more or less straight, endoral starts at the level of the anterior buccal cirrus ( Figs. 1A, C View FIGURE 1 , 2E View FIGURE 2 , 3A, B View FIGURE 3 ).

Morphogenesis. In the middle stage, frontal-ventral-transverse cirral anlagen (FVTA) begin to develop and differentiate into dividers ( Figs. 3D–G View FIGURE 3 , 4A–D View FIGURE 4 ). In the late stage, the cirri segregate from anterior to posterior in the following manner. FVTA II produces the middle frontal and buccal cirrus; FVTA III produces the rightmost cirrus and cirrus III/2; FVTA IV differentiates two or five cirri of the middle part of the left ventral cirral row and originates the postoral ventral cirrus; FVTA V contributes to the posterior part of the left ventral cirral row; FVTA VI produces the whole right ventral cirral row and the anterior part of the left ventral cirral row ( Figs. 3H–K View FIGURE 3 , 4E–H View FIGURE 4 ). Finally, the new cirri arrange in a mature pattern and replace the parental structures.

The marginal cirral row and dorsal kinety anlagen developed within the parental structures by intrakinetal proliferation ( Figs. 3D–G View FIGURE 3 , 4A–D View FIGURE 4 ). The parental cirri were replaced by new cirral rows and dorsal kineties. The two macronuclear nodules fused into a single mass. In the late dividers, the micronuclei and macronuclear segments began to divide ( Figs. 3K View FIGURE 3 , 4H View FIGURE 4 ).

Molecular analyses. The 18S rRNA gene sequence was 1,585 bp and had a GC content of 44.9% (GenBank accession number MW344121 View Materials ). The species/genera of Strongylidiidae clustered with one group. This family consisted of the genera Hemiamphisiella , Pseudouroleptus , and Strongylidium in the ML and BI trees. The genus Strongylidium is distinct from the genera Hemiamphisiella and Pseudouroleptus . All Strongylidium species were clustered together with high supporting values. The support in the Bayesian inference analyses was high (posterior probability = 1.00) and ML analyses (bootstrap value <80%) ( Fig. 5 View FIGURE 5 ). The pairwise similarities among the Strongylidium species range from 96.2% to 99.4% ( Table 3).