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               Helicotylenchus coreanus n. sp. (Nematoda: Hoplolaimidae): a new spiral nematode associated with Abies koreana Wils. from the Republic of Korea Cover

Helicotylenchus coreanus n. sp. (Nematoda: Hoplolaimidae): a new spiral nematode associated with Abies koreana Wils. from the Republic of Korea

Open Access
|May 2026

Figures & Tables

Figure 1

The state of the host plant (Abies koreana Wils.) at the type locality (a, b). (a) Dead Korean fir plant (inset: Dead, brown twigs/shoot); (b) Healthy Korean fir plant (inset: Healthy twigs/shoot).

Figure 2

Line drawings of Helicotylenchus coreanus n. sp. (a–j). (a) Female entire body; (b) head region; (c) pharyngeal region; (d–h) variation in female tail; (i) lateral field in tail region; and (j) lateral field at level of vulva.

Figure 3

Light micrographs of Helicotylenchus coreanus n. sp. (a–p). (a) Female anterior region (b, h, m, n) variation in female tail; (c) pharyngeal region; (d) vulval region (ventral view); (e, f) head region; (g) lateral field at mid-body; (i) posterior pharyngeal region; J: vulval region (lateral view); (k, l) lateral field at level of vulva; (o, p) variation in position of phasmids. The arrows labeled v, a, and p indicate the position of vulva, anus, and phasmids, respectively (scale bars: a = 50 μm and b–p = 20 μm).

Figure 4

Bayesian tree inferred under the GTR + I + G model from 18S-rRNA gene sequences of Helicotylenchus spp. Posterior probability values exceeding 50% are given on appropriate clades. The studied populations are indicated in bold text.

Figure 5

Bayesian tree inferred under the GTR + I + G model from LSU D2–D3 partial sequences of Helicotylenchus spp. Posterior probability values exceeding 50% are given on appropriate clades. The studied populations are indicated in bold text.

Figure 6

Bayesian tree inferred under the GTR + I + G model from COI gene sequences of Helicotylenchus spp. Posterior probability values exceeding 50% are given on appropriate clades. The studied populations are indicated in bold text.

Morphometrics of Helicotylenchus coreanus n_ sp_ from Korea

Type population (H03)Population two (H04)
CharacterHolotype ♀♀♀♀♀
n 1712
L 684649.5 ± 41.7 (576–716)719.6 ± 44.9 (643–774)
a 25.523.7 ± 1.5 (20.9–26.4)24.1 ± 1.7 (21.1–26.8)
b 5.85.3 ± 0.5 (4.6–6.0)5.8 ± 0.5 (4.9–6.7)
b4.64.5 ± 0.3 (4.0–4.9)4.8 ± 0.3 (4.3–5.2)
c 24.725.1 ± 3.8 (19.6–31.4)28.5 ± 6.7 (22.0–45.7)
c'1.61.5 ± 0.3 (1.0–1.9)1.4 ± 0.3 (0.9–1.9)
V 59.961.2 ± 1.4 (59.1–63.8)61.3 ± 2.0 (58.4–64.1)
G 1 16.117.6 ± 1.4 (15.7–20.5)17.0 ± 1.4 (14.7–19.4)
G 2 15.817.1 ± 1.4 (15.2–19.5)16.7 ± 1.2 (14.6–18.1)
MB49.351.6 ± 3.6 (43.9–58.3)48.1 ± 4.2 (40.1–53.5)
M 48.147.3 ± 1.8 (44.0–49.5)47.4 ± 1.0 (45.2–48.8)
O 32.532.8 ± 3.4 (26.1–37.5)34.0 ± 3.7 (28.6–41.8)
Lip height5.05.4 ± 0.5 (4.5–6.5)5.3 ± 0.6 (4.5–6.0)
Lip diam.8.08.2 ± 0.3 (7.5–9.0)8.4 ± 0.5 (7.5–9.5)
Anterior to the median bulb valve73.075.0 ± 5.7 (63.5–83.5)72.4 ± 6.6 (61.0–81.5)
Stylet length29.530.1 ± 1.1 (28.0–32.0)29.6 ± 1.6 (28.0–32.0)
Conus length14.514.2 ± 0.9 (12.5–15.5)14.0 ± 0.8 (13.0–15.5)
DGO9.59.9 ± 0.9 (8.0–11.0)10.1 ± 1.0 (8.0–12.0)
Anterior to nerve ring82.089.7 ± 7.5 (80.0–104.5)89.5 ± 7.6 (78.0–104.0)
Secretory-Excretory pore109.0112.7 ± 6.7 (96.0–123.5)116.0 ± 5.7 (104.0–123.0)
Esophageal–intestinal junction119.0124.0 ± 7.7 (110.5–144.0)125.5 ± 11.1 (105.0–138.0)
Anterior to end of glandular overlap148.0145.5 ± 7.1 (131.5–157.5)150.5 ± 3.0 (145.0–155.5)
Maximum body diam.27.027.5 ± 1.9 (24.0–31.5)29.9 ± 2.2 (26.0–33.5)
Lateral fields at mid-body7.06.7 ± 0.5 (6.0–7.5)7.4 ± 0.5 (7.0–8.5)
Lateral fields at vulva9.08.6 ± 0.7 (7.5–10.0)9.3 ± 0.4 (9.0–10.0)
Rectum length10.511.4 ± 2.0 (9.0–15.0)12.4 ± 1.8 (10.0–16.0)
Anal body diam.17.518.0 ± 1.6 (14.0–21.0)18.8 ± 1.4 (17.0–21.0)
Tail length28.026.4 ± 3.9 (19.5–31.5)26.4 ± 5.8 (15.5–34.5)
Tail annuli19.020.6 ± 3.7 (16.0–31.0)19.5 ± 3.9 (13.0–24.0)
Annuli to phasmids5.02.3 ± 2.7 *3/ (0.0–7.0)1.2 ± 2.2 (0.0–6.0)
Hyaline length4.54.2 ± 0.6 (3.0–5.0)4.3 ± 0.7 (3.0–5.5)
DOI: https://doi.org/10.2478/jofnem-2026-0013 | Journal eISSN: 2640-396X | Journal ISSN: 0022-300X
Language: English
Page range: 150 - 164
Submitted on: Feb 10, 2026
Accepted on: Mar 29, 2026
Published on: May 15, 2026
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year

© 2026 Abraham Okki Mwamula, Chang-hwan Bae, Suk-Hyung Ko, Yeong-Don Lee, Eun-Young Yim, Seung-hoon Lee, Dong Woon Lee, published by Society of Nematologists, Inc.
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.