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Description and molecular characterization of Geraldius jejuensis n. sp. (Nematoda: Chambersiellidae) from Korea

Abraham Okki Mwamula

Abraham Okki Mwamula

Research Institute of Invertebrate Vector, Kyungpook National UniversitySangju, Republic of Korea
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Mwamula, Abraham Okki
, 
Chang-hwan Bae

Chang-hwan Bae

Biodiversity Research Department, Species Diversity Research Division, National Institute of Biological ResourcesIncheon, Republic of Korea
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Bae, Chang-hwan
, 
Dae Geun Lee

Dae Geun Lee

Department of Ecological Science, Kyungpook National UniversitySangju, Republic of Korea
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Lee, Dae Geun
, 
Yi Seul Kim

Yi Seul Kim

Research Institute of Invertebrate Vector, Kyungpook National UniversitySangju, Republic of Korea
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Kim, Yi Seul
, 
Yeong-Don Lee

Yeong-Don Lee

Hallasan Research Department, World Heritage Office, Jeju Special Self-Governing ProvinceJeju, Republic of Korea
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Lee, Yeong-Don
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Dong Woon Lee

Dong Woon Lee

  • Research Institute of Invertebrate Vector, Kyungpook National UniversitySangju, Republic of Korea
  • Department of Ecological Science, Kyungpook National UniversitySangju, Republic of Korea
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Lee, Dong Woon
  
Jun 21, 2025
Description and molecular characterization of Geraldius jejuensis n. sp. (Nematoda: Chambersiellidae) from Korea's Cover Image
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Article Category: Research Paper
Published Online: Jun 21, 2025
Received: Apr 10, 2025
DOI: https://doi.org/10.2478/jofnem-2025-0023
Keywords
© 2025 Abraham Okki Mwamula et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1:

Line drawings of Geraldius jejuensis n. sp. (A–G): A: Anterior end, surface view; B: Vulval region; C: Female tail region; D: Anterior region with the entire esophagus; E: Anterior region with the corpus region; F: Female reproductive system; G: Male tail region, including the copulatory apparatus and arrangement of caudal papillae.
Line drawings of Geraldius jejuensis n. sp. (A–G): A: Anterior end, surface view; B: Vulval region; C: Female tail region; D: Anterior region with the entire esophagus; E: Anterior region with the corpus region; F: Female reproductive system; G: Male tail region, including the copulatory apparatus and arrangement of caudal papillae.

Figure 2:

Photomicrographs of Geraldius jejuensis n. sp. (A–M). A, F: Female anterior region; B: Female reproductive system; C: Lateral field; D: Ventral view of the vulva; E: Posterior region of female tail; G: Rectum and anal region; H: Female tail region; I: Anterior region of female tail, including position of phasmids; J: Anterior region with cirri; K, L, M: Variation in vulval region in lateral view. The arrow labeled eh indicates the position of excretory pore and hemizonid; v = transverse vulva; p = phasmids (Scale bars: A, B, H = 50 μm; C, D, E, G, I, J, K, L and M = 20 μm; F = 30 μm).
Photomicrographs of Geraldius jejuensis n. sp. (A–M). A, F: Female anterior region; B: Female reproductive system; C: Lateral field; D: Ventral view of the vulva; E: Posterior region of female tail; G: Rectum and anal region; H: Female tail region; I: Anterior region of female tail, including position of phasmids; J: Anterior region with cirri; K, L, M: Variation in vulval region in lateral view. The arrow labeled eh indicates the position of excretory pore and hemizonid; v = transverse vulva; p = phasmids (Scale bars: A, B, H = 50 μm; C, D, E, G, I, J, K, L and M = 20 μm; F = 30 μm).

Figure 3:

Photomicrographs of Geraldius jejuensis n. sp. (A–J). A, B, D: Posterior part of esophagus with variation in position of excretory pore and hemizonid; C: Male anterior region; E: Dorsal lateral view of the three papillae located in close proximity to cloaca; F: Arrangement of post–cloacal papillae, including the preceding trio; G, I: Male tail region with post–cloacal papillae arrangement; H: Arrangement of post–cloacal papillae in relation to phasmids; J: Male copulatory apparatus and cloacal opening with the three additional midventral papillae on anterior cloacal lip. The arrow labeled eh indicates the position of excretory pore and hemizonid; unlabeled arrows = position of papillae; p = phasmids (Scale bars: A, B, C, D, E, F, H, and J = 20 μm; G, I = 30 μm).
Photomicrographs of Geraldius jejuensis n. sp. (A–J). A, B, D: Posterior part of esophagus with variation in position of excretory pore and hemizonid; C: Male anterior region; E: Dorsal lateral view of the three papillae located in close proximity to cloaca; F: Arrangement of post–cloacal papillae, including the preceding trio; G, I: Male tail region with post–cloacal papillae arrangement; H: Arrangement of post–cloacal papillae in relation to phasmids; J: Male copulatory apparatus and cloacal opening with the three additional midventral papillae on anterior cloacal lip. The arrow labeled eh indicates the position of excretory pore and hemizonid; unlabeled arrows = position of papillae; p = phasmids (Scale bars: A, B, C, D, E, F, H, and J = 20 μm; G, I = 30 μm).

Figure 4:

Bayesian tree inferred under the GTR + I + G model from 18S–rRNA gene sequences of Geraldius spp. and other species from various genera. Posterior probability values exceeding 50% are given on appropriate clades. The studied population is indicated in bold text. Outgroup taxa: Alloionema appendiculatum, Neoalloionema tricaudatum, Strongyloides robustus and Rhabditophanes sp.
Bayesian tree inferred under the GTR + I + G model from 18S–rRNA gene sequences of Geraldius spp. and other species from various genera. Posterior probability values exceeding 50% are given on appropriate clades. The studied population is indicated in bold text. Outgroup taxa: Alloionema appendiculatum, Neoalloionema tricaudatum, Strongyloides robustus and Rhabditophanes sp.

Figure 5:

Bayesian tree inferred under the GTR + I + G model from LSU D2–D3 partial sequences of Geraldius spp. and other species from various genera. Posterior probability values exceeding 50% are given on appropriate clades. The studied population is indicated in bold text. Outgroup taxa: Steinernema glaseri and Necator americanus.
Bayesian tree inferred under the GTR + I + G model from LSU D2–D3 partial sequences of Geraldius spp. and other species from various genera. Posterior probability values exceeding 50% are given on appropriate clades. The studied population is indicated in bold text. Outgroup taxa: Steinernema glaseri and Necator americanus.

Morphometrics of Geraldius jejuensis n_ sp_ from Korea_

Character Holotype ♀ ♀♀ ♂♂
n 16 19
L 1187.0 1163.4±61.4 (1040.0–1306.0) 1112.8±92.7 (928.0–1255.0)
a 24.8 26.9±1.9 (23.6–30.3) 30.7±2.8 (26.8–36.5)
b 5.4 5.4±0.2 (4.9–5.9) 5.2±0.5 (4.1–6.0)
c 7.4 7.4±0.3 (7.0–7.9) 9.4±0.9 (8.1–11.0)
c' 6.2 6.3±0.4 (5.7–7.2) 3.7±0.4 (3.1–4.8)
V or T 48.2 48.0±0.7 (46.8–49.3) 64.2±3.9 (54.5–69.5)
G1 37.8 32.1±2.6 (27.6–37.8) –
G2 30.9 30.0±3.9 (23.9–40.3) –
Lip height 3.5 3.4±0.3 (3.0–4.0) 3.4±0.3 (3.0–4.0)
Lip diam. 10.5 10.5±0.5 (9.5–11.5) 10.3±0.6 (8.5–11.0)
Cheilostom length 5.5 5.0±0.6 (4.0–6.0) 4.7±0.5 (4.0–5.5)
Cheilostom diam. 4.5 5.1±0.9 (4.0–6.5) 5.5±0.5 (4.5–6.5)
Gymnostom length 6.5 5.7±0.8 (4.5–7.5) 5.5±0.5 (4.5–7.0)
Stegostom length 18.5 18.2±1.4 (16.0–20.0) 18.2±0.9 (17.0–20.0)
Total stoma length 31.0 28.8±1.1 (27.0–31.0) 28.5±0.8 (27.0–30.0)
Amphidial opening 12.0 10.9±0.9 (9.5–13.5) 10.9±1.1 (9.0–13.5)
Corpus length 137.0 131.4±4.5 (123.5–140.0) 127.8±6.4 (112.0–142.5)
Metacorpal diam 21.5 20.4±0.8 (19.0–22.0) 19.3±1.1 (17.0–21.0)
Isthmus length 53.5 53.2±2.2 (50.5–58.0) 53.8±3.3 (48.0–59.0)
Corpus/isthmus 2.6 2.5±0.1 (2.4–2.7) 2.4±0.1 (2.2–2.6)
Anterior to nerve ring 146.0 145.0±6.7 (131.0–155.5) 135.6±6.4 (124.0–149.0)
Anterior to Ex. pore 156.0 164.9±9.1 (148.0–183.0) 151.6±11.5 (131.0–178.0)
Anterior to Deirid 162.0 165.4±8.2 (149.0–183.0) 151.4±11.5 (132.0–179.0)
Anterior to Hemizonid 156.0 163.9±8.5 (147.5–180.0) 151.1±11.4 (131.0–177.0)
Basal bulb length 31.5 33.8±1.3 (31.5–36.0) 33.5±1.9 (30.0–36.5)
Basal bulb diam. 25.0 24.6±0.7 (23.0–26.0) 23.7±1.7 (20.0–26.0)
Esophagus length 220.5 217.2±5.4 (207.0–227.0) 213.6±8.9 (193.0–229.5)
Cardia length 10.5 9.9±1.0 (7.0–11.5) 10.2±1.4 (7.5–12.0)
Maximum body diam. 48.0 43.3±3.2 (38.0–48.0) 36.4±3.5 (30.0–43.0)
Vulval body diam. 45.5 40.4±3.3 (33.5–45.5) –
Rectum 36.0 38.5±2.7 (34.0–43.5) –
Anal / cloacal body diam. 26.0 24.8±1.0 (22.5–27.0) 32.5±3.1 (28.0–39.0)
Phasmids to anus 59.0 64.8±6.4 (55.0–78.5) 55.0±4.6 (44.5–66.0)
Tail length 160.0 156.4±9.8 (146.0–177.0) 118.9±10.6 (101.0–135.0)
Phasmids/tail (%) 39.3 41.4±2.7 (36.7–46.6) 46.5±4.8 (40.2–54.2)
Spicules – – 54.3±2.6 (50.5–59.5)
Gubernaculum – – 30.7±1.7 (27.0–33.5)
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