Cryphodera gayae n. sp. (Nematoda: Heteroderidae), from root of Lagerstroemia indica in Korea

The body is globose, varies in size (513.4–778.3 µm). Cuticle is annulated on entire body (Fig. 3A). Female is pearly white when young and becoming yellowish. Cuticle does not transform to a cyst and is partially covered by some tissue materials (Fig. 1B). Head region is not set off, labial disk is distinct and neck is distinct, usually bent laterally. Stylet is 30.1 µm long. Median bulb is nearly rounded to oval, with distinct valve plates situated centrally (Fig. 3D). Except for the stylet and median bulb, most internal structures are difficult to observe in adult females. Excretory pore is located posterior to metacorpus. Vulva is located sub-terminal to terminal, near the anus. Vulval lips are pronounced with protrusion. Vulva-anus region is slightly concave to flat (Fig. 3B). Mature females contain less than 100 eggs in various stages of development. Perineal patterns are difficult to prepare flat due to a prominent protuberance. Perineal pattern is ovoid with fine, smooth and continuous striae. Vulva is surrounded by circles of striae (Fig. 3C).

Not found.

The body is cylindrical, tapering posteriorly, straight or slightly ventrally curved after fixation (Fig. 4A). The lip region is offset, a labial disc with four annuli (Fig. 5A). Stylet is long, cone is straight, and shaft is cylindrical. Stylet knobs are well developed with distinct flat or droop to posterior. Body annuli is 1.5–1.6 µm in width at mid-body and three incisures are visible in lateral position (Fig. 4E). Tail is long conoid, gradually tapering to a sharply pointing terminus. Hyaline terminal section is 38.4 (31.7–47.8) µm long, occupying 49.4 to 62.4% of tail length. Particularly, nearly 65% of J2 specimens of the present population exhibited a distinct constriction around middle of the hyaline region (Fig. 4C).

Cryphodera gayae n. sp. has the general characteristics of the genus Cryphodera. Diagnostic characters of C. gayae n. sp. with other species are compiled (Tables 2 and 3). The new species having morphological characters of protruding vulval lips, flat to concave anus-vulva profile, three lateral lines in J2s, appears most similar to C. brinkmani but differs by the shorter stylet length of J2 (26.8–31.3 µm vs 31.6–35.4 µm), stylet knob shape of J2 (flat posteriorly vs concave), egg numbers in mature female (64–69 vs 15–45). Also, J2 of C. brinkmani exhibited a small mucro at the tip of the tail (Vovlas et al., 2013) but C. gayae n. sp. has sharply pointing tip with constriction at the middle of hyaline without mucro-like tip. C. gayae n. sp. differs from C. kalesari by the longer vulva-anus distance (51.9–54.1 µm vs 35 µm), the bigger body size of female (363.1–544.6 µm vs 272–353 µm in length), in J2, the longer tail length (59.6–76.7 µm vs 27–54 µm), longer hyaline length (31.7–47.8 µm vs 18–26 µm) and the shape of tail (sharply pointing tip with constriction at the middle of hyaline vs narrow rounded without constriction). From C. sinensis, the new species differs by the longer J2 tail length (59.6–76.7 µm vs 52.0–65.0 µm) and longer hyaline portion (31.7–47.8 µm vs 24.5–35.0 µm) of J2. C. gayae n. sp. can be distinguished from the remaining four species of Cryphodera, namely, C. eucalypti (Colbran, 1966), C. podocarpi (Wouts, 1973; Luc et al., 1978), C. nothophagi (Wouts, 1973; Luc et al., 1978) and C. coxi (Wouts, 1973; Luc et al., 1978) by the shape of the J2 tail terminus (sharply pointing tip with constriction at the middle of hyaline vs narrow rounded) and the shape of the vulval lips (pronounced protruding vs protruding slightly out of body contour).

The sequenced LSU D2–D3 segments and ITS region are 792 and 1,028 bp, respectively. A BLASTn search of C. gayae n. sp. on the LSU D2–D3 segments revealed high-scoring matches with some Cryphodera species, the most similar to C. sinensis (GenBank accession number JX566455), from ramie in Hunan Province in China. The identity of sequence was 95% (750/789), with four insertions/deletions (0.1%). A BLASTn search of C. gayae n. sp. on the ITS region also revealed similarities with some Cryphodera species, but the identities were about 85%. The highest match was C. brinkmaini (JQ965678), with only 88% identity (618/703) and 23 insertions/deletions (3%). Compared with C. sinensis (JX566457), C. gayae n. sp has 83% identity (892/1,075) and 85 insertions/deletions (7%).

The molecular phylogenetic relationships of the new species are shown in Figures 6 and 7. Figure 6 represents a phylogenetic tree based on LSU D2–D3 segments. The average nucleotide composition is as follows: 22.34% A, 22.47% C, 29.58% G and 25.61% T. Using Scutellonema brachyurus as the outgroup taxa, the molecular phylogeny strongly supports monophyly of Cryphodera (100% posterior probability). Figure 7 represents a phylogenetic tree based on ITS region. The average nucleotide composition is as follows: 21.11% A, 22.91% C, 27.17% G and 28.81% T. Using Hoplolaimus columbus as outgroup taxa, all Cryphodera sequences reside within a well-supported monophyletic clade with 100% support. The sequence of C. gayae n. sp. clade is in separate position to C. sinensis founded from ramie (Zhuo et al., 2014).

Figure 6:

Figure 7:

Cryphodera gayae n. sp. was collected from roots of crapemyrtle (Lagerstroemia indica L.), Gaya district (N35°42′45.2″, E128°17′30.9), Gyeongsangbuk-do, Korea in 2019. The soil type is sandy loam, and the local climate is marine west coast of Köppen climate classification.

Holotype (female and J2): isolated from roots from type locality and habitat. Slides T-721t and T-722t deposited in the United States Department of Agriculture Nematode Collection (USDANC), Beltsville, Maryland. Paratype (female and J2): same data and repository as holotype. Slides T-7228p and T-7229p.

The specific epithet refers to the Gaya dynasty before 400 AD in ancient history of Korea. The species habitat is the geographical capital region of Gaya. Gaya was a confederacy of territorial polities nobility in the Nakdong river basin of southern Korea.

Key to the species of Cryphodera, based on second-stage juveniles:

1. — Three lip annules (lateral)2

— Four to five lip annules (lateral)4

2. — Stylet ≤ 29 μm, knobs anteriorly flatC. kalesari

— Stylet > 29 μm3

3. — Tail of J2 with narrow roundedC. eucalypti

— Tail of J2 with point, mucro-like tipC. sinensis

4. — Four lip annules5

— Five lip annulesC. podocarpi

5. — Three lateral lines near mid-body6

— Four lateral lines near mid-bodyC. nothophagi

6. — Tail length < 60 μm, tail tip narrow roundedC. coxi

— Tail length ≥ 60 μm, tail tip pointed7

7. — Tail of J2 with mucro-like tip; stylet = 33.3 μm, DGO = 5.8C. brinkmani

— Tail of J2 with constriction at the middle of hyaline; style L = 29.8,DGO = 4.6C. gayae n. sp.