Parakongonema sinica, Zhang & Yin & Carreno & Zhang, 2021

Zhang, Ningning, Yin, Shi, Carreno, Ramon A. & Zhang, Luping, 2021, Three new genera and new species of hystrignathid nematodes (Nematoda: Thelastomatoidea) from passalid beetles (Insecta: Passalidae) from Yunnan Province, China with phylogenetic analysis of Hystrignathidae, Zootaxa 5071 (2), pp. 206-222 : 212-218

Parakongonema sinica gen. n. et sp. n.

( Figs. 3-4 )

Type-host: Aceraius grandis (Burmeister) .

Other-host: Ceracupes fronticornis (Westwood)

Type-locality: Tongbiguan Nature Reserve , Yunnan Province, China (97°39’49”N, 24°36’55”E) .

Type-material: Holotype female ( HBNU-I-2021033 ); paratypes: 11 females (HBNU-I-2021034–2021044).

Prevalence: Ex Aceraius grandis : 75 % (12 infected out of 16 examined); ex Ceracupes fronticornis : 2.6 % (3 infected out of 115 examined).

Intensity: Ex Aceraius grandis : 2-13 (mean 6) specimens; ex Ceracupes fronticornis : 1-6 (mean 4) specimens.

Site in host: Hindgut.

Representative DNA sequences: Two partial 28S and one partial 18S rDNA sequences of the new species from A. grandis are deposited in the GenBank database under the accession numbers MZ330359 , MZ330363 and MZ330360 , respectively.

Etymology: The specific epithet refers to its geographic location (China).

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Description. Female body comparatively large and robust, widening from base of first cephalic annule, with maximum body diameter near mid-body, and gradually tapering towards anus. Cervical cuticle unarmed, strongly annulated ( Fig. 4B, C ). Rest of body with marked annuli decreasing their width towards level of anus. Subcuticular longitudinal striae present. Lateral alae originating from level of nerve ring and extending to level of anus. Lateral alae relatively narrower from nerve ring to base of bulb, becoming wider behind bulb base. Posterior ends of lateral alae rounded, forming short lobes ( Figs. 3D , 4E ). Head well developed, bearing eight rounded papillae. Amphids pore-like, laterally situated. Oral opening triangular, surrounded by cuticular ring. Ring surrounded by cuticular flap ( Fig. 4B ). First cephalic annule slightly inflated, about two head-lengths long. First cephalic annule cylindrical without subcuticular longitudinal striae ( Figs. 3C , 4B ). Stoma short, about 1.5 first cephalic annule lengths in diameter, surrounded by an oesophageal collar. Oesophagus consisting of a muscular, sub-cylindrical procorpus, very short isthmus, and spherical basal bulb with valve plate well developed. Intestine simple, sub-rectilinear, anterior portion slightly dilated. Nerve ring encircling procorpus at about mid-point of oesophagus. Excretory pore situated at about one body width posterior to basal bulb. Vulva located near mid-body. Vagina muscular, directed anteriorly. Didelphic-amphidelphic. Anterior ovary reflexed at about one half body width behind excretory pore, with posterior ovary reflexed at about one body width before the anus. Eggs ovoid, ornamented with rough longitudinal ridges on shell. Tail short, sharply attenuate, and filiform ( Figs. 3A , 4E ). Male not observed. Measurements in Table II.

Remarks. Parakongonema gen. n. is similar to the following genera of hystrignathid nematodes by having an unarmed cervical cuticle, sub-cylindrical procorpus and didelphic reproductive system: Anomalostoma ; Coynema ; Kongonema and Huntia gen. n.

Anomalostoma is different from the new genus by having the anterior part of stoma strongly swollen. Parakongonema gen. n. differs from Coynema by having a sub-cylindrical procorpus and the anterior region of the intestine slightly inflated rather than having a basal dilation of the procorpus and the anterior region of the intestine notably inflated.

The new genus is different from Kongonema in the cephalic structure (first cephalic annule cylindrical in the former vs. conical in the latter). Parakongonema gen. n. differs from Huntia gen. n. by the presence of a first cephalic annule instead of the absence of first cephalic annule. SEM observation of P. sinica gen. n. et sp. n. revealed the oral opening surrounded by a cuticular flap. This structure has not been observed on the species of Coynema , Kongonema , and Huntia by SEM observations. However, whether the flap of Anomalostoma species is present needs to be identified by the SEM observation.

Figures

FIGURE 3. Parakongonema sinica gen. n. et sp. n. Female. A: Whole body, lateral view; B: Anterior part of body, lateral view; C: Cephalic end of body, lateral view (reconstructed from SEM images); D: posterior end of body, ventral view, showing the lateral alae; E: egg. scale bars: A, B, D = 100 μm, C, E = 50 μm.

FIGUR 4. Parakongonema sinica gen. n. et sp. n. Female. SEM images.A: Whole body, lateral view, showing a lateral ala; B: Cephalic end, subapical view, showing cephalic papillae (cp) and amphids (am); C: Anterior part of body, ventral view, showing beginning of lateral alae and excretory pore (ep); D: Enlarged image of excretory pore; E: Posterior end of body