Parahystrignathus tongbiguanensis, 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 : 218-219

Parahystrignathus tongbiguanensis gen. n. et sp. n.

Type-host: Ceracupes fronticornis (Westwood) .

Other-host: Aceraius grandis (Burmeister) .

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

Type-material: Holotype female ( HBNU-T001 ); paratypes: 9 females ( HBNU-T002-10 ).

Prevalence: Ex Ceracupes fronticornis : 16.5% (19 infected out of 115 examined), ex Aceraius grandis : 12.5% (2 infected out of 16 examined).

Intensity: Ex Ceracupes fronticornis : 1-27 (mean 8) specimens; ex Aceraius grandis : 2 (mean 2) specimen.

Site in host: Hindgut.

Representative DNA sequences: One partial 28S and one partial 18S rDNA sequences of the new species from C. fronticornis are deposited in the GenBank database under the accession numbers MZ330365 and MZ330361 , respectively.

Etymology: The specific epithet refers to the type locality of the species, Tongbiguan Nature Reserve, Yunnan Province, China.

Description. Female body relatively stout. Cuticle strongly annulated in spiny area and less annulated in other parts of body. Female reaching its maximum width in middle of body. Cervical cuticle bearing alternating rows of spines. First row with 16 spines ( Figs. 5B ; 6A ). Spines originating a short distance from head ( Figs. 5A, B ; 6A ), and extending to level of vulva ( Figs. 5C ; 6F ). Spine length of first row, second row and third row about 4 μm, 8 μm, and 11 μm, respectively. From third row to end of procorpus, size of spines similar in size but gradually becoming smaller after procorpus ( Fig. 5A, C ). Lateral alae absent. Head well-developed, set-off from body by a deep groove and bearing 8 papillae arranged in 4 pairs. Amphids with small, slit-like apertures. Oral opening triangular, surrounded by a cuticular ring ( Fig. 6C, D, E ). First cephalic annule absent ( Figs. 5B ; 6A ). Stoma relatively long, about 5 head lengths long, surrounded by an oesophageal collar. Oesophagus consisting of a muscular procorpus, short isthmus, and basal bulb. Procorpus clavate, bulb spherical, valve-plate well-developed. Nerve ring encircling procorpus at its midregion. Excretory pore located just posterior to base of bulb. Intestine simple, its anterior region slightly dilated. Reproductive system didelphic-amphidelphic. Vulva located posterior to mid-body. Vagina extending anteriorly, connecting with two opposite uteri. Eggs ovoid, smooth-shelled. Tail short, conical. Male not observed. Measurements in Table III.

Remarks. The new genus is similar to the following genera of hystrignathid nematodes by having a spiny cervical cuticle and didelphic reproductive system: Batwanema Morffe & García, 2013 ; Carlosia Travassos & Kloss, 1957 ; Chokwenema Morffe & García, 2013 ; Hystrignathus ; Lepidonema Cobb, 1898 ; Salesia Travassos & Kloss, 1958 ; Soaresnema Travassos & Kloss, 1958 ; Urbanonema Travassos & Kloss, 1958 and Xyo Cobb, 1898 .

Parahystrignathus gen. n. can be easily distinguished from Batwanema , Chokwenema , Lepidonema , and Salesia by having females with the cervical region armed with pointed spines instead of having scale-like projections. Carlosia differs from the new genus in the cervical region in having only two longitudinal rows of spines. Parahystrignathus gen. n. is different from Soaresnema by having females with a clavate vs. sub-cylindrical procorpus.

Parahystrignathus gen. n. differs from Hystrignathus , Urbanonema and Xyo by lacking the first cephalic annule. In addition, Hystrignathus differs from the new genus in having the cervical cuticle bearing opposite vs. alternating rows of spines. Urbanonema differs from Parahystrignathus gen. n. by having the stoma with a dilated anterior end. Xyo is different from the new genus in having the first row with 32 spines instead of 16 spines.

Figures

FIGURE 5. Parahystrignathus tongbiguanensis gen. n. et sp. n. Female. A: Anterior part of body, lateral view; B: cephalic end, lateral view (reconstructed from SEM images); C: Whole body, lateral view; D: Posterior end of body, lateral view; E: Cephalic end, en face view (reconstructed from SEM images); F: egg. scale bars: A, C, D, F = 100 μm; B = 30 μm; E = 10 μm.

FIGURE 6. Parahystrignathus tongbiguanensis gen. n. et sp. n. Female. SEM images. A: Cephalic end of body; B: Enlarged spines; C: Cephalic end, subapical view; D, E: Cephalic end, en face view, showing cephalic papillae (cp) and amphids (am); F: Vulval region, lateral view, showing the vulva and terminal part of spines; G: A part of body anterior to vulva, showing the posterior part of spines; H: A part of body at excretory pore region, showing the excretory pore and spines near the excretory pore; I: Enlarged image of excretory pore; J: Posterior end of body, showing the anus and tail.