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 Author Zhang, Ningning Author Yin, Shi Author Carreno, Ramon A. Author Zhang, Luping text Zootaxa 2021 2021-11-23 5071 2 206 222 journal article 3292 10.11646/zootaxa.5071.2.2 15c88b50-3c7a-48c4-981d-6d9239529e04 1175-5326 5723542 2D907411-3227-409E-B644-2FB86937D2FF 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. TABLE III. Morphometrics of Parahystrignathus tongbiguanensis gen. n. et sp. n. All measurements are in micrometers as range values followed by mean values in parentheses.

Parahystrignathus tongbiguanensis gen. n. et sp. n.
Holotype	Paratypes (n=6)	Paratypes (n=3)
from Ceracupes fronticornis	from Aceraius grandis
a	12.1	10.2-14.8 (12.3)	11.1-12.1 (11.5)
b	4.3	3.9-5.7 (4.7)	4.3-4.9 (4.7)
c	13.7	13.2-20.4 (16.8)	13.5-17.5 (15.7)
V	62	62-75 (65)	62-65 (63)
V’	66	67-79 (70)	67-69 (68)
Total body length	1520	1530-2150 (1910)	1630-1770 (1677)
Maximum body width	126	140-178 (156)	135-159 (147)
Stoma length	63	56-75 (68)	48-58 (53)
Head length	13	10-15 (13)	10-13 (11)
Head width	33	33-38 (35)	30-38 (34)
Total oesophagus length	345	361-448 (405)	341-376 (359)
Procorpus length	251	261-328 (291)	246-261 (254)
Isthmus length	35	33-48 (40)	28-38 (33)
Bulb length	68	65-85 (74)	68-78 (72)
Bulb width	63	60-80 (72)	60-75 (66)
Nerve ring from anterior end	205	193-225 (213)	188-208 (201)
Excretory pore from anterior end	594	584-700 (638)	512-604 (558)
Vulva from anterior end	936	970-1543 (1253)	1012-1147 (1065)
Egg length	95	95-105 (99)	98-100 (99)
Egg width	45	40-55 (48)	45-50 (48)
Tail	111	92-126 (115)	101-121 (108)

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.