Delatylus andersoni, Yu & Munawar & Gu & Ye, 2018

Yu, Qing, Munawar, Maria, Gu, Jianfeng & Ye, Weimin, 2018, Delatylus andersoni n. gen., n. sp. (Nematoda: Neotylenchidae) Isolated from White Pine (Pinus monticola) Lumber from USA and Intercepted in Ningbo, China, Journal of Nematology 50 (1), pp. 69-76 : 71-75

Delatylus andersoni n. sp. * ( Figs. 1–4 )

Only females of one form were found from these samples. Although some morphometric differences were observed between the three populations, the main morphological characters and the 28S sequences were identical.

Measurements

Measurements of the holotype and paratype females of D. andersoni n. sp. are given in Table 1 .

Description

Female: Body of the young female is nonobese and straight when heat relaxed, semiobese and dorsally curved for mature ones; cuticle with indistinct annulations; lateral fields raised with 10-12 straight lines in mid-body, fewer lines toward the ends; deirids papilla shaped; lip region about 2µm high, the oral area slightly raised, when viewed with SEM: the en face view shows both inner labial and outer labial plates; the inner labial plate is rounded and has a raised, dumbbell-shaped oral disk with six inner labial papillae, three on each side of a dorsal ventrally elongated oral aperture; the out labial plate with six sectors: four submedian ridges with four outer labial papillae and two smaller lateral ridges; amphidal apertures on and at the end of the lateral ridges, round, and not dorsally displaced; stylet with three distinct knobs of equal size that slope backwards; cone slightly shorter than the shaft, with 4 to 5 rings (1 or 2 on the cone); pharynx spindle shaped, nonmuscular, and without apparent median bulb and isthmus; dorsal gland opening about 2µm behind the base of the stylet knobs, and subventral gland openings about two stylet lengths behind the knobs, both dorsal gland and subventral glands free in the body cavity, with larger dorsal gland; pharyngo-intestinal junction forming a distinct valve or cardium of different shapes, and located immediately posterior to the nerve ring; excretory pore posterior to the nerve ring; hemizonid immediately after the excretory pore; intestinal lumen widens immediately following the pharyngo-intestinal junction, and with a broad rectum; genital system with one outstretched gonad outstretched that overlaps the dorsal gland in mature females, without a discernible spermatheca (one specimen showed a diminished spermatheca), and consists of ovary, oviduct, quadricolumella, uterus, and vagina; oocytes at anterior half with two or three rows of cells; oviduct of three-celled quadricolumella distinct with 20 to 30 cells; uterus cylindrical; and vagina directed anteriorly; vulva not protruding, the opening as wide as body width; post-uterine sac absent; anus located about the 1/3 the distance between the vulva and the tail terminus; tail narrows quickly with a conical terminus.

Male: not found.

Juvenile: Similar to female, but smaller; the body straight when relaxed; stylet knobs, pharynx, and the pharyngo-intestinal junction valve similar to those in females; the intestinal lumen relative to the body width wider than in females; tail similar to females.

Type habitat and locality: Lumber of white pine from the USA, intercepted in Ningbo Entry–Exit Inspection and Quarantine Bureau, China, in 2016 .

Type specimens: Holotype female and 10 paratypes of D. andersoni n. sp. were deposited in the Canadian National Collection of Nematodes ; Ottawa, ON, Canada, under the accession number T547 . Five paratypes were deposited in each of the following collections: USDA Nematode Collection , Beltsville , MD under the accession numbers XXX and the Ningbo Entry–Exit Inspection and Quarantine Bureau Nematode Collection , Ningbo , China. The new genus has been registered in the ZooBank database (zoobank.org) under the identifier XXXXX, and the new species binomial under the identifier XXXXX.

Etymology: The specific epithet is patronymic, honoring Dr. Roger Anderson, a distinguished nematode taxonomist with Agriculture and Agri-Food Canada.

Molecular characterization and phylogenetic analysis: The 18S, ITS 1, 5.8S rDNA, ITS 2, 28S (3256 bp) and 28S D2/D3 (805 bp) of D. andersoni n. gen., n. sp. were sequenced with GenBank accession numbers KY907662 and KY907663, respectively. The blast search on 1749 bp 18S yielded a significant match as Hexatylina species with 95% to 97% identity, including Deladenus, Howardula, Fergusobia, Tylenchomorpha, Hexatylus, and Rubzovinema. The blast search on 240 bp 5.8S is 91% identical with Deladenus, 86% identical with Tylenchomorpha, and 85% identical with Rubzovinema. The blast search on 805 bp 28S is 93% identical with Fergusobia , 88% identical with Deladenus, Psyllotylenchus, and Tylenchomorpha. Sequences of ITS 1 and ITS 2 are very variable and did not yield any significant match with the other sequenced Hexatylina genera.

The inferred phylogeny based on 18S ( Fig. 5 ) placed D. andersoni n. gen.; n. sp. in a basal position for sequenced genera in Hexatylina , no close grouping was identified between the new genus and the other sequenced Hexatylin genera. The phylogenetic tree inferred by 28S D2/D3 ( Fig. 6 ) placed it in

0.01 length units

the same clade with a Fergusobia species with 100% support. This clade is sister to Deladenus, Rubzovinema, Tylenchomorpha, and Psyllotylenchus.

Remarks: Delatylus andersoni n. gen., n. sp. shares the characters of Deladenus (pharyngo-intestinal junction at the nerve ring), Hexatylus (anterior directed vagina), and Fergusobia (obese and dorsally curved mature female). Although nematodes recovered from the lumber of the pine trees were of the mycetophagous form, and no other forms were found; this does not exclude the possibility that it may have an insect parasitic phase. Most species of the family Neotylenchidae are insect associates ( Siddiqi, 2000) with the exception of a few Deladenus, but these Deladenus species were not from pine wood. In addition, all the nematodes from this family that were extracted from pine lumber intercepted at the same port using the same method were insect associates from our previous studies ( Yu et al., 2013, 2014, 2017).

Figures

Figure 1: Line drawings of female Delatylus andersoni n. gen., n. sp: (A) head and pharynx, (B) lip region and stylet, (C) deirids, (D) vulva and the anus viewed ventrally, (E) vulva and the tail viewed laterally, (F) oviduct and quadricolumella, (G) oocytes.

Figure 2: Micrographs of females of Delatylus andersoni n. gen., n. sp: (A) entire body; (B) head region, (C) pharynx (arrow showing the position of excretory pore and hemizonid), (D) pharynx with anterior part of the gonad, (E) posterior part of the female body, (F, G) female tail (arrow showing the position of vulva and anus), H: lateral lines. (scale bars = 10 μm).

Figure 3: Micrographs of valve at the pharyngeal–intestinal junction of females of Delatylus andersoni n. gen., n. sp.

Figure 4: SEM of Delatylus andersoni n. gen., n. sp. (A, B) En face view of head and lip (aa arrows point to the amphid aperture; oa arrows point to the oral aperture; op arrows point to outer labial papillae; (C) vulva, anus, and tail; (D) lateral fields.

Figure 5: Phylogeny of Delatylus andersoni n. gen., n. sp. and closely related inferred from partial 18S rRNA gene sequences by Bayesian analysis. Phylogeny was inferred under a GTR+I+G model (−lnL = 6333.834; AIC = 12687.668; freqA = 0.2384; freqC = 0.2036; freqG = 0.267; freqT = 0.2911; R(a) = 1.1233; R(b) = 3.698; R(c) = 2.4739; R(d) = 0.7402; R(e) = 5.1375; R(f) = 1; Pinva = 0.6096; Shape = 0.8015). Posterior probability values exceeding 50% are given on appropriate clades.

Figure 6: Phylogeny of Delatylus andersoni n. gen., n. sp. and closely related inferred from 28S D2/D3 rRNA gene sequences by Bayesian analysis. Phylogeny was inferred under a TrN+G model (−lnL = 2644.97; AIC = 5301.9399; freqA = 0.2103; freqC = 0.1993; freqG = 0.3249; freqT = 0.2655; R(a) = 1; R(b) = 3.0953; R(c) = 1; R(d) = 1; R(e) = 7.2585; R(f) = 1; Pinva = 0; Shape = 0.3542). Posterior probability values exceeding 50% are given on appropriate clades.

Tables

Table 1. Morphometrics of Delatylus andersoni n. gen., n. sp. All measurements are in μm and in the form: mean ± s.d (range).

Measurements
Characters			Populations
	Holotype
		9095 (paratype)	480	484
n	1	19	20	20
L	760	756.1 ± 113.7 (526.8-943.9)	613.8 ± 96.3 (439.5-829.6)	760.0 ± 73.8 (636.6-907.2)
a	27.1	28.8 ± 2.4 (24.9-33.5)	23.7 ± 2.7 (18.3-27.9)	22.0 ± 2.7 (17.8-27.1)
b	10.8	11.1 ± 1.7 (7.5-13.7)	9.6 ± 1.6 (7.0-13.8)	11.6 ± 1.4 (9.3-13.8)
b’	5.6	5.9 ± 0.8 (4.1-7.1)	5.8 ± 0.9 (4.3-8.3)	6.6 ± 0.6 (5.4-7.4)
c	13.8	14.3 ± 2.1 (10.3-17.9)	13.7 ± 1.2 (11.3-15.5)	15.0 ± 1.7 (11.8-18.9)
c’	3.2	3.4 ± 0.2 (2.9-3.8)	3.2 ± 0.2 (2.8-3.8)	3.1 ± 0.4 (2.6-4.1)
V	89	89.9 ± 1.5 (85.6-91.8)	88.8 ± 0.8 (87.3-90.3)	89.5 ± 1.1 (87.3-91.8)
Stylet length	9.0	8.8 ± 0.3 (8.5-10.5)	8.8 ± 0.6 (7.8-9.7)	9.2 ± 0.7 (7.3-10.1)
Max. body diam.	28	26.4 ± 4.6 (18.4-33.9)	26.4 ± 6.2 (20.1-40.5)	35.1 ± 6.3 (23.5-49.8)
Gonad length	595	526.0 ± 10 (317.7-677.9)	461.1 ± 91.5 (261.6-685.5)	603.1 ± 74.7 (494.5-753.8)
Lip height	2	2.1 ± 0.2 (1.8-2.6)	2.2 ± 0.2 (1.9-2.8)	2.3 ± 0.3 (2.0-2.9)
Lip width	8	8.3 ± 0.5 (7.1-9.1)	7.4 ± 0.6 (6.6-8.7)	8.0 ± 0.7 (6.4-8.9)
Anterior end to nerve ring	65	61.1 ± 3.8 (55.1-70.8)	55.9 ± 3.2 (50.8-64.7)	58.6 ± 4.5 (50.2-66.2)
Anterior end to pharyngo-intestinal junction	70	68.3 ± 3.3 (62.5-75.1)	63.9 ± 3.8 (58.1-72.3)	65.7 ± 4.5 (55.8-73.0)
Anterior end to the hemizonid	110	104.0 ± 8.2 (91.3-122.5)	95.7 ± 13.1 (79.8-128.6)	107.0 ± 7.5 (90.7-119.9)
Distance from the nerve ring to the hemizonid	50	43.0 ± 6.4 (31.6-57.2)	36.8 ± 13.0 (23.4-69.0)	48.4 ± 9.2 (29.1-61.3)
Anterior end to the excretory pore	113	107.1 ± 7.6 (95.6-124.5)	92.6 ± 13.0 (76.7-125.4)	103.0 ± 7.4 (86.0-114.6)
Distance from the nerve ring to the excretory pore	51	46.0 ± 5.6 (37.8-59.2)	36.8 ± 13.0 (23.4-69.0)	44.4 ± 9.2 (24.4-58.1)
Anterior end to the end of pharyngeal glands	135	128.3 ± 7.7 (113.2-146.6)	106.4 ± 10.2 (90.5-127.4)	115.0 ± 5.3 (105.7-125.3)
Distance from vulva to anus	26	22.3 ± 3.3 (16.0-28.3)	23.3 ± 3.6 (18.8-31.3)	27.8 ± 3.0 (21.5-33.3)
Anal body width (ABW)	17	15.6 ± 2.0 (11.3-19.8)	14.1 ± 1.6 (11.9-16.9)	16.5 ± 2.0 (12.5-21.0)
Distance from vulva to tail terminus	81	75.3 ± 5.4 (60.0-83.9)	67.9 ± 7.2 (55.2-84.9)	78.8 ± 5.2 (72.8-89.3)
Tail length	55	53.1 ± 4.6 (39.3-58.9)	44.7 ± 4.8 (35.5-53.6)	51.0 ± 4.0 (45.8-59.6)
Ratio of vulva–anus/tail length	0.47	0.5 ± 0.1 (0.4-0.6)	0.5 ± 0.2 (0.4-0.7)	0.5 ± 0.1 (0.4-0.5)