Eudorylaimus piceae, Wu & Yu & Xu & Wang & Xie, 2018

Wu, Wen-Jia, Yu, Lu, Xu, Chun-Ling, Wang, Dong-Wei & Xie, Hui, 2018, A new species of the genus Eudorylaimus Andrássy, 1959 (Nematoda: Dorylaimida: Qudsianematidae) associated with Picea crassifolia in China, Zootaxa 4526 (4), pp. 576-588 : 578-583

Eudorylaimus piceae n. sp.

Fig 1–2 .

Measurements. See Table 1.

Material examined. Holotype ♀, from rhizosphere soil of Picea crassifolia at Helan Mountain , Alxa Left Banner , Alxa League , Inner Mongolia, China; GPS coordinates 105°51.500’ E, 38°39.717’ N; collected in August , 2014 by Lu Yu , Dong-Wei Wang , Wen-Jia Wu, and Hui Xie . Holotype and six female paratype specimens are deposited in the Lab of Plant Nematology / Research Center of Nematodes of Plant Quarantine, South China Agricultural University , Guangzhou , Guangdong 510642, China (slide numbers: M41-A, M41-B, M41-C and M41-D) .

Description. Female ( Fig.1–2 ). Body robust, curved ventrally and presenting an open ‘C’ shape after fixation. Cuticle two layers, 3.5–5.0 µm thick in anterior region, 3.5–4.5 µm at mid-body, and 5.5–7.5 µm on tail; outer layer smooth with fine transverse striations, the inner one with radial ridges. Lateral chord occupying about one-fifth of the body diameter at mid-body. Lateral body pores indistinct. Ventral body pores distinct, 14–16 in the neck region, 5–10 between neck base to vulva and 8–10 between vulva and anus; dorsal body pores only seen in the anterior region, 4–8 in the neck region. Lip region clearly offset from the body by a constriction, 2.4–3.1 times as wide as high or 27%–29.5% of the body diameter at posterior end of the neck region. Lips separated, labial and cephalic papillae protruding. Amphidial foveae cup-shaped, aperture about one-third of the lip region diameter. Odontostyle 1.1–1.4 times the lip region diameter in length, aperture about one-third of odonstostyle length. Odontophore rodlike, 1.1–1.2 times as long as the odontostyle. Guiding ring single. Nerve ring located at 34%–42% of the total neck length. Anterior part of pharynx wide and expanding gradually, basal expansion occupying 42%–50.5% of the total neck length. Locations of the pharyngeal gland nuclei as follows: D = 63%–66%, AS 1 = 14%–24%, AS 2 = 32.5%– 43%, PS1 = 59%–70%, PS2 = 72%–82%. Cardia short, conoid to rounded. Genital system didelphic-amphidelphic. Ovaries reflexed, usually not reaching the junction of oviduct and uterus, anterior one 57–85 µm and posterior one 44–66.5 µm long. Oviducts consisting of a much wider pars dilatata and a slender part, anterior one 68–84 µm and the posterior one 66–86.5 µm long. Sphincter distinct, present at the junction of oviduct and uterus. Uteri simple with wide lumen, anterior 42.5–64 µm and posterior 44–58.5 µm long. Vulva transverse. Vagina extending inwards 32%–43% of the body diameter at vulva. Pars proximalis vaginae with straight walls, 13–20 µm long and 13–17 µm wide, pars refringens vaginae with two trapezoidal sclerotizations, each measuring 3–3.5 µm long and 4–6 µm wide, pars distalis vaginae appears weakly sclerotized, 2.5–4 µm long with curved wall. Prerectum length 2.3–3.3 times and rectum length 1–1.6 times the anal body diameter. Tail conoid with rounded terminus, bent ventrally.

Male. Unknown. All soil samples were processed, but no males were found.

Habitat and type locality. Rhizosphere soil of Picea crassifolia Kom. at Helan Mountain , Alxa Left Banner, Alxa League, Inner Mongolia, China.

Etymology. The new species is named after Picea crassifolia , with which the new species is associated and which is also one of the endemic plants of China.

Diagnosis and relationships. Eudorylaimus piceae n. sp. is characterized by having a body length of 1.03– 1.27 mm; lip region distinctly offset from the body; odontostyle 20–22 µm and 1.1–1.4 times the lip region diameter long; amphid aperture 5–6.5 µm; odontophore 1.1–1.2 times the odontostyle long; basal expansion of pharynx occupying 42%–50.5% of the total neck length; genital system didelphic-amphidelphic; vulva transverse; vagina extending inwards 32%–43%; average V value greater than 60; pars refringens vaginae with two trapezoidal sclerotizations and pars distalis vaginae appearing weakly sclerotized; prerectum 72–107 µm long, 2.3–3.3 times the anal body diameter in length, and rectum length 1–1.6 times the anal body diameter; tail conoid, bent ventrally; c’ value 1.5–1.8; males unknown.

The new species can be differentiated from all other species of Eudorylaimus due to the development of the pars distalis vaginae, which appears weakly sclerotized (vs absent, or not sclerotized when present). In having body length less than 1.5 mm, amphidial foveae not quadrangular, tail curved ventrally and terminus rounded, c’ value less than 2 and b value less than 4.5 ( Andrássy 1986, 1991, 2009), Eudorylaimus piceae n. sp. is close to E. arcus ( Thorne & Swanger, 1936) Andrássy, 1959 , E. brevis (Altherr, 1952) Andrássy, 1959 , E. meridionalis Tjepkema, Ferris & Ferris, 1971 , E. minutus (Bütschli, 1873) Andrássy, 1959 , E. opistohystera ( Altherr, 1953) Andrássy, 1959 and E. subdigitalis Tjepkema, Ferris & Ferris, 1971 . Comparisons of the main characteristics differentiating the new species from these similar species are provided in Table 1. The new species comes close to E. opistohystera in having an average V value more than 60 ( Andrássy 1986, 1991, 2009), but can be differentiated by having narrower amphid aperture (5–6.5 µm vs 10 µm; Tjepkema et al. 1971), longer odontostyle and shorter odontophore (20–22 µm vs 18–20 µm, 22–25 µm vs 25–30 µm, respectively; Altherr 1953), vagina extending inwards 32%–43% (vs nearly 50%; Altherr 1953), pars refringens vaginae with trapezoidal (vs rectangular; Tjepkema et al. 1971) sclerotizations, and male unknown (vs present; Altherr 1953, Tjepkema et al. 1971). From E. subdigitalis , the new species can be differentiated by its rounded tail terminus (vs subdigitate; Tjepkema et al.1971), amphid aperture narrower (5–6.5 µm vs 8–10 µm; Tjepkema et al. 1971), odontostyle longer (20–22 µm vs 15–18 µm, Tjepkema et al. 1971; Thorne 1974), vagina extending inwards 32%–43% (vs about 70%, see Fig. 4 in Moslehi et al. 2012), tail longer (46–59 µm vs 31–45 µm; Tjepkema et al 1971, or 36.5–43 µm; Moslehi et al. 2012) and prerectum longer (72–107 µm vs 60 µm, Tjepkema et al. 1971). From the other four species, the new species can be distinguished by having a longer odontostyle (20–22 µm vs less than 17 µm) and V value on average more (vs less) than 60. The new species also differs from E. arcus by having much larger c’ value (1.5–1.8 vs about 1; Thorne 1974, Thorne & Swanger 1936), vulva transverse (vs longitudinal; Thorne 1974), pars refringens vaginae trapezoidal (vs absent; see Fig. 15 in Thorne 1974) and males unknown (vs present; Thorne 1974, Andrássy 1986, Thorne & Swanger 1936). The new species differs from E. brevis (see data provided by online database: https://nematode.unl.edu/eudobre.htm) in having pars refringens vaginae trapezoidal (vs triangular), prerectum longer (72–107 µm vs 50 µm) and tail conoid (vs arcuate-conical). From E. meridionalis (see data provided by online database: https://nematode.unl.edu/eumerid.htm), the new species can be differentiated by having pars refringens vaginae trapezoidal (vs rectangular or somewhat triangular). Finally, from E. minutus , the new species differs by having tail conoid and bent ventrally (vs tail subdigitate) ( Peña-Santiago & Ciobanu 2008).

Molecular characterization and phylogenetic analysis. Sequences of 18S rDNA and the D2-D3 region of 28S rDNA of Eudorylaimus piceae n. sp. were obtained. Inter-individual variability was observed only in 18S rDNA, and the variation was 1 bp. Two sequences for 18S rDNA (1743 bp) obtained from two clones of one nematode, and one sequence for 28S rDNA (827 bp) were deposited in GenBank (accession numbers: KY942067 and KY942068 for 18S rDNA, KY942069 for 28S rDNA). In BLAST searches using the two 18S rDNA sequences, both showed the highest similarity (99%) to the sequence of an unidentified species of the genus Allodorylaimus ( AJ966472 ) with 1 gap and 5 to 6 nucleotide differences. For the D2-D3 region of 28S rDNA, the highest similarity (94%) occurred with a sequence of E. minutus ( AY593048 ) with 11 gaps and 38 nucleotide differences. In the 18S rDNA Bayesian trees ( Fig.3 ), the sequences of the new species clustered with other sequences of Eudorylaimus spp., including E. minutus , in a single unresolved clade with 76% support. In the D2- D3 region of 28S rDNA Bayesian trees ( Fig.4 ), the sequence of Eudorylaimus piceae n. sp. clustered with two sequences of E. minutus with 100% support.

Figures

FIGURE 1. Line drawings of Eudorylaimus piceae n. sp. (Female) A: entire body; B: anterior region showing odontostyle and odontophore; C: amphidial fovea; D: vulva in lateral view; E: genital system; F, H, I: posterior region; G: anterior region showing pharynx.

FIGURE 2. Micrographs of Eudorylaimus piceae n. sp. (Female) A: entire body; B: amphidial fovea; C, D: anterior region showing odontostyle and odontophore; E: anterior region showing pharynx; F: genital system (arrowed: sphincter); G–I: posterior region; J, K: vulva in lateral view (arrowed: ‘Y’-shaped pars refringens vaginae). Scale bars: A = 200 µm; F, G = 50 µm; E, H, I = 20 µm; B–D, J, K = 10 µm.

FIGURE 3. Phylogenetic relationships of Eudorylaimus piceae n. sp. and other Dorylaimida species inferred using 18S rDNA. The Bayesian inference strict consensus tree was generated under the GTR+I+G model. Posterior probabilities higher than 50% are presented. Newly obtained sequences are indicated in bold.

FIGURE 4. Phylogenetic relationships of Eudorylaimus piceae n. sp. and other Dorylaimida species determined using the D2- D3 region of 28S rDNA. Bayesian inference strict consensus tree was generated under the GTR+I+G model. Posterior probabilities higher than 50% are presented. Newly obtained sequences are indicated in bold.