Paratylenchus shenzhenensis, Wang & Xie & Li & Xu & Yu & Wang, 2013

Wang, Ke, Xie, Hui, Li, Yu, Xu, Chun-Ling, Yu, Lu & Wang, Dong-Wei, 2013, Paratylenchus shenzhenensis n. sp. (Nematoda: Paratylenchinae) from the rhizosphere soil of Anthurium andraeanum in China, Zootaxa 3750 (2), pp. 167-175 : 168-174

Description of Paratylenchus shenzhenensis n. sp.

( Figs 1–3 )

Measurements. See Table 1.

Type material. Holotype female, 39 paratype females [Slide codes: HZ-292(1)–(5)], 20 paratype males [Slide codes: HZ-292(6)–(9)] are deposited in the Laboratory of Plant Nematology, South China Agricultural University , Guangzhou , Guangdong Province, P. R. China. Two paratype females and two paratype males [Slide codes: HZ- 292(10)–(11)] are deposited at the University of California Riverside Nematode Collection (Riverside, CA, USA).

Type habitat and locality. Rhizosphere soil of Anthurium andraeanum from a nursery in Shenzhen, Guangdong Province, China. Collected by Hui Xie in May 2011 .

Morphological description. Female. Body vermiform, ventrally curved, shape ranging from an open C to a figure 6 after heat relaxation. Distinct annuli extending to tail terminus, 1 ± 0.1 (0.9–1.2) µm wide at mid-body. Lateral field 2 ± 0.1 (1.5–2) µm wide, with four incisures. Body broadens gradually posterior to head and narrows gradually from vulva to tail tip. Head rounded, not set off, anterior end sub-truncate, four submedian lobes slightly protruding, 0.6 ± 0.1 (0.4–0.7) µm high, lateral lobes smaller, causing a slight depression at the oral area. SEM pictures ( Fig. 3 ) show the lip region to be sub-square; oral opening I-shaped. Stylet well developed, straight with stout knobs. Cone at 66 (62–72) % length of stylet. Orifice of dorsal oesophageal gland indistinct, only seen in 22 of 39 specimens, 2–4 µm from base of stylet knobs. Valve of median bulb distinct, 5 ± 0.7 (4–7) µm long. Length from anterior end to centre of median bulb valve is 38 ± 2 (34–42.5) µm. Isthmus slender, 11 ± 1.3 (8–16) µm long, encircled by nerve ring; basal bulb pyriform in shape, containing oesophageal glands. Position of excretory pore variable; opening opposite anterior or posterior part of basal oesophageal bulb. Excretory tubule moderately sclerotized. Hemizonid distinct, anterior or posterior to the excretory pore, 2–3 body annuli wide. Distinct lateral vulval flaps, extending over 3–4 body annuli. Ovary monodelphic, outstretched. Spermatheca oval or rounded, 10 ± 1.8 (7–16) µm long and 7.5 ± 1 (5.5–10) µm wide, filled with round spermatozoa. Older females slightly distended in the vulval region. Post-vulval uterine sac small, less than one vulval body width in length, imperfectly developed, sometimes with a few vestigial cells along the ventral wall of body. Anus indistinct. Tail tapers gradually, conoid, curved ventrally with a narrowly rounded terminus or sometimes slightly dorsally concave near the end forming a sub-digitate tail terminus.

Male. Body more slender than female. Body curved ventrally in a C-shape from the anterior end to the region of the cloaca and then curved dorsally behind the cloacal opening. Body annuli fine, 1 ± 0 µm wide. Lateral field 1.5 ± 0.1 (1–2) µm wide, with four obscure lines. Head rounded. Stylet absent and oesophagus degenerate. Testis outstretched, with large rounded refractive spermatozoa (diameter 0.5–1 µm). Bursa absent. Penial sheath prominent, with or without spicule protruding from the cloaca. Tail 16 ± 1.1 (15–19) µm long, narrows gradually posterior to cloaca, with a finely rounded terminus.

Juveniles. Two second-stage juveniles (L=134, 129 µm; a =17.2, 18.1; b =2.5; stylet=14 µm), three third-stage juveniles (L=164–191 µm; a =16.5–21.4, b =3.1–3.3; stylet=16–17 µm), and one fourth-stage juvenile (L=205 µm; a =18.8; b =3.5; stylet=17.5 µm) were examined in this study. Juveniles similar to females except for stylet length and sexual characteristics. All juveniles observed had stylets.

Diagnosis and relationships. Paratylenchus shenzhenensis n. sp. is characterized by having females with a ventrally curved body 249–302 µm long, stylet 17–21 µm long, lateral field with four lines, rounded head with four submedian lobes appearing to have a slight circum-oral depression when viewed laterally, oral opening I-shaped, conoid tail with rounded or narrowly digitate terminus, rounded to oval spermatheca with rounded sperm, and small post-vulval uterine sac with a few degraded cells; the body of males curved dorsally behind the cloaca, stylet absent, oesophagus degenerate, with a prominent penial sheath; and by having juveniles with a stylet.

Using the key and the compendium to species of Paratylenchus proposed by Raski (1991) and Esser (1992) respectively, Paratylenchus shenzhenensis n. sp. is similar to P. alleni Raski 1975a , P. amundseni Bernard 1982 , P. colbrani Raski 1975a , P. elachistus Steiner 1949 , P. goldeni Raski 1975a , P. longicaudatus Raski 1975a , P. microdorus Andrássy 1959 , P. minutus Linford, Oliviera & Ishii 1949 , P. nawadus Khan, Prasad & Mathur 1967 , P. pesticus Thorne & Malek 1968 , P. variabilis Raski 1975a , and P. vexans Thorne & Malek 1968 . They all have the lateral field with four lines, distinct body annuli, stylet length less than 22 µm, tail without a deep cleft and not serrated near the tip in the female; and stylet absent in the male. The characteristics of P. shenzhenensis n. sp. are particularly close to those of P. minutus , but it differs in the form of the anterior end, having submedian lobes and a slight depression at the oral area vs tiny lips which are prominent near the oral aperture and form a truncate tip. In addition it has an imperfectly developed small post-vulval uterine sac vs no sac. The new species also resembles P. canchicus Mohilal & Dhanachand 2004 in the number of lateral lines and stylet length in the female, but differs from it in having a shorter body length (249–302 µm vs 330–420 µm) and more anterior excretory pore (59–68 µm vs 81–86 µm from anterior end) in the female ( Mohilal & Dhanachand 2004; Pramodini & Mohilal 2009).

Paratylenchus shenzhenensis n. sp. differs from P. alleni ( Raski 1975a) , P. amundseni ( Bernard 1982) , P. goldeni ( Raski 1975a) , P. pesticus ( Raski 1975a) and P. nawadus ( Khan et al. 1967) by having a shorter body length (respectively, 249–302 µm vs 300–450 µm, 316–373 µm, 350–430 µm, 410–480 µm, and 310–380 µm). The new species differs from P. colbrani ( Raski 1975a) , P. elachistus ( Brzeski 1995) , P. longicaudatus ( Raski 1975a) and P. microdorus ( Andrássy 1985; Brzeski 1995) by having the dorsal gland orifice of the female opening 2–4 µm posterior to the stylet knobs vs more than 4 µm. It also differs from P. colbrani and P. longicaudatus in having the tail curved dorsally vs ventrally behind the cloacal opening in the male. In addition, P. longicaudatus has a more anteriorly located vulva (V 76–80 vs 80–84) ( Raski 1975a). Paratylenchus shenzhenensis n. sp. differs from P. elachistus in having a conoid tail with a narrowly rounded terminus vs a more slender conoid tail with a more slender rounded to almost pointed terminus in the female ( Raski 1975a; Brzeski 1995); from P. microdorus by having the female tail annulated to the tip vs not annulated and by shorter spicule length (16–19 µm vs 20–23 µm) ( Andrássy 1985). It differs from P. variabilis by having a longer stylet length (17–21 µm vs 13–16 µm) ( Raski 1975a); and from P. vexans by the more anteriorly located vulva (V 80–84 vs 84–87), relatively shorter tail (c 15– 18 vs 7.5) and longer spicule length (16–19 µm vs 12 µm) in the male ( Raski 1975a; Thorne & Malek 1968).

Molecular characterisation. Sixteen ITS-rDNA sequences of Paratylenchus shenzhenensis n. sp. were obtained. The length of these sequences (GenBank accession numbers: KF150658 – KF150666 , KF668487 – KF668493 ) was 1047–1049 bp (including partial 18S rRNA gene, ITS1, 5.8S rRNA gene, ITS2 and partial 28S rRNA gene). Intraspecific variation of ITS sequences for P. shenzhenensis n. sp. was 0–33 bp. At present, only four ITS sequences from other Paratylenchus species are available: from P. minutus (GenBank EF126180 ), P. lepidus Raski 1975a (GenBank EF126178 ), P. aculentus Brown, 1959 (GenBank EU247526), and P. bilineatus ( Brzeski, 1995) Brzeski, 1998 (GenBank EU247525). The ITS sequence identity was only 72–73% between P. shenzhenensis n. sp. and the morphologically similar P. minutus (GenBank EF126180 ), and there was at least 347 bp difference in this region between the two species. The ITS sequences of this new species differed from those of other three sequenced Paratylenchus species by 294–360 bp and the sequences identity was only 71–77%.

Nine sequences were obtained from the D2/D3 region of 28S rDNA of Paratylenchus shenzhenensis n. sp. Intraspecific variation of the sequences from the D2/D3 region (GenBank KF668516 – KF668524 ) for P. shenzhenensis n. sp. was 0–6 bp. There was at least 145 bp difference between the new species and two other sequenced Paratylenchus species , P. bukowinensis Micoletzky, 1922 and P. nanus Cobb, 1923 (GenBank AY780943 and AY780946 ) in D2/D3 region of 28S rDNA and the sequence identity was 73–74%.

Eleven newly obtained 18S rDNA sequences of Paratylenchus shenzhenensis n. sp. were 1731 bp in length and the intraspecific variation for this species was 0–10 bp. At present, only six 18S rDNA sequences from other Paratylenchus species are available: one from P. neoamblycephalus Geraert, 1965 (GenBank AY284634 ), two from P. microdorus (GenBank AY284632 and AY284633 ), two from P. straeleni (de Coninck, 1931) Oostenbrink, 1960 (GenBank AY284630 and AY284631 ) and one from P. dianthus Jenkins & Taylor, 1956 (GenBank AJ966496 ). The 18S rDNA sequences of P. shenzhenensis n. sp. (GenBank KF668494 – KF668504 ) differed from other sequenced Paratylenchus species by 119–148 bp and the sequence identity between the new species and the morphologically similar species P. microdorus was 92–93%.

Figures

FIGURE 1. Paratylenchus shenzhenensis n. sp. Female. A, K–N: Entire body; B, C: Anterior part; D: Posterior part; E: Lateral field at mid-body; F: Vulval region; G–J: Tails. Male. O–Q: Entire body; R: Anterior part; S: Posterior part.

FIGURE 2. Light micrographs of Paratylenchus shenzhenensis n. sp. A: Entire female; B: Female anterior part; C: Female lateral vulval flap; D: Female posterior part; E: Female cephalic region; F, G: Post uterine sacs; H–K: Female tails; L: Entire male; M: Male posterior part; N, O: Male tails. (Scale bars: A, L, M=20µm; B, D, E, H–K, N, O=10µm; C, F, G=5µm).

FIGURE 3. SEM photographs of Paratylenchus shenzhenensis n. sp. A–C: Lip region of female; D: Lateral field; E: Lateral vulval flap and lateral field of female; F: Tail of female tail.