Tylencholaimus koreanus, Ahmad & Park & Lee & Choi, 2009

Ahmad, Wasim, Park, Byeong-Yong, Lee, Jae-Kook & Choi, Dong-Ro, 2009, Some new and known species of Tylencholaimoidea (Nematoda: Dorylaimida) from Korea, Journal of Natural History 43 (37 - 38), pp. 2329-2356 : 2330-2334

Tylencholaimus koreanus sp. nov.

( Figures 1 and 2 ; Table 1)

Description

Female. Body ventrally curved, C-shaped upon fixation, tapering slightly towards anterior extremity. Outer cuticle finely striated; inner layer irregular and loosened from the outer layer. Radial refractive elements abundant. Lateral chords about onequarter of body width at mid-body. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, offset from the body by a deep constriction, about 2.3–2.6 times as wide as high and about one-third as wide as body width at neck base. Lips amalgamated and with their inner part scarcely elevated. Labial and cephalic papillae not interfering with labial contour. Amphids small, funnel-shaped, and with a small slitlike aperture at the level of cephalic constriction; fusus 15–16 µm from behind aperture. Odontostyle typical of the genus, about 0.75–0.78 times the lip region width long, with aperture about one-third of its length. Guiding ring simple, at 0.6–0.7 times the lip region width from anterior end. Odontophore rod-like with small basal knobs, 1.2–1.3 times the odontostyle length. Nerve ring encircling anterior slender part of pharynx at 39–42% of neck length from anterior end. Pharyngeal expansion gradual; expanded part occupying about 47–52% of neck length from anterior end. Pharyngeal gland nuclei and their orifices clear; DN large, close to pharyngeal expansion; S1N weak, located halfway between DN and S2N; S2N distinct, their locations are as follows: DO = 61–62; DN = 64–65; DO–DN = 2; S1N1 = 76–77; S1N2 = 79–80; S2N = 90–91; S2O = 91–92. Cardia short conoid. Genital system monodelphic–prodelphic. Ovary reflexed, measuring 45–102 µm with oocytes arranged in a single row except near tip. Oviduct joining ovary subterminally, 57–76 µm or 2.4–3.2 times the corresponding body width long with distinct pars dilatata. Uterus 35–50 µm or 1.5–2.3 times the corresponding body width long. Sphincter present at oviduct–uterus junction. Posterior branch represented by a large sac usually filled with spermatozoa, 43–75 µm or 2.0–3.4 times the corresponding body width. Vagina slightly less than half the corresponding body width, often bent slightly forward. Pars proximalis vaginae 7–8 µm long with convex walls encircled by weak musculature; pars refringens vaginae absent; pars distalis vaginae 2–3 µm. Vulva transverse. Prerectum 3.2–5.1 times the anal body width long. Rectum about as long as anal body width. Tail short, conoid, with bluntly rounded terminus and a distinct terminal caudal pore.

Male. Similar to female in general morphology except for the posterior region being more curved ventrally because of the presence of copulatory muscles. Supplements, an adanal pair and two well-developed ventromedians. Spicules dorylaimoid, ventrally arcuate, 1.1–1.3 times the anal body width long. Lateral guiding pieces absent. Prerectum 4.1–5.0 anal body widths long. Rectum 1.1–1.2 times anal body width long. Tail short, conoid, similar to female.

Type habitat and locality

Soil around the roots of forest trees from Heugsando, Jeollanam-do, South Korea.

Type specimens

Holotype female and a paratype male on slide Tylencholaimus koreanus sp. nov. /1; paratype females and males on slides Tylencholaimus koreanus sp. nov. /2–4, deposited with the nematode collection of the Division of Applied Entomology, National Institute of Agricultural Sciences and Technology, Suwon, Korea. Four females and two males deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India.

Diagnosis and relationships

Tylencholaimus koreanus sp. nov. is characterized by having 0.49–0.58 mm long body; lip region distinctly offset; small funnel-shaped amphid with slit-like aperture; 5.5–6.0 µm long odontostyle; odontophore with small knobs; muscular pharynx with gradually expanding basal part; monodelphic–prodelphic genital system with long post-uterine sac and short conoid tail.

The new species is closely related to T. stecki Steiner, 1914 and T. vulvulatum Rahman et al., 1987 because of perioral region not disc-like, slender part of pharynx muscular and expanding gradually and the posterior genital branch with large sac (see Steiner 1914; Rahman et al. 1987). However, it differs, from T. stecki in having smaller body size (versus 0.7–1.0 mm); the shape of lip region (versus lip region offset by a shallow constriction); in having smaller amphids (versus amphid aperture about two-thirds of lip region width); smaller expanded part of pharynx (versus 90–102 µm); longer prerectum (versus two anal body widths); shorter tail (versus 19.5–25 µm), and shorter spicules (versus 23.5–27 µm ( Peña-Santiago and Coomans 1996); 25 µm ( Sauer 1969); 27–31 µm ( Loof and Jairajpuri 1968), and in the presence of a distinct terminal caudal pore (versus absent).

From T. vulvulatum , the new species differs in having a smaller body size (versus 0.80–0.93 mm); in having symmetrical vulval lips (versus asymmetrical); shorter tail (versus 19–22 µm, c′ = 1.0 in female); tail always shorter than anal body diameter in the new species. The new species further differs from T. vulvulatum in having shorter and distinctly arcuate spicules (versus spicules 28–32 µm, slightly arched).

Figures

Figure 1. Tylencholaimus koreanus sp. nov. (A) Entire female; (B) entire male; (C) anterior region; (D) anterior end showing amphid: (E) pharyngeal region; (F) expanded part of pharynx; (G) female genital system; (H) female posterior genital branch; (I) female posterior region; (J,K) female posterior ends; (L) male posterior region.

Figure 2. Tylencholaimus koreanus sp. nov. (A,B) Anterior regions; (C) anterior region showing amphid; (D) pharyngeal expansion; (E) pharyngo-intestinal junction; (F) vulval region; (G) female genital system; (H) female posterior region; (I) female posterior end; (J,K) male posterior region.