Tylencholaimus ibericus Peña-Santiago & Coomans, 1994

Ahad, Sumaya & Ahmad, Wasim, 2016, Description of two new and six known species of the genus Tylencholaimus de Man, 1876 (Nematoda: Dorylaimida) with a diagnostic compendium and key to species, Zootaxa 4107 (4), pp. 451-490 : 464-466

Tylencholaimus ibericus Peña-Santiago & Coomans, 1994

( Figs. 7 & 8 )

Measurements: See Table 4 .

Description. Female: Small sized nematodes, slightly curved upon fixation; body cylindrical, tapering gradually towards both extremities. Cuticle with two distinct layers, 2 Μm thick at midbody and 2–3 Μm on tail. Outer cuticle finely striated; inner layer thick with distinct radial refractive elements. Lateral chords occupying about one-fourth to one-third of midbody diameter. Lateral, dorsal and ventral body pores indistinct.

Lip region cap-like, offset by constriction, 2.1–2.3 times as wide as high or about one-third of the body diameter at neck base; lips rounded and amalgamated, with their inner part scarcely elevated. Amphids cup-shaped with aperture located at level of cephalic constriction and occupying less than one-half of lip region diameter. Stoma a truncate cone. Odontostyle typical of the genus, 0.7–0.9 times the lip region diameter long, its aperture about one-fourth of the odontostyle length. Odontophore rod-like with small basal knobs, 1.0–1.2 times the odontostyle length. Guiding ring simple, refractive, at 0.5–0.7 times lip region diameter from anterior end. Pharynx consists of a slender, slightly muscular anterior part, expanding gradually into a cylindrical basal bulb, with thickwalled lumen, occupying about 34–39% of total neck length. Pharyngeal gland nuclei and their orifices are located as follows: DO = 65–68, DN = 68–70, S1N1 = 76–78, S1N2 = 80–82, S2N = 89–92, S2O = 90–92. Nerve ring located at 39–45% of neck length from anterior end. Cardia short, conoid, about one-third of the corresponding body diameter long.

Genital system mono-prodelphic. Ovary reflexed, measuring 39–67 µm long, not reaching the oviduct-uterus junction; oocytes arranged in a single row except near tip. Oviduct joining the ovary subterminally, measuring 68–99 µm, its proximal and distal parts not differentiated. Oviduct-uterus junction marked by poorly developed sphincter. Uterus short and tubular, measuring 17–19 µm. Posterior genital branch completely absent. Vagina anteriorly directed; pars proximalis vaginae 5–7 µm long, its wall encircled by circular muscles; pars distalis vaginae short with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 3.1–5.5 and rectum 0.6–1.0 anal body diameter long. Tail bluntly conoid to hemispheroid, 1.0–1.3 times anal body diameter long with a pair of caudal pores on each side.

Male: Not found.

Habitat and locality. Soil samples from unidentified forest trees from Shenyan, China collected by Prof. Wenju Liang in November 2009.

Remarks. Peña-Santaigo and Cooman s (1994) described T. ibericus from Spain. Dhanam and Jairajpuri (1999) redescribed this species from India. The morphometrics of the present population conform well with those of the type population except for having slightly longer body size (vs 0.49–0.55 mm); slightly short odontophore (vs 6–8 µm); oviduct-uterus junction poorly developed (vs well developed), and longer tail (vs 13–16 µm). This may reflect geographical variation. The present population also conforms well with the Indian population.

Peña-Santiago (2008) synonymised T. japonicus Ahmad & Araki, 2003 with T. ibericus . The morphometrics of the present population conform well with those of the population described by Ahmad and Araki (2003) from Japan. However, it differs in having slightly lower c ratio (vs 35–46), longer cardia (vs 6.5 µm), slightly shorter prerectum (vs 70–112 µm), posterior genital branch without any projection beyond vagina (vs posterior genital branch represented by a very small peg-like projection beyond vagina), and longer tail (vs 12–16 µm). This is the first report of this species from China.

Figures

FIGURE 7. Tylencholaimus ibericus Peña-Santiago & Coomans, 1994. A. Entire female; B. Anterior region; C. Anterior end showing amphid; D. Pharyngeal region; E. Pharyngeal bulb; F. Female genital system; G. Female posterior region.

FIGURE 8. Tylencholaimus ibericus Peña-Santiago & Coomans, 1994. A. Anterior region; B. Anterior end showing amphid; C. Pharyngeal bulb; D. Pharyngo-intestinal junction; E. Female genital system; F. Vulval region; G. Female posterior region. (Scale bar A, B, D, = 10 µm; C, E – G = 20 µm)

Tables

Table 4. Morphometrics of Tylencholaimus ibericus Peña-Santaigo & Coomans, 1994 (All measurements in µm)

Characters	Females
n L	15 564.8±41.8 (508-651)
Body diameter at neck base	19.6±1.1 (18-23)
Body diameter at mid body	19.8±1.06(18-23)
Body diameter at anus	14.4±0.7 (13-16)
a b	28.5±1.5 (26.1-31.4) 3.3±0.2 (2.9-3.8)
c	32.6±2.5 (28.3-37.2)
c`	1.1±0.08 (1-1.3)
V	71.1±1.3 (69.4-74.8)
G1 Lip region diameter	17.4±1.2 (15.7-20.6) 6.8±0.2 (6.5-7.0)
Lip region height	2.9±0.1 (2.5-3.0)
Amphid aperture	2.1±0.2 (2-3)
Odontostyle length	5.1±0.3 (5-6)
Odontophore length	6.0
Guiding ring from anterior end	4.2±0.4 (4-5)
Nerve ring from anterior end	70.5±2.1 (66-75)
Neck length	165.6±9.1 (151-180)
Expanded part of pharynx	59.4±3.7 (53-66)
Cardia length	7.6±0.6 (7-9)
Anterior genital branch	98.5±8.5 (87-117)
Vaginal depth	9.7±0.6 (9-11)
Vulva from anterior end	402±28.4 (359-462)
Prerectum length	59.7±8.6 (51-77)
Rectum length	11.4±1.6 (9-14)
Tail length	17.3±1.3 (15-20)