Tantunema enigmatum, Ahmad, Wasim, 2010

Ahmad, Wasim, 2010, Three new and a known species of Tylencholaimoidea (Nematoda: Dorylaimida) from Singapore, Zootaxa 2505, pp. 51-64 : 52-56

Tantunema enigmatum n. sp.

( Figs. 1 , 2 )

Measurements: Table 1

Description. Female: Body slightly curved ventrad upon fixation, tapering slightly anteriorly, posteriorly ending in a short hemispheroid tail. Outer cuticle smooth, inner cuticle transversely striated, loose, 1.0–1.5 µm thick at mid body and 1.5–2.0 µm on tail. Lateral hypodermal chords about one-third of body width at mid body. Lateral, dorsal and ventral body pores indistinct.

Lip region angular, distinctly offset, about two and a half times as wide as high and about one-half to onethird as wide as body width at neck base; lips amalgamated; labial papillae slightly raised. Circumoral sclerotization well developed. Post-labial sclerotization absent. Amphids small, aperture pore-like. Odontostyle slender, dorylaimoid, about 1.0–1.2 times lip region width long; its aperture about one-fourth of its length. Guiding apparatus a single, fixed ring at 0.55–0.68 lip region widths from anterior end. Odontophore simple rod-like, 1.0–1.2 times the odontostyle length. Nerve ring at about 44–49% of neck length from the anterior end. Anterior part of pharynx slender, weakly muscular, expanding abruptly into a cylindrical basal bulb; a distinct constriction present between two parts of pharynx. Expanded portion occupying about 35–39% of the total neck length; and seems to be divisible into a short, conical, less muscular anterior part and a posterior muscular cylindrical part with thickened inner lining; lumen of the posterior one-third of expanded portion distinctly widened and thickened. Cardia short-conoid, about onefourth of corresponding body width long. Pharyngeal gland nuclei and their orifices are located as follows: D = 73–76%; AS 1 = 24–28%; AS 2 = 41–45%; PS1 = 68–69%; PS2 = 70–72%

Genital system mono-opisthodelphic; anterior branch totally absent. Ovary reflexed, measuring 32–42 µm with oocytes arranged in single row except near tip. Oviduct joining ovary subterminally, measuring 32–39 µm long. A weak sphincter present at oviduct–uterus junction. Uterus an undifferentiated tube, measuring 16– 30 µm. Vagina about one-third of the corresponding body width deep. Pars proximalis vaginae 4–4.5 µm long with straight walls, encircled by circular musculature; pars refringens vaginae absent; pars distalis vaginae measuring 1.5–2 µm with curved wall. Vulva transverse. Prerectum 1.8–2.6 anal body widths long. Rectum about one anal body width long. Tail short, hemispheroid, 0.76–0.86 times anal body width long. Caudal pores two on each side.

Male: Not found.

Type habitat and locality. Soil around roots of forest trees from Kent Ridge Park near the National University of Singapore; Collected on September 1, 2003.

Type material. Holotype female on slide Tantunema enigmatum n. sp. /1; paratype females on slide Tantunema enigmatum n. sp. / 2–6; deposited with nematode collection of the Department of Zoology, Aligarh Muslim University, India.

Diagnosis and relationships: Tantunema enigmatum n. sp. is characterised by having 0.33–0.41 mm long body; angular, distinctly offset lip region; well developed circumoral sclerotization; odontostyle slender with aperture about 1/4th of its length; simple rod-like odontophore; anterior part of pharynx slender, weakly muscular, expanding abruptly into a cylindroid basal bulb, a distinct constriction present between two parts of pharynx; expanded portion divisible into a short conical less muscular anterior part and a posterior muscular cylindrical part with thickened inner lining; lumen of the posterior one-third of expanded portion distinctly widened and thickened; mono-opisthodelphic female genital system and short hemispheroid tail.

Tantunema enigmatum n. sp. Dorella shamimi n. sp.

Characters Holotype Paratype females Holotype Paratype Females Paratype The genus Tantunema Siddiqi, 1982 is presently represented by three known species, viz., T. bothriocepahalum Siddiqi, 1982 , T. aquaticum Ahmad & Jairajpuri, 1983 , and T. rossi (Yeates, 1979) Peña- Santiago & Coomans, 1996. In the first two species, the anterior slender part of pharynx is distinctly muscular, whereas, in T. rossi it is slender and weakly muscular but the pharyngeal expansion is gradual in all three species; the pharyngeal lumen is also not distinctly thickened. In the presence of circumoral sclerotization and nature of its pharynx, the new species is distinctly different from the three current species. It does not even completely fit the generic diagnosis of Tantunema , and may well represent a new genus. However, in general body shape, the shape of lip region, nature of odontostyle and odontophore, pore-like amphid aperture, nature of female genital system and tail shape the present species has close resemblance with the genus Tantunema and hence instead of proposing a new closely related genus, the present population has been described as a new species of Tantunema and named T. enigmatum n. sp. because of its enigmatic position.

In addition to the differences in the nature of stoma and pharynx, the new species further differs from T. bothriocepahalum Siddiqi, 1982 in having longer odontostyle (7–8 vs 4.5–6.5 µm); simple odontophore (vs odontophore swollen at base), and shorter tail (vs one anal body width).

From T. aquaticum Ahmad & Jairajpuri, 1983 , the new species differs in having shorter and robust body (vs L= 0.53–0.61 mm; a= 28–33), smaller pharynx (vs pharynx 139–142 µm; b= 3.8–4.2), comparatively longer prerectum (vs prerectum 33–45 µm), and shorter tail (vs c’= 1.2–1.5).

From T. roosi Yeates, 1979 , the new species differs in having smaller body size (vs 0.43–0.52 mm), in the shape of lip region (vs lip region rounded), comparatively longer odontostyle (vs 6 µm), and anterior vulva position (vs V= 54–58).

Andrássy (2009) transferred Tylencholaimus intermedius Peña-Santiago & Coomans, 1996 to the genus Tantunema . This act has not been accepted here.

Etymology: The species epithet enigmatum refers to the enigmatic position of this species under the genus Tantunema .

Figures

FIGURE 1. Tantunema enigmatum n. sp. A: Entire female. B: Anterior region. C: Pharyngeal region. D-E: Expanded part of pharynx. F: Female genital system. G: Female posterior region.

FIGURE 2. Tantunema enigmatum n. sp. A: Anterior region. B: Anterior region showing stoma thickening. C: Expanded part of pharynx. D: Expanded part of pharynx showing thickened valvular chamber. E: Female genital system. F: Female posterior region. (scale bar = 10 um)

Tables

TABLE 1. Morphometrics of Tantunema enigmatum n. sp. and Dorella shamimi n. sp. All measurements in µm (except L) and in the form: mean standard deviation (range).

n		9	6	2
L	328	360 ± (346–407) 531	597 ± 11.3 (585–619)	508, 589
a	21.8	22.2 ± 0.60 (21.5–23.5) 31.6	33 ± 1 (31.5–34)	33.4, 32.7
b	3.03	3.3 ± 0.15 (3.2–3.6) 4.18	4.2 ± 0.12 (4.1–4.3)	3.6, 4.4,
c	36.4	35.3 ± 1.9 (33–39) 31.2	31 ± 2 (28.0–33.5)	25.5, 29.4
c`	0.85	0.83 ± 0.03 (0.76–0.87) 1.41	1.4 ± 0.13(1.26–1.64)	1.66, 1.48
V	49	48 ± 1.02 (46–49) 70.3	69 ± 2 (65.7–71.5)	–
G1	-	- 26	25 ± 7(14.5–31)	-
G2	12.5	15.3 ± 2.4 (13–18.5) -	2 ± 1(1.4–3.2)	-
Lip region width	7.2	6.8 ± 0.3 (6.5–7.0) 7.2	7.3 ± 0.5 (6.5–8.0)	8, 8
Lip region height	2.5	2.8 ± 0.31(2.5–3.0) 4	4.1 ± 0.4 (4–5)	4, 4.5
Amphid aperture	-	- 4.8	4.7 ± 0.3 (4–5)	4
Odontostyle length	8	7.8 ± 0.3 (7–8) 10.5	10.2 ± 0.2 (10.0–10.5)	9.6, 10
Odontophore length	8	8.4 ± 0.5 (8.0–9.5) 4	3.3 ± 0.3 (3.0–4.0)	4, 5
Guiding ring from ant. end	4.5	4.4 ± 0.3 (4.0–4.5) 4.8	5.0 ± 0.4 (4.5–6.0)	4.8, 5
Nerve ring from ant. end	53	51.5 ± 1.6 (48–53) 61	66.5 ± 2.2 (65–71)	66.5, 64
Neck length	108	109 ± 4.6 (101–113) 127	139.5 ± 5.0 (133–148)	141, 131
Expanded part of pharynx	38.5	41.7 ± 1.9 (40–44) 24	24.5 ± 0.7 (23.5–25.5)	25.5, 26
Cardia length	4	4.2 ± 0.4 (4–5)	5.3 ± 1.25 (4–7)	5
Body width at neck base	15	16.3 ± 0.9 (15.0–17.5)	16 ± 1.5 (15–18)	17
Body width at mid body	15	16.16 ± 1.02(15.0–18.5) 16.8	18 ± 0.3 (17.5–18.5)	15, 18
Body width at anus/cloaca	10.5	12.2 ± 0.8 (12.0–13.5) 12	13.2 ± 1.0(12–15)	12, 13.5
Anterior genital branch	-	- 138	150 ± 37.7 (90–182)	-
Posterior uterine sac	41	55.5 ± 9.4(48.0–69.5) 14	14 ± 4.4 (8–20)	-
Vaginal depth	-	- -	8.3 ± 0.47 (8–9)	-
Vulva from anterior end	162	174 ± 9.8(164–195) 374	409 ± 11 (389–420)	-
Prerectum length	25.5	25.8 ± 3.25 (22–32) 54	56 ± 5.6 (48–62)	60, 68
Rectum length	14.5	13 ± 1.0 (12.0–14.5) 11	14 ± 2.1(11–17)	19
Tail length	9	10.2 ± 0.6 (9.6–10.5) 17	19.2 ± 1.0 (18–21)	20, 20
Spicules length	-	- -	-	18.5, 18
Lateral guiding pieces	-	- -	-	3.5–4
Ventromedian supplement	-	- -	-	1