Axonchium meghalayense, Naz, Tabbasam & Ahmad, Wasim, 2012

Naz, Tabbasam & Ahmad, Wasim, 2012, Description of two new and five known species of the genus Axonchium Cobb, 1920 (Nematoda: Dorylamida) from India with diagnostic compendia and keys to species of the genera Axonchium and Syncheilaxonchium Coomans & Nair, 1975, Zootaxa 3264, pp. 1-37 : 23-27

Axonchium meghalayense n. sp.

( Figs. 11–12 )

Measurements. Table 6 .

Description. Female: Body curved ventrad upon fixation, tapering towards both extremities. Cuticle with fine transverse striations, 3 µm thick at mid body and 6 µm on tail. Lateral chords with distinct glandular bodies, about one-eighth as wide as body width at midbody. Lateral, dorsal and ventral body pores indistinct.

Lip region offset, about one-fifth of body width at neck base. Amphids cup-shaped, their aperture 0.7 times as wide as lip region width. Odontostyle fusiform, about one lip region width long, its aperture about one-third of its length. Guiding ring single, at 0.7–1.0 times lip region width from anterior end. Odontophore linear, 1.3 times the odontostyle length. Nerve ring at 20–22% of neck length from anterior end. A short isthmus separates the anterior part of pharynx from posterior expanded part, the latter occupying 63–66% of total neck length and enclosed in muscle sheath with straight bundles. Cardia conoid, about one-third of corresponding body width long.

Genital system mono-opisthodelphic. Anterior branch represented by a simple uterine sac, 1.8–3.2 times the corresponding body width in length and filled with sperms. Posterior branch well developed; ovary reflexed, not reaching or surpassing the oviduct-uterus junction, measuring 130–155 µm with oocytes arranged in a single row except near tip. Oviduct joining ovary subterminally, measuring 80–135 µm, consisting of a long slender part with prismatic cells and a slightly wider pars dilatata with wide lumen. Sphincter present at oviduct-uterus junction. Uterus 80–160 µm long, tripartite, with distal expanded pars dilatata, a narrow tube-like intermediate region and a proximal wide tube with wide lumen. Vulva transverse. Vagina slightly bent posteriad, extending inwards about half of the corresponding body width; pars proximalis vaginae 18–19 µm long with outer convex walls; pars refringens vaginae absent; pars distalis vaginae well developed, 10–12 µm long with curved walls. Prerectum 4.5–7 times anal body width long. Rectum about one anal body width long. Tail bluntly conoid to rounded, 0.8–1.06 times anal body width long. Caudal pores two on each side.

Characters Holotype female Paratype females Paratype male Male: Similar to female in general morphology, except for posterior region being more curved ventrad because of the presence of copulatory muscles. Spicules arcuate, slightly ventrally curved, 1.2 times the cloacal body width long. Lateral guiding pieces about one-third of the spicule length with bifurcated ends. Supplements an adcloacal pair and five regularly spaced ventromedians, beginning anterior to the range of spicules. Prerectum about six times cloacal body width long. Rectum about one cloacal body width. Tail similar to female, about as long as cloacal body width. Caudal pores two on each side.

Type habitat and locality: Soil around unidentified grasses and herbs from seven miles, upper Shillong, Meghalaya, India. GPS coordinate 25.51965/91.93535; latitude 25o34'N, longitude 91o53'E

Type specimens: Holotype female on slide Axonchium meghalayense n. sp. /1; paratype females and males on slides Axonchium meghalayense n. sp. / 2–7; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India. A paratype female and a male deposited with the nematode collection of the Universidad de Jaén, Spain.

Etymology. The new species is named after the state where it was collected.

Diagnosis and relationships. Axonchium meghalayense n. sp. is characterized by its 1.6–1.9 mm long body, lip region offset by constriction; 9.5–10 µm long odontostyle, the short isthmus-like structure present between the two parts of the pharynx, vagina slightly bent posteriad; the long, sac-like anterior uterine branch, and rounded tail in females, and, 41 µm long spicules, lateral guiding pieces with bifurcated distal ends and five ventromedian supplements starting above the range of the spicules in males.

In the presence of a long anterior uterine sac, the shape of its vagina and number and arrangement of ventromedian supplements, the new species comes close to A. heynsi Nair, 1973 , but differs in having a smaller and more robust body (L = 1.6–1.9 vs 2.1–2.8 mm, a = 31–38 vs 40–67), shorter prerectum (4.5–7 vs 10–15 times anal body width), longer tail (c = 48–60 vs 73–108) and in having differently shaped spicules (distal end of spicule less thick vs much more robust spicules).

In vaginal characters and tail shape, the new species also resembles A. saccatum Jairajpuri, 1964 but differs in having a slightly narrower lip region (9–9.5 vs 10–11 µm), shorter prterectum (4.5–7 vs 11 times anal body width), longer tail (c= 48.6–59.7 vs 64–95), in having comparatively slender spicules (vs more robust spicules), and in the number and arrangement of ventromedian supplements (5 beginning anterior to vs 6–8 starting within the range of the spicules).

The new species is also related to A. phukani Rahman, Jairajpuri & Ahmad, 1985 in having a long anterior uterine sac and in the shape of the vagina and tail, but differs in having a differently shaped cardia (hemispheroid vs conoid), in the position of ventromedian supplements (vs starting within the range of spicules), and in the shape of the spicules and lateral guiding pieces (vs more robust spicules and lateral guiding pieces without bifurcated ends).

Figures

FIGURE 11. Axonchium meghalayense n. sp. A: Entire female. B: Entire male. C: Anterior region. D: Anterior end showing amphid. E – F: Junction between two parts of pharynx. G: Pharyngo-intestinal junction. H: Female genital system. I: Vulval region. J: Female posterior end. K: Male posterior region. L: Spicule. M: Lateral guiding piece.

FIGURE 12. Axonchium meghalayense n. sp. A: Anterior region. B: Anterior end showing amphid. C: Junction between two parts of pharynx. D: Pharyngo-instestinal junction. E: Vulval region. F: Anterior uterine sac showing proximal constriction. G: Female posterior end. H: Ventromedian supplements. I – J: Male posterior end. (Scale bars A, B = 10 µm; C – J = 20 µm).

Tables

TABLE 6. Morphometrics of Axonchium meghalayense n. sp. (All measurements in µm (except L) and in the form: mean ± standard deviation (range).

n:	1	4	1
L (mm)	1.7	1.76±0.11 (1.6–1.9)	1.8
a	32.2	34.6±3.24 (30.8–38.2)	39.2
b	2.5	2.7±0.23 (2.4–2.9)	3.08
c	50.7	55.5±4.77 (48.6–59.7)	70.7
c`	0.9	0.91±0.09 (0.8–1.06)	0.76
V	59.0	55±4.07 (51–60)	-
G1	8.8	7.4±1.49 (5.4-8.8)	-
G2	15.0	13.2±1.57 (10.9–15)	-
Lip region width	9	9.1±0.22 (9–9.5)	9.5
Lip region height	4	4±0 (4)	4
Amphid aperture	8	7.37±1.10 (6–8.5)	9
Odontostyle length	10	9.7±0.28 (9.5–10)	9.5
Odontophore length	12	11.7±0.57 (11–12)	11
Guiding ring from anterior end	8	8.5±1.29 (7–9)	9
Nerve ring from anterior end	140	140±6.12 (130–145)	130
Neck length	688	652±20.6 (635–688)	585
Expanded part of pharynx	455	424±18.3 (408–455)	370
Cardia length	21	20.16±2.04 (17–23)	17
Body width at mid body	53.5	51.6±1.78 (49.5–53.5)	46
Body width at neck base	54.5	52.5±1.69 (50–54.5)	48.5
Body width at anus/cloaca	35.5	35.8±1.35 (34.5–38)	34
Anterior genital branch	153	133±22.12 (100–160)	-
Posterior genital branch	250	236±20.59 (200–260)	-
Vaginal depth	30	25.4±4.54 (20–30)	-
Vulva from anterior end	1015	987±24.30 (962–1018)	-
Prerectum length	215	236±27.24 (200–265)	201
Rectum length	40	39±5.47 (30–45)	-
Tail length	34	32.8±0.83 (32–34)	34
Spicules length	-		41
Lateral guiding pieces	-		13
Ventromedian supplements	-		5