A revision of the genus Metarhabditis (Nematoda: Rhabditidae) with description of three known species, a key to the identification of congeners and discussion of their relationships Author Asif, M. Nematode Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh 202002, India; Author Prasad, J. S. Department of Entomology, Directorate of Rice Research, Rajendranagar, Hyderabad, India Author Khan, R. Nematode Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh 202002, India; Author Somasekhar, N. Department of Entomology, Directorate of Rice Research, Rajendranagar, Hyderabad, India Author Tahseen, Q. Nematode Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh 202002, India; text Journal of Natural History 2013 2013-07-16 47 41 - 42 2599 2622 https://www.mendeley.com/catalogue/8e84047b-3bf7-37d5-b733-7ade97140392/ journal article 10.1080/00222933.2013.798702 1464-5262 5197855 Metarhabditis andrassyana Tahseen et al., 2004 ( Figures 3 and 4 ) Measurements See Table 1 . Description Female. Body straight or slightly arcuate, tapering at both extremities, more towards posterior end. Cuticle with both outer and inner layers striated. Longitudinal striae moderately to faintly developed. Lateral lines three in few specimens splitting into five to six in posterior body region. Lip region almost continuous to adjoining body. Lips round, in doublets forming three sectors (one subdorsal and two subventral). Amphids inconspicuous. Stoma rhabditoid type , long, narrow, 1.8–3.0 times the lip diameter in length. Cheilostom conspicuous, moderately cuticularized; gymnostom smaller than stegostom. Pharyngeal collar surrounding 55–60% of stoma. Metastegostom isomorphic and isotopic with each plate bearing four to six denticles having knobbed heads. Telostegostom isoglottoid. Pharynx differentiated into 120–143 µm long, cylindrical, weakly developed corpus, slightly narrower, 59–70 µm long isthmus and a round, basal bulb of 28–32 × 23–26 µm dimension with a prominent grinder and faintly double-chambered haustrulum. Nerve ring at 66–78% of pharyngeal length. Secretory–excretory pore slightly anterior to basal bulb or 75–81% of pharyngeal length with distally cuticularized duct. Hemizonid usually observed anterior to secretory–excretory pore. Pharyngeal corpus ca .1.3–1.7 times longer than isthmus and basal bulb together. Body at pharyngeal end 2.9–5.4 times the labial diameter in length. Cardial flaps conoid, 5–7 µm long. Intestine with refractive lumen lining. Rectum slightly longer than anal body diameter with dilated lumen; three conspicuous rectal glands present. Prerectum markedly differentiated in few specimens only. Reproductive system didelphic, amphidelphic with well-developed, dorsally reflexed ovaries. Anterior ovary on right and posterior on left side of intestine. Oviduct leading to offset, ovoid spermathecae containing rounded sperm, demarcated from uterus by distinct sphincters. Two to fifty intrauterine eggs observed in different stages of embryonation. Vagina thick-walled, at right angle to longitudinal body axis, about one-third of vulval body diameter in length. A pair of globular pieces associated with vagina reflect muscles in cross-section. Vulva a wide transverse slit, almost extending the full width of the body diameter at the level of the vulva, with an epiptygma and distinct cuticular flap. Tail long, filiform. Phasmids tubular, at base of conical part of tail or 28–36 µm posterior to anal level. Male. Similar to female in general morphology except in pronounced posterior body curvature. Testis single, reflexed ventrally on left side of intestine. Vas deferens a broad tube, filled with sperm without demarcation of seminal vesicle. Ejaculatory glands absent. Spicules long, robust having round capitula with attenuated ventral and distally notched dorsal arm. Spicule lenght 1.2–1.7 times the anal body diameter. Gubernaculum slightly curved plate with curved proximal end, 40–47% of spicule length. Bursa fairly developed, open leptoderan type , not enclosing small tail spike. Bursal margins often crenate. Tail spicate with fine terminus. Genital papillae eight pairs in 1 + 1/1 + 3 + 2 + P configuration. GP1 , GP2 spaced, precloacal; GP3 shifted posterior to cloaca; out of other six postcloacal pairs – GP4 , GP5 and GP6 closely placed; GP5 , GP7 dorsally oriented; GP8 anterior to fine tubular phasmids. Copulatory muscles six-paired faintly visible bands extending anteriorly to spicules. Figure 3. Metarhabditis andrassyana Tahseen et al., 2004 . (A) Entire female; (B) entire male; (C) anterior region; (D) pharyngeal region; (E) female genital branch; (F) female tail region; (G) male tail region. Figure 4. Metarhabditis andrassyana Tahseen et al., 2004 . (A–C) Anterior region (C is a scanning electron micrograph); (D) pharyngeal region; (E) posterior region of pharynx; (F) vulval region; (G, H) body region showing lateral field; (I) reflexed ovary; (J) reflexed testis; (K) vulval region; (L–N) female tail region; (O–S) male tail region. Scale bar = 10 µm. Table 1. Morphometrics of populations of Metarhabditis amsactae ( Ali et al., 2011 ) Sudhaus, 2011 , Metarhabditis andrassyana Tahseen et al., 2004 and Metarhabditis costai ( Martins, 1985 ) Sudhaus, 2011 . Measurements in µm and in the form: mean ± standard deviation (range).

Character	M. amsactae Pop. 1	M. amsactae Pop. 2	M. amsactae Pop. 3	M. andrassyana	Metarhabditis costai
Male ( n = 8)	Male ( n = 8)	Male ( n = 10)	Male ( n = 7)	Male ( n = 7)
Body length	757.3 ± 71.7 (683−868)	695.7 ± 96.82 (515−852)	717.7 ± 64.9 (619−813)	975.2 ± 93.2 (841−1073)	777.8 ± 136.3 (608−1058)
Body diameter	36.1 ± 5.3 (26−40)	41.4 ± 7.4 (33−54)	41.1 ± 9.2 (33−55)	40.1 ± 3.9 (35−46)	32.1 ± 12.0 (27−42)
a	21.3 ± 2.7 (18.15−21.7)	16.9 ± 1.7 (14.6−18.4)	23.1 ± 2.8 (19.0−28.4)	24.1 ± 1.1 (22.7−26.3)	21.2 ± 2.3 (17.0−26.4)
b	4.4 ± 0.1 (4.3−4.5)	4.4 ± 0.5 (4.2−5.2)	4.3 ± 0.2 (3.9−4.6)	4.6 ± 0.3 (4.0−5.3)	4.2 ± 0.5 (3.6−5.5)
c	12.5 ± 0.2 (11.5−13.7)	12.1 ± 1.4 (9.3−13.9)	12.1 ± 1.0 (10.8−13.7)	18.2 ± 2.7 (14.6−22.7)	26.6 ± 4.2 (20.7−33.2)
cl	2.7 ± 0.1 (2.5−3.0)	2.6 ± 0.1 (2.4−2.9)	2.9 ± 0.1 (2.6−3.1)	1.9 ± 0.4 (1.4−2.5)	1.2 ± 0.2 (1.0−1.8)
T	77.0 ± 15.9 (50.1−90.0)	90.9 ± 2.5 (89.3−93.2)	74.4 ± 7.7 (63.3−83.5)	77.4 ± 5.8 (65.0−83.6)	63.5 ± 20.0 (56.5−76.2)
Lip height	4.0 ± 0 (4−4)	4.0 ± 0 (4−4)	4.0 ± 0 (4−4)	4.5 ± 0.4 (4−5)	4.0 ± 0.7 (4−5)
Lip diameter	9.8 ± 0.4 (9−10)	8.3 ± 0.3 (8−9)	9.7 ± 0.6 (9−10)	11.5 ± 1.1 (10−14)	11.8 ± 1.1 (10−13)
Stoma length	19.5 ± 0.8 (18−20)	18.8 ± 0.6 (18−20)	19.0 ± 1.1 (17−23)	24.5 ± 1.3 (22−26)	34.1 ± 2.2 (30−38)
Stoma diameter	4.0 ± 0 (4−4)	4.0 ± 0 (4−4)	4.5 ± 0.5 (4−5)	3.2 ± 0.3 (3.5−4.0)	3.2 ± 0.2 (3.0−3.5)
Pharynx length	168.1 ± 13.0 (155−190)	156.6 ± 5.9 (151−168)	163.3 ± 1.2 (155−181)	210.2 ± 13.1 (185−224)	181.7 ± 16.4 (161−210)
Nerve ring	112.2 ± 10.8 (100−127)	102.5 ± 6.0 (100−118)	114.3 ± 9.3 (100−135)	153.5 ± 11.2 (130−165)	132 ± 9.4 (120−150)
Secretory-	126.5 ± 9.4 (119−141)	116.4 ± 4.8 (110−120)	129.6 ± 7.4 (118−135)	180.4 ± 14.6 (150−196)	153.4 ± 12.3 (133−175)
excretory
pore
Anal body	21.8 ± 1.7 (20−24)	21.4 ± 1.5 (20−25)	19.6 ± 0.9 (18−21)	27.7 ± 1.5 (26−30)	23.0 ± 2.7 (19−28)
diameter
Tail length	60.3 ± 4.7 (58−67)	57.2 ± 5.2 (53−61)	59.3 ± 2.5 (57−64)	54.5 ± 10.3 (40−65)	30 ± 6.8 (20−40)
Spicule length	36.8 ± 2.0 (33−39)	36.7 ± 1.5 (35−40)	38.8 ± 2.9 (34−40)	40.0 ± 4.1 (32−45)	34.1 ± 2.3 (30−38)
Gubernaculum	17.6 ± 1.9 (14−20)	18.2 ± 1.6 (16−20)	16.5 ± 1.3 (15−19)	19.0 ± 1.7 (16−20)	14.0 ± 1.6 (12−16)
length

( Continued ) Table 1. (Continued).

Female	Female	Female	Female	Female
( n = 8)	( n = 8)	( n = 10)	( n = 9)	( n = 8)
Body length	840 ± 83.06 (786−902)	837.2 ± 99.7 (726−1022)	825.2 ± 87.7 (631−977) 1254.2 ± 167.7 (964−1515)		859 ± 65.8 (791−978)
Body diameter	36.2 ± 5.3 (26−40)	47.8 ± 5.8 (40−60)	41.1 ± 9.2 (33−55)	50.2 ± 7.7 (40−68)	42.3 ± 2.8 (38−46)
a	21.6 ± 1.7 (19.2−23.5)	17.5 ± 0.9 (16.8−18.9)	20.2 ± 1.7 (18.7−21.7)	24.5 ± 1.4 (21.5−27.4)	20.3 ± 1.3 (18.2−22.7)
b	4.4 ± 0.3 (4.1−5.0)	4.9 ± 0.3 (4.4−5.5)	4.1 ± 0.6 (4.0−5.0)	5.5 ± 0.8 (4.4−6.8)	4.3 ± 0.4 (3.7−4.7)
c	10.2 ± 0.7 (9.6−11.2)	10.3 ± 0.4 (10−11)	9.1 ± 0.6 (8.7−9.9)	7.5 ± 0.5 (6.3−8.0)	11.7 ± 1.6 (9.3−13.6)
cl	4.2 ± 0.2 (3.8−4.5)	3.7 ± 0.3 (3.4−4.1)	4.5 ± 0.3 (4.2−5.0)	6.5 ± 0.4 (6.2−7.2)	3.8 ± 0.7 (2.8−5.1)
V	52.6 ± 1.6 (50.8−55.1)	51.1 ± 1.3 (49.0−53.2)	51.0 ± 0.4 (50.5−51.6)	50.2 ± 1.2 (48.4−52.4)	54.6 ± 1.6 (52.2−56.3)
G1	35.0 ± 6.8 (27.6−47.1)	34.5 ± 5.5 (27.4−42.0)	37.4 ± 10.9 (20.7−48.4) 45.3 ± 6.2 (32.6−55.1)		38.2 ± 4.7 (31.2−44.4)
G2	36.1 ± 8.3 (27.3−51.2)	36.4 ± 4.1 (34.4−43.2)	37.9 ± 2.1 (35.1−40.2)	41.2 ± 5.2 (30.6−46.8)	36.8 ± 5.6 (30.3−43.4)
Lip height	4.0 ± 0 (4−4)	4.0 ± 0 (4−4)	3.9 ± 0.3 (3−4)	4.6 ± 0.6 (4−6)	3.2 ± 0.1 (3−3.5)
Lip diameter	9.8 ± 0.4 (9−10)	10.11 ± 0.3 (10−11)	9.9 ± 0.3 (8−10)	11.3 ± 1.4 (9−13)	11.8 ± 0.9 (10−13)
Stoma length	21.5 ± 1.7 (20−25)	20.3 ± 1.8 (17−23)	18.3 ± 1.2 (16−20)	25.6 ± 0.8 (24−27)	24.3 ± 2.6 (21−29)
Stoma diameter	4.0 ± 0 (4−4)	4.0 ± 0 (4−4)	4.8 ± 0.4 (4−5)	3.7 ± 0.5 (3−5)	3.9 ± 0.8 (3−5)
Pharynx length	188.3 ± 18.1 (177−218)	156.6 ± 30.3 (150−185)	168.1 ± 14.1 (143−185)	227.6 ± 11.2 (212−242)	197.8 ± 17.4 (182−227)
Nerve ring	121.6 ± 12.3 (110−143)	116.6 ± 6.7 (112−125)	111.3 ± 8.5 (100−125)	162.8 ± 10.1 (140−173)	143.3 ± 13.2 (130−160)
Secretory-	130.5 ± 13.7 (121−160)	129.5 ± 9.8 (120−138)	129.9 ± 14.9 (104−148)	183.5 ± 10.2) (165−195)	163.5 ± 12.8 (154−180)
excretory
pore
Anal body	20.1 ± 1.7 (19−22)	21.1 ± 1.2 (20−24)	19.7 ± 2.2 (17−24)	24.0 ± 1.5 (21−26)	19.5 ± 2.4 (16−23)
diameter
Rectum length	37.3 ± 9.2 (30−49)	34.4 ± 3.5 (31−40)	36.5 ± 1.5 (32−39)	33.2 ± 4.5 (24−40)	25.0 ± 1.2 (24−27)
Tail length	84.6 ± 8.7 (81−100)	80.3 ± 8.6 (69−92)	89.9 ± 8.8 (77−100)	166.5 ± 14.6 (150−195)	74.8 ± 14.5 (60−93)
V− A distance/	3.7 ± 0.2 (3.4−4.5)	4.0 ± 0.2 (3.7−4.4)	3.4 ± 0.3 (2.8−3.9)	2.7 ± 0.2 (2.2−3.1)	4.3 ± 0.5 (3.2−4.9)
tail

Habitat and locality Moist soil samples collected from a ditch with decaying matter at Sasni (Geographic coordinates 27 ◦ 51 l 42.78 ll N, 78 ◦ 04 l 14.37 ll E), Aligarh, Uttar Pradesh , India . Voucher material Eight females and six males on slide Metarhabditis andrassyana NOS /1-7 deposited in the Nematode Collection, Department of Zoology , Aligarh Muslim University, Aligarh, Uttar Pradesh , India . One female and one male on slide Metarhabditis andrassyana NOS /8 deposited at the Laboratory of Nematology , Wageningen University and Research Center ( WUR ), 6700 ES Wageningen , the Netherlands . Remarks The present population conforms to Metarhabditis andrassyana Tahseen et al., 2004 in most morphometric and morphological characteristics. However, some minor differences can be noted: distinct (versus indistinct) lateral fields; faint (versus distinct) longitudinal striae; smaller (versus larger) and four to six (versus seven to eight) metastegostomal denticles on each plate; nearly undifferentiated (versus slightly differentiated) corpus; and a relatively posteriorly located GP3 (versus adcloacal position of GP3 reported in Metarhabditis andrassyana Tahseen et al., 2004 ). Another important feature observed is the conspicuously dilated though short rectum uniformly present in all specimens.