Anaplectus labiosulcus, Jahan & Khan & Mahboob & Tahseen, 2020

Jahan, Rehmat, Khan, Rahmat, Mahboob, Mohammad & Tahseen, Qudsia, 2020, A detailed taxonomic study on two new and one known species of Anaplectus De Coninck & Schuurmans Stekhoven, 1933 (Nematoda: Plectidae), Zootaxa 4877 (2), pp. 329-344 : 335-342

Anaplectus labiosulcus sp. nov.

( Figs. 3 , 4 )

Measurements. Table 2 .

Description. Female: Body arcuate, more so towards posterior extremity. Outer cuticle annulated, 1.5–2.0 μm thick, relatively loose in lip region; annules 1.5 μm wide; inner cuticle not striated. Somatic setae indistinct. Lat-eral fields extending from nerve ring up to middle of tail length, ca 1/5 th– 1/6 th corresponding body diameter wide, appearing as three lines under LM as the two lateral alae are closely placed. Amphidial aperture a transverse or elliptical slit, located at 3 rd or 4 th body annule. Sub-cuticular sublateral, round to ovoid, hypodermal glands, opening through 115–123 conspicuous, cuticularised pores; running from anterior to posterior body end laterodorsally and lateroventrally. Except for the anteriormost 5–6 hypodermal glands, which lie in a single row laterally, the glands run in two rows with opposite as well as alternate positions and with the laterodorsals usually larger than the lateroventrals. First hypodermal gland opens 2–3 μm posterior to amphidial opening. Lip region low, slightly offset from adjoining body. Cephalic setae 3–4 μm long, arising at level of 3 rd annule. Lips six, closely placed or amalgamated with cuticularised semicircular interlabial grooves. Stoma comprising of non-cuticularised cheilostom, strongly arched, C-shaped gymnostom, and parallel-walled stegostom surrounded by pharyngeal sleeve; gymnostom wall often bends before joining the stegostom, giving the gymnostom an appearance of double-arched structure. Pharynx differentiated into anterior corpus, a somewhat indistinct isthmus and a pyriform basal bulb with post-bulbar extension surrounded by cardia. Basal pharyngeal bulb ovoid, 23–26 µm long and 17–20 μm wide in dimension with a grinder comprising of 5–7 pairs of denticulate ridges and a haustrulum. Nerve ring encircling corpus at 51–53% of pharyngeal length; pharyngeal region narrow and compressed at level of nerve ring. Secretory-excretory pore posterior to nerve ring at 56–60% of pharyngeal length, duct cuticularised and coiled extending to a posteriorly located uninucleate excretory cell. One pair of ovoid pseudocoelomocytes present posterior to cardia. Intestine appearing granular and thin-walled. Rectum thick-walled, smaller than anal body diameter, without rectal glands.

Reproductive system didelphic, amphidelphic. Ovaries well developed, reflexed; anterior ovary on right and posterior on left side of intestine. Oocytes arranged in 2–3 tiers distally; intra-uterine eggs present with spinose shells. Sperms not observed in genital tract. Vagina straight, 1/4 th of vulval body diameter, provided with two pairs of muscles appearing elliptical in cross section. Vulval lips flush with the main body or slightly protruding. Tail plump, conoid, ventrally arcuate with four caudal setae. Three caudal glands arranged in a group and opening through a conspicuous, cuticularised spinneret.

Male: Not found.

Type habitat and locality. Sample containing Anaplectus labiosulcus sp. nov. was collected from soil from the grass at the bank of a drain at Khair, Aligarh, India at coordinates N 27° 56’ 24.38”, E 77° 50’ 34.54” .

Type material. Holotype female on slide Anaplectus labiosulcus sp. nov. NOK/1 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh. Five paratype females on slides Anaplectus labiosulcus sp. nov. NOK/2–6 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh.

Diagnosis and relationship. Anaplectus labiosulcus sp. nov. is characterised by medium-sized females having thick, annulated cuticle; 115–123 sublateral hypodermal glands on each side of body with dorsals usually larger than ventrals; 5–6 anteriormost glands unpaired arranged linearly; slightly offset labial region; lips with cuticularised, semicircular interlabial grooves; amphids located in anterior part of stoma; gymnostom arched, occasionally double-arched; stegostom parallel-walled; ovoid to rounded basal bulb; vulval lips slightly protruded; four caudal setae and caudal glands grouped opening through a cuticularised spinneret.

The new species most closely resembles A. eurycerus in most of the morphometric details and the absence of males but differs in having smaller a (19.2–23.2 vs 25) value; slightly offset lip region with cuticularised semicircular interlabial grooves (vs lip region usually continuous, cuticularised interlabial grooves absent); relatively anterior position of amphids (located at anterior vs middle level of stoma) and stoma 2.5 [vs 3.5 times lip region diameter long in A. eurycerus ( Massey, 1964) ].

The new species also resembles A. octo in most of the morphometric details and in absence of males but differs in having smaller a (19.2–23.2 vs 26–27) and ć (1.8–2.2 vs 3.3) values; greater c (13.9–16.4 vs 11–13) and V (53.9–55.6 vs 51) values; gymnorhabdia single or double-arched (vs always double-arched or hourglass-shaped) and relatively larger stoma [25–27 μm vs 23–24 μm in A. octo ( Zullini,1973) ].

A. labiosulcus sp. nov. further resembles A. granulosus in most of the morphometric details but differs in having relatively smaller individuals (0.7–0.8 mm vs 0.7–1.5 mm); relatively lower a (19.2–23.2 vs 20–39) and b (4.0–4.3 vs 4–6) values; smaller number of hypodermal glands (115–123 vs 160); dorsolaterals usually larger than dorsoventrals (vs no size differences observed); greater number (five to six vs one) of unpaired hypodermal glands in the anterior region; four pairs (vs three pairs) of caudal setae and male absent [vs present in A. granulosus ( Bastian, 1865) De Coninck & Schuurmans Stekhoven, 1933 ].

Etymology. The name of the species labiosulcus stands for labial grooves which are conspicuously cuticularised.

Anaplectus granulosus ( Bastian, 1865) De Coninck & Schuurmans Stekhoven, 1933

( Fig. 5 )

- Plectus granulosus Bastian, 1865

- Plectus schneideri de Man, 1880

- Plectus tubifer Cobb, 1914

- Plectus blanci Hofmänner in Hofmänner & Menzel, 1914

- Marinoplectus tetrapapillatus Kreis, 1963

- Anaplectus arenicola Killick, 1964

Measurements. Table 3 .

Description. Female: Body more or less C-shaped after fixation, more ventrally arcuate towards posterior extremity with maximum body width observed in the mid-region. Outer cuticle coarsely annulated, 2.0–3.0 μm thick, annules 1.5 μm wide; inner cuticle not striated. Lateral fields consist of three lateral lines under LM originating near the anterior pharyngeal region and extending almost to tail terminus. Amphid aperture a transverse slit, located at 8 th or 9 th body annule. Sub-cuticular hypodermal glands distinct, opening through conspicuous, cuticularised pores; running from anterior to posterior body end laterodorsally and lateroventrally (except for the 1 or 2 anteriormost linearly-arranged glands). Laterodorsals and lateroventrals large and of almost similar size, running in two rows with opposite as well as alternate positions comprising a total of 120–125 lateroventral and laterodorsal pores on each side. First hypodermal gland opens 2–3 μm posterior to amphid opening. Cervical papillae located just posterior to amphid or near to first lateral pore. Lip region slightly offset from adjoining body. Lip region consists of six separate lips; labial sensilla indistinct. Cephalic setae 2–4 μm long, arising at level of 2 nd or 3 rd annule. Stoma comprising of non-cuticularised cheilostom bordered by lips, arcuate cuticularised gymnostom, shorter than wide; stegostom surrounded by thin pharyngeal sleeve, subdivided into two parts: anterior broad cylindrical tube comprising of fused pro-, meso- and metastegostom and posterior narrow telostegostom, enveloped by muscular pharyngeal tissue. Pharynx differentiated into anterior corpus, a somewhat distinct isthmus and basal bulb. Corpus gradually widening posteriorly. Isthmus narrower and slightly demarcated from corpus. Basal pharyngeal bulb rounded, 25–28 µm long and 18–24 μm wide in dimensions with grinder composed of 5–7 pairs of denticulate ridges and haustrulum. Postbulbar extension elongate or conoid, enveloped by cardia. Nerve ring encircling corpus at 54–57% of pharyngeal length. Secretory-excretory pore posterior to nerve ring at 58–62% of pharyngeal length, duct cuticularised extending to a posteriorly located uninucleate excretory cell. Deirids papilliform; located inside lateral field posterior to nerve ring or adjacent to secretory-excretory pore. Intestine thin-walled without distinct lumen. Rectum thickwalled, smaller than anal body diameter.

Reproductive system didelphic, amphidelphic. Ovaries well developed, reflexed; anterior ovary on right and posterior on left side of intestine. Each genital branch possesses a prominent spermatheca, and crustaformeria followed by spacious uterus. Single intra-uterine egg present measuring 62 μm long x 37 μm wide in dimension with spinose shell. Sperms not found in genital tract. Vagina straight, 1/3 th -1/4 th of vulval body diam. Vulval lips slightly protruding. Tail conoid, ventrally arcuate, with bluntly rounded terminus. Caudal glands three, distinct. Cuticularised spinneret present. Two pairs of small caudal setae observed in the posterior half of the tail length.

Male: Not found.

Habitat and locality. The sample containing Anaplectus granulosus was collected from manure at Java, Aligarh, Uttar Pradesh, India at coordinates 27.9392° N, 77.8424° E.

Voucher specimens. Four females on slide Anaplectus granulosus RJ-JV 2/1–3 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India.

Remarks. Allen and Noffsinger (1968) provided a detailed description of the poorly known type species A. granulosus The original description ( Bastian 1865) of A. granulosus was based upon females, however, Allen and Noffsinger (1968) described the male, and also collected from the type locality and designated the neotype from soil around stubble from Broadmoor, England. They also synonymised A. areniocola Killick, 1964 with A. granulosus on the basis of slit-like amphid apertures. The specimens described here agree well with the redescription of A. granulosus as given by Allen and Noffsinger (1968) in morphological as well as morphometric characteristics. A few minor differences were observed, including a relatively smaller body (L = 0.7–0.9 mm vs 0.7–1.5 mm); smaller a (19.2–24.6 vs 20.0–39.0) value; smaller number of hypodermal glands (120–125 vs 160) and two pairs of caudal setae (vs three pairs). This population also conforms well with the population of A. granulosus described by Holovachov et al. (2004), with some minor differences, including lower a (19.2–24.6 vs 24.0–29.9) and c (14.5–17.5 vs 17.2–20.0) values. The present population lacks males as also reflected by spermathecae with no sperms.

Figures

FIGURE 3. A. labiosulcus sp. nov. A: Entire female. B: Anterior end showing hypodermal glands. C: Anterior end. D: Female pharyngeal region. E: Female reproductive system. F. Hypodermal glands flanking lateral fields. G: Female posterior region.

FIGURE 4. A. labiosulcus sp. nov. A: Anterior end (SEM). B, C: Anterior end. D: Head region (SEM). E, F: Body region showing hypodermal glands. G: Pharyngeal region. H–J: Vulval region. K: Body region showing lateral fields. L: Posterior body region (SEM). M: Tail region (LM). N: Tail region (SEM) (Scale bars = 10 μm).

FIGURE 5. A. granulosus. (Bastian, 1865) De Coninck & Schuurmans Stekhoven, 1933 A: Anterior end. B: Neck region. C: Anterior pharyngeal region. D–F: Posterior pharyngeal region. G: Anterior genital branch. H: Uterine region. I: Posterior genital branch. J: Vulval region. K: Body region showing lateral fields. L, M: Posterior body region. N: Tail terminus (Scale bars = 10 μm).