Plectonchus longevulvus, Khan & Hussain & Tahseen, 2012

Khan, R., Hussain, A. & Tahseen, Q., 2012, Descriptions of one new and two known species of Panagrolaimoidea (Nematoda) from India, Journal of Natural History 46 (13 - 14), pp. 867-884 : 876-881

Plectonchus longevulvus sp. nov.

( Figures 5 , 6 )

Measurements

See Table 2.

Description

Female. Body small to medium-sized, ventrally curved upon fixation, tapering more towards posterior end. Cuticle distinctly loose, 2–5 µm thick, transversely striated, annuli 0.2–0.5 µm wide in different body regions. Longitudinal lines and lateral field indistinct. Lip region continuous with adjoining body contour. Labial sensilla papilliform. Amphids inconspicuous. Stoma 0.6–1.2 labial diameter long. Cheilostom indistinguishable. Gymnostom and stegostom fused to form weakly sclerotized funnelshaped chamber narrowing into pharyngeal lumen. Pharynx panagrolaimoid type comprising of 57–70 µm long, cylindrical corpus, narrower 35–38 µm long isthmus and ovoid basal bulb of 13–17 × 11–13 µm dimension with a grinder and single-chambered haustrulum. Nerve ring encircling isthmus at 60–76% of pharyngeal length, surrounding isthmus. Excretory pore located above nerve ring or at 44–57% of pharyngeal length at posterior level of pharyngeal corpus. Body at pharyngeal end 2.5–2.8 labial diameter wide. Cardia conoid, 2–4 µm long. Intestine granular with wide lumen. Rectum thin-walled, 1.4–1.7 anal body diameter long. Anus a crescentshaped opening. Female reproductive system monodelphic, prodelphic. Ovary dorsally reflexed at right side of intestine with distal end not reaching vulva. Oocytes arranged in two rows in germinal zone but in single row beyond that. Spermatheca distinctly offset, oval, filled with sperms. Vagina anteriorly directed, about 1 / 2 of corresponding body diameter long. Ovoid glandular cells found associated with dorsal and ventral uterine walls. Usually one intra-uterine egg of 39 × 11 µm dimension present. Postuterine sac absent. Vulva–anus distance 43–68 µm or about 2.8–4.4 times anal body diameter. Tail elongate, conoid with pointed terminus. Phasmids located at middle of tail.

Male. Similar to female in general morphology but smaller in size with pronounced posterior curvature. Testis monorchic, ventrolaterally reflexed, on the right of intestine; occasionally outstretched distally. Vas deferens narrowing into ejaculatory duct. Spicules stout, slightly ventrally curved with round capitula and beak-like distal ends, 1.0–1.4 anal body diam. long. Gubernaculum lancet-shaped, proximally hooked, 0.7–0.9 times spicule length. Bursa absent. Caudal papillae seven pairs: two precloacal and five postcloacal pairs in 1+1 / 1+P+1+2+1 configuration. GP1 and GP2 ventrolateral, GP1 located at about 1.3–1.5 spicule length from cloacal opening; GP2 at middle level of spicules; GP3 ventrolateral located at about half of cloacal body diam. form cloacal opening; GP4 subdorsal; GP5 and GP6 subventral, closely placed, located at end of conoid part of tail; GP7 laterodorsal, slightly posterior to end of conoid part of tail. Phasmid located between GP3 and GP4. Tail conoid tapering to a narrow pointed terminus.

Diagnosis

Plectonchus longevulvus sp. nov. is characterized by thick cuticle; indistinct lateral field; weakly sclerotized funnel-shaped stoma; cylindrical pharyngeal corpus gradually narrowing into isthmus; posterior vulva; presence of ovoid glandular cells associated with dorsal and ventral uterine walls; spicules having prominent capitula and beak-like distal ends; lancet-shaped, proximally hooked gubernaculum and seven pairs of caudal papillae in 1+1 / 1+P+1+2+1 configuration.

Differential diagnosis and relationships

The new species most closely resembles P. molgos Massey, 1974 but differs in having smaller b and greater V values, papilliform labial sensilla, presence of glandular cells found associated with dorsal and ventral uterine walls, greater number of postcloacal papillae and tail with a terminal spike (versus b = 5.1–5.6, V = 75, labial sensilla setiform, absence of ovoid glandular cells, four pairs of post-cloacal papillae and finger-like peg in tail reported in P. molgos ).

The new species differs from P. ateri Fuchs, 1930 in having smaller b and greater V values, smaller stoma, smaller tail and greater number of genital papillae (versus b = 6, V = 73.7, stoma = 10 µm long, tail = 78 µm long and six pairs of genital papillae present in P. ateri ).

Plectonchus longevulvus sp. nov. also differs from P. extrematus Gunhold, 1952 in having smaller females, smaller a and greater c values, presence of ovoid glandular cells associated with dorsal and ventral uterine walls and larger gubernaculum (versus L = 0.75–0.90 mm, a = 32–34, c = 8–9, absences of ovoid glandular cells and gubernaculum is 11–12 µm long in P. extrematus ).

The new species differs from P. wyganti Massey, 1964 in having smaller females, smaller c′ and greater V values, loose cuticle, indistinct lateral field, narrower and weakly sclerotized stoma, presence of ovoid glandular cells associated with dorsal and ventral uterine walls, gubernaculum with pointed head and greater number of genital papillae (versus L = 0.7 mm, c′ = 5, V = 77, cuticle of normal thickness, lateral field two incisures, stoma = 5 µm wide and strongly sclerotized, absences of ovoid glandular cells, head of gubernaculum is rounded and six pairs of genital papillae in P. wyganti ).

Type habitat and locality

The sample containing Plectonchus longevulvus sp. nov. was collected from a ditch (alluvium soil) at Kishtwar , Jammu and Kashmir and Khair, Aligarh, Uttar Pradesh, India at 33 ◦ 19 ′ N, 75 ◦ 46 ′ E .

Type material

Holotype female, 13 paratype females and 11 paratype males on slide Plectonchus longevulvus sp. nov. No. NOJ &K / 1-10 deposited in the Nematode Collection, Department of Zoology , Aligarh Muslim University, Aligarh, Uttar Pradesh, India. One female paratype and one male paratype on slide P. longevulvus sp. nov. No. NOJ &K / 11, deposited at the Laboratory of Nematology, Wageningen University and Research Center (WUR), 6700 ES Wageningen, the Netherlands.

Etymology

The Latin epithet of the species (longe = far; vulvus = vulva) reflects the farthest location of vulva reaching up to 86% of the body length.

Figures

Figure 5. Plectonchus longevulvus sp. nov. (A) Female, entire; (B) male, entire; (C) anterior end; (D) pharyngeal region; (E) female reproductive system; (F) caudal region, female; (G) caudal region, male.

Figure 6. Plectonchus longevulvus sp. nov. (A) En face view; (B) anterior end; (C) pharyngeal region; (D) body region showing pharyngeal bulb; (E, F) vulva-anal region; (G) caudal region, female; (H) posterior region, male; (I–K) male cloacal region showing spicules and gubernaculum; (L) caudal region, male (scale bar = 10 µm).