Mylonchulus contractus Jairajpuri, 1970

Tahseen, Qudsia, Asif, Mohammad, Mustaqim, Malka, Ahlawat, Shikha & Bert, Wim, 2013, Descriptions of ten known species of the superfamily Mononchoidea (Mononchida: Nematoda) from North India with a detailed account on their variations, Zootaxa 3646 (4), pp. 301-335 : 323

Mylonchulus contractus Jairajpuri, 1970

( Fig. 11 )

Measurements. Table 2

Description. Adult: Body small-sized, C-shaped upon fixation, males with greater posterior curvature than females due to presence of copulatory musculature. Cuticle smooth, 1–2 µm thick at different body regions. Body pores indistinct. Lip region offset, angular in shape and distinctly wider than the adjacent body. Amphids cupshaped with oval-shaped aperture located at level of dorsal tooth apex. Labial papillae prominent and slightly raised. Buccal cavity funnel-shaped with thick cuticularised walls. Dorsal wall of buccal cavity bearing a large, anteriorly directed dorsal tooth, 7–8 µm long × 5–6 µm wide, located at ca 4–5 um from anterior end of buccal capsule or at ca 67–75% from its base. Each subventral wall bearing 5 transverse rows of closely spaced, smallsized denticles and a small subventral tooth posterior to them. Pharynx highly muscular, cylindrical with thick lumen. Orifices of pharyngeal glands: DO located at ca 59–63%, SV1O1 and SV1O2 at ca 70–75% and SV2O1 and SV2O2 at ca 95–97% of pharyngeal length from anterior body end. Nerve ring surrounding pharynx at 31–35% of its length from the anterior end. Excretory pore faintly visible at 34–38% of pharyngeal length. Pharyngo-intestinal junction non-tuberculate; cardia flattened to slightly overhanging. Intestinal lumen with traces of dead nematodes. Intestine with wide lumen, bordered by prominent and conspicuous microvilli ( Fig. 11 J, O). Intestine contracted in the region of gonads but some individuals showed a partial overlap. Rectum approximately the length of anal body diameter. Tail short and curved ventrally at right angle terminating gradually to a narrow terminus. Caudal glands well developed, grouped, with their duct opening through a subdorsal spinneret.

Female: Reproductive system didelphic, amphidelphic with both branches on one side of intestine. In most specimens one genital branch well developed while other one reduced or rudimentary. Oviduct provided with distinct pars dilatata. Vagina with thick, petal-shaped pars refringens.

Male: Genital system diorchic with opposed testes measuring 64–66 µm. Spicules ventrally arcuate (angular) with slightly broader manubrium; gubernaculum simple trough-shaped. Ventromedian supplements 10 in number, regularly spaced or equidistant, starting within the spicular range.

Locality and habitat: Moss containing M. contractus was collected from the bark of trees from district Sonebhadra, Uttar Pradesh, India, located at 24°33'3"N 83°4'1"E coordinates.

Voucher specimens. Nine females and one male on slide Mylonchulus contractus Jairajpuri, 1970 no. BS05/1- 4 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India. One female deposited at USDANC, Beltsville, MD, USA.

Salient characters. Small to medium-sized species with buccal cavity funnel-shaped with thick cuticularized walls; dorsal tooth large, situated in anterior half of buccal cavity; subventral wall bearing five transverse rows of denticles; subventral teeth present; female genital system amphidelphic; intestine contracted in the region of gonad; tail conoid, ventrally arcuate, bent at right angle; caudal glands usually grouped; spinneret subdorsal.

Remarks. The present specimens conform well to M. contractus in morphometrics and morphological features. The species has so far been reported from India, Dominica and Costa Rica. A few minor differences that may be noted including the greater number (= 10) of ventro-median supplements in the single male specimen of the present population whereas only 9 supplements were reported in M. contractus apud Khan & Jairajpuri (1979) . Furthermore, the female reproductive system indicated a transition between amphidelphic and monodelphic condition with either of the branches in rudimentary form in most specimens.

Figures

FIGURE 11. Mylonchulus contractus Jairajpuri, 1970. A – G: Anterior end with buccal armature. H: Anterior end showing amphids. I, J: Pharyngo-intestinal junction. K – N: Female genital system. O: Intestinal region. P: Vulval region. Q – S: Caudal region (female). T, U: Caudal region (male) with genital papillae indicated by arrows. (Scale bar = 10 µm).