Mylonchulus obtusicaudatus (Daday, 1899) Andrássy, 1958

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 : 316-318

Mylonchulus obtusicaudatus (Daday, 1899) Andrássy, 1958

( Fig. 7 )

= Mononchus obtusicaudatus Daday, 1899 (Cobb, 1916)

Measurements. Table 2 .

Description. Adult: Body medium-sized, ventrally arcuate with sharply curved ventro-posterior region. Cuticle smooth 3–6 µm thick at different body regions. Body pores indistinct. Lip region offset, about 2.5–3.0 times as wide as high, lip sensilla slightly projecting above labial contour, almost indiscernible in some specimens. Amphids cup-shaped, 4–5 µm across, located 9–14 µm from anterior end. Buccal cavity goblet-shaped, about 1.6– 1.8 times as long as wide with strongly sclerotized vertical and oblique plates. Dorsal wall bearing large, 11–12 µm long and 7–8 µm wide, anteriorly-directed tooth, located at 8–9 µm from anterior end of buccal capsule or ca 76– 84% from its base. Each subventral wall with 6 transverse rows of prominent, rasp-like denticles: denticles of anterior row regular and larger while those of posterior ones relatively smaller, irregularly arranged; one subventral tooth present below the level of rasp-like denticles. Pharyngeal sleeve surrounding stoma at 1/3–1/4 of its length from base. Pharynx cylindroid, muscular, 24–26% of body length. Outlets of pharyngeal glands, DO situated at ca 51–56%, SV1O1 and SV1O2 at ca 65–67%, SV2O1 and SV2O2 at ca 91–93% of pharyngeal length from anterior end. Nerve ring encircling pharynx at 27–29% of pharyngeal length from anterior end. Excretory pore faintly visible and about 31–35% of pharyngeal length from anterior end. Pharyngo-intestinal junction non-tuberculate, cardial flap small conical to long tubular ranging from 17–25 µm in length. Intestine made of polygonal cells, intestinal lumen wide. Rectum 0.6–0.9 times anal body diameter in length. Tail conoid, ventrally arcuate with rounded to subclavate terminus. Caudal glands well developed, tandem in arrangement. Spinneret terminal in position.

Female: Reproductive system didelphic, amphidelphic with short, compact, reflexed ovaries. Oocytes arranged in single tier except at distal end of ovary. Sphincter present at junction of oviduct and uterus. Vagina about one-third of corresponding body diameter, provided with conspicuous, ovoid pars refringens.

Male: Not found.

Locality and habitat. Moist soil sample containing M. obtusicaudatus was collected from Keoladeo National Park, Bharatpur, Rajasthan, India, at 27°13ʹN 77°29ʹE coordinates.

Voucher specimens. Five females on slide Mylonchulus obtusicaudatus (Daday, 1899) Andrássy, 1958 , no. 8B /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. Large-sized species with buccal cavity ca 1.6–1.8 times as long as wide; dorsal tooth large, situated in anterior half of buccal cavity; each subventral wall bearing six transverse rows of denticles and a relatively posterior tooth; female genital system amphidelphic with conspicuous, ovoid pars refringens; tail conoid, ventrally curved with blunt terminus; caudal glands in tandem; spinneret terminal.

Remarks. The present population conforms well to M. obtusicaudatus (Daday, 1899) Andrássy, 1958 in morphometric and morphological details. The buccal cavity showed intrapopulation variations in the shape ranging from funnel-shaped to goblet-shaped. Usually six subventral rows of prominent rasping denticles present. The subventral teeth in a few specimens appeared crooked in shape or the tip seemed to be broken off ( Fig. 7 H), perhaps during the capture of prey. The cardial flaps also showed variation in shape and length ( Fig. 7 K–N) in different individuals. In females the reproductive system generally comprised of two short compact ovaries, oviducts demarcated from uterus by sphincters ( Fig. 7 O–Q) and pars refringens conspicuously rounded or ovoid ( Fig. 7 R) in a few individuals. The obtuse or blunt tail tip, the signature feature of this species, showed some degree of variation ( Fig. 7 T–V) from blunt to a more or less rounded tip.

Figures

FIGURE 7. Mylonchulus obtusicaudatus (Daday, 1899) Andrássy, 1958, A – I: Anterior end with buccal armature. J: Anterior end showing amphids. K – N: Pharyngo-intestinal junction. O – Q: Anterior genital branch. R, S: Vulval region. T – V: Posterior body region. (Scale bar = 10 µm).