Clarkus papillatus (Bastian, 1865) Jairajpuri 1970

Clarkus papillatus (Bastian, 1865) Jairajpuri, 1970

(Fig. 1)

= Mononchus papillatus Bastian, 1865

= Mononchus (Prionchulus) papilIatus Bastian, 1865 (Schneider, 1939) = Prionchulus papillatus (Bastian, 1865) Schneider, 1939 = Mononchus cristatus Bastian, 1865

= Clarkus koreanus Choi, Khan & Lee, 1999

Measurements. Table 1

Description. Adult: Body medium-sized, ventrally curved upon fixation. Cuticle smooth 2–3 µm thick in different body regions. Body pores not visible. Lip region set off, ca 2.4–2.6 times as wide as high, distinctly wider than adjoining body, with very small or inconspicuous labial and cephalic sensilla. Amphids cup-shaped with oval apertures, 3–4 µm across, located anterior to dorsal tooth or 10–11 µm from anterior end. Buccal cavity barrelshaped tapering at base about 2–3 times as long as wide with heavily cuticularised parallel vertical and oblique walls; vertical walls consisting of a tooth-bearing dorsal wall and two toothless sub-ventral walls. Dorsal tooth prominent, 3–4 µm in thickness, situated in the anterior half of buccal cavity or about 82–83% of buccal capsule from its base; anterior margin of the tooth somewhat straight. Subventral walls of buccal cavity with a longitudinal ridge extending from the point opposite to dorsal tooth’s apex to posterior part of vertical plates. Pharyngeal sleeve surrounding stoma at 1/3–1/4 of its length from base. Pharynx cylindroid, muscular ca 26–28% of body length. Nerve ring at 31–38% of pharyngeal length. Excretory pore 35–42% of pharyngeal length from the anterior end. Orifices of the pharyngeal glands: DO at ca 53–58%, SV1O1 and SV1O2 at ca 72–75%, and SV2O1 and SV2O2 at ca 94–97% of pharyngeal length. Pharyngo-intestinal junction non-tuberculate. Intestinal lumen wide, intestinal wall made up of large polygonal cells. Rectum ca 0.8–1.1 times anal body diameter long. Tail conoid, ventrally arcuate with acute terminus. Caudal glands absent, rudimentary in one specimen; spinneret absent.

Female: Reproductive system didelphic, amphidelphic; ovaries reflexed, of robust size, about as wide as corresponding body diameter, with 7–10 oocytes arranged alternately or in single row in each ovary; and distal end with a cluster of proliferating oogonial cells. Oviduct narrow connected to uterus without any sphincter in between. Uterus muscular, accommodating usually one egg at a time, occasionally with two large-sized, smooth-shelled eggs, 76–80 µm long × 48–49 µm wide. Vagina extending more than half of corresponding body diameter with small, moderately sclerotised pars refringens. Vulva an oval slit of 9–12 µm diameter.

Male: Not found.

Locality and habitat. Soil containing Clarkus papillatus was collected from around the roots of Pinus sp. from Dehradun, Uttarakhand, India, located at 30.3157°N 78.0336°E coordinates.

Voucher specimens. One female on slide Clarkus papillatus (Bastian, 1865) Jairajpuri, 1970 no. D13/1 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. Medium-sized nematodes; buccal cavity barrel-shaped, dorsal wall bearing a mediumsized tooth; each subventral wall provided with non-denticulate ridge. Pharyngo-intestinal junction nontuberculate. Female genital system amphidelphic. Tail short, conoid, ventrally arcuate with acute terminus. Caudal glands rudimentary or absent; spinneret absent.

Remarks. This is the most widely distributed species of the genus, and has been reported from all continents (Andrássy, 2006) except Antarctica. The present specimens show morphological as well as morphometric characteristics similar to specimens of Clarkus papillatus described earlier (Jairajpuri, 1970a; Andrássy, 2006); however, the uterine eggs were relatively smaller (76–80 × 48–49 µm vs 80–92 × 32–44 µm) than those reported for C. papillatus apud Andrássy (2006). The lip region was variable from rounded to angular. The buccal cavity also showed variation in shape with the vertical walls straight to slightly curved. The inconspicuous caudal glands and absence of spinneret are typical features of this species, although the tails exhibited variation in degree of ventral curvature of the two specimens studied.