Description of Oionchus sindhicus n . sp . , and Morphometric Data on O . paraobtusus Jairajpuri and Khan , 1982 and O . obtusus Cobb , 1913 ( Nematoda : Mononchida ) from Pakistan

Uzma Ishaq1, Shahnaz Dawar2, Nasira Kazi1, Erum Iqbal1* and Saboohi Raza3 1National Nematological Research Centre, University of Karachi, Karachi 2Department of Botany, University of Karachi, Karachi 3Department of Agriculture and Agribusiness Management, University of Karachi, Karachi, Pakistan Article Information Received 10 September 2020 Revised 21 October 2020 Accepted 28 October 2020 Available online 16 July 2021

T he genus Oionchus Cobb, 1913 belong to the family Mononchulidae De Coninck, 1965 of the suborder Bathydontina Coomans and Loof, 1970 according to Ahmad and Jairajpuri (2010). The family Mononchulidae is characterized by buccal cavity strongly sclerotized with long anterior subventral tooth and 2-6 rows of transverse denticles, pharynx with five gland nuclei with anterior one dorsal, located about middle of pharynx far posterior to gland orifice. The family contain two genera Mononchulus Cobb, 1918 andOionchus Cobb, 1913. The genus Oionchus includes predatory soil nematodes which have buccal cavity encircled by pharyngeal tissues. Metastome sclerotized with a very large, grooved tooth on right or left ventro-sublateral side. Telostone elongate. Amphids near or slightly posterior to tip of tooth. Three cardiac glands present. Vulva posterior to mid body. Tail short, hemispherical with caudal glands and a terminal or slightly dorsally subterminal spinneret.
Currently this genus has three normal species (Ahmad and Jairajpuri, 2010) O. obtusus Cobb, 1913 as type species, O. obtusicaudatus (Kreis, 1932) Thorne, 1935 andO. paraobustus Jairajpuri andKhan, 1982. In this paper a new species of Oionchus sindhicus is described along with two known species as a new record from Pakistan.

Materials and methods
Nematodes were isolated from soil samples by Cobb's wet sieving technique (Cobb, 1918) followed by a modified Baermann funnel method (Baermann, 1917). Extracted nematodes were killed by gradual heat, fixed in TAF and mounted in dehydrated glycerine (Siddiqi, 1986). Illustrations were made by using a drawing tube attached to the compound microscope. Nikon Eclipse E400 and photographed with a Nikon DS-Fi1 Camera, attached to the same microscope, and edited by Adobe Photoshop. The classification of mononchs given by Ahmad and Jairajpuri (2010) was followed here.

O n l i n e F i r s t A r t i c l e
subventral walls bearing two transverse rows of denticles. Nerve ring located at 60-66 µm from anterior and or at 30-44% of neck length. Three cardiac glands present, 8-10 µm diameter. Distance between posterior end of pharynx and vulva equal to 2.2-2.7 pharyngeal length. Female reproductive organs mono-prodelphic, rather short and simple occupying 10-12%of body length. Posterior branch represented by a small post uterine sac, measuring 10-16 µm, less than corresponding body diameter long.

Type habitat and locality
The specimens were recovered from soil around the roots of cotton (Gossypium hirsutum L.) at Umerkot, Sindh, Pakistan.

Type material
Holotype female and nine paratypes female deposited in the Nematode Collection of National Nematological Research Centre, University of Karachi, Karachi, Pakistan.

O n l i n e F i r s t A r t i c l e Etymology
The specific epithet refers to the locality where the species has been recovered.

Remarks
Specimens for the present study were obtained from around the roots of cotton (Gossypium hirsutum L.) from Umerkot, Sindh. Measurements and morphological characters are quite similar to those given by Jairajpuri and Khan, 1982. Only difference was found in terminal spinneret against spinneret subterminal ventrally. Cobb, 1913 ( Table II)  Description Female: Body short, straight to slightly ventrally curved when relaxed by heat, cuticle smooth 2 µm thick at mid body. Lip region 9-10 µm wide and 2-3 µm high. Buccal cavity encircled by pharyngeal tissue. Anterior wider part of buccal cavity 4-5 µm wide and 4-7 µm long. Pharynx 214-220 µm long, cylindrical, slightly thickening posteriorly. Cardiac glands present. Nerve ring at 48-50 Description of Nematode Species from Pakistan O n l i n e F i r s t A r t i c l e µm from head end. Reproductive system monoprodelphic with posterior branch represented by a small sac 10-14 µm or less than on vulval body diameter. Ovary reflexed. Sphincter indistinct. Vulva slightly posterior to mid body. Rectum 14 µm or less than one anal body width long. Tail short hemispheroid, less than one anal body width long. Caudal gland present. Spinneret subterminal dorsally.