Prionchulus muscorum (Dujardin, 1845)

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 : 306

Prionchulus muscorum (Dujardin, 1845) Wu & Hoeppli, 1929

( Fig. 2 )

= Oncholaimus muscorum Dujardin, 1845

= Mononchus muscorum (Dujardin, 1845) Bastian, 1865 = Mononchus (Prionchulus) muscorum (Dujardin, 1845) Bastian, 1865 (Cobb, 1916) = Mononchus bastiani de Man, 1876

= Mononchus (Prionchulus) longicollis Cobb, 1917 = Mononchus papillatus macrodon Fuchs, 1930

= Prionchulus medius Eroshenko, 1975

= Prionchulus paucidentatus Zell, 1985

= Prionchulus ferox Winiszewska & Susulovsky, 2003 = Prionchulus olexandri Winiszewska & Susulovsky, 2003 = Prionchulus prasadi Saha, Lal & Singh, 2006

= Prionchulus ukhrum Mohilal & Dhanachand, 1997 = Prionchulus pachydermis Khan, Choi, Lee & Choi, 2000

Measurements. Table 1 .

Description. Adult: Body medium to large-sized, straight to open ‘C’-shaped on fixation, strongly curved in tail region, broad at anterior end but tapering at posterior extremity. Body pores indistinct. Cuticle smooth, about 3.0–3.5 µm thick in different body regions. Lip region slightly offset from the body contour, about 2.0–2.5 times as wide as high; labial sensilla prominent, slightly raised. Amphids cup-shaped, 5–6 µm across, located anterior to dorsal tooth, at 18–23 µm from anterior end of body and 32–34 µm from base of buccal cavity. Buccal cavity large, elongate barrel-shaped, about 1.6 times as long as wide, with thick, heavily cuticularised vertical and oblique walls. Dorsal wall bearing a sharp, pointed, 10–12 µm long and 5–6 µm wide dorsal tooth, directed forward, located in the anterior half of buccal cavity at 73–75% from its base; each sub-ventral wall bearing a longitudinal denticulate ridge with 11–16 closely placed denticles. Pharyngeal collar surrounding buccal cavity at 1/3–1/4 of its length from base or up to the level of oblique plates. Pharynx cylindroid, muscular, 25–30% of body length. Orifices of pharyngeal glands, DO located at ca 54–55%, SV1O1 and SV1O2 at ca 67–68%, SV2O1 and SV2O2 at ca 94–96% of pharyngeal length from anterior end. Nerve ring at 30–32% of pharyngeal length, conspicuous in few specimens only. Excretory pore at 34–36% of pharyngeal length. Pharyngo-intestinal junction non-tuberculate. Intestine with narrow lumen, in some specimens containing cuticularised structures of devoured nematode prey. Rectum 1.2–1.3 times the anal body diameter. Tail conoid, strongly curved ventrally ending in acute terminus. Caudal glands and terminal opening absent.

Female: Reproductive system didelphic, amphidelphic; ovaries reflexed with oocytes arranged in a single row, except at the tip. Vagina about half of corresponding body diameter with ovoid, dorso-ventrally compressed pars refringens. Vulva post-equatorial, a transverse slit with slightly cuticularised lips.

Male: Not found.

Locality and habitat. Soil sample containing Prionchulus muscorum was collected from around grasses ( Agrostis sp.), Dehradun, Uttarakhand, India, located at 30°20'38"N 77°59'52"E coordinates.

Voucher specimens. Four females on slide Prionchulus muscorum (Dujardin, 1845) Wu & Hoeppli, 1929 no. D12/1–2 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 to large-sized species; buccal cavity of moderate size with parallel vertical walls; dorsal wall bearing medium-sized tooth; each subventral vertical wall provided with denticulate ridge having 11– 16 denticles; Pharyngo-intestinal junction non-tuberculate; female reproductive system amphidelphic; tail short conoid with rudimentary or no caudal glands; spinneret absent.

Remarks. P. m u s c o r u m (Dujardin, 1845) Wu & Hoeppli, 1929 is a widely distributed species reported from a large number of countries of Europe, Asia, Africa, America and Australia (Andrássy, 2006), predominantly from soil and occasionally from moss as well as aquatic habitats. The species seems to be facultatively parthenogenetic as it is often represented by females in populations, with males extremely rare or absent.

The present specimens conformed well in most morphological and morphometric characteristics to P. muscorum (apud Jairajpuri, 1970a; Andrássy, 1985) except in having a smaller a value (16–20 vs 21–33). Most characters were in total agreement with those specified for P. muscorum apud Arpin et al. (1984) viz., dorsal tooth located at 73–75% of the length of the buccal cavity from its base, smooth-shelled intra-uterine eggs, buccal cavity with prominently ridged subventral walls having 11–16 denticles and a relatively slender, conoid tail. However, presence of additional features considered to be specific for P. punctatus raise questions regarding the reliability and credence of these characters in diagnosis. The buccal cavity was observed to be relatively small and rectangular in some individuals ( Fig. 2 A); the thickness of the ridge as well as the arrangement of denticles exhibited variation ( Fig. 2 E–H). The tail in a few individuals was observed to be short and conoid with a slightly swollen ( Fig. 2 N), fusiform terminus ( Fig. 2 O). Thus the only character for P. m u s c o r u m that appears differentiating and reliable is the smooth (not echinulate) egg shell surface. The intraspecific variations in P. muscorum as also reported by Clark (1960), Mulvey (1967) and Arpin et al. (1984) can be due to the cosmopolitan nature of species that occurs in different biogeographical locations.

Figures

FIGURE 2. Prionchulus muscorum (Dujardin, 1845) Wu & Hoeppli, 1929 female. A – D: Anterior end. E – H: Subventral wall with denticulate ridge. I: Body region showing excretory pore. J – L: Pharyngo-intestinal junction. M: Vulval region. N, O: Posterior body region. P: tail tip. (Scale bar = 10 µm).