Morphometric data of females of Pratylenchus elamini
(all measurements in um, except L)
|L (mm)||0.385||0.407 ± 0.042 (0.335-0.505)||0.442 (0.390-0.480)|
|A||28||28 ± 2 (24-32)||27 (24-30)|
|B||4.8||5.8 ± 0.6 (4.7-6.8)||5.7 (5.4-6.0)|
|B’||3.4||3.8 ± 0.4 (3.3-4.5)||4.1 (3.9-4.2)|
|C||17||18 ± 1 (16-20)||19 (17-21)|
|C’||2.6||2.6 ± 0.4 (2.0-3.7)||2.9 (2.4-3.4)|
|V00||75||75 ± 1 (72-77)||75-76|
|M00||50||49 ± 1 (48-50)||49 (48-50)|
|Head diameter||8.0||8.0 ± 0.5 (7.5-8.5)||8.0 (7.5-8.5)|
|Head height||2.5||3.0 ± 0.5 (2.5-3.5)||3.0 (2.5-3.5)|
|Stylet Length||13.5||14.0 ± 0.5 (13.0-14.5)||13.5-14.0|
|Stylet knob W||3.0||3.5 ± 0.5 (3.0-4.0)||3.5-4.0|
|Stylet cone L||7.0||6.5-7.0||6.5-7.0|
|DGO||2.5||2.5 ± 0.5 (2.0-3.0)||2.5-3.0|
|Nerve ring – AE||61||61 ± 3 (57-66)||58 (51-63)|
|Hemizonid – AE||69||61 ± 6 (50-70)||68 (58-75)|
|Excretory Pore – AE||73||70 ± 2 (67-73)||72 (62-78)|
|Phasmid – AE||11||12 ± 2 (9-14)||12-13|
|Vagina length||6.0||6.0 ± 0.5 (5.0-7.0)||6.0 (5.0-7.0)|
|PUS||35.5||25.0 ± 4.0 (19.0-31.5)||28 (20-31)|
|VBD||12.5||14.0 ± 1.5(12.5-17.0)||16 (14-19)|
|PUS VBD||2.9||1.8 ± 0.3 (1.5-2.9)||2.1 (1.8-2.3)|
|Tail length||23||24 ± 3 (18-27)||24 (19-27)|
|Tail annuli||24||19 ± 2 (16-22)||20 (18-22)|
|Oesophagus L||115||108 ± 13 (85-129)||108 (99-115)|
|BMD||14||15 ± 1 (13-17)||16 (15-18)|
L = length; W = width; DGO = Dorsal oesophageal gland orifice; AE = Anterior body end; PE = Posterior body end; PUS = Post vulval uterine sac; VBD = Vulval body diameter; BMD = Body maximum diameter.
Description (Based on specimens from the type population)
Females: Short nematodes with slender bodies, showing various body postures upon relaxation varying from rather straight (three females), sharply curved anteriorly (two), showing C (nine) and almost U-shape (one) or spiral forms (two). Cuticle transversely striated with less than 1 um wide annuli. The lateral field starts about four annuli posterior to lip region with two lines which increase to reach four in ten females and five in seven specimens; outer incisures areolated; on the tail the lateral lines decrease to three or four. Lip region with three annuli and heavily sclerotized framework with the outer margins extending posteriorly between the first and second body annuli. SEM studies shows a dome-shaped head, distinctly offset from rest of body with three annuli (sometimes partly subdivided) and an undivided front with the six labial sensilla appearing as pits close to the mouth opening and two slit-like amphidial apertures in dorso-ventral direction. Stylet well developed, with the conical part almost equal to or slightly shorter than shaft; basal knobs with rounded and anteriorly slightly indented margins. Oesophagus with elliptical median bulb and rather long glandular lobe that overlaps intestine over poorly developed oesophago-intestinal junction. Hemizonid about two annuli wide and situated one or two annuli anterior to excretory pore. Female genital tract anteriorly outstretched with long post-vulval uterine branch. Oocytes are arranged in a single file and spermatheca oval and devoid of sperms. Vulva a transverse slit, slightly raised from body contour in most females. Tail conical in shape with an almost conical smooth terminus. Phasmids pore-like.
Male: Not found.
Type Habitat and Locality
Soil samples collected from the rhizosphere of Citrus paradisi in a fruit orchard about one kilometer north of Hantoub town (on the eastern bank of the Blue Nile river situated just across the river to Wadmedani City), Central Sudan, June 1987.
Holotype female and three paratype females mounted on Slides Nos. 3329, 3330, and 3331, deposited within the collection of the State University of Gent, Instituut voor Dierkunde, Ledeganckstraat 35, 9000 Gent, Belgium; two females sent to USDA Nematology collection, Beltsville, MD, USA; two females sent to Nematology collection, Agricultural University, Wageningen, The Netherlands and three females in the collection of the first author.
Other Material, Habitat and Locality
Three females; two kept within the collection of the University of Gent, mounted on Slide No. 3332 and the third one kept within the collection of the first author, collected from the rhizosphere of Psidium guajava from a fruit orchard about two kilometers north of Kassala City (latitude 15o 30’ N and longitude 36o 30’ E), Eastern Sudan during June 1987.
Diagnosis and Relationships
Pratylenchus elamini n. sp. is characterized by short body, 0.335-0.505 mm long, with wide variation of body shape upon relaxation, variable anterior body shape, three labial annuli, short stylet (13.0-14.5 um), anterior vulva position (72-77 %), a long post-vulval uterine sac (1.5-2.9 times corresponding vulval body diameter), smooth conical tail terminus, without males and with empty spermatheca.
The new species is comparable by the small body length, the three labial annuli, the short stylet, the anterior vulva and the smooth tail terminus to: P. kralli Ryss, 1982; P. sudanensis and P. uralensis Romaniko, 1977 (considered species inquirenda by Frederick and Tarjan, 1989). P. sudanensis (with males) and P. uralensis (without males) have a subcylindroid tail with a truncate terminus and a short post-vulval uterine branch. The main difference between our populations and P. kralli is that P. kralli is a bisexual species whereas P. elamini sp. n. is a parthenogenetic one. This difference is commonly used in Pratylenchus although we do not know if it has to have such a significance; Frederick and Tarjan (1989) gave the character less importance and synonymized P. sefaensis Fortuner, 1974 (without males) with P. pseudopratensis Seinhorst, 1968 (with males) although they continued considering them as two different species in their article; we suggest to use both names.
Frederick and Tarjan (1989) synonymized P. ventroprojectus Bernard, 1984 with P. kralli. The tail terminus in P. ventroprojectus is described as “truncate with a distinct subventral projection”; in P. kralli the tail terminus is drawn and described in a similar way. In P. elamini sp. n. the tail tip is almost conical without any ventral projection. Moreover the post-vulval uterine branch can be longer in P. elamini (1.5-2.9 times vulval body diameter) than in P. kralli (more than 1.5) and in P. ventroprojectus (0.9-1.8).
The following species are also morphologically similar, but differ in some measurement(s): P. delattrei (stylet = 16-18 um); P. emarginatus Eroshenko, 1978 (V = 68-73 %); P. microstylus Bajaj & Bhatti, 1984 (stylet = 11-12 um); P. sefaensis (V = 77-80 %); P. thornei Sher & Allen, 1953 (stylet = 15-19 um) and P. zeae (stylet = 15-17 um).
The SEM view of the head of P. elamini n. sp. is not different from that of P. yassini n. sp. and so resembles the species mentioned there.