Ditylenchus valveus Thorne & Malek, 1968

Karani, Hossein Mirbabaei, Eskandari, Ali, Ghaderi, Reza, Heydari, Ramin & Miraeez, Esmaeil, 2017, Morphological characterisation of a new and two known species of Ditylenchus Filipjev, 1936 (Nematoda: Anguinidae) from Iran, Zootaxa 4216 (4), pp. 355-368 : 361

Ditylenchus valveus Thorne & Malek, 1968

( Figs 3 & 4 )

Measurements. See Table 2 & 3 .

Female. Medium sized nematodes. Body slightly ventrally arcute after heat relaxation, slightly tapering towards both ends. Cuticle with fine transverse annulations, annuli about 1–2 µm wide at mid-body. Lateral field with six lines. Head low, anteriorly flat, continuous with body contour, 2–3 µm high and 7–8 µm wide; outer margins appearing striated especially at the base of the head. Stylet delicate, conus shorter than shaft (31–38 % of total stylet length); DGO opens just posterior to knobs; knobs rounded and symmetrical. Pharyngeal median bulb oval, with central sclerotised thickenings of lumen. Basal bulb elongated-cylindrical, offset; isthmus slender, ending to a pyriform basal pharyngeal bulb; pharyngeal gland lobe never overlapping intestine. Nerve ring surrounding isthmus; excretory pore opposite of anterior to base of pharynx and immediately posterior to hemizonid. Female reproductive tract monodelphic-prodelphic 371–568 µm in length, ovary outstretched with oocytes arranged in single to double rows, Crustaformeria quadricolumellate, with four distinct cells in each column followed an elongated spermatheca packed with large rounded sperm. Vulva a transverse slit with slightly raised lips, vagina at right angle with body axis, reaching near halfway across body. Post-uterine sac 40–52 µm, as long as 1.3–1.8 times vulval body diameter and extending about half to one-fourth of the vulva-anus distance. Tail conical, regularly tapering towards to a sharply pointed terminus.

Male. Similar to female, but usually with shorter body length. Spicules simple, curved ventrally, gubernaculum simple and short. Bursa 47–60 µm long, beginning after proximal end of spicule and covering only the cloacal region (leptoderan).

Ditylenchus valveus was originally described from Avon, South Dakota , United States of America, collected from a plowed field by Thorne & Malek (1968). Later, this species was reported from a mushroom compost sample amended with sugar beet pulp from Manitoba , Canada by Anderson (1983). The latter author examined type specimens and emended the original description and broadened the morphometric ranges and morphological features. Brzeski (1991) collected several populations from different locations in Poland and Bulgaria and added some new information for this species. Our population was collected from the rhizosphere of olive trees ( Olea europium L.) from an orchard in Nodije , a village located west of Gorgan (GPS coordinates: N 36° 83', E 54° 27') , Golestan province, northern Iran . Morphology and morphometrics of the Iranian population of D. valveus in the present study completely fit these various descriptions of the species ( Thorne & Malek 1968, Anderson 1983, Brzeski 1991) with slight variations in some measurements, especially in a and c' ratios and in the pharynx length (see. Tables 2 & 3 ). In light of the great similarity in almost all other characters, the authors consider these small differences merely intraspecific variation. With six lateral lines, a delicate stylet, V ratio of 75–81, short PUS and pointed tail terminus, D. valveus should be compared with D. tenuidens Gritzenko, 1971 , D. medicaginis Wasilewska, 1965 and D. myceliophagus Goodey, 1958 . The Iranian population differs from D. tenuidens in having a striated head and greater spicule length. It differs from D. medicaginis by having striated head, more posterior position of vulva and different tail shape. It differs from D. myceliophagus in having generally offset pharynx and larger spicules, as well as different tail shape and tail terminus. The present study reports, describes and illustrates D. valveus for the first time from Iran .

Figures

FIGURE 3. Iranian population of Ditylenchus valveus, female (A, C – F) and male (B, G, H). A, B: Entire body; C: Mid-body showing lateral lines; D: Pharyngeal region; E – H: Tail. (Scale bars: A, B = 80 µm; C, D = 20 µm; E – F = 10 µm).

FIGURE 4. Iranian population of Ditylenchus valveus, female (B, D, E, G, H, J, M) and male (C, F, I, K, L). A: Male and female entire body; B – D: Anterior end; E: Vulval region; F, G, J – M: Posterior end; H: Mid-body showing lateral lines; I: Cloacal region. (Scale bars: A = 100 µm; B – D, E, H – M = 10 µm; F, G: 20 µm).

Tables

TABLE 3. Morphometrics of the males of Ditylenchus valveus in present study and other populations worldwide. All measurements are in µm and in the form: mean ± s. d. (range).

n	Present study (Iran) Gorgan 5	Anderson, 1983 (Canada) Manitoba 3	Brzeski, 1991 (Poland) Oltarzew 1	Brzeski, 1991 (Bulgaria) Varna 6
L a	828 ± 80 (741–937) 31.4 ± 3.1 (28–34.7)	755–850 37–43	756 46	661 (586–731) 39 (35–44)
b	5.6 ± 0.6 (4.9–6.4)	6.5–7.3	5.7	5.3 (4.7–6.2)
c c'	10.7 ± 1 (9.6–12.2) 4.2 ± 0.5 (3.9–4.9)	8.7–9.1 6.5–6.8	9.5 5.9	11.3 (8.9–12.2) 4.8 (3.9–5.7)
T	54 ± 6.4 (44.5–57)	37–43	-	-
Stylet m	7.2 ± 0.6 (6.5–8) 36.1 ± 2 (33.3–38.5)	9 -	7 -	7.9 (7–8.5) -
MB	37.2 ±1.1 (35–38.4)	-	3 9	38 (35–42)
Pharynx Excretory pore	147 ± 3.6 (144–152) 110 ± 16.3 (82–122)	- 79–91	1 3 3 89	126 (117–134) 94 (89–100)
Tail length	78 ± 9 (70–89)	-	7 9	59 (48–81)
Spicules Gubernaculum	22.8 ± 0.8 (22–23.5) 8 ± 0.0	19–20 5–6	20 -	18.5 (16–23) 5–7