Ditylenchus triformis Hirschmann & Sasser 1955

9. Ditylenchus triformis Hirschmann & Sasser, 1955 (Figure 4) 9 females: L = 621 (493–729) µm; stylet = 7.0 (7–8) µm; pharynx = 118 (97–131) µm; tail = 56.9 (44–66) µm; a = 39.3 (34.7–46.1); b = 5.3 (4.6–6.0); c = 10.9 (9.1–12.7); c′ = 5.4 (4.7–6.6); V = 78.3 (76.2–80.2); V′ = 86.2 (83.3–88.3); PUS / VBW = 1.7 (1.3–2.7); PUS /V-A = 32.6 (22.2–48.2) %; V-A/T = 1.4 (1.1–1.8). 2 males: L = 462, 581 μm; stylet = 6.5, 7 μm; pharynx = 97, 117 µm; tail = 51, 56 µm; a = 42.4, 44.7; b = 4.8, 5.0; c = 9.0, 10.3; c ′ = 6.9, 5.6; spicules = 14, 16 µm. Diagnosis. D. triformis is characterised by six lateral field incisures that reduced to four at anus level, delicate, short stylet with rounded knobs, elongate basal pharyngeal bulb that is usually offset and sometimes slightly overlapping (up to 6 µm), posterior position of vulva, rather long post-vulval uterine sac, usually rounded, seldom dull or pointed, tail tip, and short spicules. The Iranian population of D. triformis is close to 11 species, including D. acutatus, D. dauniae, D. geraerti, D. medicaginis, D. myceliophagus, D. silvaticus, D. valveus, D. virtudesae, D. apus, D. elegans and D. tenuidens. It differs from all of these species by the reduction of lateral field incisures at the anus region to four. In addition, it can be distinguished from D. virtudesae by longer spicules (14–16 vs. 11 μm), from D. acutatus and D. elegans by lower PUS / VBW ratio (1.3–2.7 vs. 2.8–4.1, 3.2, respectively) and different tail tip shape (usually rounded vs. pointed or dull), and from D. apus by greater PUS / VBW ratio (1.3–2.7 vs. 0.2–0.4) and the nature of the basal pharyngeal bulb (pyriform to elongate, offset or with slight overlap vs. elongated and with long overlap). It differs from D. myceliophagus by different basal plate of cephalic skeleton (weak to moderate vs. refractive and crescentic), from D. silvaticus and D. tenuidens by striated (vs. smooth) head and different tail tip shape (usually rounded vs. pointed), and from D. valveus by shorter spicules (14–16 vs. 16–23 µm). The only difference between D. triformis and the three remaining species is the number of incisures at the anus region.
Published as part of Hashemi, Kobra & Karegar, Akbar, 2019, Description of Ditylenchus paraparvus n. sp. from Iran with an updated list of Ditylenchus Filipjev, 1936 (Nematoda: Anguinidae), pp. 85-113 in Zootaxa 4651 (1) on page 96, DOI: 10.11646/zootaxa.4651.1.6, http://zenodo.org/record/3359134
{"references":["Hirschmann, H. & Sasser, J. N. (1955) On the occurrence of an intersexual form in Ditylenchus triformis, n. sp. (Nematoda, Tylenchida). Proceedings of the Helminthological Society of Washington, 22, 115 - 123."]}