Diphtherophora obesa Thorne, 1939

Ghaderi, Reza, Kashi, Leila, Karani, Hossein Mirbabaei & Karegar, Akbar, 2017, A new and four known species of Diphtherophora (Nematoda: Diphtherophoridae) from Iran, with a diagnostic compendium of its species, Zootaxa 4365 (3), pp. 311-330 : 317

Diphtherophora obesa Thorne, 1939

( Figs 3 ; 6 E ; 7 C ; 8 E, F ; 9 E, F )

Measurements. See Table 2 .

Female. Body habitus slightly curved ventrally when killed and fixed. Cuticle very thick, about one-third to half of the body width; without transverse striations, but some fold or encrustations at anterior end of body observed in some specimens. Subcuticle layer about 1 µm thick. Head region continuous with the body contour. Amphids with oval-shaped aperture. A pair of lateral pores situated at the spear base. Spear typical of the genus, guiding apparatus arched, relatively well-sclerotised. Pharynx with rounded to pyriform basal bulb. Nerve ring at mid-pharynx region. Secretory-excretory pore located at the posterior end of isthmus. Cardia not observed. Reproductive system with two antidromous tracts and reflexed ovaries. Spermatheca absent, but small sperm cells usually distributed along the uteri with distinct rounded to oval-shape nuclei (2–3 µm in diameter). Vulva a transverse slit; vagina at right angles to the body axis; with well-developed musculature and a sclerotised ring. Rectum 12–15 µm or two-fifths to one-half of the anal body width. Tail conoid, symmetrical, about as long as the anal body width; with subdigitate terminus. Sublateral caudal pores absent near tail terminus.

Male. Body straight to slightly curved ventrally. Ventromedian cervical papillae not observed. A pair of lateral pores located at spear base. Reproductive system monorchic, extending to near mid-body. Sperm cells with a large lemon- to oval-shaped central nucleus. Two ventromedian precloacal supplements (SP) observed in spicule region: SP1 poorly visible and situated slightly anterior to cloacal aperture; SP 2 16–20 µm anterior to cloacal aperture; ca. about 4–5 µm posterior to spicule head. Spicules without marked capitulum, proximal part cylindrical, suddenly narrowing about mid-spicule, then expanding again and gradually tapering to the distal end and a bifurcated tip. Mid-spicule region surrounded by bristle-like structures. Gubernaculum simple and relatively long.

Remarks. Our population has comparable morphometrics with the type population from the USA ( Thorne 1939), but extends ranges for many of these characters. D. obesa comes close to D. lata Thorne, 1974 and D. perplexans ( Cobb, 1913) de Coninck, 1931 . It differs from D. lata in having a tail with subdigitate terminus, in number of ventromedian cervical papillae (2 vs unknown), the position of the second ventromedian precloacal supplement (located at the level of retracted spicules vs more anterior) and spicule shape. It can be distinguished from D. perplexans in having more swollen body (a = 10–15 vs 13–22), by tail shape, and by presence of males (vs very rare). In D. obesa , the tail is conoid, basically symmetrical, ventrally and dorsally tapering to a subdigitate terminus, while in D. perplexans , the tail is dorsally convex-conoid, but almost straight on the ventral side, appearing asymmetrical, and often with a digitate terminus. Males of D. obesa , based on shape of spicules and sperm, are similar to those of D. tenera but can be separated by tail shape (not bent vs with dorsally bent terminus) and tail length (27–38 vs 39–45 µm).

This species has been described from virgin and cultivated soil in the USA (see Thorne 1939). Our population is a new record for Iran and was collected from around trees in Kabudval forest, Ali Abad-e-Katul, Golestan province, northern Iran.

Figures

FIGURE 3. Diphtherophora obesa Thorne, 1939. Female (A–C, E, F) and male (D, G). A: Entire body; B, C: Anterior end; D: Pharyngeal region; E: Part of reproductive system; F, G: Posterior end.

FIGURE 6. Anterior ends of Diphtherophora species from Iran. Females (A, B, D–I, K) and males (C, J, L). A–C: D. caudata; D: Diphtherophora sp.; E: D. obesa; F–H: D. perplexans; I, J: D. geraerti sp. n.; K, L: D. tenera. All scale-bars = 10 µm.

FIGURE 7. Pharyngeal regions (A–F) and spermatozoa (G–J) of Diphtherophora species from Iran. Females (A–E) and males (F–J). A, G: D. caudata; B, H: Diphtherophora sp.; C: D. obesa; D, I: D. geraerti sp. n.; E, F, J: D. tenera. All scale-bars = 10 µm. (e: excretory pore; v: ventromedian cervical papillae).

FIGURE 8. Female tails of Diphtherophora species from Iran. A, B: D. caudata; C, D: Diphtherophora sp.; E, F: D. obesa; G, H: D. geraerti sp. n.; I–K: D. perplexans; L: D. tenera. All scale-bars = 10 µm.

FIGURE 9. Male posterior ends of Diphtherophora species from Iran. A, B: D. caudata; C, D: Diphtherophora sp.; E, F: D. obesa; G, H: D. geraerti sp. n.; I–K: D. tenera. All scale-bars = 10 µm. (s = preanal supplements).