Morphological and Molecular Characterization of Coslenchus paramaritus n. sp. and C. cancellatus (Cobb, 1925) Siddiqi, 1978 (Nematoda: Tylenchidae) from Iran

Female

Body almost straight to slightly ventrally curved. Body annuli distinct, 2.6 to 3.0 µm wide at mid-body, and 2.3 to 2.7 µm at the Esophageal region. Lateral field protruded, longitudinal incisures begin 5 to 8 annuli posterior to head and continue until 15 to 22 annuli to anus, with two prominence ridges and four incisures, 5.3 to 7.5 µm wide, covering 26 to 40% of body. Cuticle with further 18 longitudinal ridges excluding lateral lines. Head continuous to the body contour or slightly offset by a depression, 2.8 to 4.0 µm high and 5.8 to 6.9 µm wide, narrower than the rest of body. Head with distinct transverse striae separating four narrow annuli, cephalic framework weakly developed. Amphidial apertures indistinct. Stylet short and delicate, with distinct knobs 2.0 to 3.2 µm wide, conus less than half of the total stylet length, 5.2 to 6.6 µm long; dorsal gland orifice 1.0 to 2.0 µm behind stylet knobs. Esophageal median bulb oval, 9.8 to 12.3 µm in length and 5.9 to 7.7 µm in width, filling 39 to 54% of the body diameter with small valve apparatus. Terminal bulb pear-shaped, 14 to 19 µm long and 7.7 to 9.5 µm wide. Excretory pore 76 to 86 µm from anterior end, or anterior to terminal bulb, at level or one annulus posterior to hemizonid; Nerve ring encircling middle of isthmus, 62 to 73 µm from anterior end. Deirids located at the same level, 76 to 87 µm from anterior end. Esophageal-intestinal valve distinct. Rectum small, curved. Anus usually indistinct. Female reproductive system monodelphic, anteriorly directed; vulva with lateral flaps about two annuli long. Vagina with thick walls, slightly bent anteriorly; post-vulval uterine sac short, 8 to 12 µm, about half of the vulval body width (45 to 60%). Spermatheca offset, usually bilobed, filled with globular to slightly oval sperm, about 1 µm in diameter. Tail elongated, with sharply pointed to filiform terminus.

Male

Body straight to ventrally curved. Cuticle annuli 2.4 to 3.0 µm apart at mid-body and 2.3 to 3.0 µm at the Esophageal region. Lateral field 4.5 to 5.0 µm wide, occupying 30 to 36% of the body diameter, with two prominent separate ridges, hence four distinct incisures can be observed on mostly body length, without areolation. The cephalic region truncated, continuous or slightly set off from body with four annuli, 6.1 to 6.8 µm wide and 3.6 to 4.1 µm high. Cephalic framework not refractive. Stylet knobs well developed and globular, 2.1 to 2.5 µm in diameter. Esophageal median bulb oval, (5.8–6.5) × (9.8–12.0) µm. Bursa limited to the cloacal region, with crenate margins. Spicules slightly curved ventrally, with pointed tip. Gubernaculum simple, about one-third of spicule length. Tail elongated ending to a pointed to filiform terminus.

Diagnosis and relationships

The new species, Coslenchus paramaritus n. sp., can be characterized by having wide annuli, a long tail, the presence of males and the absence of sexual dimorphism in head shape of females and males. Coslenchus paramaritus n. sp. most closely resembles C. maritus Andrássy, 1991, but differs from it by wider cuticular annuli (2.6–3.0 µm vs 1.5–2.3 µm), longer tail (94–128 µm vs 83–91 µm), and the absence of sexual dimorphism in head shape (vs presence, male head is the widest in its middle). However, in general characteristics and number of longitudinal ridges, C. paramaritus n. sp. resembles certain other species namely C. lateralis (Andrássy, 1982), C. major Gagarin, 2004, C. franklinae (Siddiqi, 1981), C. leiocephalus (Brzeski, 1998), C. japonicus (Mizukubo and Minagawa, 1984), and C. areolatus (Egunjobi, 1967) (Siddiqi, 1978).

The new species differs from C. lateralis, by longer stylet (12–14 vs 11–12 µm), number of longitudinal ridges in the lateral field region (6 vs 4), and presence of male individuals (vs absence). From C. major, it can be distinguished by smaller body, stylet and tail (508–572 vs 780-990 µm, 12–14 vs 17–18 µm and 94–128 vs 133-168 µm, respectively), and spermatheca shape (elongated-bilobed vs elongated-rounded, 28–39 µm long). From C. franklinae, our population can be differentiated by longer stylet (12–14 vs 9–12 µm), number of annuli on the cephalic region (4 vs 2-3), and the presence of male individuals (vs absence). From C. leiocephalus, our population can be distinguished by a longer stylet (12-14 vs 10-12 µm), the number of head annuli (4 annuli vs smooth head), presence of a post-vulval uterine sac (vs absence) and presence of males (vs absence). The new species differs from C. japonicus by higher values for body length, pharynx length, tail length, cuticular annuli width, the number of head annuli and spicules length (508-572 vs 430-450 µm, 85-107 vs 77-89 µm, 94-128 vs 73-99 µm, 2.6-3.0 vs 1.9-2.5 µm, 4 vs 3 and 13-15.5 vs 11-14 µm, respectively), as well as presence of post-vulval uterine sac (vs absence). C. paramaritus n. sp. differs from C. areolatus in the presence of male individuals (vs absence), having a longer stylet (12-14 vs 10-12 µm), annuli number of cephalic region (4 vs 3) and in the shape of tail (elongated, terminus sharply pointed to filiform vs thick tail often covered by small scale-like annuli, terminus always finely rounded).

Type habitat and locality

Soil around of wild fig (Ficus carica subsp. rupestris) in Dezful, Khuzestan Province, southwestern Iran (GPS coordinates: 48°49'30″N, 32°46'24″E).

Type material

Holotype, 10 paratype females and 7 males were deposited in the collection of the Department of Plant Protection, College of Agriculture, University of Zanjan, Zanjan, Iran.

Etymology

The species epithet refers to the proximity of the new species with the other known species, C. maritus.

Coslenchus cancellatus (Cobb, 1925) Siddiqi, 1978.

(Figs. 3 & 4; Table 1).

Figure 3:

Figure 4:

Female

Body almost straight to slightly ventrally curved. Body annuli pronounce and wide, 2.4 to 3.3 µm at mid-body, and 2.3 to 2.9 µm at the posterior region of esophagus. Lateral field protruded, with two prominence ridges, 4.0 to 7.5 µm wide, occupying 28 to 39% of the body diameter. Head slightly offset by a depression, 2.5 to 3.3 µm high and 6.3 to 7.1 µm wide, narrower than its adjacent body, cephalic framework weakly developed. Amphidial apertures indistinct. Stylet short and delicate, with distinct knobs 2.2 to 2.7 µm wide; conus less than half of stylet length, 4.6 to 5.3 µm long, dorsal gland orifice 1.0 to 1.8 µm behind stylet knobs. Esophagus median bulb oval, 7.8 to 10.3 µm wide, filling 52 to 66% of the corresponding body diameter. Posterior bulb pear-shaped, 15 to 20 µm long and 8 to10 µm wide. Excretory pore from anterior end 59 to 103 µm, i.e. at the level of terminal bulb, at the same level with hemizonid or posterior to it; deirids at the same level or slightly posterior. Nerve ring encircling middle of isthmus, 55 to 78 µm from anterior end. Deirids at the level of excretory pore, 68 to 110 µm from anterior end. Esophageal-intestinal valve distinct. Rectum small, curved. Anus usually indistinct. Female reproductive system monodelphic-prodelphic. Lateral vulval flaps about two annuli or 4.2 to 6.8 µm long; vagina bent anteriad with thick walls, post-vulval uterine sac absent. Spermatheca offset, devoid of sperm. Tail conical with finely rounded to pointed terminus.

Male

Not found.

Remarks

This species was first described by Cobb (1925) from USA as Tylenchus cancellatus (Cobb, 1925), then Siddiqi (1978) transferred it to the genus Coslenchus. This species is most similar to C. costatus (de Man, 1921) (Siddiqi, 1978) and C. pycnocephalus (Siddiqi, 1981) in having 14 longitudinal ridges. It differs from C. costatus in the shape of posterior part of tail (pointed to minutely rounded vs spicate or filiform) and width of cuticular annuli at mid-body (about 4.0 vs 2.1-3.6 µm) and lesser number of tail annuli (28-36 vs more than 50). It differs from C. pycnocephalus in the head structure (smooth or having only one head annulus vs annulated with four or five distinct annuli). In general appearance C. cancellatus is also comparable with C. oligogyrus (Brzeski, 1987); but can be distinguished form it by different number of longitudinal ridges and head annuli (14 vs 10-12 and usually 5 vs 3, respectively) and a different ratio of tail to vulva–anus distance (1.2-1.6 vs 0.8-1.2).

Our population was recovered from the rhizosphere of Alpine Milkvetch (Astragalus alpinus L.) in Dezful, Khuzestan Province, southwestern Iran. Voucher specimens including 12 females were deposited in the collection of the Department of Plant Protection, College of Agriculture, University of Zanjan, Zanjan, Iran.