Description of Longidorella (Saevadorella) caspica n. sp. (Dorylaimida: Nordiidae) from north Iran

Female: Body fusiform, tapering gradually towards both ends, very slightly curved ventrad. Cuticle with two layers, 3 to 4 μm thick at anterior body region and mid body, 4 to 5 μm thick at the anterior lip of anus, with very delicate transverse striae visible at the dorsal side of the tail. Cephalic region separated from the rest of the body by a deep constriction. Labial papillae protruding, large and distinct. Amphidial fovea cup-shaped, large, their opening ca. 75% of cephalic region width wide, at the level of constriction. Odontostyle long and thin, 2.5 to 3.0 times longer than cephalic region width. Odontophore rod-like, its base simple, muscles at its base slightly swollen, but not flanged or sclerotized, approximately equal in size with odontostyle or slightly longer. Guiding ring single. Pharynx dorylaimoid, the anterior part narrower, enlarging gradually to the pharyngeal bulb. Location of pharyngeal glands’ nuclei follow: DN = 65 to 68, S1N = 32 to 40, S2N = 76 to 79. Cardia hemispheroid, 10-17 × 9-12 μm. Intestine simple with no specific features. Reproductive system didelphic-amphidelphic, genital branches 150 to 160 μm long, each branch composed of an ovary 90 to 120 μm long, oviduct and sphincter, a tubular uterus 55 to 60 μm long usually containing sperm, vagina 30 to 37% of body width, composed of pars proximalis vaginae 8-10 × 7-10 μm in size, pars refringens vaginae with two weakly sclerotized pieces triangular to trapezoid with 4 μm height and 3 to 5 μm width, pars distalis vaginae 2 to 4 μm long, and vulva a small rounded pore. Prerectum twice the anal body diameter and rectum equal to the anal body width in length. Tail conical with finely rounded tip, ventrally nearly straight, dorsally convex with a very weak dorsal concavity at the end, appearing slightly sub-digitate.

Male: Similar to females in general morphology except for the posterior body end more ventrally bent. Spicules dorylaimoid, almost slender, about five times longer than wide, their head (capitulum) narrow, a well-developed hump and deep hollow (sensu Peña-Santiago et al., 2014) lacking. Lateral guiding pieces cylindroid, 8 to 10 μm long. The copulatory supplements composed of a cloacal pair at 7 to 10 μm anterior to cloacal aperture, and a series of five to seven ventromedian supplements ending at 48 to 55 μm from the cloacal pair. Tail similar to that in female.

Rhizosphere of grasses, Mazandaran province, north Iran. GPS coordinates: 36°38ʹ6.225ʺN, 51°33ʹ52.236ʺE.

Holotype female, paratype females and males were deposited in Nematology Collection of Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran (slide accession codes: TM5100-TM5103). The ZooBank Life Science Identifier (LSID) for this publication is as follows: urn:lsid:zoobank.org:pub:1915B3CE-4B79-480B-8117-E926CA3CD090.

The specific epithet was derived from Caspian Sea, from where the new species was recovered in its vicinity.

Longidorella (Saevadorella) caspica n. sp. is mainly characterized by its cephalic region separated from the rest body by a deep constriction and prominent labial papillae. It was further characterized by 788 to 874 μm long females having 92 to 94 μm long odontostyle in females and 80 to 91 μm in males, with didelphic-amphidelphic reproductive system, vulva at 52.5 to 59.0%, 33 to 38 µm long dorsally convex tail in females, males with 32 to 35 µm long dorylaimoid spicules, and five to seven ventral supplements.

The new species was morphologically compared with seven nominal species under the subgenus viz. Longidorella (Saevadorella) arenicola (Vinciguerra and Zullini, 1980), L. (S.) cuspidata (Andrássy, 1964; Jairajpuri and Hooper, 1969), L. (S.) magna (Loof, 1971), L. (S.) perplexa (Siddiqi, 2007), L. (S.) saadi (Siddiqi, 2007), L. (S.) saeva (Siddiqi, 1982) and L. (S.) tharensis (Nasira et al., 2010) as follow.

From Longidorella (Saevadorella) arenicola by a longer body of female (788-874 vs 630-750 μm), shorter odontostyle (32-33 vs 40-42 μm), greater b (3.5-3.8 vs 2.7-3.3) value, pore-like vulval opening (vs transverse slit), less ventromedian male copulatory supplements (five to seven vs nine) with the last supplement distantly placed to the spicules’ head (vs close).

From L. (S.) cuspidata by a longer body of female (788-874 vs 510-760 μm), greater a (16.8-21.3 vs 12.5-14.7), b (3.5-3.8 vs 2.6-3.0), and c (20.7-37.0 vs 16.5-20.0) ratios, vulva pore-like (vs transverse, after its original drawing) and tail ventrally slightly convex (vs concave).

From L. (S.) magna by a shorter body of female (788-874 vs 1,050-1,100 μm), longer odontophore (33-38 vs 20-24 μm) and shorter tail (33-38 vs 47-50 μm).

From L. (S.) perplexa by a longer body of female (788-874 vs 580-680 μm), greater b (3.5-3.8 vs 2.5-3.0), anteriorly located vulva (V = 52-59 vs 58-67), shorter odontostyle (32-33 vs 38-46 μm), shorter odontophore (33-38 vs 39-44 μm), pore-like vulval opening (vs transverse slit), longer spicules (32-35 vs 31-32 μm), and five to seven male copulatory supplements (vs three).

From L. (S.) saadi by a shorter odontostyle (32-33 vs 40-50 μm), shorter odontophore (33-38 vs 40-44 μm), less c′ (0.9-1.5 vs 1.4-1.7) value, different range of V (52.5-59.0 vs 54-66), longer prerectum (47-65 vs 20-30 μm) and shorter spicules (32-35 vs 40 μm).

From L. (S.) saeva by shorter odontostyle (32-33 vs 39-42 μm), shorter odontophore (33-38 vs 42-48 μm), pore-like vulval opening (vs transverse), smaller c′ (0.9-1.5 vs 1.2-2.0), shorter spicules (32-35 vs 38-40 μm) and number of copulatory supplements of male (five to seven vs two).

From L. (S.) tharensis by cephalic region separated from the rest body by a deep constriction (vs slightly offset), shorter odontostyle (32-33 vs 35-38 μm), longer neck (227-231 vs 197-223 μm), longer pharyngeal bulb (92-94 vs 67-68 μm), pore-like vs transverse vulval slit and longer tail of female (33-38 vs 20.2-26.4 μm).

Based on similar general morphology, the new species was further compared with two species under the subgenus Longidorella (Enchodorella) (Siddiqi, 2007) viz. L. (E.) deliblatica (Krnjaic, 1971) and L. (E.) murithi (Altherr, 1950) as follow.

From L. (E.) deliblatica by a longer body (788-874 vs 602-700 μm), slightly longer odontostyle (32-33 vs 26.8-31.4 μm) and odontophore (33-38 vs 22.4-30.0 μm), narrower tail tip (vs wider) and almost slender spiclues (vs with deep hollow).

From L. (E.) murithi by a cephalic region separated from the rest body by a sharp constriction (vs not), shorter odontostyle (32-33 vs 40-44 μm) and tail tip not remarkably narrowing (Andrássy, 2009).

Sequencing of D2-D3 expansion segments of 28S rDNA of the new species yielded a single fragment of 800 nt long. A total number of 53 sequences of 28S rDNA D2-D3 of Longidorella spp., other nordiids as well as some other dorylaimids (ingroup sequences) were retrieved from GenBank for phylogenetic analyses. The outgroup sequences belonged to two mononchid species (Table 1). Figure 4 represents the Bayesian phylogenetic tree reconstructed using this dataset. The nordiid genera occupied separate placements in this tree. The new species fell into a highly supported major clade including five other sequences of the genus Longidorella and two other dorylaimid genera. The clade including two sequences with accession numbers AY593042 and AY593042 assigned to Longidorella sp. and Longidorella cf. macramphis, represents the tentative sister clade to the new species.

Figure 4: