Zalonema granda, Fadeeva, Natalia, Mordukhovich, Vladimir & Zograf, Julia, 2016

Fadeeva, Natalia, Mordukhovich, Vladimir & Zograf, Julia, 2016, Free-living marine nematodes of Desmodorella and Zalonema (Nematoda: Desmodoridae) with description of two new species from the deep sea of the North Western Pacific, Zootaxa 4175 (6), pp. 501-520 : 512-517

Zalonema granda sp. nov.

( Figs 8–10 )

Type material. Holotype: adult male, mounted on slide MN st11-4sd2-20fr500. Paratypes: nine males and three females deposited in the nematode collections of the Division of Biological Sciences , Zoological Museum of Far Eastern Federal University , Vladivostok, Russia (Table 2).

Locality. Table 1 .

Etymology. The specific epithet is derived from the Latin word grandis (=grand or major).

Measurements. See Table 2.

Description. Large yellowish to brownish nematodes with pigmented epidermal inclusions; with cylindrical body with rounded high head capsule and conical tail. Distinct finely annulated cuticle, not marked by longitudinal structures or lateral differentiation. Cuticle annulated posterior to cephalic capsule. Annuli narrower at mid-body, may be fused or split. The body may carry numerous suctorian ciliates. Anterior retractable lip region, cuticle around the mouth opening wrinkled in irregular folds. Six inner (only seen using SEM) and six outer labial papilliform sensillae, four cephalic setae. Eight subcephalic setae (10 µm long) located on anterior region of cephalic capsule. Cephalic capsule convex, walls apically thin and gradually thickening posterior to become thicker than body cuticle. Cephalic capsule 25–27 µm high, 48–50 µm in diameter at posterior edge, the latter has minute pores with thin canals. Whorled, multispiral (2.2–2.3 turns) amphideal fovea larger in males (23–28 µm) than in females (15–19 µm), located at anterior edge of cephalic capsule. Eight longitudinal rows of somatic setae (~ 10 µm long), reduced to six rows at mid-body and four rows in posterior region. A sub-ventral row of longer setae located between vulva and anus. Rows (4–5) of post-anal long setae located 12–23 µm posterior to anus.

Pharynx evenly muscular throughout its length, with pyriform terminal bulb, gradually widening towards the base. No ventral gland found. Buccal cavity with one large dorsal tooth and two small ventrosublateral teeth. Large cardia. Nerve ring located 140–170 µm from anterior end. Tail conical, showing sexual dimorphism, i.e., markedly bent in females with broad pre-anal and small post-anal swellings, more regularly conoid and without swelling in males. Annulation of tail only seen with SEM.

Male. Reproductive system with single anterior outstretched testis situated to right of intestine. Spicules elongated 1.5 (1.4–1.6 c.b.d. long), curved, broadening before round capitulum, and pointed distally. Tubular gubernaculum weakly developed. A field of long sub-ventral setae (14–17 µm) arranged by longitudinal rows extends from cloaca to anterior end. Conical tail with short non-annulated terminus. Three pairs of minute setae situated close to tail tip.

Female. Distance from posterior end of amphid to the end of cephalic capsule 7–9 µm. Reproductive system didelphic, amphidelphic with equally developed genital branches; ovaries reflexed. Anterior genital branch situated to the left of the intestine; posterior one to the right. Vulva a transverse slit. A field of long sub-ventral setae (14–15 µm) extends from vulva to anus. Two minute setae present on tail close to terminus.

Diagnosis and relationships. Zalonema granda sp. nov. is characterized by having a very long body (3.3– 4.3 mm), long cephalic setae (6–8 µm), convex cephalic capsule, 8 longitudinal rows of cervical setae (16 –21 µm long) located at the posterior region of cephalic capsule, multispiral amphid (with 2.1–2.2 turns), buccal cavity with one large dorsal tooth and two small ventrosublateral teeth, eight longitudinal rows of short somatic setae (~ 7–9 µm long), reduced to six rows at mid-body and four rows in the posterior region extending to tail tip. Males have elongate curved spicules (76–84 µm or 1.4–1.6 c.b.d. long), broadening before a round capitulum, pointed distally; a weakly developed tubular gubernaculum, no pre-anal supplements, a conical tail with a short non-annulated terminus and three pairs of minute caudal setae situated close to tip.

Table 2.Morphometrics of Desmodorella tenuispiculum Allgen, 1928 , Zalonema kamchatkaensis sp.novand Z. granda sp. nov. Data presented as minimum-maximum values. All measurements in µm Zalonema granda sp. nov. is similar to congeners: Z. maldivensis ( Gerlach, 1963) , Z. mariae Larrazábal- Filho, Silva & Esteves, 2015, and Z. kamchatkaensis sp. nov., but differs by having a larger body (3.3–4.3 mm vs in most species up to 1.5–2.5 mm long) and spicules (77–84 vs in most species up to 38–74 µm); and the presence of three pairs of minute caudal setae situated close to the tail tip. The new species is close to Z. maldivensis in shape of the cephalic capsule, tail, and shape of the amphid. However, Z. granda sp. nov. differs from Z. maldivensis in numerous respects, including form of the cephalic capsule (with a thickened cuticle vs a thinner capsule); female amphideal fovea shape (multispiral vs loop-shaped), absence of supplements (vs presence of supplements); and by having three pairs of minute caudal setae situated close to the terminus(vs absence). Zalonema granda sp. nov. is similar to Z. kamchatkaensis sp.nov. in many measurements (see Table 2) but differs in body size (3.3–4.3 mm vs 2.00– 2.8 mm); spicule shape (curved elongated spicules, with broadening posterior to round capitulum vs short, strongly cuticularized spicules) and shape of the tail tip (with three pairs of minute caudal setae vs with cuticular ribs). Zalonema granda sp. nov. is distinguished from Z. mariae Larrazábal-Filho, Silva & Esteves, 2015 by a combination of the following features: very large body (3.3 mm – 4.3 mm vs 1.1–2.6 mm), spirally whorled in 2.1–2.2 turns amphidial fovea (vs 3.5 turns) in males; absence of lateral and ventral alae, and having 8 longitudinal rows of cervical setae (16 –21 µm long).

Remarks. Zalonema propingua ( Allgen, 1951) Gerlach, 1963 is considered by most authors as species inquirendae (Versschelde et al. 1998; Larrazábal-Filho et al. 2015).

Figures

FIGURE 8. Zalonema granda sp. nov. Male: A. Entire body; B. Head; C. Tail region. Female: D. Entire body; E. Head. F. Pharynx; G. Tail region; H. Reproductive system. Scale bars: A, D, G, H— 100 µm; B, C, E— 50 µm; F— 150 µm; I— 45 µm.

FIGURE 9. Zalonema granda sp. nov. Light micrographs. A. Entire male, lateral view. B. Entire females, lateral view. C. Posterior body region of female with a vulva, lateral view. D. Posterior body region of male, lateral view. E. Tip of tale. F. Anterior body region of male, lateral view. G. Spicules. H. Testis. I. Head of male showing fovea amphidialis. G. Head of male showing tooth. Scale bar: A, B— 500 µm; C, H— 100 µm; D, F— 50 µm; E, G, I, J— 10 µm; G— 25 µm.

FIGURE 10. Zalonema granda sp. nov. SEM. A. Posterior body region, lateral view. B. Head, ventrolateral view. Scale bar: A— 20 µm; B— 10.