Zalonema kamchatkaensis, 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 : 507-512

Zalonema kamchatkaensis sp. nov.

( Figs 5–7 )

Type material. Holotype: adult male, mounted on slide MN st 2–5sd 2–20 fr500 (2) and paratypes: three males and three females (Table 2), formalin-fixed, deposited in the nematode collection of the Division of Biological Sciences , Zoological Museum of Far Eastern Federal University , Vladivostok, Russia. Locality. Table 1 .

Etymology. The specific epithet refers to the locality of collection, the Kamchatka Peninsula. Measurements. See Table 2.

Description. Yellowish to brownish nematodes with cylindrical body, rounded high cephalic capsule and conical tail; body cuticle with distinct fine striations, not marked by longitudinal structures or lateral differentiation. Annuli narrower at mid-body, may be fused or split. Body may bear numerous suctorian ciliates. Eight longitudinal rows of short somatic setae (~ 7–9 µm long), reduced to six rows at mid-body length and to four rows in the posterior region. The length of postcaudal setae increases up to 4–5 µm.

Anterior retractable lip region, cuticle around the mouth opening wrinkled in irregular folds. Six inner (only seen with SEM) and six outer labial setiform papillae (1 µm long). Four cephalic setae (4 µm long) and eight cervical setae (3–4 µm long) located at posterior region of cephalic capsule, with a few minute pores with thin canals. Cephalic capsule smooth, convex, gradually thickening posteriorly to become thicker than body cuticle (2– 4 µm). Cephalic capsule relatively high and somewhat conoid. Amphideal fovea large (bigger in males than in females), spirally coiled with 2.1–2.2 turns, situated laterally in middle of the cephalic capsule.

Buccal cavity with one dorsal tooth (5–6 µm long) and two small ventro-sublateral teeth and one circle of denticles. Pharynx slender, evenly muscular throughout its length, with pyriform terminal bulb, gradually widening towards the base. Cardia large. No ventral gland found. Nerve ring located posterior to mid-pharynx length.

Tail conical, showing sexual dimorphism; i.e., markedly bent, anteriorly expanded with small swellings in females, more regularly conical and without swellings in males. Annulation of tail only seen using SEM.

Male. Cephalic capsule 34 1 (28–34) µm in height, diameter 52 (39–45) µm at level of amphideal fovea. Width

1. Measurements of the holotype are before the parenthesis of amphideal fovea 69 (55–66) % of corresponding body diameter. Reproductive system monorchic, single anterior outstretched testis situated to right of intestine. Spicules strongly cuticularised, elongated 1.6 (1.3–1.8 c.b.d. long), with rounded capitulum, pointed distally. Gubernaculum well-developed, parallel plate to distal parts of spicules. Tail with ribbed terminus. Caudal setae 7–10 µm long.

Female. Cephalic capsule 24–28 µm high, 41–44 µm in diameter at the level of amphideal fovea. Width of amphideal fovea 36–43% of corresponding body diameter. 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 of intestine. Vulva a transverse slit. Post-anal setae 7–9 µm long. Two minute setae on tail close to terminus.

Diagnosis and relationships. Zalonema kamchtkaensis sp. nov. is characterized by having a moderately long body (2.0– 2.8 mm), short cephalic setae (4 µm), convex cephalic capsule, subcephalic setae (3–4 µm long) located in the middle and at the posterior region of cephalic capsule, very large spiral amphidial fovea with 2.1–2.2 turns occupying almost entire lateral surface of the cephalic capsule, sexual dimorphism in amphidial fovea size: larger in males than in females, buccal cavity with one large dorsal tooth, two small subventral ventrosublateral teeth and one circle of denticles, a slender pharynx; eight longitudinal rows of short somatic setae (~ 7–9 µm long), reduced to six rows at mid-body length and four rows in the posterior region extending to the tail tip.

Males are characterized by having short, strongly cuticularised spicules (64–77 µm long), no preanal supplements, and the ribbed caudal terminus.

Based on body size, the new species belongs to a group of species: Z. maldivensis Gerlach, 1963 , Z. mariae Larrazábal-Filho, Silva & Esteves, 2015 , Z. vecentei Larrazábal-Filho, Silva & Esteves, 2015 and Z. granda sp. nov., characterized by having a large body size (most species are 1–6 mm long) and short conical tail with a rounded tail tip.

Zalonema kamchatkaensis sp. nov. mostly resembles Zalonema myrianae Verschelde & Vincx, 1996 , Z. megalosoma ( Steiner, 1918) and Z. granda sp. nov.

The new species differs from Z. megalosoma ( Steiner, 1918) by its longer body (2.0– 2.8 mm vs 1.1–1.4 mm); bigger amphideal fovea size (30–45 µm vs 10–16 µm); absence of supplements and shape of the cephalic capsule. It can be distinguished from Z. myrianae Verschelde & Vincx, 1996 by the larger amphids (30–45 µm vs 6–7 µm); position of the cervical setae (closer to the posterior edge of the cephalic capsule vs closer to cephalic setae), and cephalic capsule shape (rounded vs cone-shaped).

Zalonema kamchatkaensis sp. nov. has some similar features with Z. granda sp. nov.: specifically, in the shape of the body and cephalic capsule, the value of b and c, shape of the tail and length of the gubernaculum, but differs in body size (2.00– 2.8 mm vs 3.3–4.3 mm); presence of one circle of denticles in the buccal cavity, shape of the spicule, shape of the gubernaculum, length of the cephalic and pre-anal setae (3–5 vs 6–8 µm and 7–10 vs 12–17 µm); sexual dimorphism in amphideal fovea size (presence vs absence); bigger amphids (30–45 µm vs 15–21 µm); and shape of the spicules and caudal terminus. Zalonema kamchatkaensis sp. nov. can be distinguished from Z.

vecentei Larrazábal-Filho, Silva & Esteves, 2015 and Z. mariae Larrazábal-Filho, Silva & Esteves, 2015 by having spiral amphidial fovea with 2.1–2.2 turns (vs 3.5 turns); the absence of long lateral alae (vs long alae, one-fifth of total body length) and by small ventral alae (vs 304 µm long).

Figures

FIGURE 5. Zalonema kamchatkaensis sp. nov. Male: A. Entire body; B. Head; C. Tail region. D. Entire body. Female: E. Head. F. Posterior body region of female. Scale bars: A— 100 µm; B, C, E— 50 µm; D— 500 µm; F— 200 µm.

FIGURE 6. Zalonema kamchatkaensis sp. nov. Light micrographs. A. Entire male, lateral view. B. Entire females, lateral view. C. Posterior body region of female, lateral view. D. Posterior body region of male, lateral view. E. Spicules. F. Head of female. G. Head of male. Scale bar: A, B— 500 µm; C— 100 µm; D— 50 µm; E – G— 25 µm.

FIGURE 7. Zalonema kamchatkaensis sp. nov. SEM. A. Head of female, lateral view. B. Head of male, ventrolateral view. C. Posterior body region of female, ventral view. D. Posterior body region of male, lateral view. D. Tip of tale. Scale bar: A, B— 10 µm; C, D— 20 µm; E— 4 µm.

Tables

TABLE 1. Localities, depth and sampling data

Station	Latitude[N]	Longitude[E]	Depth [m]	Date	Species
A2-5	44°56,64'	137°12,11'	515	13.08.2010	Desmodorella tenuispiculum Allgen, 1928
A2-6	44°56,49'	137°12,08'	550	13.08.2010	Desmodorella tenuispiculum Allgen, 1928
A3-6	44°48,05'	137°15,25'	1473	14.08.2010	Desmodorella tenuispiculum Allgen, 1928
A3-7	44°47,65'	137°15,30'	1530	14.08.2010	Desmodorella tenuispiculum Allgen, 1928
SO223-1	43° 58,18'	157° 19,84'	5422	29.07.2012	Desmodorella tenuispiculum Allgen, 1928
SO223-2	46° 13,95'	155° 33,15'	4868	0 2.08.2012	Zalonema kamchatkaensis sp. nov.
SO223-3	47° 14,32'	154° 42,26'	4982	0 4.08.2012	Zalonema kamchatkaensis sp. nov., Zalonema granda sp. nov.
SO223-4	46° 58,00'	154° 32,37'	5766	0 7.08.2012	Zalonema kamchatkaensis sp. nov.
SO223-5	43° 35,01'	153° 58,09'	5379	10.08.2012	Zalonema kamchatkaensis sp. nov.
SO223-6	42° 28,98'	153° 59,97'	5297	13.08.2012	Zalonema kamchatkaensis sp. nov.
SO223-7	43° 2,31'	152° 59,16'	5222	16.08.2012	Zalonema kamchatkaensis sp. nov.
SO223-8	42° 14,57'	151° 43,51'	5130	19.08.2012	Zalonema kamchatkaensis sp. nov.
SO223-9	40° 35,03'	151° 0,06'	5404	23.08.2012	Zalonema kamchatkaensis sp. nov., Zalonema granda sp. nov.