Loveninema tubulosa, Holovachov, Oleksandr & Boström, Sven, 2012

Holovachov, Oleksandr & Boström, Sven, 2012, Swedish Plectida (Nematoda). Part 3. The genus Loveninema gen. n., Zootaxa 3505, pp. 26-38 : 27-33

Loveninema tubulosa gen. n., sp. n.

( Figs 1–4 ; Table 1 )

Type material. Holotype female (slide # 8376), as well as three female and four male paratypes (slides # 8377–8379) deposited in the type collection of the Department of Invertebrate Zoology, Swedish Museum of Natural History, Stockholm, Sweden. Five female and six male paratypes were used for SEM.

Type locality. Coarse sediment with algae from 45–55 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 32'', E 11° 11' 24''), 0 9 August 2011, legit O. Holovachov (nine females, ten males and four juveniles).

Etymology. The specific epithet refers to the presence of tubular supplements in male.

Description. Adult. Body cylindrical over most of its length, tapering anteriorly in anterior half of pharyngeal region and posteriorly on tail; ventrally curved upon fixation, more strongly curved ventrad in posterior part in males. Maximum body diameter at vulva in female; male body more cylindrical. Cuticle finely annulated; annules without ornamentation. Lateral field absent. Crystalloids absent. Body pores and epidermal glands absent. Somatic sensilla present in both sexes, most prominent along the pharyngeal region and on tail. Labial region rounded, weakly offset from the remaining body contour by a shallow depression, lips fused. Midventral labial projection short, under 1 µm long. Anteriormost body annule, which demarcates labial region, located posterior to amphid. Labial framework in the shape of a conoid ring with three long projections extending posteriorly: one mid-dorsal, one left-subventral and one right-subventral; the projections are longer than the ring they are connected to. Inner labial sensilla indistinct. Outer labial sensilla papilliform, discernible under SEM only; lateral pair of outer labial sensilla is shifted towards the dorsal body side. Cephalic sensilla papilliform. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea slit-like, located anterior to the cephalic sensilla bases. Nerve ring surrounding pharynx at two-fifth of its length. Hemizonid not seen. Secretory-excretory system present; renette cell large, located to the left of intestine, far behind the pharyngo-intestinal junction, just anterior to the reproductive system; it extends anteriorly along ventral side of pharynx and forms an excretory ampulla just posterior to nerve ring level. Excretory canal weakly cuticularised, extends from excretory ampulla anteriorly towards the lip region and opens to the exterior via a pore on ventral side of labial region, somewhat anterior to cephalic sensilla bases. Oral opening subterminal, shifted slightly towards the dorsal body side. Buccal cavity uniformly tubular: cheilostom well developed, surrounded by a sclerotised labial framework; gymnostom short, barrel-shaped; stegostom tubular, with uniformly thickened lumen. Pharynx muscular, cylindrical anteriorly, expanding posteriorly; not distinctly subdivided into sections; without bulbs; valvular apparatus absent. Anterior cylindrical part of pharynx uniformly muscular, posterior expanded part of pharynx with strongly developed pharyngeal glands. Dorsal pharyngeal gland orifice opens at the base of stoma; orifices of subventral pharyngeal glands indistinct. Cardia short cylindrical, embedded in intestine. A number of large coelomocytes are present on each body side along the posterior part of pharynx and anterior part of intestine, their cell bodies extend anteriorly into narrow ducts that are located along the lateral body sides. Tail similar in shape in both sexes, conoid, ventrally curved. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 62–105 µm long (equal to 5.7–11.5% of total body length), located on left-hand (n = 1) or right-hand (n = 3) side of intestine, posterior genital branch 57–128 µm long (equal to 6.6–14.0% of total body length), located on right-hand (n = 1) or left-hand (n = 3) side of intestine. Oviduct a short tube. Spermathecae present, axial, filled with small oval spermatozoa. Uterus short. Vagina straight, 0.3–0.4 times vulval body diameters long; pars proximalis vaginae encircled by single sphincter muscle. Epiptygmata, pars refringens vaginae and sensitive structures around vulva (advulval sensilla) absent. Rectum 0.9–1.2 anal body diameters long. Tail with two pairs of sublateral papilliform sensilla, one pair along the middle part of the tail and another pair close to the spinneret.

Male. Reproductive system monorchic, dextral; terminal part of testis reflexed to the left body side. Spicules paired, symmetrical, with arcuate subcylindrical shaft and ovoid manubrium; the manubrium is straight, not inclined ventrally. Gubernaculum plate-like, apophysis absent. Accessory apparatus composed of 12–15 midventral tubular supplements extending from cloaca towards anterior end; posterior 6–9 tubules are located to the right of intestine, anterior 6–9 tubules are located to the left of intestine. Posteriormost tubular supplement 21–38 µm anterior to cloaca, anterior to spicules. Alveolar supplements absent. Midventral precloacal sensilla absent. Tail with four pairs of papilliform sensilla: the first and the third pair (counting from anterior end) are subventral, the second and the fourth pair are ventrosublateral.

Diagnosis. Loveninema tubulosa gen. n., sp. n. is particularly characterised by the 0.66–1.12 mm long body; short midventral labial projection; straight vagina without sclerotisations; male without alveolar and with 12–15 tubular supplements, 15.0–21.5 µm long spicules, and with gubernaculum.

Relationships. The new species differs from the only known second species of the genus, Loveninema unicornis gen. n., sp. n., in having shorter labial projection (1.0 µm vs. 6.0–7.0 µm), tubular supplements present in males (15 vs. absent), alveolar supplements absent in male (vs. present), differences in shape (arcuate vs. straight shaft) and size of spicules (15.0–21.5 µm vs. 11.5–14.0 µm) and gubernaculum present (vs. absent).

Figures

FIGURE 1. Loveninema tubulosa gen. n., sp. n., entire view of holotype female (A) and paratype male (B). Scale bar: A – B = 50 µm.

FIGURE 2. Loveninema tubulosa gen. n., sp. n., holotype female (A – C) and paratype male (D). A: Pharyngeal region, median section; B: Anterior end, surface view; C: Female tail; D: Male posterior region. Scale bar: A – D = 20 µm.

FIGURE 3. Loveninema tubulosa gen. n., sp. n., female (A – B) and male (C – F). A: Anterior end, ventral view; B – C: Anterior end, sub-apical view (ventral side down, arrow in C points at midventral labial projection); D: Anterior end, apical view (ventral side down, arrows point at outer labial sensilla); E: Anterior end, left lateral view (arrows point at outer labial sensilla); F: Anterior end, ventral view. Scale bars: A – F = 2.5 µm.

FIGURE 4. Loveninema tubulosa gen. n., sp. n., female (A – D, F) and male (E, G – H). A: Entire nematode; B: Female tail, ventral view; C: Vulva; D: Spinneret, apical view; E: Male posterior end (arrows point at supplements); F: Female tail, lateral view; G: Male tail, lateral view; H: Male posterior end (arrows point at supplements). Scale bars: A = 100 µm; B, E = 20 µm; C – D = 5 µm; F – H = 10 µm.

Tables

TABLE 1. Morphometrics of Loveninema tubulosa gen. n., sp. n. and L. unicornis gen. n., sp. n. (all measurements are in µm, except for the ratios a, b, c, c', V, T and NR).

Species		L. tubulosa		L. unicornis
	Holotype Ƥ	8 Ƥ	10 33	Holotype Ƥ 4 Ƥ 5 33
Body length	881	902±122 (743–1119)	771±89 (664–914)	847±95 743±83 805 (766–978) (653–826)
a	30.8	33.7±4.1 (25.6–38.5)	34±3 (29.1–39.3)	34.7±3.2 33±5.2 30.5 (29.9–37) (27.1–39.3)
b	4.3	4.4±0.4 (3.7–4.9)	4.1±0.3 (3.7–4.7)	5.5±0.3 5±0.3 5.5 (5.1–5.7) (4.7–5.4)
c	18.1	17.5±1.4 (15.6–19.6)	14.4±1.1 (12.3–15.8)	11.9±0.5 10.8±0.5 12.8 (11.4–12.6) (10.2–11.3)
c'	3	2.9±0.3 (2.5–3.2)	3.1±0.3 (2.6–3.6)	4±0.2 3.7±0.4 3.4 (3.8–4.3) (3.1–4.1)
V or T (%)	54	55.5±1.9 (53.8–59.4)	40.9±2.7 (36.1–43.4)	53.2±1.2 37.9±0.5 55.2 (51.9–54.7) (37.1–38.5)
Body diameter	28.5	27.0±3.4 (19.0–29.0)	22.8±3.3 (18.0–28.0)	24.6±3.8 22.8±3.3 26.5 (21.0–28.5) (18.5–27.0)
Pharynx length	204	205±15 (186–235)	187±9 (175–205)	154±13 149±17 146 (139–171) (131–171)
Tail length	48.5	51.7±5.9 (45.0–61.5)	53.6±4.9 (46.0–59.0)	70.9±4.8 68.4±5.4 63.0 (67.0–78.0) (62.0–74.0)
Anal or cloacal body diam.	16.5	18.0±1.5 (15.0–20.0)	17.1±1.5 (15.0–20.0)	17.9±2.0 18.8±2.1 18.5 (16.5–21.0) (16.0–21.0)
Labial region diameter	6.5	6.5±0.5 (6.0–7.0)	6.0±0.6 (5.0–7.0)	7.0±0.9 6.7±0.4 6.5 (6.0–8.0) (6.5–7.0)
Cephalic setae length	0.5	0.5	0.5	1.0 1.0 1.0
Amphid from ant. end	1.0	1.5	1.5	1.0 1.0 1.0
Amphid width	1.5	1.5–2.0	1.5–2.0	1.5 1.5 1.5
Labial projection length	1.0	1.0	1.0	6.0 6.0–6.5 6.0–7.0
Stoma length	21.0	21.3±2.7 (18.5–25.0)	17.9±2.3 (14.0–21.0)	18.7±3.4 17.7±1.5 21.5 (16.0–23.5) (15.0–18.5)
Nerve ring from ant. end	89.0	92.2±6.9 (85.0–105.0)	87.6±7.0 (78.5–96.0)	88.5±10.8 89.8±14.4 89.0 (78.5–100.0) (79.0–113.5)
NR (%)	43.9	44.9±2.1 (42.6–47.7)	46.7±1.9 (44.6–49.6)	57.3±1.2 60.2±3.6 61.3 (56.5–58.6) (57.6–66.3)
Vagina length	10.0	8.9±1.5 (6.0–11.0)	-	9.1±1.7 11.5 - (8.0–11.5)
Rectum length	20.0	20.0±2.5 (17.0–25.0)	-	17.5±2.2 18.5 - (15.0–20.0)
Spicule length	-	-	17.7±1.8 (15.0–21.5)	13.0±1.1 - - (11.5–14.0)
Gubernaculum length	-	-	6.5±0.9 (5.0–8.0)	- - absent
Tubular supplements	-	-	12–15	- - absent