Loveninema unicornis, 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 : 33-36

Loveninema unicornis gen. n., sp. n.

( Figs 5–6 ; Table 1 )

Type material. Holotype female (slide # 8380), as well as four female and five male paratypes (slides # 8381–8387) deposited in the type collection of the Department of Invertebrate Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. Coarse gravel with detritus from 30–50 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 58'', E 11° 10' 05''), 0 9 August 2011, legit O. Holovachov (one female).

Additional localities. 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 (three females and five males); mainly algae from 15–55 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 24'', E 11° 10' 48''), 0 9 August 2011, legit O. Holovachov (one female);

Etymology. The specific epithet refers to the presence of long labial projection on the anterior body end, distantly resembling the one in the unicorn.

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 long, 6–7 µm long.

Anteriormost body annule, which demarcates labial region, located posterior to amphid. Labial framework in the shape of a conoid ring with three short projections extending posteriorly: one mid-dorsal, one left-subventral and one right-subventral; the projections are shorter than the ring they are connected to. Inner labial sensilla indistinct. Outer labial sensilla papilliform; 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 cephalic sensilla bases. Nerve ring surrounding pharynx at three-fifth of its length. Hemizonid not seen. Secretory-excretory system present; renette cell large, located to the left of intestine, far behind the pharyngointestinal 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 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 45–60 µm long (equal to 5.7–7.9% of total body length), located on right-hand side of intestine (n = 4), posterior genital branch 55–60 µm long (equal to 6.2–8.1% of total body length), located on left-hand side of intestine (n = 4). 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 0.9–1.1 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 almost straight subcylindrical shaft and weakly developed manubrium; the manubrium is straight, not inclined ventrally. Gubernaculum absent. Alveolar supplements present along the pharyngeal region, as many as 20 were observed in one individual, extending to the level of vas deferense, however only the 3–5 anteriormost supplements are clearly visible in the majority of specimens. Tubular supplements absent. Midventral precloacal sensilla absent. Tail with four pairs of papilliform sensilla: the second and the third pair (counting from anterior end) are subventral, the first and the fourth pair are ventrosublateral.

Diagnosis. Loveninema unicornis gen. n., sp. n. is particularly characterised by the 0.65–0.98 mm long body; long midventral labial projection; straight vagina without sclerotisations; male with up to 20 alveolar and without tubular supplements, 11.5–14.0 µm long spicules, and without gubernaculum.

Relationships. The new species differs from the type and only other known species of the genus, Loveninema tubulosa gen. n., sp. n., in having longer labial projection (6.0–7.0 µm vs. 1.0 µm), tubular supplements absent in males (vs. present, 15 in number), alveolar supplements present in male (vs. absent), shape and size of spicules (11.5–14.0 µm vs. 15.0–21.5 µm) and gubernaculum absent (vs. present).

Figures

FIGURE 5. Loveninema unicornis gen. n., sp. n., entire view of holotype female (A) and paratype male (B). Scale bar: A – B = 50 µm.

FIGURE 6. Loveninema unicornis 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.