Leptolaimoides tubulosus Vitiello, 1971

Holovachov, Oleksandr, 2015, Swedish Plectida (Nematoda). Part 9. The genus Leptolaimoides Vitiello, 1971, Zootaxa 3955 (1), pp. 83-100 : 89

Leptolaimoides tubulosus Vitiello, 1971

( Fig 4 ; Table 2 )

Material examined. One male and four females (slides # 140616 – 140618) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Habitat and locality. Gravel, mud and algae from 30–70 m deep, Skagerrak off the coast of Sweden (N 58° 22' 14'', E 11° 05' 00''), 0 9 August 2011, legit O. Holovachov (one male and four females).

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; straight upon fixation, curved ventrad only in posterior part in males. Maximum body diameter at vulva in female; male body more cylindrical. Cuticle annulated; annuli 1.4–2.1 µm wide at mid-body, without ornamentation; annulation at level of amphid same as annulation along rest of body. Lateral field present, consists of single alae (two incisures), 1.5–2 µm wide at mid-body; arising some distance posterior to amphid (metacorpus) and extending posteriorly to anterior 2/5th of tail. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; several pairs of body pores are present along pharyngeal region; several body pores scattered over rest of body. Anterior-most body pore located posterior to amphid, at level of procorpus. Labial region rounded, continuous with body contour, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla papilliform. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea elongated, an inverted Ushaped, inner borders often visible; located at level of posterior part of stoma and anterior part of procorpus. Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretory-excretory system indistinct. Buccal cavity uniformly tubular: cheilostom and gymnostom short, undifferentiated; stegostom tubular, with uniformly thickened lumen. Pharynx muscular, cylindrical anteriorly, with weakly developed pyriform basal bulb; valvular apparatus absent. Anterior cylindrical part of pharynx subdivided by breaks in muscular pharyngeal tissue into cylindrical procorpus, cylindrical metacorpus and narrow isthmus. Pharyngeal glands and their orifices indistinct. Cardia cylindrical, its posterior part embedded in intestine. Tail almost similar in shape in both sexes (more curved ventrad in male), elongate-conoid in its proximal part (equal to 38–41% of total tail length in females and 29% in male), subcylindrical in distal. Three caudal glands present, nuclei incaudal. Spinneret functional.

Male. Reproductive system diorchic; anterior testis outstretched, located on right hand side of intestine; posterior one reflexed. Spicules paired, symmetrical, with arcuate cylindrical calamus and ovoid manubrium. Gubernaculum 6 µm long, plate-like, with caudal apophysis 8 µm long. Accessory apparatus composed of one midventral precloacal papilliform sensillum located at level with spicules, two midventral tubular supplements extending for 62 µm from cloaca towards anterior end; alveolar supplements absent. Tubular supplements weakly arcuate in shape, with blunt tips. Posterior-most tubular supplement 40 µm anterior to cloaca, anterior to spicules. Sublateral precloacal sensilla absent, four caudal sensilla arranged in two subventral pairs. Four small papillae located at the posterior edge of lateral field, one subventral pair and one subdorsal pair.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 45–69 µm long (equal to 6–9% of total body length), located on right-hand side of intestine (n=4), posterior genital branch 64–86 µm long (equal to 9–12% of total body length), located on left-hand side of intestine (n=4). Oviduct a narrow tube. Two offset, oval, sac-like spermathecae located on each (right and left) side of each (anterior and posterior) gonoduct. Spermathecae and oviducts filled with oval spermatozoa. Uterus a short tube. Vagina straight, 0.3 times vulval body diameters long; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae absent. Vulva midventral. Epiptygmata and sensory structures around vulva absent. Supplements absent. Rectum 1.0–1.3 anal body diameters long; surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis (supplemented with literature data). Leptolaimoides tubulosus is particularly characterised by the 548–821 µm long body; cephalic sensilla papilliform; amphid 21–32 µm long, located 9–17 µm from anterior end; first body pore located 45–50 µm from anterior end; lateral field simple, originating 59–65 µm from anterior end; female without supplements, vagina without pars refringens, vulva midventral; male with two–three tubular and without alveolar supplements; spicules arcuate and 25 µm long.

Remarks. Current specimens agree well with the type specimens in general morphology, shape of anterior end, amphids, lateral alae, spicules and gubernaculum. The only differences are longer body (679–821 µm vs 548 µm in holotype) and fever tubular supplements (two vs three in holotype). Differences in spicule length between our male (25 µm) and holotype male (13 µm) are caused by different ways of measuring this character (along the arch vs along the chord).

Figures

FIGURE 4. Leptolaimoides tubulosus Vitiello, 1971, male (A, D – E) and female (B – C). A: Pharyngeal region, median section; B: Female tail; C: Female reproductive system (anterior part); D: Anterior end, surface view; E: Male posterior region. Scale bar: A – E = 20 µm.