Leptolaimoides filicaudatus, Holovachov, Oleksandr, 2015

Holovachov, Oleksandr, 2015, Swedish Plectida (Nematoda). Part 9. The genus Leptolaimoides Vitiello, 1971, Zootaxa 3955 (1), pp. 83-100 : 87-88

Leptolaimoides filicaudatus sp. n.

( Fig 3 ; Table 1 )

Type material. Holotype male (slide # Type-8621) and two female paratypes (slides # Type-8622 and Type-8323) deposited in the type invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Additional material. One male and one female (slides # 140599 – 140600) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

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

Additional localities. Mud and gravel from 40–60 m deep, Skagerrak off the coast of Sweden (N 58° 18' 06'', E 11° 05' 22''), 0 9 August 2011, legit O. Holovachov (one male); 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 female).

Etymology. The specific epithet " filicaudatus " refers to very long filiform tail in this species.

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; straight or variously 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; annuli without ornamentation; annulation at level of amphid same as annulation along rest of body. Lateral field present, consists of single alae (two incisures), 1 µm wide at mid-body; arising short distance posterior to amphid and extending posteriorly to proximal 1/5th of tail. Posterior-most part of the lateral field (along tail) becomes areolated. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; usually three 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; 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, elongate-conoid in its proximal part (equal to 18–21% of total tail length), filiform in its distal part. Caudal glands indistinct. Spinneret absent.

Male. Reproductive system diorchic; anterior testis outstretched, located on right hand side of intestine; posterior one reflexed. Spicules paired, symmetrical, with arcuate subcylindrical calamus and ovoid manubrium. Gubernaculum 5 µm long, plate-like, with 10 µm long caudal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located at level with spicule manubrium; tubular and alveolar supplements absent. 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 50–65 µm long (equal to 9–15% of total body length), located on right-hand side of intestine (n=3), posterior genital branch 28–56 µm long (equal to 5–13% of total body length), located on left-hand side of intestine (n=3). 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 spermatozoa. Uterus a short tube. Vagina straight, 0.2–0.3 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 0.9–1.3 anal body diameters long; surrounded by three gland-like cells at intestinerectum junction.

Diagnosis. Leptolaimoides filicaudatus sp. n. is particularly characterised by the 431–543 µm long body; cephalic sensilla papilliform; amphid 23–26 µm long, located 9–10 µm from anterior end; first body pore located 35–37 µm from anterior end; lateral field simple along most of body, areolated on tail, originating 36–40 µm from anterior end; female without supplements, vagina without pars refringens, vulva midventral; male without tubular and without alveolar supplements; spicules arcuate and 16 µm long.

Relationships. The new species can be easily separated from all other species of the genus in having unusually long tail, simple lateral field that becomes areolated only along posterior part of tail, and midventral precloacal papilliform sensillum located at level with spicule manubrium. Additional characters separating new species from other members of Leptolaimoides are listed in Table 4 .

Figures

FIGURE 3. Leptolaimoides filicaudatus sp. n., holotype male (A, C, E) and paratype female (B, D). A: Male posterior region; B: Female tail; C: Anterior end, surface view; D: Female reproductive system (anterior part); E: Pharyngeal region, median section. Scale bar: A – E = 20 µm.