Leptolaimus danicus Jensen, 1978

Holovachov, Oleksandr & Boström, Sven, 2013, Swedish Plectida (Nematoda). Part 4. The genus Leptolaimus de Man, 1876, Zootaxa 3739 (1), pp. 1-99 : 15-18

Leptolaimus danicus Jensen, 1978

( Figs 2 G–H , 5 ; Table 4)

Material examined. 33 males and 64 females (slides # 129924–129937, 129963) deposited in the general invertebrate collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden .

Habitat and locality. Muddy sediment from 53 m deep, Skagerrak off the west coast of Sweden (N 58° 20' 06'', E 11° 09' 24''), 09 August 2011, legit O. Holovachov (two males and 20 females) ; gravel, mud and algae from 30–70 m deep, Skagerrak off the west coast of Sweden (N 58° 22' 14'', E 11° 05' 00''), 09 August 2011, legit O. Holovachov (three males and three females) ; muddy sediment from 55–70 m deep, Skagerrak off the west coast of Sweden (N 58° 22' 19'', E 11° 04' 55''), 09 August 2011, legit O. Holovachov (one male and one female) ; soft mud from 30 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 25'', E 11° 27' 30''), 11 August 2011, legit O. Holovachov (five males and 11 females) ; soft mud from 44 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 37'', E 11° 27' 43''), 11 August 2011, legit O. Holovachov (21 male and 29 females) .

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; ventrally arcuate upon fixation, more strongly curved ventrad in posterior part in males. Maximum body diameter at vulva in female; male body more cylindrical. Cuticle annulated; annuli 2.0–2.5 µm wide at mid-body, without ornamentation. Lateral field present, consists of single ala (two incisures), 1.5–2.5 µm wide at mid-body; originating at level of procorpus or metacorpus (posterior to first body pore) and extending posteriorly to middle of tail. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; usually four pairs of body pores are present along pharyngeal region; several body pores scattered over rest of the body. Anteriormost body pore located at level of procorpus. Labial region truncate-conoid, continuous with body contour, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla setiform, equal to 40–100% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea rounded, located at level of middle of stoma. 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 distinct oval 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 similar in shape in both sexes (more curved ventrad in male), elongate-conoid, gradually narrowing distally with subcylindrical terminal part. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. Three long setae emerging through second, third and fourth pairs of body pores. Reproductive system diorchic; anterior testis outstretched; posterior one reflexed. Spicules paired, symmetrical, with arcuate conoid calamus and ovoid manubrium. Gubernaculum plate-like, with dorsal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, usually five (rarely four or six) evenly spaced midventral tubular supplements extending for 136–153 µm from cloaca towards anterior end; usually six (rarely seven) alveolar supplements. Tubular supplements almost straight, with expanded dentate tips; surrounded by sclerotized ring. Posteriormost tubular supplement 28–33 µm anterior to cloaca, anterior to spicules. Alveolar supplements with inner sclerotized ring, and with short and narrow sclerotized tube connected to unicellular gland. Anteriormost alveolar supplement 130–147 µm from anterior end, at level of anterior part of intestine. Sublateral precloacal and caudal sensilla present: two (one pair) precloacal setae at level of cloaca and usually eight (four pairs) caudal setae arranged in two subventral and two subdorsal pairs. One subventral pair of papilliform sensilla located at the bases of the second (from cloaca) pair of caudal setae.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 57–76 µm long (equal to 10.0–12.6% of total body length), located on right-hand side (n=6) or lefthand side (n=1) of intestine, posterior genital branch 52–74 µm long (equal to 8.5–13.0% of total body length), located on left-hand side (n=6) or right-hand side (n=1) of intestine. Oviduct a narrow tube. Two offset, oval, saclike spermathecae located on each (right and left) side of each (anterior and posterior) gonoduct; the spermatheca on one side of the gonoduct is often more developed than on the other side. Spermathecae often filled with oval spermatozoa. Uterus a wide and short tube. Vagina straight; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae present, triangular. Vulva usually right-ventrosublateral (n=9) or right-subventral (n=6), rarely left-ventrosublateral (n=1) or left-subventral (n=1). Handedness of vulva position does not correspond with handedness of ovaries. Epiptygmata and sensitive structures around vulva (advulval sensilla) absent. Supplements absent. Rectum 1.0–1.6 anal body diameters long; surrounded by three gland-like cells at intestinerectum junction.

Diagnosis (supplemented with literature data). Leptolaimus danicus is particularly characterised by the 516– 609 µm long body; truncate-conoid labial region continuous with body contour; cephalic setae 1.5–3.0 µm long; amphid located 8.5–12.0 µm from anterior end; first body pore located 28.0–43.0 µm from anterior end; lateral field originating 34.0–58.0 µm from anterior end; female without supplements, vagina with triangular pars refringens, vulva usually right-ventrosublateral or right-subventral; male with 5 (4–6) tubular and 6 (6–7) alveolar supplements, tubular supplements straight with expanded dentate tips, alveolar supplements with sclerotized ring; spicules arcuate and 21.5–24.0 µm long.

Remarks. Current material completely agrees with the single known type specimen in general morphology, measurements, number and shape of tubular and alveolar supplements, shape of spicules and gubernaculum.

Figures

FIGURE 2. Leptolaimus primus sp. n. (A–B), Leptolaimus papilliger de Man, 1876 (C–D), Leptolaimus cupulatus Lorenzen, 1972 (E–F) and Leptolaimus danicus Jensen, 1978 (G–H). A, C, E, G: Entire female; B, D, F, H: Entire male. Scale bar: A–H = 50 µm.

FIGURE 5. Leptolaimus danicus Jensen, 1978, male (A–C) and female (D–E). A: Anterior end, surface view; B: Pharyngeal region, median section; C: Male posterior region; D: Female tail; E: Female reproductive system. Scale bar: A–E = 20 µm.