Leptolaimus donsi ( Allgén, 1947 ) Holovachov & Boström, 2013

Holovachov, Oleksandr & Boström, Sven, 2013, Swedish Plectida (Nematoda). Part 4. The genus Leptolaimus de Man, 1876, Zootaxa 3739 (1), pp. 1-99 : 22-26

Leptolaimus donsi ( Allgén, 1947) comb. n.

( Figs 8 , 9 , 10 A–C ; Table 6)

Type material. Lectotype female (slide # Type-3620) from the collection of C. Allgén.

Additional material. 11 males and 21 females (slides # 129938–129949) deposited in the general invertebrate collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden .

Type locality. North Atlantic Ocean , Trondheimsfjord, off Storfosen island, Norway (N 63° 39.5', E 9° 24’) ( Allgén, 1947)

Additional localities. Sandy sediment from 5–17 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 09'', E 11° 27' 51''), 21 August 2010, legit M. Clément (one male) ; mud from 30–39 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 13'', E 11° 27' 31''), 21 August 2010, legit M. Clément (one male and one female) ; sand and shells from 15–22 m deep, Bonden island in Skagerrak off the west coast of Sweden (N 58 12' 37'', E 11 18' 53''), 09 August 2011, legit O. Holovachov (one male and four 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 (five males and eight females) ; muddy sand from 25–50 m deep, Skagerrak off the west coast of Sweden (N 58° 22' 20'', E 11° 09' 26''), 09 August 2011, legit O. Holovachov (one female) ; coarse sediment with algae from 45–55 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 32'', E 11° 11' 24''), 09 August 2011, legit O. Holovachov (three males and seven females) .

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; straight or 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 annulated; annuli 1.5–2.4 µm wide at mid-body, without ornamentation. Lateral field present, consists of single ala (two incisures), 1.5–3.5 µm wide at mid-body; originating at level of posterior edge of amphid (at level with first body pore) and extending posteriorly to posterior third of tail. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; usually six pairs of body pores are present along pharyngeal region; numerous body pores scattered over rest of the body. Anteriormost body pore located at posterior edge of amphid, at level of anterior part of stoma. Labial region truncated, continuous with body contour, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla setiform, equal to 40–60% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea round, located close to cephalic setae bases, at level of anterior third of stoma. Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretoryexcretory system present; excretory pore located posterior to nerve ring. 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. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. Two pairs of short setae emerging through second and fourth pairs of body pores. Reproductive system diorchic; anterior testis outstretched; posterior one reflexed. Spicules paired, symmetrical, with arcuate subcylindrical calamus and ovoid manubrium. Gubernaculum plate-like, with dorsal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, two midventral tubular supplements extending for 89–100 µm from cloaca towards anterior end; 9–14 alveolar supplements. Tubular supplements weakly arcuate in shape, with bluntly rounded tips. Posteriormost tubular supplement 45–53 µm anterior to cloaca, anterior to spicules. Alveolar supplements without inner sclerotized ring. Anteriormost alveolar supplement 158–185 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 six (three pairs) caudal setae arranged in one subventral and two subdorsal pairs. One subventral pair of papilliform sensilla located at the bases of the second (from cloaca) pair of caudal setae.

Aberrant male ( Fig. 10 C ). Similar to typical males except for the smaller body size and the following features. One midventral tubular supplement extending for 40–43 µm from cloaca towards anterior end; 13–14 alveolar supplements. Anteriormost alveolar supplement 133–152 µm from anterior end, at level of anterior part of intestine.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 103–135 µm long (equal to 10.5–15.7% of total body length), located on right-hand side of intestine (n=10), posterior genital branch 86–128 µm long (equal to 9.4–12.6% of total body length), located on left-hand side (n=8) or right-hand side (n=2) of intestine. Oviduct a narrow tube. Two offset, oval, sac-like spermathecae located on each (right and left) side of each (anterior and posterior) gonoduct. Spermathecae filled with oval spermatozoa. Uterus a wide and long tube. Vagina straight, 0.2–0.3 times vulval body diameters long; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae present, bacilliform. Vulva rightventrosublateral. Epiptygmata and sensitive structures around vulva (advulval sensilla) absent. Supplements absent. Rectum 1.1–2.4 anal body diameters long; surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis (including data for lectotype, but excluding aberrant male specimens). Leptolaimus donsi is particularly characterised by the 776–1103 µm long body; truncated labial region continuous with body contour; cephalic setae 4.0–6.0 µm long; amphid located 2.0–5.0 µm from anterior end; first body pore located 11.5–14.0 µm from anterior end; lateral field originating 8.0–13.0 µm from anterior end; female without supplements, vagina with bacilliform pars refringens, vulva right-ventrosublateral; male with two tubular and 9–14 alveolar supplements, tubular supplements weakly arcuate with blunt tips, alveolar supplements without sclerotized inner ring; spicules arcuate and 30.0–33.5 µm long.

Remarks. Current material agrees well with the type specimen in general morphology, measurements, shape of amphids, position of the first body pore and anterior end of lateral field, presence of pars refringens vaginae and right-ventrosublateral position of vulva. Two males with single tubular supplement found in Gullmarn Fjord are smaller in size than males with two tubular supplements from Skagerrak, but there are no significant morphological or morphometrical differences to justify considering them different species.

Figures

FIGURE 8. Leptolaimus donsi (Allgén, 1947) comb. n., 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 (anterior part). Scale bar: A–E = 20 µm.

FIGURE 9. Leptolaimus donsi (Allgén, 1947) comb. n., lectotype. Scale bar: 50 µm.

FIGURE 10. Leptolaimus donsi (Allgén, 1947) comb. n. (A–C) and Leptolaimus tertius sp. n. (D). A: Entire female; B– D: Entire male. Scale bar: A–D = 50 µm.