Leptolaimus papilliger de Man, 1876

Holovachov, Oleksandr & Boström, Sven, 2013, Swedish Plectida (Nematoda). Part 4. The genus Leptolaimus de Man, 1876, Zootaxa 3739 (1), pp. 1-99 : 9-11

Leptolaimus papilliger de Man, 1876

( Figs 2 C–D , 3 ; Table 2)

Material examined. 17 males and 30 females (slides # 129910–129920) deposited in the general invertebrate collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden .

Habitat and locality. Sediment (top layer), Baltic off the east coast of Sweden (N 58° 46' 00'', E 17° 49' 52''), 26 May 2011, legit C. Raymond (15 males and 30 females) ; sediment (top layer), Baltic off the east coast of Sweden (N 59° 27' 15'', E 19° 19' 16''), 22 May 2011, legit C. Raymond (1 male and 3 females) ; soft clay (top layer) from 64 m deep, Bothnian sea off the east coast of Sweden (N 63° 23' 21'', E 19° 51' 27''), 26 May 2011, legit J. Albertsson (1 male and 3 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 1.4–2.1 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 (anterior to, at level with or just 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 three 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 flattened, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla papilliform. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea round, located at level of middle of stoma. Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretory-excretory system present; excretory pore located just 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 (shorter and more curved ventrad in male), elongate-conoid, gradually narrowing distally, often with clavate tail tip. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. One pair of short and two pairs of long setae emerging through first, second and third pairs of body pores. Reproductive system diorchic; anterior testis outstretched; posterior one reflexed. Spicules paired, symmetrical, with arcuate conoid calamus and ovoid manubrium. Gubernaculum arcuate, plate-like, with long arcuate dorsal apophysis that curves towards anterior end. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, four evenly spaced midventral tubular supplements extending for 64–73 µm from cloaca towards anterior end; 17–25 alveolar supplements. Tubular supplements with ovoid "manubrium" and straight cylindrical body; tips of tubules with hook-like projections on their posterior side. Posteriormost tubular supplement 17–20 µm anterior to cloaca, anterior to spicules. Alveolar supplements with inner sclerotized ring. Anteriormost alveolar supplement 79–94 µm from anterior end, at level of isthmus. Sublateral precloacal and caudal sensilla present: two (one pair) precloacal setae at level of spicules and usually eight (four pairs) caudal setae arranged in two subventral and two subdorsal pairs. Additional individual setae may be present on the dorsal body side anterior or posterior to cloaca. A pair of alveole-like invaginations with sclerotized lining is located on the ventral side of the tail, just anterior to the second pair of subventral caudal setae.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 66–93 µm long (equal to 12.5–15.3% of total body length), located on right-hand side of intestine (n=5), posterior genital branch 67–107 µm long (equal to 12.5–17.6% of total body length), located on left-hand side of intestine (n=5). Oviduct a narrow tube. Two offset, oval, sac-like spermathecae located on each (right and left) side of each (anterior and posterior) gonoduct, obscure in some specimens. Spermathecae usually filled with oval spermatozoa. Uterus a wide and short tube. Vagina straight, 0.3–0.4 times vulval body diameters long; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae present, T-shaped. Vulva midventral. Epiptygmata and sensitive structures around vulva (advulval sensilla) absent. Supplements absent. Rectum 1.4–1.9 anal body diameters long; surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis (supplemented with literature data). Leptolaimus papilliger is particularly characterised by the 350– 609 µm long body; rounded labial region continuous with body contour; cephalic setae papilliform; amphid located 6.0–10.0 µm from anterior end; first body pore located 25.0–32.0 µm from anterior end; lateral field originating 21.5–36.5 µm from anterior end; female without supplements, vagina with T-shaped pars refringens, vulva midventral; male with four tubular and 12–27 alveolar supplements, tubular supplements straight with hook-like tips, alveolar supplements with sclerotized ring; spicules arcuate and 13.0–19.0 µm long.

Remarks. Current material agrees well with the original description in general morphology, measurements, shape of labial region, spicules and gubernaculum, and the number of supplements. Unfortunately, the original description of this species is insufficiently illustrated to allow any further comparison. Specimens described by Lorenzen (1969) are smaller (405–520 µm vs. 491–609 µm in current population) with marginally smaller spicules (13.0–17.0 µm vs. 15.0–19.0 µm in current specimens). The population from the Far East is much smaller than current population from the Baltic (350–480 µm vs. 491–609 µm in current population), has fewer alveolar supplements (12–14 vs. 17–25 in current specimens) and has lower values for some measurements, but does not show sufficient deviation to be assigned a different species ( Alekseev, 1981).

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 3. Leptolaimus papilliger de Man, 1876, 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.