Leptolaimus primus, 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 : 6-9

Leptolaimus primus sp. n.

( Figs 1 , 2A–B ; Table 1)

Type material. Holotype male (slide # Type-8452) and one male paratype (slide # Type-8453) deposited in the invertebrate type collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden.

Additional material. Two males and five females (slides # 129907-129909) 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 west coast of Sweden (N 58° 17' 32'', E 11° 11' 24''), 09 August 2011, legit O. Holovachov (two males) .

Additional localities. 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 (two males and five females) .

Etymology. The specific epithet " primus " is translated as " the first " and refers to the sequential number of the new species described in this publication.

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 1.1–1.8 µm wide at mid-body, without ornamentation. Lateral field present, consists of single ala (two incisures), 1–2 µm wide at mid-body; originating at level of metacorpus (posterior to the first body pore) and extending posteriorly to proximal part 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 stoma base or procorpus. Labial region rounded, 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 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 posterior to nerve ring, at level of middle of isthmus. 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 proximally and subcylindrical distally. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. Three pairs of short 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 plate-like, with caudal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip and four alveolar supplements extending for 55–67 µm from cloaca towards anterior end; midventral tubular supplements absent. Alveolar supplements without inner sclerotized ring. Posteriormost alveolar supplement 11–14 µm anterior to cloaca, anterior to spicules. Anteriormost alveolar supplement 195–236 µm from anterior end, at level of posterior part of intestine. 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.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 48–66 µm long (equal to 11.4–13.9% of total body length), located on right-hand side of intestine (n=5), posterior genital branch 47–117 µm long (equal to 9.9–25.6% 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. Spermathecae usually filled with oval spermatozoa. Uterus a wide and 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 sensitive structures around vulva (advulval sensilla) absent. Supplements absent. Rectum 1.1–1.4 anal body diameters long; surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis. Leptolaimus primus sp. n. is particularly characterised by the 319–472 µm long body; rounded labial region continuous with body contour; cephalic setae 1.5–2.0 µm long; amphid located 7.0–11.5 µm from anterior end; first body pore located 18.5–28.0 µm from anterior end; lateral field originating 35 µm from anterior end; female without supplements, vagina without pars refringens, vulva midventral; male without tubular and with four alveolar supplements, alveolar supplements without sclerotized inner ring; spicules arcuate and 13.5–16.0 µm long.

Relationships. The new species belongs to a group of species in which males have only alveolar supplements and include Leptolaimus pumicosus Vitiello, 1970 and L. pocillus de Bovée, 1974 . Leptolaimus primus sp. n. differs from both species in having fewer alveolar supplements (four in L. primus sp. n. vs. 35 in L. pumicosus and 11 in L. pocillus ) and shorter spicules (13.5–16.0 µm in L. primus sp. n. vs. 20 µm in L. pumicosus and 21–22 µm in L. pocillus ). Furthermore, it differs from L. pumicosus in the shape of gubernaculum (with caudal apophysis vs. with dorsal apophysis in L. pumicosus ) and from L. pocillus in the shape of alveolar supplements (without sclerotized ring vs. with sclerotized ring in L. pocillus ).

Figures

FIGURE 1. Leptolaimus primus sp. n., holotype male (A–C) and paratype 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.

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.