Leptolaimus alatus Vitiello, 1971

Holovachov, Oleksandr & Boström, Sven, 2013, Swedish Plectida (Nematoda). Part 4. The genus Leptolaimus de Man, 1876, Zootaxa 3739 (1), pp. 1-99 : 53-56

Leptolaimus alatus Vitiello, 1971

( Figs 22 C–D , 23 ; Table 15)

Material examined. Seven males and 22 females (slides # 130715–130722) deposited in the general invertebrate collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden .

Habitat and locality. 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 (seven males and 20 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 (one female) ; 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 (one female) .

Description. Adult. Body fusiform, strongly tapering anteriorly in pharyngeal region and posteriorly on tail; ventrally curved or coiled 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 1.6–2.2 µm wide at mid-body, without ornamentation. Lateral field present, consists of single ala (two incisures), 1.5–2.0 µm wide at mid-body; originating at level of posterior part of stoma (anterior to first body pore) in males or at stoma base (close to first body pore) in females, 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 five pairs of body pores are present along pharyngeal region; numerous body pores scattered over rest of the body. Anteriormost body pore located at level of stoma base. Labial region truncate, offset from body contour, lips fused. Inner labial sensilla indistinct; outer labial sensilla large and papilliform, located on the outer surface of lips. Cephalic sensilla setiform, equal to 30–50% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea round, located at level of anterior third 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. 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), conoid, gradually narrowing distally. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. Long setae emerging through first, second and fifth 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 dorsocaudal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, six–eight evenly spaced midventral tubular supplements extending for 132–205 µm from cloaca towards anterior end; alveolar supplements absent. Tubular supplements weakly S-shaped, with blunt tips. Posteriormost tubular supplement 17.0–28.0 µm anterior to cloaca, at level of spicules. Sublateral precloacal and caudal sensilla present: two (one pair) precloacal setae at level of spicules and several caudal setae of which only one pair can be clearly seen in all specimens; remaining setae (if present) are indistinct due to filamentous debris covering distal parts of tails in all studied males.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 48–61 µm long (equal to 11.6–14.2% of total body length), located on right-hand (n=11) or left-hand (n=3) side of intestine, posterior genital branch 56–88 µm long (equal to 13.416.9% of total body length), located on left-hand (n=11) or right-hand (n=3) side of intestine. Oviduct a narrow tube. Spermathecae obscure. Uterus a wide tube. Vagina straight, 0.3–0.5 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 1.0–1.7 anal body diameters long, S-shaped in lateral view in some specimens; surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis (supplemented with literature data). Leptolaimus alatus is particularly characterised by the 376–595 µm long body; truncate labial region offset from body contour; cephalic setae 1.5–2.0 µm long; amphid located 6.0–10.0 µm from anterior end; first body pore located 26.0–37.0 µm from anterior end; lateral field originating 20.0–34.0 µm from anterior end; female without supplements, vagina without pars refringens, vulva midventral; male with six–eight tubular and without alveolar supplements, tubular supplements weakly S-shaped with blunt tips; spicules arcuate and 26.0–40.0 µm long.

Remarks. Current specimens are similar to the type and only specimen of L. alatus in general morphology, shape of labial region, size of outer labial sensilla, position of amphid, anterior body pore, lateral field, number and shape of tubular supplements, and shape of gubernaculum. The major differences are body size (376–518 µm vs. 595 µm in L. alatus ) and length of spicules (31.0–40.0 µm vs. 26.0 µm in L. alatus ).

Figures

FIGURE 22. Leptolaimus sextus sp. n. (A–B) and Leptolaimus alatus Vitiello, 1971 (C–D). A, C: Entire male; B, D: Entire female. Scale bar: A–D = 50 µm.

FIGURE 23. Leptolaimus alatus Vitiello, 1971, 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.