Leptolaimoides hexatubulosus Hoang Lai-Phu, Blome, Nguyen Vu Thanh & Saint-Paul, 2009

Holovachov, Oleksandr, 2015, Swedish Plectida (Nematoda). Part 9. The genus Leptolaimoides Vitiello, 1971, Zootaxa 3955 (1), pp. 83-100 : 90-93

Leptolaimoides hexatubulosus Hoang Lai-Phu, Blome, Nguyen Vu Thanh & Saint-Paul, 2009

( Fig 5 ; Table 2 )

Material examined. Three males and one female (slides # 140612 – 140613) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Habitat and locality. Gravel, mud and algae from 30–70 m deep, Skagerrak off the coast of Sweden (N 58° 22' 14'', E 11° 05' 00''), 0 9 August 2011, legit O. Holovachov (three males and one female).

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; straight or weakly 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 µm wide at mid-body, without ornamentation; small region at level of amphid without annulation. Lateral field present, consists of three alae, middle ala smooth, outer alae areolated, 3.5–4 µm wide at mid-body; originating at posterior end of amphid and extending posteriorly to anterior 2/5th 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 body. Anterior-most body pore located posterior to amphid, at level of procorpus. Labial region rounded, continuous with body contour, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla papilliform. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea elongated; located at level of posterior part 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 weakly developed pyriform 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 almost similar in shape in both sexes (more curved ventrad in male), elongate-conoid in its proximal part (equal to 39–42% of total tail length), subcylindrical in its distal part. Three caudal glands present, nuclei incaudal. Spinneret functional.

Male. Reproductive system diorchic; anterior testis outstretched, located on right hand side of intestine; posterior one reflexed. Spicules paired, symmetrical, with arcuate conoid calamus and ovoid manubrium. Gubernaculum 4–5 µm long, plate-like, with 8.5–11 µm long caudal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, five evenly spaced midventral tubular supplements extending for 100–106 µm from cloaca towards anterior end; alveolar supplements absent. Tubular supplements straight or weakly curved in shape, with blunt tips. Posterior-most tubular supplement 20–27 µm anterior to cloaca, anterior to spicules. Sublateral precloacal sensilla absent, four caudal sensilla arranged in two subventral pairs. Four small papillae located at the posterior edge of lateral field, one subventral pair and one subdorsal pair.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 67 µm long (equal to 11% of total body length), located on right-hand side of intestine (n=1), posterior genital branch 79 µm long (equal to 13% of total body length), located on left-hand side of intestine (n=1). Oviduct a narrow tube. Two offset, oval, sac-like spermathecae located on each (right and left) side of each (anterior and posterior) gonoduct. Spermathecae and oviducts filled with oval spermatozoa. Uterus a 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 sensory structures around vulva absent. Supplements absent. Rectum surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis (supplemented with literature data). Leptolaimoides hexatubulosus is particularly characterised by the 529–638 µm long body; cephalic sensilla papilliform; amphid 11–16 µm long, located 8–12 µm from anterior end; first body pore located 30–35 µm from anterior end; lateral field areolated, arising 23–24 µm from anterior end; female without supplements, vagina without pars refringens, vulva midventral; male with five–six tubular and without alveolar supplements; spicules arcuate and 20–21 µm long.

Remarks. Current specimens agree well with the type specimens in general morphology, shape of anterior end, amphids, lateral alae, spicules and gubernaculum. The only differences are longer body length (593–638 µm vs. 529 µm in holotype), fewer tubular supplements (five vs six in holotype), shorter amphid (11.0–13.5 µm vs 16 µm in holotype). Differences in spicule length between our male (20–21 µm) and holotype male (12 µm) are caused by different ways of measuring this character (along the arc vs along the chord).

Figures

FIGURE 5. Leptolaimoides hexatubulosus Hoang Lai-Phu, Blome, Nguyen Vu Thanh & Saint-Paul, 2009, 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.

Tables

TABLE 2. Morphometrics of Leptolaimoides tubulosus Vitiello, 1971 and Leptolaimoides hexatubulosus Hoang Lai- Phu et al., 2009 from the Swedish west coast (all measurements are in µm, except for the ratios a, b, c, c', V, NR).

	Leptolaimoides tubulosus	Leptolaimoides hexatubulosus
	1 ♂ 4 ♀♀	3 ♂♂ 1 ♀
Body length	821 708±24 (679–733)	593–638 605
a	38.3 37.5±2.9 (34.9–41.0)	37.2–46.1 40.4
b	6.5 5.4±0.2 (5.1–5.7)	5.4–5.7 5.3
c	5.5 5.6±0.4 (5.2–6.0)	5.4–5.7 6.7
c'	9.1 10.5±1.7 (8.8–12.4)	8.2–8.6 7.2
V(%)	– 43.7±1.0 (42.8–44.7)	– 45.9
Body diameter	21.5 18.9±0.9 (18–20)	13–17 15
Pharynx length	126 130±4 (126–136)	113–114 114
Tail length	149 127±11 (118–142)	108–111 90
Anal or cloacal body diam.	16.5 12.2±1.4 (10–13.5)	13–13.5 12.5
Labial region diam.	5 4.8±0.4 (4–5)	4–5 4
Amphid length	24 30.5±0.9 (29–31.5)	11–12 13.5
Amphid width	3 3.7±0.4 (3.5–4)	3–3.5 3
Amphid from ant. end	17 14.6±0.7 (14–16)	12 11
First body pore	49 48.0±2.1 (45–50)	35 30
Lateral field from ant. end	58.5 63.5±2.0 (62–65)	23–24 23.5
Stoma length	22 22.0±1.1 (21–23)	21.5–23 22
Nerve ring from ant. end	? 78	71–72?
NR (%)	? 62	62–63?
Vagina length	– 5.7±0.6 (5–6.5)	– 5
Rectum length	– 13.9±0.6 (13.5–15)	–?
Spicule length	25 –	20–21 –
Supplements	2 tubular 0	5 tubular 0