Leptolaimoides leptomicron, Holovachov, Oleksandr, 2015

Holovachov, Oleksandr, 2015, Swedish Plectida (Nematoda). Part 9. The genus Leptolaimoides Vitiello, 1971, Zootaxa 3955 (1), pp. 83-100 : 93-96

Leptolaimoides leptomicron sp. n.

( Fig 6 ; Table 3 )

Type material. Holotype male (slide # Type-8714) deposited in the type invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Additional material. One male and one female (slides # 140614 – 140615) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. Soft bottom 232–240 m deep, Skagerrak, Sweden (N 58° 27' 36.7'' –43.3'', E 10° 32' 52.0'' - 59.4''), 12 September 2012, legit "Inventering Bratten" (one male).

Additional localities. Soft bottom 248–316 m deep, Skagerrak, Sweden (N 58° 28' 22.1'' -19.2'', E 10° 29' 35.6'' -43.6''), 11 September 2012, legit "Inventering Bratten" (one male); soft bottom 221–260 m deep, Skagerrak, Sweden (N 58° 28' 28.0'' –31.1'', E 10° 33' 19.1'' –23.80''), 11 September 2012, legit "Inventering Bratten" (one female).

Etymology. The specific epithet " leptomicron " is a combination of generic names Lepto laimoides and Anto micron and refers to superficial similarity of this species to both genera.

Description. Adult. Body tapering anteriorly in pharyngeal region and posteriorly on tail; strongly 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 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, 6–6.5 µm wide at mid-body; arising at posterior end of amphid and extending posteriorly to proximal third of tail. Prominent body pores in sublateral position at both sides of lateral field present, arising from oval lateral epidermal gland cells; usually four 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, an inverted Ushaped, inner borders strongly developed; 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 34–36% of total tail length), subcylindrical in its distal part. Three caudal glands present, their nuclei are 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 cylindrical calamus and ovoid manubrium. Gubernaculum 6.5 µm long, plate-like, with 12–13.5 µm long caudal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, three evenly spaced midventral tubular supplements extending for 86–94 µm from cloaca towards anterior end; alveolar supplements absent. Tubular supplements straight or weakly arcuate in shape, with blunt tips. Posterior-most tubular supplement 31–33 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 112 µm long (equal to 13% of total body length), located on right-hand side of intestine (n=1), posterior genital branch 78 µm long (equal to 9% 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 1.2 anal body diameters long; surrounded by three gland-like cells at intestine-rectum junction.

Diagnosis. Leptolaimoides leptomicron sp. n. is particularly characterised by the 776–847 µm long body; cephalic sensilla papilliform; amphid 15–17 µm long, located 9–13 µm from anterior end; first body pore located 40–46 µm from anterior end; lateral field areolated, originating 26–28 µm from anterior end; female without supplements, vagina without pars refringens, vulva midventral; male with three tubular and without alveolar supplements, spicules arcuate and 28–29 µm long.

Relationships. The new species can be easily separated from all other species of the genus in the combination of following characters: largest body size (0.77-0.85 mm) and spicule length (28–29 µm) in the genus, strongly developed inner borders of amphidial fovea, making it almost an elongated 0-shape; distinct area of cuticle at level of amphid without annulation. Other characters separating new species from other members of Leptolaimoides are listed in Table 4 .

Figures

FIGURE 6. Leptolaimoides leptomicron sp. n., holotype male (A – B, D) and paratype female (C, E). A: Anterior end, surface view; B: Pharyngeal region, median section; C: Female tail; D: Male posterior region; E: Female reproductive system (anterior part). Scale bar: A – E = 20 µm.

Tables

TABLE 3. Morphometrics of Leptolaimoides leptomicron sp. n. from the Swedish west coast (all measurements are in µm, except for the ratios a, b, c, c', V, NR).

	Leptolaimoides leptomicron sp. n.
	Holotype, ♂ 1♂	1 ♀
Body length	776 776	847
a	30.2 43.5	26.3
b	5.4 5.8	6.3
c	4.6 4.7	4.8
c'	8.4 8.3	9.7
V(%)	– –	45.2
Body diameter	26 18	32
Pharynx length	144 133	134
Tail length	168 166	176
Anal or cloacal body diam.	20 20	18
Labial region diam.	7 7	8.5
Amphid length	15 17	15
Amphid width	5 5	4
Amphid from ant. end	13 9	11.5
First body pore	46 40	41.5
Lateral field from ant. end	28 27	26.5
Stoma length	33 30	31
Nerve ring from ant. end	91 84	82
NR (%)	63 63	61
Vagina length	– –	10
Rectum length	– –	21.5
Spicule length	28.5 29	–
Supplements	3 tubular 3 tubular	0