Leptolaimus quartus, 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 : 32-35

Leptolaimus quartus sp. n.

( Figs 7E , 13 ; Table 9)

Type material. Holotype male (slide # Type-8459) deposited in the invertebrate type collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden.

Additional material. Three males (slides # 129936, 129962–129963) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. Coarse gravel from 30–50 m deep, Skagerrak off the west coast of Sweden (N 58° 17' 58'', E 11° 10' 05''), 09 August 2011, legit O. Holovachov (one male) .

Additional localities. 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); muddy sediment from 55–70 m deep, Skagerrak off the west coast of Sweden (N 58° 22' 19'', E 11° 04' 55''), 09 August 2011, legit O. Holovachov (one male) .

Etymology. The specific epithet " quartus " is translated as " the fourth " 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; strongly curved ventrad in posterior part. Cuticle annulated; annuli 1.4–2.0 µm wide at mid-body, without ornamentation. Lateral field present, consists of single ala (two incisures), 1.0 µm wide at mid-body; originating at level of stoma base or procorpus (anterior 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 four 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 rounded, continuous with body contour, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla setiform, equal to 50–80% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea round, located at level of anterior 2/5th of stoma. Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretoryexcretory system obscure. 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 elongate-conoid, gradually narrowing distally. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. Three or four long setae emerging through first, second, third and often fourth 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 dorsal apophysis bending anteriad. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, three evenly spaced midventral tubular supplements extending for 95–119 µm from cloaca towards anterior end; eight–nine alveolar supplements. Tubular supplements almost straight, with blunt expanded tips. Posteriormost tubular supplement 28–36 µm anterior to cloaca, anterior to spicules. Alveolar supplements with inner sclerotized ring. Anteriormost alveolar supplement 142–159 µm from anterior end, at level of anterior part of intestine. Sublateral precloacal and caudal sensilla present: two (one pair) precloacal setae at level of cloaca and usually eight (four pairs) caudal setae arranged in two subventral and two subdorsal pairs. One subventral pair of papilliform sensilla located at the bases of the second (from cloaca) pair of caudal setae.

Female. Not found.

Diagnosis. Leptolaimus quartus sp. n. is particularly characterised by the 597–686 mm long body; rounded labial region continuous with body contour; cephalic setae 2.0–3.5 µm long; amphid located 5.0–7.0 µm from anterior end; first body pore located 23.5–27.0 µm from anterior end; lateral field originating 19.0–27.0 µm from anterior end; male with three tubular and 8–9 alveolar supplements, tubular supplements straight with blunt expanded tips, alveolar supplements with sclerotized inner ring; spicules arcuate and 23.0–25.0 µm long.

Relationships. In general morphology and measurements, the new species is most closely related to L. mixtus and L. secundus sp. n. Leptolaimus quartus sp. n. differs from both these species in number of tubular and alveolar supplements (3 tubular and 8–9 alveolar vs. 1 tubular and 9–15 alveolar in L. secundus sp. n. vs. 4 tubular and 2–3 alveolar in L. mixtus ).

Figures

FIGURE 7. Leptolaimus secundus sp. n. (A–B), Leptolaimus mixtus Lorenzen, 1972 (C–D) and Leptolaimus quartus sp. n. (E). A, C: Entire female; B, D, E: Entire male. Scale bar: A–E = 50 µm.

FIGURE 13. Leptolaimus quartus sp. n., holotype male. A: Anterior end, surface view; B: Pharyngeal region, median section; C: Male posterior region. Scale bar: A–C = 20 µm.