Leptolaimus tertius, 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 : 26-29

Leptolaimus tertius sp. n.

( Figs 10 D , 11 ; Table 7)

Type material. Holotype male (slide # Type-8457) and one male paratype (slide # Type-8458) deposited in the invertebrate type collection of the Department of Zoology , Swedish Museum of Natural History, Stockholm, Sweden.

Type 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 (two males) .

Etymology. The specific epithet " tertius " is translated as " the third " 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, strongly curved ventrad in posterior part in males. Cuticle annulated; annuli 1.5–1.6 µm wide at mid-body, without ornamentation. Lateral field present, consists of single ala (two incisures); originating at level of stoma base (posterior to first body pore) 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; seven pairs of body pores are present along pharyngeal region, and one at level of cardia; numerous body pores scattered over rest of the body. Anteriormost body pore located at level of posterior 1/5th of stoma. Labial region rounded, continuous with body contour, lips fused. Inner and outer labial sensilla indistinct. Cephalic sensilla setiform, equal to 30% of labial region diameter. Subcephalic and cervical sensilla and ocelli absent. Amphidial fovea round, located anterior to middle 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 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 conoid, gradually narrowing distally. Three caudal glands present, their nuclei are incaudal. Spinneret functional.

Male. Two pairs of short setae emerging through third 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 dorsal apophysis. Accessory apparatus composed of one midventral precloacal papilliform sensillum located on anterior cloacal lip, four evenly spaced midventral tubular supplements extending for 118–131 µm from cloaca towards anterior end; 7–10 alveolar supplements. Tubular supplements weakly arcuate in shape, with bluntly rounded tips. Posteriormost tubular supplement 31–34 µm anterior to cloaca, anterior to spicules. Alveolar supplements with prominent inner sclerotized ring. Anteriormost alveolar supplement 160–172 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 ten (five pairs) caudal setae arranged in three subventral and one subdorsal pairs.

Female. Not found.

Diagnosis. Leptolaimus tertius sp. n. is particularly characterised by the 576–579 µm long body; rounded labial region continuous with body contour; cephalic setae 2 µm long; amphid located 4–5 µm from anterior end; first body pore located 21.0–23.5 µm from anterior end; lateral field originating 26–29 µm from anterior end; male with four tubular and 7–10 alveolar supplements, tubular supplements weakly arcuate with blunt tips, alveolar supplements with sclerotized inner ring; spicules arcuate and 25–26 µm long.

Relationships. Leptolaimus tertius sp. n. is particularly characterised by the very anterior position of amphid and in this respect closely resembles L. donsi , from which it differs in having shorter body (576–579 vs. 776–1103 in L. donsi ), more posterior position of the first body pore (21–24 µm vs. 11–14 µm in L. donsi ), shorter spicules (25–26 µm vs. 30–34 µm in L. donsi ), number of tubular supplements (4 vs. 2 in L. donsi ). It should also be compared with L. mixtus and L. danicus , males of which have (or may have) four tubular supplements and a number of alveolar supplements. L. danicus has alveolar supplements with distinct sclerotized tube, that is absent in L. tertius sp. n. Moreover, the new species differs from L. danicus in the shape of tubules (with blunt tips vs. with dentate tips in L. danicus ), position of the amphid (4–5 µm vs. 8–12 µm in L. danicus ), first body pore (21–24 µm vs. 28–43 µm in L. danicus ) and anterior end of the lateral field (26–29 µm vs. 34–58 µm in L. danicus ). From L. mixtus the new species differs in the number of alveolar supplements (7–10 vs. 2–3 in L. mixtus ) reaching anterior part of intestine (vs. reaching midbody level in L. mixtus ).

Figures

FIGURE 10. Leptolaimus donsi (Allgén, 1947) comb. n. (A–C) and Leptolaimus tertius sp. n. (D). A: Entire female; B– D: Entire male. Scale bar: A–D = 50 µm.

FIGURE 11. Leptolaimus tertius sp. n., holotype male. A: Anterior end, surface view; B: Pharyngeal region, median section; C: Male posterior region. Scale bar: A–C = 20 µm.