Oloncholaimus piipi gen. et sp. nov. (Nematoda, Oncholaimidae) from Piip submarine volcano, the Bering Sea Author Mordukhovich, Vladimir V. Author Zograf, Julia K. A. V. Zhirmunsky National Scientific Centre of Marine Biology FEB RAS, Vladivostok 690041, Russia & zojulia @ yandex. ru; https: // orcid. org / 0000 - 0002 - 4723 - 7078 Author Saulenko, Anastasiia A. Far Eastern Federal University, Vladivostok 690091, Russia & saulenko. aa @ mail. ru; https: // orcid. org / 0000 - 0002 - 3487 - 9338 Author Fadeeva, Natalya P. Far Eastern Federal University, Vladivostok 690091, Russia & nfadeeva 2006 @ yandex. ru; https: // orcid. org / 0000 - 0003 - 1968 - 4521 text Zootaxa 2020 2020-06-24 4802 3 556 568 journal article 10.11646/zootaxa.4802.3.10 1175-5326 3907608 ADA3638F-A28E-4BB6-8D20-25FE42E51AC2 Oloncholaimus piipi gen. et sp. nov. ( Figs 2–7 ; Table 1 ) urn:lsid:zoobank.org:act: 61C64D5C-B879-4F4F-9B51-DD1613941533 Diagnosis. Oloncholaimus . Body large, 5960–6820 μm long in males and 6497–7045 μm in females. Six outer labial and four cephalic setae equal in size (5–7 μm). Buccal cavity 40–45 μm long and 17–21 μm wide in males, 44–49 μm long and 20–23 μm wide in females. Excretory pore situated at a distance of 96–108 μm (males) and 101 μm (female) from cephalic apex. Spicules equal, 110–131 μm long, without gubernaculum. In front of cloacal open- ing one complex supplementary organ composed of 8–9 cylindrical processes. Tail conico-cylindrical, 131–143 μm long in males and 167–175 μm in females. Type material. Whole mount specimens of holotype male and three paratype males ( MN BS 1178 Ol1), and three paratype females ( MN BS 1178 Ol2) are deposited in the Zoological Museum of Far Eastern Federal University , Vladivostok , Russia . Other material. Au-coated SEM specimens. Etymology. The species is named in reference to the area it was found. Type locality. Sandy sediments at the South Summit of the Piip volcano in the Bering Sea ( 55.382° N , 167.261° E ), outside the area with hydrothermal activity, water depth 470 m . Measurements. See Table 1 . TABLE 1 . Morphometrics (μm) of Oloncholaimus piipi gen. et sp. nov.
Characters Holotype Paratypes
Males (n=3) Females (n=3)
Body length 6820 5960–6670 6497–7045
a 74.9 71.3–85.5 60.8–83.9
b 8.1 7.7–7.8 7.1–8.5
c 52.1 43.2–44.9 37.1–40.3
c’ 2.8 3.6–4.1 3.6–3.7
V 80.1–83.8
Head diameter at level of cephalic setae 35 35–36 36–40
Body diameter at level of amphideal fovea 41 36–37 40–43
Body diameter at level of cardia 85 75–88 81–91
Maximum body diameter 91 78–90 84–110
Anal or cloacal body diameter 46 34–49 46–47
Length of cephalic setae 6 5–7 6–7
Amphid from anterior end 23 17–21 20–26
Width of amphideal fovea 11 11–14
Total buccal cavity length 41 40–45 44–49
Maximal buccal cavity width 17 17–21 20–23
Length of dorsal tooth from tip to posterior end of rhabdion 25 24–25 26–31
Length of left ventrosublateral tooth from tip to posterior end of rhabdion 30 31–33 32–36
Length of right ventrosublateral tooth from tip to posterior end of rhabdion 24 26–27 26–34
Excretory pore from anterior end 103 96–108 101 (n=1)
Nerve ring from anterior end 305 319–347 300–367
Pharyngeal length 837 769–867 825–915
Spicule length 121 110–131
Tail length 131 138–143 167–175
FIGURE 2. Oloncholaimus piipi gen. et sp. nov. A: Female head, right lateral view (paratype); B: Male head, left lateral view (holotype); C: Male body (paratype); D: Anterior end of female (paratype); E: Posterior end of female with reproductive structures (paratype); F: Female tail (paratype); G: Male tail (paratype). Scale bars: A, B—25 μm; C—500 μm; D, E—100 μm; F, G—50 μm. Abbreviations: cop.p.—copulatory pore; d.e.—ductus entericus; d.u.—ductus uterinus; int—intestine; m.d.—main duct; u—uterus; uv—uvette; v—vulva. FIGURE 3. Oloncholaimus piipi gen. et sp. nov. Scanning electron microscopy. A: Anterior end of female; B: Female head; C: Female tail; D, E: Cross section through the anterior part of buccal cavity with ventrosublateral teeth; F: Right ventrosublateral tooth; G: Left ventrosublateral tooth apex. Arrows indicate orifices of pharyngeal glands. Scale bars: A, C—20 μm; B—10 μm; D–G—2 μm. FIGURE 4. Oloncholaimus piipi gen. et sp. nov. A–E, J—Light microscopy, DIC; F–I—Scanning electron microscopy. A: Anterior end of male (paratype); B–E: Male head (paratype); F: Male tail; G: Precloacal region of the male, ventral view; H: Supplementary organ; I: Mail tail tip; J: Male body (paratype). Scale bars: A—50 μm; B–E—25 μm; F, I—20 μm; G—10 μm; H—1; J—500 μm. Abbreviations: a—amphid; e.p.—excretory pore; o.f.g.—orifice of the pharyngeal gland. FIGURE 5. Oloncholaimus piipi gen. et sp. nov. Male paratype. Light microscopy, DIC. A: Posterior testis with growth zone and ripening zone; B: Seminal vesicle with spermatozoa; C: Sphincter between vas deferens and ductus ejaculatorius; D: Growth zone of anterior testis; E: Male cardia; F: Male copulatory apparatus, arrow indicates striation in the middle part of the spicules; G: preanal copulatory muscles bundles. Scale bars: A, B—100 μm; C–G—50 μm. Abbreviations: d.ej.—ductus ejaculatorius; g.z.—growth zone; p.c.m.—preanal copulatory muscles bundles; p.t.—posterior testis; r.z.—ripening zone; sp—spermatozoa; v.d.—vas deferens. FIGURE 6. Oloncholaimus piipi gen. et sp. nov. Female paratype. Light microscopy, DIC. A: Female body; B: Posterior part of female with reproductive system; C: Main duct with sperm; D: Vulva region; E: ductus uterinus; F: ductus entericus; G: Main duct; H: copulatory pore. Scale bars: A, B—500 μm; C–F—50 μm; G—100 μm; H—25 μm. Abbreviations: cop.p.—copulatory pore; d.e.—ductus entericus; d.u.—ductus uterinus; m.d.—main duct; sp—sperm; uv—uvette. Description. Males : body length 5960–6820 μm; maximum diameter 78–91 μm. Cuticle looks smooth under optical microscope, but with fine transverse striation under SEM. Six triangular lips with rounded tips, each lip bearing a minute rounded inner labial papilla ( Fig. 3B ). Six outer labial and four cephalic setae in one circle, equal in size (5–7 μm). Head diameter 35–36 μm. Large buccal cavity with sclerotized walls, 40–45 μm deep and 17–21 μm wide ( Fig. 4 B–E). Three teeth present, left ventrosublateral typical oncholaimoid tooth is the largest (30–33 μm). Right ventrosublateral and dorsal teeth almost equal in size (24–27 μm) and have complex structure with onchium and api- cal antler-shaped extension (5–6 μm width) ( Figs. 3D , E–G, 4B, C). Amphids pocket-like with elliptical openings, 11–14 μm wide (0.3–0.4 corresponding body diameter), and 7–11 μm in height, located 17–23 μm from anterior end ( Figs 3B , 4A ). The left ventrosublateral tooth is perforated by the subterminal outlet of the corresponding pharyngeal gland. In the right ventrosublateral and dorsal teeth the pore of the pharyngeal gland lies in the middle part of the tooth ( Figs 3D , E–G, 4B, C, E). FIGURE 7. Oloncholaimus piipi gen. et sp. nov. Light microscopy, DIC. A–E: Examples of intestine content. Scale bars: A–D—50 μm; E—25 μm. Pharynx muscular and cylindrical, 0.1 times body length. Excretory pore opening at about 0.12–0.13 times pharynx length from anterior end (2.0–2.7 times buccal cavity length, 96–108 μm), nerve ring at 0.36–0.42 times pharynx length. Short somatic setae are sparsely distributed throughout the body, but mainly near both ends ( Fig. 3A ). Glandular organs occur at irregular intervals, mainly in the lateral chords. Orthometanemes present. Tail conico-cylindrical, ventrally bent, 131–143 μm long (2.8–4.1 cloacal body diameter) ( Fig. 4F ). Two pairs of short ventral and one pair of dorsal setae in the middle of tail. In addition, about 3 scattered subdorsal caudal setae. Tail tip slightly swollen and rounded with four small terminal setae ( Fig. 4I ). One circle of circumcloacal setae, 7–8 pairs. In front of cloacal opening one complex supplementary organ composed of 8–9 cylindrical processes ( Fig. 4G, H ). Genital musculature represents a long series of preanal and postanal dorsoventral copulatory muscle bundles ( Fig. 5G ). Two opposed testes to the right side of intestine. Anterior one 1457–2003 μm long, posterior one 1442– 1687 μm. Three zones can be distinguished along the testis: germinal zone, growth zone, and ripening zone. The germinal zone is filled with small, tightly packed cells near the blind end of the testes. The growth zone is composed of very big cells, each with a large nucleus, arranged in a single row ( Fig. 5A, D ). The ripening zone is filled with smaller cells containing condensed chromatin and arranged in two rows ( Fig. 5A ). Both testes join at the seminal vesicle that contains a number of broad oval spermatozoa ( Fig. 5B ) and that further leads to the vas deferens The latter is set off from ductus ejaculatorius by a sphincter about 805–1143 μm anterior to cloaca ( Fig. 5C ). This ductus joins the rectum from the ventral side. The whole vas deferens is situated on the right and ventral side of the intestine. Spicules equal, 110–131 μm (2.6–3.7 cloacal body diameter), slightly ventrally curved, with some striation in the middle part, proximally slightly cephalate ( Fig. 5F ). Females : very similar to males but differ in several dimensions and sexual characteristics. Body length 6497– 7045 μm, maximum body diameter 84–110 μm. Tail somewhat longer than in males, 167–175 μm long (3.6–3.7 anal body diameter). Only anterior reproductive branch is developed with reflexed ovary, lying to the right side of the intestine ( Fig. 6B ). Two or three intra-uterine eggs in the paratypes , 183–249 μm long and 63–76 μm wide. Vulva at 80–84% of body length. Demanian system well-developed ( Fig. 6B, C , E–H). Ductus uterinus posterior to uterus (102–196 μm long) connecting to the main duct through uvette. Ductus entericus anterior to uvette (about 135 μm long) connecting to dorsal side of intestine through osmosium. Main duct branched to the two long blind sacs pierced by the multiple terminal ducts ending in terminal pores. The edge of the sacs situated at a distance of 458–656 μm from uvetta and at 188–203 μm from the anus. Gut content. About 80% of studied male and 50% of female specimens have empty intestine. The intestinal contents of other specimens consist of usually difficult to recognize material ( Fig. 7A, C ) and in two females intestine contains material that looks like some protozoa shells ( Fig. 7B, D, E ).