New deep-sea species of Aborjinia (Nematoda, Leptosomatidae) from the North-Western Pacific: an integrative taxonomy and phylogeny Author Zograf, Julia K. A. V. Zhirmunsky National Scientific Center of Marine Biology, FEB RAS, 690041, Vladivostok, Russia zojulia@yandex.ru Author Semenchenko, Alexander A. Federal Scientific Center of the East Asia Terrestrial Biodiversity, FEB RAS, 690022, Vladivostok, Russia Author Mordukhovich, Vladimir V. A. V. Zhirmunsky National Scientific Center of Marine Biology, FEB RAS, 690041, Vladivostok, Russia & Far Eastern Federal University, 690922, Vladivostok, Russia text ZooKeys 2024 2024-01-17 1189 231 256 http://dx.doi.org/10.3897/zookeys.1189.111825 journal article http://dx.doi.org/10.3897/zookeys.1189.111825 1313-2970-1189-231 FCBFC6313C494B98BD021C63654837FE B3209808DF775FA99E2105DDC703973E Aborjinia profunda sp. nov. Figs 2 , 3 , 4 , 5 , 6 Diagnosis. Body 22.9-27.7 mm long in males. Six outer labial and cephalic sensilla papilliform, situated 19-21 µm from anterior end. Amphideal aperture located 37-40 µm from anterior end. Pharynx tubular without any valves or bulbs, tightly surrounded by the glandular tissue. Nerve ring situated ~ 40% of pharynx length from anterior end. Intestine well developed with wide lumen. Spicules slightly bent, 364-372 µm long. No pre- or postcloacal sensilla or supplements. Spinneret present. Type material examined. Three males (holotype and two paratypes). The holotype (SMF 14457) and paratype (SMF 14458) are deposited in the Senckenberg Museum, Frankfurt am Main, Germany. Paratype (MIMB 42307) is deposited in the Zoological Museum of A.V. Zhirmunsky National Scientific Center of Marine Biology, Vladivostok, Russia. Other material examined. One formalin-preserved specimen (male) and two DESS-preserved specimens (males). The Kuril-Kamchatka Trench, water depth 5477 m ( 45.0°N , 151.1°E ), 6114 m depth ( 45.9°N , 152.8°E ) Deposited in the Zoological Museum of A.V. Zhirmunsky National Scientific Center of Marine Biology , Vladivostok, Russia (MIMB 42308) . Type locality. The Kuril-Kamchatka Trench, water depth 8235 m ( 44.7°N , 151.5°E ) (Fig. 1 , Table 1 ). Additional locality. The Kuril-Kamchatka Trench, water depth 5477 m ( 45.0°N , 151.1°E ), 6114 m depth ( 45.9°N , 152.8°E ) (Fig. 1 , Table 1 ). Etymology. Species name derived from the Latin profundus that means deepwater and refers to the deepwater habitat of described species. Nucleotide sequences. GenBank accession numbers OP600452.1, OP600453.1 (small subunit ribosomal RNA gene, partial sequence; internal transcribed spacer 1, 5.8S ribosomal RNA gene, and internal transcribed spacer 2, complete sequence; and large subunit ribosomal RNA gene, partial sequence); OP407645.1, OP407646.1 (large subunit ribosomal RNA gene, partial sequence). Description. Large nematodes, 22.9-27.7 mm long, with an average diameter 0.2-0.4 mm. Body cylindrical, tapering towards both extremities (Figs 2 , 3 ). The cuticle finely striated under SEM, and thin (~ 5 µm ; Fig. 6 ). Hypodermis and muscle layers are thin, cords are prominent (Fig. 5 ). Body pores distinct, irregularly arranged. Measurements tabulated in Table 2 . Figure 2. Examined species of Aborjinia , entire bodies, light microscopy A Aborjinia sp., female (assembled panorama) B Terebelus sp. with juvenile of Aborjinia sp. C Aborjinia profunda sp. nov., male. Scale bars: 5000 µm . Figure 3. Aborjinia profunda sp. nov. A anterior end of male B head of male C male reproductive system D male tail. Abbreviation: c.s - cephalic sensilla. Scale bars: 100 µm ( B ); 200 µm ( D ); 500 µm ( A ); 2000 µm ( C ). Table 2. Morphometrics (μm) of Aborjinia profunda sp. nov. and Aborjinia sp. (abbreviations of characters defined in the Materials and methods).

-	Aborjinia profunda sp. nov.			Aborjinia sp.
	HT♂	♂	♂	HT ♀
L	27740	22900	25700	172000
Tail length	263	218	193	524
Nerve ring from anterior end	500	513	501	-
Head diam. at level of cephalic setae	91	83	87	-
Anal body diam.	289	217	230	467
Maximum body diam.	355	264	290	850
Pharyngeal length	1250	1199	1158	2148
Amphid from anterior end	33	37	43	-
Spicule length	364	297	335	-
Renetta cells from anterior end	792	742	725	5053
a	78.1	86.7	88.6	202.3
b	22.2	19.1	22.2	78.8
c	105.5	105	133.2	328.2
c'	0.91	1	0.83	1.1

Head narrow, bluntly rounded with three lips. Inner labial sensilla papilliform, hardly visible under light microscope. Papilliform outer labial sensilla and cephalic sensilla in one circle, 1-2 µm long, situated 19-21 µm from anterior end (Fig. 6A, B ). Amphideal opening pore-like, located 37-40 µm from anterior end. Pharynx tubular without any valves or bulbs, tightly surrounded by the glandular tissue (Figs 3A , 4 ). Nerve ring situated ~ 40% of pharynx length from anterior end. Intestine well developed with wide lumen. Ventral gland consists of two cells. Cell bodies ~ 80 μm long and 75 μm wide (~ 30% of corresponding body diam.), arranged in tandem and situated 725-792 µm from anterior end (Fig. 4D, E ). Excretory pore not observed. Figure 4. Aborjinia profunda sp. nov., male. Light microscopy, DIC A-C head D, E cellular bodies of the cervical excretory gland F crystalloid bodies G, H posterior end region I the vesicula seminalis region. Abbreviations: a - amphid, a.t. - anterior testis, c.s. - cephalic sensillum, c.e.g. - cervical excretory gland, n.r. - nerve ring, p.t. - posterior testis, s. - spinneret, sp. - spicules, vd - vas deferens. Scale bars: 50 µm . Figure 5. Aborjinia profunda sp. nov. Light microphotographs of transverse sections A buccal cavity at the upper level of the head (h) B buccal cavity surrounded with pharyngeal glands C pharyngeal region tightly filled with pharyngeal glands bodies D midbody with intestine and gonad E posterior region at the level of distal part of spicules F posterior region close to cloacal opening. Abbreviation: bc - buccal cavity, c - cloaca, cu - cuticle, gc - germinal cells, h - heilostoma, i - intestine, lc - lateral chords, pg - pharyngeal glands, s - spicules, vc - ventral chords. Scale bars: 20 µm ( A-C ); 50 µm ( E, F ); 100 µm ( D ). Figure 6. Aborjinia profunda sp. nov. SEM A anterior end of male B head of the male C amphideal fovea D posterior end of the male E spicules protruding from cloacal opening F spicules G tail tip with spinneret opening. Scale bars: 2 µm ( C ); 20 µm ( B, D, E, F, G ); 100 µm ( A ). Male reproductive system didelphic, testes outstretched. Spicules paired, symmetrical, slightly bent, 364-372 µm long (Figs 3 , 4 ). Gubernaculum not found. No pre- or postcloacal sensilla or supplements. Rectum and anal opening functional. Tail conical with terminal spinneret, caudal glands not observed. Remarks. The new species differs from A. eulagiscae by the location of the ventral gland cell bodies (posterior to the nerve ring vs posterior to the cardia), by the smaller body size (23-28 mm vs 103-132 mm), and the shorter tail (193-263 µm vs 500-850 µm ).