Paramphimonhystrella longispicula, Shi & Yu & Xu, 2017

Shi, Benze, Yu, Tingting & Xu, Kuidong, 2017, Two new species of Paramphimonhystrella (Nematoda, Monhysterida, Xyalidae) from the deep-sea sediments in the Western Pacific Ocean and adjacent shelf seafloor, Zootaxa 4344 (2) : -

publication ID	https://doi.org/ 10.11646/zootaxa.4344.2.6
publication LSID	lsid:zoobank.org:pub:F5B752A7-F0F9-41DA-964D-6DC7BE274C4B
DOI	https://doi.org/10.5281/zenodo.6008872
persistent identifier	https://treatment.plazi.org/id/D06287ED-FFCE-FFB9-FF14-AC9E3322FB96
treatment provided by	Plazi
scientific name	Paramphimonhystrella longispicula
status	sp. nov.

Treatment

Paramphimonhystrella longispicula sp. n.

( Figures 2 View FIGURE 2 , 3 View FIGURE 3 ; Table 1)

Diagnosis. Body length 842–942 µm. Buccal cavity elongated cylindro-conical, 12–16 µm deep and 5 µm wide. Six inner labial setae about 1–2 µm long, six outer labial setae and four cephalic setae united in one circle and about 3–4 µm long. Amphideal fovea circular to longitudinal oval-shaped, with double contours. Roughly two groups of cervical setae each composed of 12–14 setae, with anterior group of setae 2–3 µm long and posterior group 9–13 µm long. Two opposed testes, outstretched, with anterior testis on the left of intestine and posterior one on the right. Spicules long and slender, 3.2–3.9 anal body diameters long. Gubernaculum short and tubular with pointed distal end. Single anteriorly outstretched ovary on the left of intestine. Tail conico-cylindrical, with cylindrical part occupying about half of tail length. Two long and two short terminal setae.

Type material. Two males and one female. Male holotype on slide KP-D18-1. Male paratype on slide KP- D08-1. Female paratype on slide KP-D81-1.

Type locality and habitat. Muddy sediments at stations D18 (14°39'N, 134°51'E), D08 (13°05'N, 134°52'E) and D81 (13°35'N, 135°39'E) from an abyssal plain of the Philippine Sea near the Southern Kyushu-Palau Ridge in the tropical Western Pacific Ocean ( Fig. 1 View FIGURE 1 ). Station D18, water depth 4472 m, median particle diameter 6 µm, organic matter content 0.55%. Station D08, water depth 3920 m. Station D81, water depth 5176 m, median particle diameter 5 µm, organic matter content 0.14%.

Etymology. Composition of the Latin adjective longus (long) and the Latin noun spicula (spicule), referring to the long spicules of the species.

Description. Morphometric data shown in Table 1. Body slender, gradually tapering towards tail end, with head region narrower than body trunk ( Fig. 2A View FIGURE 2 ). Cuticle very faintly striated, indistinct as observed under light microscope, about 8 µm per 10 annulations. Somatic setae sparse, 4–5 µm long, irregularly arranged along the body ( Fig. 2A View FIGURE 2 ). Buccal cavity elongate cylindro-conical, unarmed and cuticularized, 12–14 µm deep and 5 µm wide ( Figs 2B, C View FIGURE 2 , 3A, B View FIGURE 3 ). Six inner labial setae about 1 µm long, six outer labial setae and four cephalic setae united in a circle of six groups and about 3 µm long ( Figs 2B, C View FIGURE 2 , 3A–C View FIGURE 3 ).

Amphideal fovea slightly longitudinally oval and strongly cuticularized with double contours ( Figs 2B, C View FIGURE 2 , 3B View FIGURE 3 ). Roughly two groups of cervical setae each composed of 12 setae: anterior group of setae located at same level of amphideal fovea, 2–3 µm long; posterior group situated about 1.5 corresponding body diameters posteriorly, 9–11 µm long ( Figs 2B View FIGURE 2 , 3A, B View FIGURE 3 ). Pharynx cylindrical, with weak radial muscular striation, slightly widened at base, occupying 16.6–16.7% of total body length. Cardia small, cordate, and surrounded by intestine tissue ( Fig. 3E View FIGURE 3 ). Nerve ring located in middle portion of pharynx. Excretory pore and ventral gland not observed.

Tail conico-cylindrical, 7.1–9.5 anal body diameters long, cylindrical part occupying about half of tail length ( Fig. 2A, E View FIGURE 2 ). Three caudal glands confined within the tail, one conspicuously larger than the others ( Figs 2E View FIGURE 2 , 3D View FIGURE 3 ). Four terminal setae, two long ones 12–14 µm long and two short ones 3–7 µm long ( Figs 2E View FIGURE 2 , 3F View FIGURE 3 ).

Males. Two opposed testes, outstretched, with the anterior one on the left of intestine, and the posterior one on the right of intestine. Two long and slender spicules, 3.2–3.9 anal body diameters long, slightly cuticularized ( Figs 2D View FIGURE 2 , 3D View FIGURE 3 ). Gubernaculum short and tubular, with pointed distal end, 13–17 µm long. Precloacal supplements absent ( Figs 2D View FIGURE 2 , 3D View FIGURE 3 ).

Female. Similar to males but with circular amphideal fovea ( Fig. 2C View FIGURE 2 ; vs. slightly longitudinally oval in males) and a slightly higher number of cervical setae in the first group (14 vs. 12). Single anteriorly outstretched ovary on the left of intestine ( Fig. 2A View FIGURE 2 ). Postvulvar sac short with numerous sperm cells ( Figs 2A View FIGURE 2 , 3G View FIGURE 3 ). Vulva located at midbody ( Figs 2A View FIGURE 2 , 3G View FIGURE 3 ).

Species differentiation. Within the genus Paramphimonhystrella , only the new species P. longispicula sp. n., P. eurystoma sp. n. described below, and P. barbula Leduc, 2014 possess long and slender spicules (>2.7 anal body diameters), while the other species have short spicules (<1.7abd) ( Fig. 7 View FIGURE 7 ). Both P. longispicula sp. n. and P. barbula were found from the deep-sea sediments and the former species represents the deepest record for the genus. Paramphimonhystrella longispicula sp. n. can be easily separated from P. barbula by the broad buccal cavity (5 µm vs. 1–2 µm wide), the unequally long cervical setae (2–3 µm long in the anterior group and 9–13 µm long in the posterior group vs. all of equal length and about 3–6 µm long), and a higher number of terminal setae (4 vs. invariably 2). Paramphimonhystrella longispicula sp. n. differs distinctly from P. eurystoma sp. n. by the number of terminal setae (4 vs. 2), the short and simple gubernaculum (vs. long and peculiar gubernaculum with two capitula) and the absence of a hammer-shaped cuticularized piece which is situated ventrally and posterior to vagina (vs. presence).

Diagnosis. Body length 1167–1208 µm. Buccal cavity cylindro-conical, 14–23 µm deep and 9–12 µm wide. Six inner labial setae about 3–4 µm long; six outer labial setae 7–8 µm long and four cephalic setae 4–5 µm long, forming a circle. Amphideal fovea slightly oval with double contours. Roughly two groups of cervical setae, 8–11 µm long in anterior group and 12–18 µm long in posterior group. Two outstretched testes on the left of intestine. Spicules long and slender, 64–71 µm (2.4–2.8 anal body diameters). Gubernaculum strongly cuticularized with two capitula in proximal end, 25–28 µm long (one anal body diameter). Single ovary anteriorly outstretched on the left of intestine. A hammer-shaped cuticularized piece immediately posterior to vagina. Tail conico-cylindrical, with cylindrical part occupying about half of tail length. Two terminal setae, 23–31 µm long.

Type material. Five males and one female. Male holotype on slide DH5-2-1. Male paratypes on slides DH5-2- 2, DH5-2-3, DH5-2-4 and DH5-2-5. Female paratype on slide CJ-6-1.

Type locality and habitat. Muddy sediments at stations DH5-2 (28°47' N, 122°50' E) and CJ-6 (32°30' N, 125° 00' E) in the East China Sea. Station DH5-2, water depth 64 m, water temperature at the sediment-water interface 21.0°C, salinity 32.7, median particle diameter 19 µm, silt-clay 87.1%, and organic matter 1.3%. Station CJ-6, water depth 55 m, water temperature at the sediment–water interface 18.1°C, salinity 34.2, median particle diameter 235 µm, silt-clay 46.5%, and organic matter 0.4%.

Etymology. Composite of the Greek adjective eurys (broad) and the Greek noun stoma (mouth), refers to the broad buccal cavity of the species.

Description. Morphometric data shown in Table 2. Body slender, gradually tapering towards tail end, with head region narrower than body trunk ( Fig. 4A View FIGURE 4 ). Cuticle striated, about 17 µm per 10 annulations. About 13–15 setae located within 4.8–7.3 corresponding body diameters behind pharynx base, 11–19 µm long; other somatic setae sparse, irregularly arranged along body, 3–10 µm long ( Fig. 4A View FIGURE 4 ). Buccal cavity cylindro-conical, unarmed and cuticularized, 14–20 µm deep and 9–10 µm wide ( Figs 4B, C View FIGURE 4 , 5B View FIGURE 5 ). Six inner labial setae about 3–4 µm long; six jointed outer labial setae 7–8 µm long and four slightly jointed cephalic setae 4–5 µm long, united in a circle ( Figs 4B, C View FIGURE 4 , 5A View FIGURE 5 ).

Amphideal fovea slightly oval and strongly cuticularized, with double contours ( Figs 4B, C View FIGURE 4 , 5A, C View FIGURE 5 ). Roughly two groups of cervical setae: setae in anterior group 8–11 µm long and at same level of amphideal fovea, those in posterior group 12–18 µm long and situated about 1.5 corresponding body diameters posteriorly ( Figs 4B, C View FIGURE 4 , 5A, B View FIGURE 5 ). Pharynx cylindrical, with weak radial muscular striation, slightly widened at base, occupying 14.6–15.7% of total body length. Cardia surrounded by intestine tissue, small and cordate. Nerve ring located in middle portion of pharynx. Excretory pore and ventral gland not observed.

Tail conico-cylindrical, 9.0–10.3 anal body diameters long, cylindrical part occupying about half of tail length ( Fig. 4A, C View FIGURE 4 ). Three caudal glands confined within tail, one conspicuously larger than the others ( Figs 4A, C View FIGURE 4 , 5F View FIGURE 5 ). Two long and robust terminal setae 23–31 µm long ( Figs 4A, C View FIGURE 4 , 5H View FIGURE 5 ).

Males. Two opposed testes, outstretched, both on the left of intestine ( Fig. 4A View FIGURE 4 ). Spicules long and slender, 64– 71 µm long, 2.4–2.8 anal body diameters ( Figs 4D View FIGURE 4 , 5J View FIGURE 5 ). Gubernaculum short and strongly cuticularized, 25–28 µm long, about 1 anal body diameter, with two capitula in the proximal end ( Figs 4D, E View FIGURE 4 , 5I, J View FIGURE 5 ). Precloacal supplements absent. A longitudinal line on the right side of cuticle, 292–326 µm long and more or less twisty ( Figs 4F View FIGURE 4 , 5D View FIGURE 5 ).

Female. Single ovary anteriorly outstretched on the left of intestine ( Fig. 4G View FIGURE 4 ). Postvulvar sac long, with numerous sperm cells ( Figs 4G View FIGURE 4 , 5E View FIGURE 5 ). Mature eggs up to 93 µm long and 20 µm wide ( Fig. 4G View FIGURE 4 ). Vulva located at mid-body. A hammer-shaped cuticularized piece situated ventrally and immediately posterior to vagina, about 14 µm long and 2 µm wide ( Figs 4G View FIGURE 4 , 5E View FIGURE 5 ).

Species differentiation. Paramphimonhystrella eurystoma sp. n. possesses a distinctive hammer-shaped cuticularized piece situated ventrally and immediately posterior to vagina, a structure present also in females of P. glossalga Leduc, 2014 and P. scutula Leduc, 2014 . This is a rather peculiar feature in the order Monhysterida , while its function is still not known ( Leduc 2014). Paramphimonhystrella eurystoma sp. n. can be distinguished from P. glossalga and P. scutula by the peculiar gubernaculum with two capitula in the proximal end ( Fig. 3E View FIGURE 3 ). In all the other congeners including the new species P. longispicula sp. n., the gubernaculum is either small and simple or absent.