Parasphaerolaimus sinensis, Zhai & Liu & Huang, 2025

Parasphaerolaimus sinensis sp. nov.

( Figures 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6 , Table 2 View TABLE 2 )

Type material. Three males and three females were found. Holotype on slide 3400-3-0-2 . GoogleMaps Paratypes: M2 on slide 3400-3-0-1 , GoogleMaps M3 on slide 3400-3-2-8 , GoogleMaps F1 on slide 3400-3-0-1 , GoogleMaps F2 and F3 on slide 3400-1-0-1 . GoogleMaps

Type locality and habitat. Sea floor silt sediment at Station 3400-3   GoogleMaps (34°0′ N, 121°12′ E, water depth 64 m) and Station 3400-1   GoogleMaps (34°0′ N, 120°48´E, water depth 48 m) in the Yellow Sea.

Etymology. The species epithet “ sinensis ” refers to the country of origin, China.

Measurements. All measurement data are given in Table 2 View TABLE 2 .

Descriptions

Males. Body plump, nearly cylindrical, anterior end blunt. Cuticle finely striated with a clear lateral alae, 15 µm wide, extending along the body from about the level of the nerve ring to the middle of the tail. Inner labial sensilla papilliform; six outer labial setae (4‒5 µm long) and four slightly longer cephalic setae (6‒7 µm long) joined in a single circle. A circle of eight groups of subcephalic setae situated below the level of cephalic setae, each group with 2‒3 setae, 14‒22 µm long. Cervical and somatic setae numerous, 16‒25 µm long, scattered along the body. Buccal cavity large, divided into two sections. Cheilostoma with longitudinal ribs and six regular sclerotized plates. Gymnostoma with three plates at posterior part. Stegostoma funnel-shaped with longitudinal ribs. Amphidial fovea circular, 15–17 µm in diameter or 33‒40% of corresponding body diameter, located at the level of junction of the gymnostoma and the stegostoma, i.e.25–27 µm from the anterior end. Nerve ring situated anterior to the middle of pharynx, i.e. 39% of pharynx length from anterior end of body. Secretory-excretory pore located behind nerve ring, 132–144 µm from anterior end of body. Ventral gland cell body located posterior to the cardia, lateral to the intestine. Pharynx cylindrical; cardia small, about 11 µm long, enveloped by intestinal tissue.

Reproductive system with a single outstretched testis. Spicules slender, slightly curved, 1.3–1.8 cloacal body diameter, proximally slightly enlarged and distally tapered. Gubernaculum with a pair of dorso-caudal apophyses, 10‒12 µm long. Tail conico-cylindrical, 3.2–3.6 cloacal body diameter, with three caudal glands. Somatic setae irregularly distributed along the tail. Three terminal setae, 11–20 µm in length.

Females. Similar to males in morphological characteristics, but bodies slightly longer (1650–2148 µm), cervical and somatic setae few and short, amphidial fovea smaller, 6 µm in diameter or 11‒13% corresponding body diameter, 30‒36 µm from anterior end of the body. Single anterior outstretched ovary extending forward, close to the cardia. Posterior to the oocytes region there is a sequence of developing eggs, shelled embryos, and sometimes a few hatched juveniles. Vulva situated far posteriorly, 80–122 µm from the anal opening, i.e. 84–87% of body length from the anterior end. Tail conico-cylindrical, with three terminal setae, 16–19 µm long.

Dignosis and discussion. Parasphaerolaimus sinensis sp. nov. is characterized by amphidial fovea 15–17 µm wide in males and 6 µm in females, and all located at the level of junction of the gymnostoma and the stegostoma, length of longest subcephalic setae 19–20 µm in males, 6–7 µm in females, cuticle with lateral longitudinal ridge, 15 µm wide in males, 8 µm in females, slender and slightly curved spicules 1.3–1.8 cloacal body diameter, gubernaculum with a pair of dorso-caudal apophyses, 9–11 µm long, position of the vulva very close to the anus and ovoviviparity.

The new species resembles P. Jintiani Fu, Boucher & Cai, 2017 and P. magdolnae Cavalcanti & Venekey, 2017 in the presence of only one testis, lateral alae and females with intrauterine development of their offspring. It differs from P. Jintiani by longer subcephalic setae (14–22 µm vs 6 µm) in males, relatively shorter and slender spicules slightly swollen proximally (63–74 µm vs spicules 109 µm, with developed swollen proximal ends), shorter gubernaculum with apophyses (vs longer gubernaculum, 48 µm, without apophyses). Moreover, the body size of males is smaller than in females, while in P. Jintiani , male is longer than females. The new species differs from P. magdolnae by longer subcephalic setae (14–22 µm vs 7–8 µm) in males, shorter and slightly arcuate spicules without a ventral indentation near the proximal end (vs spicules curved with a ventral indentation near the proximal end, 126–234 µm long), shorter gubernaculum with apophyses (vs longer gubernaculum, 27–38 µm, without apophyses). The new species is also similar to P. dispar ( Filipjev, 1918) Filipjev, 1946 , P. lodosus ( Gerlach, 1956) Zograf, Pavlyuk, Trebukhova & Nguyen, 2017 and P. pilosus Zograf, Pavlyuk, Trebukhova & Nguyen, 2017 in body size and shape, length of spicules and guberculum with apophyses. It differs from P. dispar by the latter species without lateral alae, tail with posterior filiform portion, vulva located at 62–70% of body length from anterior end and oviparity. The new species differs from P. lodosus , by the latter having cephalic setae and cervical setae very short (shorter than 10 µm), diameter of amphidial fovea 9–10 µm in males and 5 µm in females. The new species differs from P. pilosus , by the latter presenting diameter of amphidial fovea 11.5–12 µm in males and 6.5–7 µm in females, spicules shorter than 60 µm, gubernaculum with small proximal apophyses, vulva located at 55–67% of body length from anterior end and oviparity.

Furthermore, Parasphaerolaimus sinensis sp. nov. is distinguished from P. paradoxus Ditlevsen, 1918 by a smaller body size (1212–2148 µm vs 2300–2400 µm), smaller De Man ratio a (18.7–23.6 vs 37–49), shorter cephalic and subcephalic setae in females (4–6 µm vs 24–34 µm), and longer spicules (63–74 µm vs 47.5 µm). In addition, the vulva located less than 67% of body length from anterior end in the latter species.