Axonolaimus rushanensis Lv & Yu & Wang 2025, sp. nov.

Axonolaimus rushanensis sp. nov. urn:lsid:zoobank.org:act: 59FF09A0-9CB4-490F-ABA0-BC98C29F499C (Figures 2–3, Table 1) Type material. Two males and three females were studied. Holotype: ♂ 1 on slide 2021RSGHGY4–2–2, paratypes: ♂ 2 on slide 2021RSGHGY4–1–9, ♀ 1 on slide 2021RSGHGY4–2–2, ♀ 2 on slide 2021RSGHGY4–2–22 and ♀ 3 on slide 2021RSGHGY4–2–18. Type locality and habitat. Specimens were collected from intertidal sandy sediments at Rushan, Shandong Province, China. 36º95´N, 121º96΄E (Figure 1). Etymology. The species epithet refers to the place where sediments were collected in Rushan. Measurements. All measurement data are given in Table 1. Descriptions. Males. Body cylindrical and slender, tapering slightly towards both extremities. Cuticle finely striated with somatic setae. Inner and outer labial sensilla not observed; four cephalic setae, 21–24 μm (1.7–2.1 cephalic diameter) in length. Two subcephalic setae, 19–21 μm (1.4–1.8 cephalic diameter) in length, amphidial fovea loop-shaped with rounded outline at the level of buccal cavity. Buccal cavity funnel-shaped, 17–18 μm in depth. Pharynx muscular, 171–190 μm in length, anterior portion surrounding posterior part of buccal cavity, widening slightly posteriorly, without pharyngeal bulb. Cardia short. Nerve ring situated 99–102 μm (0.5–0.6 of pharynx length) from anterior end. Tail conical, 131 μm (5.0–5.2 cloacal body diameter) in length, with sparse subventral and subdorsal setae. Three caudal glands. Testes outstretched and opposed, anterior testis to the left of intestine, posterior testis to the right of intestine. Spicules arcuate, strongly cuticularised, with straight capitulum, 33–38 μm in length (1.2–1.4 cloacal body diameter). Gubernaculum with strong dorso-caudal apophyses, 10–13 μm in length. Females. Similar to males in most characters. Reproductive system with two opposed, outstretched ovaries. Anterior ovary to the left of the intestine, posterior ovary to the right of the intestine. Vulva located slightly posterior to the mid-body (57.5–58.5% body length). Differential diagnosis and discussion. Axonolaimus rushanensis sp. nov. is characterized by body medium sized, amphidial fovea loop-shaped with rounded outline at level of buccal cavity, spicules short and arcuate, cuticularised and with straight capitulum, gubernaculum with dorso-caudal apophyses, tail conical. According to the morphometric characters of 34 valid species of the genus (Table 2), the new species is similar to A. caudostriatus, A. seticaudatus, A. steineri and A. typicus in body length and presence of subcephalic setae; but differs from A. caudostriatus in the amphidial fovea shape (loop-shaped with rounded outline vs. loop-shaped with elongated outline), gubernaculum apophyses length (10–13 μm vs. 19–20 μm) and tail shape (conical vs. conico-cylindrical); differs from A. seticaudatus in the amphidial fovea shape (loop-shaped with rounded outline vs. loop-shaped with elongated outline), subcephalic setae number (2 vs. 6); subcephalic setae length (19–21 μm vs. 7 μm); gubernaculum apophyses length (10–13 μm vs. 23 μm) and tail shape (conical vs. conico-cylindrical); differs from A. steineri in the amphidial fovea shape (loop-shaped with rounded outline vs. loop-shaped with elongated outline), subcephalic setae number (2 vs. 4); subcephalic setae length (1.4–1.8 cephalic diameter vs. 1.2 cephalic diameter); gubernaculum apophysis shape (dorso-caudal directed vs. dorsal, slightly directed to caudal position) and tail shape (conical vs. conically attenuated with blunt tip); differs from A. typicus in the cephalic setae length (1.7–2.1 cephalic diameter vs. 0.3 cephalic diameter), subcephalic setae number (2 vs. 4) and tail shape (conical vs. conico-cylindrical).