Haploniscus nyx Knauber & Riehl, 2025

Knauber, Henry, Schell, Tilman, Brandt, Angelika & Riehl, Torben, 2025, Across trench and ridge: description of five new species of the Haploniscus belyaevi Birstein, 1963 species complex (Isopoda, Haploniscidae) from the Kuril-Kamchatka Trench region, Zoosystematics and Evolution 101 (2), pp. 813-853 : 813-853

publication ID	https://doi.org/10.3897/zse.101.137663
publication LSID	lsid:zoobank.org:pub:1764B434-B419-4430-B297-6D6380572DFB
DOI	https://doi.org/10.5281/zenodo.15263769
persistent identifier	https://treatment.plazi.org/id/F15FB4C7-6CF0-51AA-9A30-1C37681E021D
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Haploniscus nyx Knauber & Riehl
status	sp. nov.

Treatment

Haploniscus nyx Knauber & Riehl sp. nov.

Figs 22 View Figure 22 , 23 View Figure 23 , 24 View Figure 24 , 25 View Figure 25 , 26 View Figure 26

Holotype.

SKB Hap 34, adult male (stage VI), 3.4 mm, MIMB 50320 View Materials . GoogleMaps

Paratypes.

SKB Hap 21, adult female (stage IV), 3.0 mm, MIMB 50321 GoogleMaps .

Type locality.

St. LV 71–10 – 07, RV “ Akademik M. A. Lavrentyev ”, SokhoBio expedition, EBS, 4469 m, 46°07.8'N, 152°10.3'E, Northwest Pacific, abyssal branch of the Kuril-Kamchatka Trench into the Bussol Strait GoogleMaps .

Further records.

St. LV 71–10 – 07: SKB Hap 35 (adult male), SMF 56552 .

Distribution.

Only known from type locality. Northwest Pacific, abyssal region adjacent to the Kuril-Kamchatka Trench to the northwest, depth 4769 m. Visualized in Fig. 27 View Figure 27 .

Etymology.

The epithet “ nyx ,” a noun in apposition, is derived from “ Nyx ” (Ancient Greek Νύξ), the goddess of the night in Greek mythology.

Synonymy.

Haploniscus SO - WTA (see Knauber et al. 2022).

Diagnosis.

Haploniscus nyx sp. nov. differs from other species of the belyaevi - complex in the following character: pleotelson posterior margin concave in males; Plp I medial lobes convexly rounded, tapering to an obtuse point, distally without a hook-shaped protrusion.

Molecular diagnosis.

differing in the 16 S gene from other species of the belyaevi - complex in the nucleotides G (position 25 of the alignment) and C (312) as well as the nucleotides C (124), G (148), C (193), T (206), C (304), G (334), C (346), G (481), T (496), C (508), C (520), G (553), G (556), and C (628) of the COI gene.

Description.

Male. Body (Fig. 22 B View Figure 22 ) length 2.2 width; subrectangular; anterior body length (Ceph – Prn 4) 0.99 posterior body length (Prn 5 – Plt); lateral margin continuous.

Cephalothorax (Fig. 22 B, D View Figure 22 ) length 0.30 width, 0.07 body length, width 0.55 body width; frontal margin width 0.46 Ceph width; rostrum curved upwards.

Pereonite 1 (Fig. 22 B View Figure 22 ) posterior tergite margin through Prn 5 anterior tergite margin delicately serrated, setose; Prn 2–5 anterolateral angles slightly projecting; Prn 1–4 posterolateral angles slightly projecting; Prn 4 lateral margin length 1 Prn 5 lateral margin length.

Pleotelson (Figs 22 B View Figure 22 , 26 L View Figure 26 ) length 0.72 width, 0.23 body length, trapezoidal, posterior margin concave; tergite surface smooth; with posterolateral tergal ridge between uropod insertion and posterolateral process; posterolateral processes minute, 0.13 Plt length, straight, oriented posteriorly.

Antenna I (Fig. 23 B View Figure 23 ) length 0.16 body length; flagellum with 5 articles.

Antenna II (Fig. 23 A View Figure 23 ) length 0.61 body length; article 3 dorsal projection triangular, projection length 0.36 article 3 length; article 5 projection length 0.23 article 5 length; flagellum with 15 articles.

Mandible (Fig. 24 B, C View Figure 24 ) incisor with 5 cusps, left Md lacinia mobilis with 4 cusps.

Maxillipeds (Fig. 24 A View Figure 24 ) with 3 coupling hooks each.

Pereopod I (Fig. 23 C View Figure 23 ) length 0.37 body length. PII (Fig. 23 D View Figure 23 ) length 0.45 body length. PIII (Fig. 23 E View Figure 23 ) length 0.52 body length. PV length 0.65 body length. PVI length 0.70 body length; P lengths gradually increasing from PI to PVI, PVII shorter than PVI.

Pleopod I (Figs 25 A View Figure 25 , 26 L View Figure 26 ) medial lobes convexly rounded, tapering to an obtuse point; adjoining at the apex.

Pleopod II (Fig. 25 B, C View Figure 25 ) protopod semi-circular, with distal lobe extending beyond protopod distal margin; endopod stylet 2.1 protopod length.

Female. Differs from male in the following characters:

Body (Fig. 22 A View Figure 22 ) length 2.1 width; oval; anterior body length (Ceph – Prn 4) 0.98 posterior body length (Prn 5 – Plt).

Cephalothorax (Fig. 22 A, C View Figure 22 ) length 0.46 width, 0.12 body length, width 0.55 body width; frontal margin width 0.46 Ceph width.

Pereonite 4 (Fig. 22 A View Figure 22 ) lateral margin length 1.05 Prn 5 lateral margin length.

Pleotelson (Figs 22 A View Figure 22 , 26 K View Figure 26 ) length 0.83 width, 0.27 body length, posterior margin rounded, convex; posterolateral processes short, 0.19 Plt length.

Antenna I (Fig. 22 A View Figure 22 ) length 0.16 body length; flagellum with 4 articles.

Antenna II (Fig. 22 A View Figure 22 ) length 0.50 body length; flagellum with 15 articles.

Operculum (Fig. 26 K View Figure 26 ) length 0.98 width, 0.66 Plt length; distal margin with numerous, evenly distributed long setae; lateral margins with fewer, evenly distributed short setae.