Haploniscus erebus Knauber & Riehl 2025, sp. nov.
Creators: name: Knauber, Henry
name: Schell, Tilman
name: Brandt, Angelika
name: Riehl, Torben
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Haploniscidae
Haploniscus
Haploniscus erebus

description: Haploniscus erebus Knauber & Riehl sp. nov.
Figs 1, 10, 11, 12, 13, 26
Holotype.
SKB Hap 54, adult male (stage VI), 3.3 mm, MIMB 50317.
Paratypes.
SKB Hap 49, adult female (stage IV; genome), SMF 56566; SKB Hap 50, adult female (stage IV), 3.3 mm, MIMB 50315.
Type locality.
St. LV 71–02 – 07, RV “ Akademik M. A. Lavrentyev ”, SokhoBio expedition, EBS, 3352 m, 46°40.9'N, 147°28.5'E, Northwest Pacific, Sea of Okhotsk, Kuril Basin.
Further records.
St. LV 71–02 – 07: SKB Hap 26 (manca) MIMB 50312, SKB Hap 28 (manca) MIMB 50313; St. LV 71–04 – 09: SKB Hap 10 (manca) MIMB 50311; St. LV 71–04 – 10: SKB Hap 09 (manca) SMF 56526; St. LV 71–11 – 06: SKB Hap 29 (manca) MIMB 50314, SKB Hap 30 (manca) SMF 56547, SKB Hap 31 (manca) SMF 56548, SKB Hap 51 (manca) MIMB 50316, SKB Hap 52 (manca) SMF 56569, SKB Hap 53 (manca) SMF 56570, SKB Hap 63 (manca) SMF 56580.
Distribution.
Northwest Pacific, Sea of Okhotsk, Kuril Basin, depth 3210–3366 m. Visualized in Fig. 27.
Etymology.
From “ Erebus ” (Ancient Greek: Ἔρεβος), the Greek mythological personification of darkness. It is a noun in apposition.
Synonymy.
Haploniscus aff. belyaevi (see Knauber et al. 2022).
Diagnosis.
Haploniscus erebus sp. nov. differs from other species of the belyaevi - complex in the following characters: rostrum straight, near triangular in lateral view; Plt shape rectangular, posterior margin straight in males; posterolateral processes long, more than 0.50 Plt length in males, straight, oriented posteriorly.
Molecular diagnosis.
Differing in the 16 S gene from other species of the belyaevi - complex in the nucleotides G (position 56 of the alignment), G (64), T (66), G (71), - (150), A (155), T (156), A (204), G (206), C (243), C (342), A (350), G (355), and C (358) as well as the nucleotides T (151), T (154), T (268), T (284), A (286), C (301), G (313), T (352), G (376), C (385), C (388), T (418), A (436), T (451), G (472), G (475), G (502), G (562), and G (565) of the COI gene.
Description.
Male. Body (Figs 1 C, 10 B) length 2.2 width; subrectangular; anterior body length (Ceph – Prn 4) 1.1 posterior body length (Prn 5 – Plt); lateral margin interrupted between Prn 7 and Plt, otherwise continuous.
Cephalothorax (Figs 1 C, 10 B, D) length 0.45 width, 0.13 body length, width 0.61 body width; frontal margin width 0.50 Ceph width; rostrum straight, near triangular laterally.
Pereonite 1 (Figs 1 C, 10 B) posterior tergite margin through Prn 5 anterior tergite margin delicately serrated, setose; Prn 2–5 anterolateral angles slightly projecting; Prn 2–4 posterolateral angles slightly projecting; Prn 4 lateral margin length 0.89 Prn 5 lateral margin length.
Pleotelson (Figs 1 C, 10 B, 26 B) length 0.64 width, 0.23 body length, rectangular, posterior margin straight; tergite surface smooth; with posterolateral tergal ridge between uropod insertion and posterolateral process; posterolateral processes long, 0.53 Plt length, straight, oriented posteriorly.
Antenna I (Fig. 11 B) length 0.18 body length; flagellum with 6 articles.
Antenna II (Fig. 11 A) length 0.68 body length; article 3 dorsal projection triangular, projection length 0.42 article 3 length; article 5 projection length 0.28 article 5 length; flagellum with 16 articles.
Mandible (Fig. 12 B, C) incisor with 5 cusps, left Md lacinia mobilis with 5 cusps.
Maxillipeds (Fig. 12 A) with 3 coupling hooks each.
Pereopod I (Fig. 11 C) length 0.43 body length. PII (Fig. 11 D) length 0.49 body length. PIII length 0.58 body length. PIV length 0.60 body length. PV length 0.75 body length. PVI (Fig. 11 E) length 0.81 body length. PVII length 0.79 body length; P lengths gradually increasing from PI to PVI, PVII shorter than PVI.
Pleopod I (Figs 13 A, 26 B) medial lobes subtriangular, projecting caudolaterally; separated at the apex by a narrow gap.
Pleopod II (Fig. 13 B, C) protopod semi-circular, with distal lobe extending beyond protopod distal margin; endopod stylet 1.8 protopod length.
Female. Differs from male in the following characters:
Body (Fig. 10 A) length 2.3 width; oval; anterior body length (Ceph – Prn 4) 0.99 posterior body length (Prn 5 – Plt).
Cephalothorax (Fig. 10 A, C) length 0.36 width, 0.09 body length, width 0.59 body width; frontal margin width 0.55 Ceph width.
Pereonite 4 (Fig. 10 A) lateral margin length 1.0 Prn 5 lateral margin length.
Pleotelson (Figs 10 A, 26 A) length 0.74 width, 0.24 body length, trapezoidal, posterior margin rounded, convex; posterolateral processes short, 0.34 Plt length, oriented posterolaterally.
Antenna I (Fig. 10 A) length 0.14 body length; flagellum with 4 articles.
Antenna II (Fig. 10 A) length 0.61 body length; flagellum with 13 articles.
Operculum (Fig. 26 A) length 0.93 width, 0.81 Plt length; distal margin with numerous, evenly distributed long setae; lateral margins with fewer, evenly distributed short setae.
description: Published as part of 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, pp. 813-853 in Zoosystematics and Evolution 101 (2) on pages 813-853, DOI: 10.3897/zse.101.137663