Haploniscus erebus Knauber & Riehl, 2025

Haploniscus erebus Knauber & Riehl sp. nov.

Figs 1 View Figure 1 , 10 View Figure 10 , 11 View Figure 11 , 12 View Figure 12 , 13 View Figure 13 , 26 View Figure 26

Holotype.

SKB Hap 54, adult male (stage VI), 3.3 mm, MIMB 50317 View Materials . GoogleMaps

Paratypes.

SKB Hap 49, adult female (stage IV; genome), SMF 56566 GoogleMaps ; SKB Hap 50, adult female (stage IV), 3.3 mm, MIMB 50315 GoogleMaps .

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   GoogleMaps .

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 View Figure 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 View Figure 1 , 10 B View Figure 10 ) 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 View Figure 1 , 10 B, D View Figure 10 ) 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 View Figure 1 , 10 B View Figure 10 ) 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 View Figure 1 , 10 B View Figure 10 , 26 B View Figure 26 ) 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 View Figure 11 ) length 0.18 body length; flagellum with 6 articles.

Antenna II (Fig. 11 A View Figure 11 ) 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 View Figure 12 ) incisor with 5 cusps, left Md lacinia mobilis with 5 cusps.

Maxillipeds (Fig. 12 A View Figure 12 ) with 3 coupling hooks each.

Pereopod I (Fig. 11 C View Figure 11 ) length 0.43 body length. PII (Fig. 11 D View Figure 11 ) 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 View Figure 11 ) 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 View Figure 13 , 26 B View Figure 26 ) medial lobes subtriangular, projecting caudolaterally; separated at the apex by a narrow gap.

Pleopod II (Fig. 13 B, C View Figure 13 ) 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 View Figure 10 ) length 2.3 width; oval; anterior body length (Ceph – Prn 4) 0.99 posterior body length (Prn 5 – Plt).

Cephalothorax (Fig. 10 A, C View Figure 10 ) 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 View Figure 10 ) lateral margin length 1.0 Prn 5 lateral margin length.

Pleotelson (Figs 10 A View Figure 10 , 26 A View Figure 26 ) 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 View Figure 10 ) length 0.14 body length; flagellum with 4 articles.

Antenna II (Fig. 10 A View Figure 10 ) length 0.61 body length; flagellum with 13 articles.

Operculum (Fig. 26 A View Figure 26 ) length 0.93 width, 0.81 Plt length; distal margin with numerous, evenly distributed long setae; lateral margins with fewer, evenly distributed short setae.