Haploniscus belyaevi Birstein 1963
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 belyaevi

description: Haploniscus belyaevi Birstein, 1963
Figs 1, 2, 3, 4, 5, 26
Neotype.
SKB Hap 46, adult male (stage VI), 3.4 mm, MIMB 50300.
Paraneotypes.
SKB Hap 04, adult female (stage IV; genome), SMF 56521; SKB Hap 24, adult female (stage IV), 3.2 mm, MIMB 50294; SKB Hap 06, adult male (stage VI), 3.6 mm, SMF 56523.
Type material.
As pointed out by Knauber et al. (2022), the original male syntype of H. belyaevi as depicted in the original species description was lost. Instead, the species’ type material is lumped together with additional material of Haploniscus menziesi Birstein, 1963. Most specimens are in poor condition, lacking either the distal AII with the characteristic spine on the fifth peduncular article or the pleotelson, rendering identification beyond genus level difficult. Three specimens can be identified as members of the belyaevi - complex, yet, as all of them are (ovigerous) female stages, allocation to one of the herein described member species of the belyaevi - complex remains uncertain. The type material is missing associated information about the sampling locality, and as the original description by Birstein does not define a type locality, H. belyaevi does not possess a definite type locality.
Based on I) the lack of a definite type locality, II) the presence of multiple haploniscid species in the type material of H. belyaevi, III) the absence of the original male syntype, and IV) uncertainty about where the material at hand stems from and whether it represents the type material, H. belyaevi is considered a nomen dubium. In an attempt to resolve the taxonomic identity of H. belyaevi, the species is therefore defined by the illustrations depicted in the original description by Birstein (1963), and a male neotype alongside additional paratypes were assigned from recent material of the SokhoBio expedition (compare H. SO - KIR from Knauber et al. 2022), which exhibit a strong morphological resemblance to H. belyaevi as featured in the original description. This goes alongside the designation of a type locality, which is in the vicinity of a “ Vityaz ” station, where H. belyaevi was historically sampled.
Type locality.
LV 71–09 – 07, RV “ Akademik M. A. Lavrentyev ”, SokhoBio expedition, EBS, 3374 m, 46°12.2'N, 152°03.1'E, Northwest Pacific, abyssal branch of the Kuril-Kamchatka Trench into the Bussol Strait.
Further records.
St. LV 71–01 – 08: SKB Hap 25 (manca) MIMB 50295; St. LV 71–04 – 09: SKB Hap 39 (manca) SMF 56556, SKB Hap 42 (manca) MIMB 50297, SKB Hap 43 (manca) MIMB 50298, SKB Hap 60 (adult female) MIMB 50305, SKB Hap 61 (adult female) MIMB 50306; St. LV 71–04 – 10: SKB Hap 07 (adult male) SMF 56524, SKB Hap 17 (adult female) SMF 56534, SKB Hap 38 (manca) SMF 56555; St. LV 71–07 – 03: SKB Hap 12 (manca) SMF 56529, SKB Hap 19 (adult male) SMF 56536, SKB Hap 20 (manca) MIMB 50293, SKB Hap 56 (adult male) MIMB 50302, SKB Hap 57 (adult female) SMF 56574, SKB Hap 58 (adult male) MIMB 50303, SKB Hap 59 (adult male) MIMB 50304; St. LV 71–07 – 04: SKB Hap 03 (adult female) MIMB 50292, SKB Hap 40 (adult female) MIMB 50296, SKB Hap 41 (adult female) SMF 56558, SKB Hap 44 (manca) MIMB 50299, SKB Hap 45 (manca) SMF 56562; St. LV 71–09 – 06: SKB Hap 15 (manca) SMF 56532, SKB Hap 23 (adult female) SMF 56540; St. LV 71–09 – 07: SKB Hap 05 (adult male) SMF 56522, SKB Hap 16 (manca) SMF 56533, SKB Hap 32 (adult male) SMF 56549, SKB Hap 33 (manca) SMF 56550, SKB Hap 47 (adult male) MIMB 50301.
Distribution.
Northwest Pacific, Sea of Okhotsk, Kuril Basin, and abyssal regions to the northwest of the Kuril-Kamchatka Trench, depth 3299–3386 m. Given its occurrence on both sides of the Kuril Island Ridge, it might be possible that this species’ lowest bathymetric limit might lie even shallower, as it most likely dispersed across the Bussol Strait in one or other direction with a maximum depth of 2,350 m. The original species description of H. belyaevi depicts a distributional range extending far into the KKT area, yet despite sampling these areas during the above-mentioned expeditions, H. belyaevi was solely recorded in the vicinity of the Bussol Strait. One can therefore only hypothesize that Birstein, potentially due to limited material, lumped the distributional patterns of multiple belyaevi - complex members together, not realizing that he was dealing with multiple species. Visualized in Fig. 27.
Synonymy.
Haploniscus SO - KIR (see Knauber et al. 2022).
Diagnosis.
The species differs from other members of the belyaevi - complex in the following characters: rostrum curved upwards, anteriorly flat; Prn 1 anterior tergite margin delicately serrated, setose; Prn 1 anterolateral angles with minute acute projection; posterolateral processes short, more than 0.10 Plt length, curved in males, oriented posteriorly.
Molecular diagnosis.
Differing in the 16 S gene from other species of the belyaevi - complex in the nucleotide C (position 249 of the alignment) as well as the nucleotides G (199), C (334), T (376), C (409), A (412), and G (592) of the COI gene.
Description.
Male. Body (Figs 1 B, 2 B) length 2.3 width; subrectangular; anterior body length (Ceph – Prn 4) 1.0 posterior body length (Prn 5 – Plt); lateral margin interrupted between Prn 7 and Plt, otherwise continuous.
Cephalothorax (Figs 1 B, 2 B, D) length 0.38 width, 0.10 body length, width 0.58 body width; frontal margin width 0.50 Ceph width; rostrum curved upwards, frontally plane.
Pereonite 1 (Figs 1 B, 2 B) anterior tergite margin through Prn 5 anterior tergite margin delicately serrated, setose; Prn 1–5 anterolateral angles slightly projecting; Prn 1–4 posterolateral angles slightly projecting; Prn 4 lateral margin length 1.04 Prn 5 lateral margin length.
Pleotelson (Figs 1 B, 2 B, 26 H) length 0.74 width, 0.25 body length, rectangular, posterior margin rounded, convex; tergite surface smooth; with posterolateral tergal ridge between uropod insertion and posterolateral process; posterolateral processes short, 0.31 Plt length, curved, oriented posteriorly.
Antenna I (Fig. 3 B) length 0.17 body length; flagellum with 5 articles.
Antenna II (Fig. 3 A) length 0.31 body length (without missing peduncular article 6 and flagellum); article 3 dorsal projection triangular, projection length 0.30 article 3 length; article 5 projection length 0.28 article 5 length; flagellum with 17 articles (inferred from male paratype).
Mandible (Fig. 4 B, C) incisor with 5 cusps, left Md lacinia mobilis with 4 cusps.
Maxillipeds (Fig. 4 A) with 3 coupling hooks each.
Pereopod I (Fig. 3 C) length 0.40 body length. PII (Fig. 3 D) length 0.49 body length. PIII length 0.53 body length. PIV length 0.53 body length. PV length 0.64 body length. PVI (Fig. 3 E) length 0.71 body length; P lengths gradually increasing from PI to PVI, PVII shorter than PVI.
Pleopod I (Figs 5 A, 26 H) medial lobes subtriangular, projecting caudolaterally; separated at the apex by a narrow gap.
Pleopod II (Fig. 5 B, C) protopod semi-circular, with distal lobe extending beyond protopod distal margin; endopod stylet 1.6 protopod length.
Female. Differs from male in the following characters:
Body (Fig. 2 A) length 2.3 width; oval; anterior body length (Ceph – Prn 4) 0.95 posterior body length (Prn 5 – Plt).
Cephalothorax (Fig. 2 A, C) length 0.48 width, 0.13 body length, width 0.60 body width; frontal margin width 0.47 Ceph width.
Pereonite (Fig. 2 A) 4 lateral margin length 1.05 Prn 5 lateral margin length.
Pleotelson (Figs 2 A, 26 G) length 0.83 width, 0.27 body length, trapezoidal; posterolateral processes 0.20 Plt length, straight.
Antenna I (Fig. 2 A) length 0.16 body length; flagellum with 4 articles.
Antenna II (Fig. 2 A) length 0.57 body length; flagellum with 12 articles.
Operculum (Fig. 26 G) Length 1.0 width, 0.77 Plt length; distal margin with numerous, evenly distributed long 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