Haploniscus kerberos 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 kerberos

description: Haploniscus kerberos Knauber & Riehl sp. nov.
Figs 18, 19, 20, 21, 26
Holotype.
KBII Hap 136, adult male (stage VI), 3.1 mm, SMF 56418.
Paratypes.
KBII Hap 122, adult female (stage IV; genome), SMF 56405; KBII Hap 123, adult female (stage IV), 2.4 mm, SMF 56406.
Type locality.
St. SO 250–010, RV “ Sonne ”, KuramBio II expedition, EBS, 5120 m, 43°49.43'N, 151°46.96'E, Northwest Pacific, abyssal plains southeast of the Kuril-Kamchatka Trench.
Further records.
St. LV 71–10 – 06: SKB Hap 13 (manca) MIMB 50318; St. LV 71–10 – 07: SKB Hap 01 (ovigerous female) SMF 56518, SKB Hap 22 (adult male) SMF 56539, SKB Hap 37 (adult male) MIMB 50319; St. SO 250–008: KBII Hap 200 (manca) SMF 56482, KBII Hap 219 (adult female) SMF 56501, KBII Hap 229 (manca) SMF 56511; St. SO 250–010: KBII Hap 119 (adult male) SMF 56402, KBII Hap 120 (adult male) SMF 56403, KBII Hap 121 (adult female) SMF 56404, KBII Hap 135 (ovigerous female) SMF 56417, KBII Hap 228 (manca) SMF 56510; St. SO 250–065: KBII Hap 211 (manca) SMF 56493, KBII Hap 212 (manca) SMF 56494; St. SO 250–085: KBII Hap 222 (adult male) SMF 56504, KBII Hap 223 (adult male) SMF 56505, KBII Hap 224 (adult male) SMF 56506; St. SO 250–087: KBII Hap 218 (ovigerous female) SMF 56500, KBII Hap 225 (adult male) SMF 56507, KBII Hap 235 (ovigerous female) SMF 56517.
Distribution.
Northwest Pacific, abyssal regions adjacent to the Kuril-Kamchatka Trench, depth 4469–5755 m. Visualized in Fig. 27.
Etymology.
As a noun in apposition, the epithet “ kerberos ” refers to “ Kerberos ” (Ancient Greek Κέρβερος) from Greek mythology, the creature guarding the gates of the underworld. This name relates to this species’ distributional range, which, according to the available data, is limited to the abyssal plains adjacent to the hadal Kuril-Kamchatka Trench.
Synonymy.
Haploniscus KKT abyssal (see Knauber et al. 2022).
Diagnosis.
Haploniscus kerberos sp. nov. is highly similar to H. hades sp. nov. in also possessing the characteristic Plt shape with posterolateral tergal ridges terminating on the posterolateral processes and the posterior margin tergal plates projecting above the uropods. It differs from its sister species in the following characters: rostrum basally without dorsal bulge in males (basally with dorsal bulge in H. hades sp. nov.) and AII article 3 dorsal projection triangular (hook-shaped in H. hades sp. nov.).
Molecular diagnosis.
differing in the 16 S gene from other species of the belyaevi - complex in the nucleotides G (position 173 of the alignment) and G (228), as well as the nucleotides T (61), C (91), C (298), G (346), G (430), G (607), T (625), and G (649) of the COI gene.
Description.
Male. Body (Fig. 18 B) length 2.5 width; oval; anterior body length (Ceph – Prn 4) 1.1 posterior body length (Prn 5 – Plt); lateral margin continuous.
Cephalothorax (Fig. 18 B, D) length 0.35 width, 0.08 body length, width 0.59 body width; frontal margin width 0.54 Ceph width; rostrum curved upwards.
Pereonite 1 (Fig. 18 B) posterior tergite margin through Prn 5 anterior tergite margin delicately serrated, setose; Prn 2–4 anterolateral angles slightly projecting; Prn 2–4 posterolateral angles slightly projecting; Prn 4 lateral margin length 0.92 Prn 5 lateral margin length; Prn 5 anterolateral angle not projecting, rectangular.
Pleotelson (Figs 18 B, 26 D) length 0.68 width, 0.22 body length, trapezoidal, posterior margin concave; tergite surface tuberculate, less distinct than in remaining body; with posterolateral tergal ridge on posterolateral process and posterior margin tergal plates projecting above uropods; posterolateral processes minute, 0.09 Plt length, straight, oriented posteriorly.
Antenna I (Fig. 19 B) length 0.20 body length; flagellum with 6 articles.
Antenna II (Fig. 19 A) length 0.77 body length; article 3 dorsal projection triangular, projection length 0.31 article 3 length; article 5 projection length 0.22 article 5 length; flagellum with 16 articles.
Mandible (Fig. 20 B, C) incisor with 5 cusps, left Md lacinia mobilis with 4 cusps.
Maxillipeds (Fig. 20 A) with 3 coupling hooks each.
Pereopod I (Fig. 19 D) length 0.43 body length. PVI (Fig. 19 C) length 0.70 body length; P lengths gradually increasing from PI to PVI, PVII shorter than PVI.
Pleopod I missing.
Pleopod II (Fig. 21 A, B) protopod elongated, suboval; endopod stylet 2.0 protopod length.
Female. Differs from male in the following characters:
Body (Fig. 18 A) length 2.7 width; anterior body length (Ceph – Prn 4) 0.94 posterior body length (Prn 5 – Plt).
Cephalothorax (Fig. 18 A, C) length 0.50 width, 0.12 body length, width 0.66 body width; frontal margin width 0.55 Ceph width.
Pereonite 4 (Fig. 18 A) lateral margin length 0.80 Prn 5 lateral margin length.
Pleotelson (Figs 18 A, 26 C) length 0.84 width, 0.24 body length, posterior margin rounded, convex; with posterolateral tergal ridge between uropod insertion and posterolateral process; posterolateral processes short, 0.23 Plt length.
Antenna I (Fig. 18 A) length 0.14 body length; flagellum with 4 articles.
Antenna II (Fig. 18 A) length 0.67 body length; flagellum with 12 articles.
Operculum (Fig. 26 C) length 1.1 width, 0.75 Plt length; distal margin with numerous, evenly distributed long setae; lateral margins with 2 short setae each.
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