Eperopeus vermiculatus sp. nov.

Figs 1, 2, 3, 4, 5

Type material.

Holotype: Pacific • female (with setose oostegites), 3.6 mm (13 slides); Clarion-Clipperton Zone; 10.3773°N, 117.1558°W; depth 4302 m; 14 / 05 / 2021; NORI-D contract area, RV Maersk Launcher, Cruise C 5 D, Station STM_168, Box Core BC_395; NHMUK 2025.28 (Specimen 7249_TH_AMP_1), 16 S (PV 075086). Paratypes: Pacific • female (without oostegites), 2.9 mm; Clarion-Clipperton Zone; 10.8397°N, 116.1504°W; depth 4132 m; 25 / 05 / 2021; NORI-D contract area, RV Maersk Launcher, Cruise C 5 D, Station SPR_160, Box Core BC_412; NHMUK 2025.29 (Specimen 8233_TH_AMP_1) • female (with setose oostegites), 4.1 mm; Clarion-Clipperton Zone; 10.3315°N, 117.1872°W; depth 4284 m; 28 / 05 / 2021; NORI-D contract area, RV Maersk Launcher, Cruise 5 D, Station STM_195, Box Core BC_415; NHMUK 2025.30 (Specimen 8571_TH_AMP2), 16 S (PV 075086), 28 S (PV 075089) • female (without oostegites), 2.9 mm; Clarion-Clipperton Zone; 10.3559°N, 117.1688°W; depth 4277 m; 11 / 11 / 2020; NORI-D contract area, RV Maersk Launcher, Cruise 5 A, Station STM_010, Box Core BC_355; NHMUK 2025.31 (specimen 8803 _ TH _ AMP 1) • Male (with expanded callynophore), 4.3 mm; Clarion-Clipperton Zone; 10.3336°N, 117.186°W; depth 4279 m; 02 / 12 / 2022; NORI-D contract area, MV Island Pride, Cruise 7 B, Station TF_007 _ 01, Box Core BC_478; NHMUK 2025.32 (specimen 10333_TH_AMP_1), COI (PV 077102), 16 S (PV 075087), 28 S (PV 075090), H 3 (PV 078005).

Other material.

Pacific • female, 4.0 mm; Clarion-Clipperton Zone; 10.3773°N, 117.1558°W; depth 4302 m; 14 / 05 / 2021; NORI-D contract area, RV Maersk Launcher, Cruise C 5 D, Station STM_168, Box Core BC_395; DISCOLL -TMC-AMP-7251-a (specimen 7251_TH_AMP 1) • female (no obvious oostegites), 2.3 mm; Clarion-Clipperton Zone; 10.3553°N, 117.169°W; depth 4274; 09 / 09 / 2022; NORI-D contract area, MV Island Pride, Cruise 7 A, STM_010, Box Core BC_337; DISCOLL -TMC-AMP-9393-a (specimen 9393_TH_AMP_1) • female, 3.1 mm; Clarion-Clipperton Zone; 10.3281°N, 117.1817°W; depth 4286 m; 24 / 11 / 2023; NORI-D contract area, MV Coco, Cruise 8 A, Station IM 013 _ BCR 2, Box Core BC 487; DISCOLL -TMC-AMP-12535-a (specimen 12535_TH_AMP_1), COI (PV 077103), 16 S (PV 075088) • female (with oostegites), 4.5 mm; Clarion-Clipperton Zone; 10.3541°N, 117.2424°W; depth 4290 m; 13 / 12 / 2023; NORI-D contract area, MV Coco, Cruise 8 A, Station IM 003 _ BC, Box Core BC 501; CMNC 2025-0001 (specimen 12548_TH_AMP_3) • male; not measured, Clarion-Clipperton Zone; 11.892°N, 117.489°W; depth 4193–4256 m; 10 / 05 / 2016; BGR contract area, RV Kilo Moana, Cruise MANGAN 16, Station SO 262-96, Epibenthic Sledge; DSB_3704, COI (PQ 734521).

Type locality.

Abyssal Pacific Ocean, Clarion-Clipperton Zone, 10.3773°N, 117.1558°W; depth 4302 m.

Diagnosis.

Gnathopod dactyls inner margin lacking teeth; gnathopod 2 carpus narrower than that of gnathopod 1; pereopods 3–4 dactyls short, length 0.8–0.9 × respective propodus; pereopods 5–6 dactyls length 1.2 × propodus; mandibular palp article 1 elongated, 0.9 × length of article 2; maxilla 1 palp article 2 widened; uropod 1 rami length 0.8 × peduncle; telson longer than wide, bluntly rounded distally, length 1.1 × width.

Description.

Based on holotype female with setose oostegites, 3.6 mm, NHMUK 2025.28.

Body (Figs 1, 2): vermiform, pereonites and pleonites subequal or longer than deep. Pleonite 1, 2 (Fig. 2) smooth, lacking dorsal teeth. Urosomite 1 (Fig. 2) smooth, lacking dorsal teeth. Epimeron 1 (Fig. 2) with a rounded posterodistal corner and a small seta. Epimeron 2, 3 (Fig. 2) subquadrate, anterodistal corner broadly rounded, distal margin convex, posterodistal corner not produced, posterior margin straight. Coxae 1 – 7 (Fig. 2) reduced and shallow, much shorter than corresponding pereonites.

Head (Fig. 2): shorter in length than pereonites 1–2 combined; rostrum not obvious. Lateral cephalic lobe broadly triangular. Eye not apparent in preserved specimens. Antenna 1 very short, length 0.17 × body, geniculate; peduncular article 1 length 1.8 × width, angled on lateral margin so inner margin is longer; peduncular articles 2–3 short, length less than peduncle 1; flagellum five-articulate, first article of flagellum not callynophorate, each article with a large aesthetasc; accessory flagellum short, two-articulate, first article slightly broader. Antenna 2 slightly longer than antenna 1, gland cone small; peduncular articles 4–5 subequal, very weakly spinose and setose; flagellum five-articulate.

Mouthparts (Figs 2, 3): Epistome (Fig. 2) level with and scarcely differentiated from upper lip. Mandible (Fig. 3) incisor weakly dentate; left lacinia mobilis three-dentate; accessory spine row with four setae; molar absent; palp strong, article 1 elongate, length 2.36 × width and 0.9 × length of article 2, article 2 slightly shorter than article 3, not expanded, with one distal seta, article 3 cylindrical, subacute distally, with four strong setae; right mandible incisor four-dentate, teeth large, accessory spine row with one spine and fine setae. Lower lip (Fig. 3) outer lobe broad, mandibular lobe narrow. Maxilla 1 (Fig. 3) inner plate missing; outer plate with four strong teeth; palp two-articulate, article 2 strongly widened distally, with six nodular setae. Maxilla 2 (Fig. 3) slightly reduced, inner plate slightly shorter and broader than outer, tapering distally, both with long pappose apical setae. Maxilliped (Fig. 3) inner plate reduced, distal margin with two long setae; outer plate subovate, reaching distomedial end of palp article 1, with two apical and three medial setae, medial margin straight; palp short, weakly setose medially, articles 1–2 slightly expanded, article 3 narrow, article 4 long, length 0.8 × article 3.

Pereon (Figs 2, 4): Gnathopod 1 (Fig. 2) carposubchelate; coxa narrow, length 2.5 × width, anterodorsal corner rounded, posterior margin nearly straight, distal margin straight; basis short, strongly expanded, length 1.3 × width; ischium shorter than merus; carpus broad, length 1.6 × width, posterior margin with five strong pectinate setae; propodus narrow and curved, length 0.64 × carpus, posterior margin with two strong pectinate setae, lacking palm; dactylus narrow, inner margin lacking teeth. Gnathopod 2 (Fig. 2) carposubchelate; coxa subrectangular, length 1.7 × width, anterodorsal corner rounded, posterior margin convex, distal margin straight; basis short, expanded, length 2.1 × width: ischium shorter than merus; remaining articles as in gnathopod 1 except carpus narrower, length 2.4 × width. Pereopod 3 (Fig. 4) coxa crescent-shaped, shallow, length 2.3 × width, ventral margin convex; merus widening distally, triangular, slightly shorter than carpus; carpus dilated, ovate, posterior margin with two long pectinate setae; propodus subequal in length to carpus, anterodistal corner acute; dactylus straight, length 0.8 × propodus. Pereopod 4 (Fig. 4) similar to pereopod 3 except coxa longer; merus slightly narrower; carpus narrow and dactylus longer, length 0.9 × propodus. Pereopod 5 (Fig. 4) coxa narrow, length twice width, anterodistal and posterodistal margins rounded; basis narrow, length 3.2 × width, anterior and posterior margins slightly convex; merus length 0.7 × carpus-propodus; carpus, posterodistal corner with two spines; propodus narrow, longer than carpus, posterodistal corner acute with spine; dactylus straight, length 1.2 × propodus. Pereopod 6 (Fig. 4) coxa narrowly ovate, length 2.9 × width; basis narrow, length 3 × width, anterior margin strongly convex, posterior margin slightly concave; rest of pereopod articles as in pereopod 5. Pereopod 7 (Fig. 4) long, length 1.3 × pereopod 5–6; coxa small, narrowing posteriorly, margins round; basis narrow, length 2.8 × width, anterior margin convex proximally, posterior margin straight; merus slightly shorter than carpus, with one posterodistal spine; carpus long, anterior margin with two spines, posterodistal corner with one spine; propodus long, length 1.2 × carpus, with two spines; dactylus partially missing.

Urosome: Uropod 1 (Fig. 5) peduncle length 1.36 × rami, dorsolateral corner with three or four small spines; rami lanceolate, equal in length, lacking spines. Uropod 2 (Fig. 5) Peduncle subequal in length to outer ramus, dorsomedial margin with one strong spine and seven very small spines; rami lanceolate, inner ramus longer than peduncle and outer ramus, margins microsetose, both lacking spines. Uropod 3 (Fig. 5) Peduncle short, length 0.65 × biarticulate outer ramus; outer ramus cylindrical, second article short, 0.26 × length of article 1; inner ramus slightly shorter than outer, strongly tapering with margin microsetose, with one apical seta. Telson (Fig. 5): Short, entire, length 1.1 × width, lateral margins with one submarginal seta, distal margin bluntly rounded, straight.

Oostegites (Fig. 4): present on pereopods 3–5, short, subrectangular with two or three medium length apical brood setae.

Gills (Fig. 4): present on pereopods 3–6. Subovate to cylindrical, shorter than basis.

Male: as for female except Antenna 1 (Fig. 2): peduncular article 1 length 2.2 × width; callynophore present. Accessory flagellum with a single flattened, broad, scale-like article, distal articles not apparent.

Etymology.

The species name, vermiculatus, is from the Latin, meaning “ like worms ” or “ of worms ”. It was chosen to honour both the vermiform morphology of this new amphipod, and in recognition of the World Register of Marine Species (WoRMS 2025), a wonderful resource for all marine taxonomists.

Remarks.

This is the second species of Eperopeus described and the first record of this rarely reported genus from the Pacific Ocean. A list of differences between the two species is provided in Table 2. These differences are minor but allow for the separation of the two species (for which a key is also provided).

Molecular identification.

The species has received a Barcode Index Number from Barcode of Life Data Systems: BOLD: AEB 4130 (https://doi.org/10.5883/BOLD:AEB4130).

Distribution.

Abyssal Pacific Ocean, Clarion-Clipperton Zone, 4132–4302 m.