Neopleustes schwentneri, Lörz & Tandberg, 2025

Lörz, Anne-Nina & Tandberg, Anne Helene S., 2025, North Atlantic Pleustidae (Crustacea, Amphipoda) with a focus on cold-water coral associations, European Journal of Taxonomy 1009, pp. 1-50 : 7-23

Neopleustes schwentneri sp. nov.

urn:lsid:zoobank.org:act:EC3471B1-C6EA-4222-83C8-2789A9E0BAA7

Figs 1A–C , 4–16

Neopleustes aff. boecki Schwentner & Lörz, 2021: 7 , fig. 3, tab. 1.

Diagnosis

Based on the female holotype, 8.2 mm, SMF 62626.

Body, pereon segments 1–3 without carination, strongly carinated posteriorly from segment 6 to pleon segment 2, pleon segment 3 with sloping low ridge dorsally.

Etymology

This species is named in honour of Dr. Martin Schwentner, a great crustacean researcher and friend. The name is derived of the Latin genitive of his surname.

Type material

Holotype

ICELAND – off Reykjanes • ♀ adult, 8.2 mm, ethanol fixed; Reykjanes Ridge; 59.25°N, 30.484383 °W; depth 866 m; 17 Jul. 2018; MSM 75, IceAGE-RR exped., station 80-11; collected by ROV KIEL6000, from Plexauridae / Paramuricea ; SMF 62626.

Paratype ICELAND – off Reykjanes • 1 ♂ adult, 11 mm, glycerin fixed; Reykjanes Ridge; 59.25123°N, 30.485016°W; depth 867 m; 28 Jul. 2018; MSM75 , IceAGE-RR exped., station 149-6; collected by ROV KIEL6000, from Plexauridae ; SMF 62627.

Additional material

ICELAND – off Reykjanes • 6 specs., SEM-stubs; same data as for holotype; DZMB 61786 b-e, 62804e, 62850 • 1 adult; same data as for holotype; DZMB-HH 62367 . • 1 spec.; Reykjanes Ridge; 60.23661°N, 29.13605°W; depth 646 m; 1 Aug. 2018; MSM75 , IceAGE-RR exped., station 188-4; collected by ROV KIEL6000; DZMB-HH 61712 . • 1 ♀ adult, oovigerous; Reykjanes Ridge; 60.23741°N, 29.114833°W; depth 644 m; 1 Aug. 2018; MSM75 , IceAGE-RR exped., station 188-6; collected by ROV KIEL6000; DZMB-HH 61725 • 1 adult; Reykjanes Ridge; 59.25123°N, 30.485016°W; depth 867 m; 28 Jul. 2018; MSM75 , IceAGE-RR exped., station 149-6; collected by ROV KIEL6000; ZMH-K 60035 • 1 adult; Reykjanes Ridge; same data as for paratype; ZMH-K 60036 • 9 adults; Reykjanes Ridge; same data as for paratype; ZMH-K 58755 • 1 adult; Reykjanes Ridge; same data as for paratype; ZMH-K 58756 .

For a full overview of the examined material (36 further specimens), see Supplementary file 2. See Schwentner & Lörz (2021) under “ Neopleustes aff. boecki ” for the genetic analyses on this species.

Description

Head with anterodorsal crest. Rostrum medium length, about 0.25 times as long as peduncular segment 1 of antenna 1, apex acute; anterior head lobe rounded, lateral cephalic lobe very deeply recessed sinus, anteroventral corner acute.

Eye large, reniform, pigmented. Antenna 1 very long, longer than body; peduncular segment 1 elongate and strong, equal to segments 2 and 3 together; flagellum length a little over 4 times as long as peduncle, with approximately 90 articles, articles posterodistally with short setae. Antenna 2 is half as long as antenna 1, flagellum with 43 articles.

Mandible, molar rounded and setose, incisor margins with 7 small teeth and two larger on the outer part of the margin; left lacinia mobilis 10-dentate, present on the left side only; accessory spine rows with 13 raker setae; palp very large; palp segment 3 flat, subequal in length to segment 2, inner margin lined with strong pectinate setae, apex with 3 long strong pectinate setae; segment 2, inner margin with few setae only; segment 1 without setae, 1/3 of length of either of the other segments. Lower lip, outer lobes angular, widely spread. Maxilla 1, inner plate with single plumose apical seta, outer plate with 9 slender pectinate setae (spine-like setae); palp extending beyond outer plate, apex subtruncate, with a row of 7 cuspidate setae. Maxilla 2, inner plate slightly shorter and broader than outer plate; both plates with smooth apical seta. Maxilliped, inner plate very short, apex subtruncate; outer plate short, slightly longer than first palp segment, apex narrowly subtruncate; palp narrow, segment 2 subequal in length to segment 3; dactylus slender, slightly curved and slightly shorter than palp segment 3, the distal process of palp segment 3 is strongly present and densely setose on the inner side.

Coxal plates 1–3 posteroventrally multi-cuspate, lower margins rounded; coxal plate 4 much broader, deeply excavated posteroproximally, rounded below; coxal plates 5–6 broadly posterolobate, posteriorly roundly subquadrate, coxal plate 7 trapezoidal, rounded anteroventrally.

Gnathopods 1–2 subchelate, similar in shape. Gnathopod 1, basis with anterior setae, carpus long, about three quarter as long as propodus, posterior lobe broad, shallow; propodus subrectangular, narrow, palm oblique, with small mid-palmar tooth, with clusters of spine-like setae, posterior margin with groups of setae; dactylus as long as palm, with an unguis, inner margin with minuscle setae.

Gnathopod 2, carpus long, about 0.7 times as long as propodus, carpal lobe similar to gnathopod 1; propodus palm oblique, palmar margin with medial tooth and with clusters of strong posterodistal setae, posterior margin with transversal setae clusters; dactylus as long as palm, with an unguis.

Pereopods 3–4 medium strong; basis linear, dactylus slender, 0.3 times as long as propodus. Pereopods 5–7 similar in form, size increasing; all bases bearing ridge, with posterior rounded wing; merus posterodistally produced, acute, anterior and anterior margins with strong setae. Merus: carpus: dactylus is about 3:2:3; dactylus half the length of propodus.

Epimeral plates 1–3, lower margin with short spine-like setae, posteroventral corners acute, slightly produced, posterior margin minutely serrated. Pleopods regular.

Uropod 1, peduncle slightly shorter than inner ramus; margins of peduncle and rami with short spine-like setae. Uropod 2, peduncle three quarter length of inner rami, outer ramus three quarter length of inner rami, margins of peduncle and rami with short spine-like setae. Uropod 3, inner ramus twice as long as peduncle, with a row of small spine-shaped setae along lateral and medial margins each, with acute and naked apex; outer ramus about half as long as inner; outer ramus with a row small spine-shaped setae along lateral and medial margins each.

Telson linguiform, apically rounded, length about 1.5 × width, with proximal ventral keel, with lateral subapical short setae.

Ecology

Neopleustes schwentneri sp. nov. was collected from the corals Paramuricea sp. and Paragorgia arborea (Linnaeus 1758) . Collected in July, several females had eggs.

Distribution

Reykjanes Ridge, south of Iceland, depth 644– 992 m.

Taxonomic remarks

There is a high variability in the dorsal carination. While the specimens belong to the same genetic haplotype, there are two morphotypes in respect of the sculpturing of pereonites and pleonites. Morphotype A is more robust, extensions start on pereonite 4 ( Fig. 8 ), whereas morphotype B is smoother, the carinae starts on pereonite 7 ( Fig. 13 ). Both morphotypes occur sympatrically, on the same coral. SEM photos of morphotype A are Figs 8–12 , for morphotype B Figs 13–16 .

Neopleustes schwentneri sp. nov. is generally morphologically closest to N. boecki ( Hansen, 1888) . The main morphological differences between N. schwentneri and N. boecki are summarized in Table 2.

Genbank numbers for N. schwentneri sp. nov., as listed in Schwentner & Lörz (2021) as Neopleustis aff boecki are: MT317424 , MT317425 , MT317427 , MT317428 , MT317432 – MT317452 . Additional samples with Bold accession-numbers: AMPIV 316-22; AMPIV 317-22; AMPIV 319-22; AMPIV 303- 22; AMPIV 310-22; 311-22; for details see Supp. file 2.

Figures

Fig. 1. Photos of live animals. A. Neopleustes schwentneri sp. nov., DZMB-HH 61725. B. N. schwentneri sp. nov., DZMB-HH 62367. C. N. schwentneri sp. nov., DZMB-HH 61712. D. Stenopleustes jeskulkeae sp. nov., holotype, DZMB-HH 62317. E. Stenopleustes jeskulkeae sp. nov., DZMN-HH 62368. F. S. jeskulkeae sp. nov., DZMN-HH 61711. Scale bars = 2 mm. Photos: A.H.S. Tandberg.

Fig. 4. Neopleustes schwentneri sp. nov., paratype, SMF 62627. A. Habitus. B. Coxae 1–3. C. Pereopod 1. D. Uropods 1–3. Scale bars: A = 1 mm, B–D = 0.5 mm.

Fig. 5. Neopleustes schwentneri sp. nov., holotype, SMF 62626. A. Habitus. B. Pereopod 1. Scale bars: A = 1 mm, B = 0.5 mm.

Fig. 6. Neopleustes schwentneri sp. nov., holotype, SMF 62626. A. Maxilla 1. B. Antenna 1. C. Antenna 2. D. Maxilla 1. E. Maxilla 2. F. Labium. G. Mandible. H. Maxilliped. Scale bars = 0.5 mm (shared scale bars for A, D, E–G; for B–C, separate for H.).

Fig. 7. Neopleustes schwentneri sp. nov., holotype, SMF 62626. A. Pereopod 5. B. Pereopod 6. C. Pereopod 7. D. Telson tip (no representative scale bar). E. Telson, Uropod 3. F. Uropod 2. G. Uropod 1. Scale bars = 0.5 mm.

Fig. 8. Neopleustes schwentneri sp. nov., DZMB 62804e (A–C), DZMB 62850 (D–F). A. Habitus. B. Urosome. C. Head. D. Epimeron and urosome, dorsal view. E. Epimeron. F. Epimeral plate 2.

Fig. 9. Neopleustes schwentneri sp. nov., DZMB 62804e (A–E), DZMB 62850 (F). A. Urosome, dorsal view. B. Telson. C. Telson setation. D. Telson, seta at tip. E. Telson, ‘swan-neck’ setae. F. Uropods 2–3 (peduncles).

Fig. 10. Neopleustes schwentneri sp. nov., DZMB 62804e (A–B), DZMB 62850 (C–F). A. Mandible. B. Mandible palp tip. C. Mandible. D. Mandible palp tip. E. Mandible incisor. F. Mandible incisor, closeup.

Fig. 11. Neopleustes schwentneri sp. nov., DZMB 62804e (A–B), DZMB 62850 (C–F). A. Maxilliped, ventral view. B. Maxilliped, closeup inner plate, ventral view. C. Maxilliped, right side, ‘upside’ view. D. Maxilliped, left side, ventral view. E. Maxilliped, right inner plate. F. Maxilliped, left dactylus.

Fig. 12. Neopleustes schwentneri sp. nov., DZMB 62804e (A–B), DZMB 62850 (C–F). A. Pereopod 1. B. Pereopod 1, propodus palm and dactylus. C. Pereopod 2. D. Pereopod 2, propodus palm and dactylus, closeup. E. Pereopod 2. F. Pereopod 2, closeup palmar setae.

Fig. 13. Neopleustes schwentneri sp. nov., DZMB 61786b (A–B), DZMB 61786e (C), 61786b (D, F), 61786d (E). A. Habitus. B. Epimeron. C. Head, dorsal view. D. Head, lateral view. E. Antenna 1, tip. F. Coxa 2, serrations.

Fig. 14. Neopleustes schwentneri sp. nov., DZMB 61786e (A, C, F), DZMB 61786c (B, D), DZMB 61786d (E). A. maxilliped. B. Maxilliped palp. C. Maxilliped palp dactylus. D. Maxilliped palp propodus. E. Pereopod 1. F. Pereopod 2.

Fig. 15. Neopleustes schwentneri sp. nov., DZMB 61786e (A, C–F), DZMB 61786c (B). A. Mandible. B. Mandible palp. C. Mandible incisor. D. Mandible palp article 3 tip. E. Mandible raker setae. F. Maxilla 1.

Fig. 16. Neopleustes schwentneri sp. nov., DZMB 61786d (A–B, D–F), DZMB 61786c (C). A. Urosome. B. Telson. C. Uropod 2, outer ramus. D. Telson, setae. E. Epimeron, dorsal keel. F. Telson, ‘swan-neck’ setae.