Niphargus luxemburgensis Weber, Weigand & Brad 2025, sp. nov.

Niphargus luxemburgensis Weber, Weigand & Brad sp. nov. urn:lsid:zoobank.org:act: 1522BA40-BBC2-44B7-9E92-D0AE85085217 Figs 3–11 Diagnosis Medium-sized Niphargus species, poorly setose. Right posteroventral angle of epimeral plates. Outer 6 spines of maxilla I on outer lobe with 1 tooth each; 1 spine with several smaller teeth. Mandibular palp with small number (1–2) of B setae. Gnathopods with 1 seta along outer margin of dactylopodites. Pereiopod VII, the longest leg, almost half of total body length. Pleopods retinaculum with 2 hooks. Uropod I, longer exopodite. Uropod II, longer endopodite. Uropod III sexually dimorphic, exopodite elongated in males. Telson with 3 apical spines on each lobe. The COI marker shows two pure diagnostic sites at positions 55 (C) and 358 (C). Six 28S rDNA alleles are diagnostic (with 13 heterozygous specimens) as well as 79 COI barcodes. Etymology The species name derives from the Grand Duchy of Luxembourg, where it was first discovered. In Weber et al. (2023), this species was treated as N. aquilex F, F’. Material examined Holotype LUXEMBOURG • ♂; Girst, Gutland, basin of a spring in the center of the hamlet of Girsterklaus; 49.7847° N, 6.4989° E; 19 Mar. 2018; Dieter Weber leg.; kept intact in 96% ethanol; 180319-10; MNHNL130574. Paratypes LUXEMBOURG • 1 ♂; same collection data as for holotype; 30 Jan. 2018; dissected and appendages drawn; 180130-32; ISER microscope slide DW180130-32 • 1 ♀; same collection data as for preceding; dissected and appendages drawn; 180130-45; ISER microscope slide DW180130-45 • 1 ♂; same collection data as for holotype; 27 Mar. 2017; ISER DW170327-02 • 1 ♀; same collection data as for holotype; 19 Mar. 2018; ISER DW180319-09 • 1 ♀; same collection data as for holotype; 19 Mar. 2018; ISER DW180319-13 • 1 ♀; same collection data as for holotype; 27 Mar. 2017; ISER DW 170327-06; MNHNL130575. Molecular data COI and 28S rDNA sequences of specimens belonging to Niphargus luxemburgensis sp. nov. were deposited in GenBank. COI and 28S rRNA accession numbers are present in Supp. file 6 and Supp. file 9, respectively. Description (male paratype ISER DW 180130-32) Measurements Total body length 7.7 mm (Fig. 3). Head Head (Fig. 3) 8.60% of total body length. Eyes and rostrum absent. Antennae Antenna I (Fig. 4A): with the main flagellum formed of 18 articles representing 41% of total body length. Peduncle length ⅓ of total length of antenna I. The accessory flagellum (Fig. 4B) biarticulated; proximal article slightly longer than first article of main flagellum; distal article ¼ of total length of accessory flagellum, with 2 apical setae of different lengths and 1 aesthetasc. Aesthetascs ⅓ of respective flagellum articles (Fig. 4C). Antenna II (Fig. 4D): flagellum formed of 8 articles and representing 40% of total length of antenna II. Most flagellum articles bear 1 short aesthetasc. Mouthparts Labium (Fig. 5A): large inner lobes with no setae. Outer lobes with 1 row of fine setae subapically on inner sides. Labrum (not shown) typical, subovoid shape. Maxilla I (Fig. 5B): with 4 apical setae on distal article of palp. Six spines of outer lobe with 1 tooth each and 1 spine with several small teeth. Inner lobe with 1 apical seta. Maxilla II (Fig. 5C): with inner lobe slightly shorter than outer lobe. 1 apical row of setae and 1 subapical seta on each lobe. Left mandible (Fig. 5D): 5 teeth on incisor process. 5 teeth on lacinia mobilis. 5 serrated setae, alternated with 6 trifid setae, between lacinia mobilis and molar process. Right mandible (Fig. 5E): 5 teeth on incisor process. 7 small teeth on lacinia mobilis. 3 serrated and 2 trifid setae between lacinia mobilis and molar process. Long seta on molar process. Mandibular palps (Fig. 5D–E): highly similar and of same length. 3 articles account for 19% (article 1), 39% (article 2) and 42% (article 3) of total length of palp. Proximal article without setae, median article with 6–9 ventral setae. Distal article of palp with one group of 5 A setae, three groups with 1–2 B setae, 14 D setae and 4 E setae. Maxilliped (Fig. 6A): with palp formed of 4 articles. Article 1 asetose. Article 2 with 18 setae aligned along inner margin. Article 3 with 5 apical setae, one group of 8 dorsal setae and one group of 5 setae on inner margin. Article 4 with 1 seta located on outer margin and 2 setae at nail insertion. Outer lobe with 7 apical setae and 8 flattened setae on inner margin. Inner lobe with 6 apical setae. Gnathopods Gnathopod I (Fig. 6B): coxal plate in shape of rectangular trapezoid, with depth larger than width (ratio depth:width 1.0:0.85). Basis length:width ratio 1.0: 0.43. Ischiopodite with one posteroventral group of 5 setae. Basis length: carpus length ratio 1.0: 0.54. Carpus with row of 10 setae of various lengths along ventral margin, group of 4 setae located anterodorsally and two groups of 3–5 setae on carpus surface close to ventral margin. Propodite nearly as long as wide, five groups of 2–4 setae on ventral margin, one group of 2 setae on dorsal margin, one group of 6 anterodorsal setae, one group of 6 anteroapical setae, 1 mesial seta on lateral surface, one group of 2 setae on lateral surface close to ventral margin and one group of 2 setae close to palmar corner. 1 strong palmar spine, 1 supporting spine and 2 denticulate spines present in palmar corner. Dactylopodite with claw 35% of total dactylopodite length and 1 seta along outer margin. Gnathopod II (Fig. 6C): slightly larger than gnathopod I, with coxal plate in shape of rectangular trapezoid; coxal plate width almost similar in length with depth (ratio width: depth 1.0: 0.95). Ovoid gill. Basis length: width ratio is 1.0: 0.34. Ischiopodite with one posteroventral group of 5 setae. Basis length: carpus length ratio 1.0:0.56. Carpus with row of 12 setae of various lengths along ventral margin, group of 3 setae located anterodorsally and one group of 4 setae on carpus surface close to ventral margin. Propodite as long as wide, 6 groups of 2–5 setae on ventral margin, 1 seta on dorsal margin, one group of 4 anterodorsal setae and 5 anteroapical setae. 1 mesial seta on lateral surface, 2 setae close to palmar corner. 1 strong palmar spine, 1 supporting spine and 2 denticulate spines present in palmar corner. Dactylopodite with claw 37% of total dactylopodite length and 1 seta along outer margin. Pereopods Pereopod III (Fig. 7A): coxal plate in shape of rectangular trapezoid, ratio width-depth 1.0: 0.9. Propodite length: dactylus length ratio 1.0:0.4. Dactylus, with nail measuring half of total length of dactylus, 1 dorsal seta with plumose tip. Pereopod III equal in length to pereopod IV (pereopod III length: pereopod IV length ratio 1.0: 1.0). Pereopod IV (Fig. 7B): relatively rectangular coxal plate, with concavity on posterior margin, width: depth ratio 1.0: 0.82. Propodite length: dactylus length ratio 1.0: 0.46. Robust dactylus, with nail measuring 0.44% of total length of dactylus; 1 dorsal seta with plumose tip and 1 seta at nail base. Pereopod V (Fig. 8A): coxal plate of irregular shape, with deep concavity on ventral side and 1 anterior seta. Basis ovoid-rectangular shaped, length: width ratio 1.0: 0.66, 6 setae on posterior margin, 4 setae on anterior margin, 3 anteroapical setae of different lengths. Dactylus with one dorsal seta with plumose tip, 1 seta and 1 spine at nail base, which represents ⅓ of total dactylus length. Propodite length:dactylus length ratio 1.0: 0.45. Pereopod VI (Fig. 8B): coxal plate smaller than that of pereopod V, but highly similar in shape and 1 posterior seta. Basis ovoid-rectangular shaped, length: width ratio 1.0: 0.67, 6 setae on posterior margin, 5 setae on anterior margin, 3 anteroapical setae of different lengths. Dactylus with 1 plumose seta on outer margin and 1 spine near nail base. Nail length slightly more than ⅓ of total dactylus length. Ratio propodite length: dactylus length 1.0:0.4. Pereopod VII (Fig. 8C): longest leg (3.1 mm) of inspected paratype male. Coxal plate trapezoidal, with 1 seta on posterior margin. Basis ovoid-rectangular, ratio length: width 1.0: 0.6, 8 setae on posterior margin, 2 setae on anterior margin and 3 anteroapical setae of different lengths. Dactylus with 1 plumose seta on outer margin and 1 spine near nail base. Nail length slightly more than ⅓ of total dactylus length. Ratio propodite length: dactylus length 1.0: 0.36. Pereopods V: VI: VII ratio 1.0: 1.34: 1.49. Pleopods Similar in shape and size (pleopod I depicted in Fig. 9A), with unequal rami and 2 hooks on retinaculum. Epimeral plates (Fig. 9B) Epimeral plate I with right postero-ventral angle, relatively straight ventral margin, convex posterior margin with 5 setae. Epimeral plate II with right postero-ventral angle, relatively straight ventral margin with 2 spines, convex posterior margin with 6 setae. Epimeral plate III with right posteroventral angle, relative straight ventral margin with 1 spine, convex posterior margin with 6 setae. Uropods Uropod I (Fig. 10A): with two dorso-lateral rows of 4 spines on peduncle. Exopodite slightly longer than endopodite, and ratio of exopodite length:endopodite length 1.0: 0.85. 1 strong spine at base of uropod I. Uropod II (Fig. 10B): with 1 dorsal spine and 3 apical spines. Endopodite longer than exopodite, endopodite length:exopodite length ratio 1.0:0.81, both rami with low number of spines. Uropod III (Fig. 10C): sexually differentiated, longer in males. Peduncle with 4 apical spiniform setae. Short endopodite about half the length of peduncle, with 2 apical setae. Proximal segment of exopodite longer than distal segment (ratio 1.0:0.77). Anterior margin of proximal segment of exopodite with 5 groups of 2–3 setae; posterior margin of exopodite with 3 groups of 1–2 setae; one group of 3 posteroapical setae. Distal segment of exopodite with 3 groups of 2 setae on anterior margin, 3 groups of 1–2 setae on posterior margin and 4 apical setae of different lengths. Telson Tel