Pseudocrangonyx seomjinensis Lee & Min 2024, sp. nov.
Creators: name: Lee, Chi-Woo
name: Min, Gi-Sik
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Pseudocrangonyctidae
Pseudocrangonyx
Pseudocrangonyx seomjinensis

description: 1. Pseudocrangonyx seomjinensis sp. nov.
urn:lsid:zoobank.org:act: 5F17DD49-0931-4E8C-A999-1D704F6C817B
[New Korean name: seom-jin-gang-dong-gul-yeop-sae-u]
(Figs. 2A, 3–6)
Material examined. Holotype: NNIBRIV69642, female, BL 4.1 mm, collected from Seomjin River (35°11.402′N, 127°23.108′E), Gyesan-ri, Gurye-eup, Gurye-gun, Jeollanam-do, Korea, on 20 Mar 2015, by C. -W. Lee.
Paratypes: NNIBRIV69643, 1 male, BL 3.3 mm, NNIBRIV69641, 1 female, BL 3.9 mm; collection data same as for holotype.
Diagnosis. Antennal sinus with rounded angle; eyes absent; pereonites 7 with short dorsal setae; dorsal margin of urosomite 1–3 with setae; sternal gill absent; female antenna 1 being 0.34 times as long as body length; male antenna 2 with calceoli; mandible palp article 3 longer than article 2; maxilla 1 outer plate with 7 serrate teeth; maxilla 2 inner plate with oblique inner row of 2 setae; palmar margins of propodi of gnathopods 1 and 2 with 3–5 and 7–9 robust setae, respectively; pleopod peduncles lacking marginal setae, inner margin of inner rami without bifid setae; uropod 1 inner ramus 0.86 times as long as peduncle, inner margin with robust seta, outer margin bare, basal part with slender seta, outer ramus marginally bare; uropod 2 inner ramus 1.3 times as long as peduncle, inner and outer rami marginally bare; uropod 3 terminal article longer than adjacent robust setae; telson each lobe with apical robust seta and 1 penicillate seta.
Description. Female holotype (NNIBRIV69642): Head (Fig. 2A) with short dorsal setae; rostrum reduced; lateral cephalic lobe rounded; antennal sinus shallow with rounded angle; eyes absent. Dorsal margin of pleonites 1–3 and urosomites 1–2 with setae (Fig. 2A). Ventral margin of urosomite 1 without setae (Fig. 2A). Ventral margin of epimeral plate 1 without seta, posteroventral corner rounded with seta (Fig. 2A); ventral and posterior margins of plate 2 each with seta, posteroventral corner rounded with seta (Fig. 2A); ventral and posterior margins of plate 3 each with seta, posteroventral corner rounded without seta (Fig. 2A).
Antenna 1 (Fig. 3A) 0.34 times as long as body length, peduncular articles 1 to 3 in length ratio of 1.0: 0.6: 0.4; accessory flagellum (Fig. 3B) 2-articulate, terminal article with 3 setae and 1 aesthetasc; primary flagellum 9- articulate, 1 aesthetasc on some articles. Antenna 2 (Fig. 3C) 0.63 times as long as antenna 1; flagellum 0.68 times as long as peduncular articles 4 and 5 combined, consisting of 4 articles; calceoli absent.
Upper lip (Male paratype, Fig. 3D) with rounded anterior margin, bearing fine setae. Mandibles (Female paratype, Fig. 3E, F) with left and right incisors with 5- dentate, respectively; left lacinia mobilis 5- dentate, right lacinia bifid, bearing many teeth; molar process triturative; accessory setal rows of left and right mandibles with 3- and 2- pectinate setae, respectively; palp 3-articulate, article 3 with 1 A-, 4 D-, and 4 E-setae. Lower lip (Fig. 3G) with broad outer lobes with fine setae, mandibular process of outer lobe rounded apically; inner lobes indistinct. Maxilla 1 (Fig. 3H) with inner and outer plates, and palp; inner plate subovate with 2 plumose setae; outer plate subrectangular with 7 serrate teeth apically; palp 2-articulate, longer than outer plate, article 2 with 3 apical robust setae. Maxilla 2 (Fig. 3I) with oblique inner row of 2 setae on inner plate. Maxilliped (Fig. 3J) with inner and outer plates, and palp; inner plate with apical robust seta; outer plate with 2 plumose setae and some medial setae; palp 4-articulate, medial margin of article 2 lined with setae, article 4 with nail.
Gnathopod 1 (Fig. 4A) with subquadrate coxa, bearing setae on anterodistal corner and medial, width 2.0 times as long as depth; posterior margin of basis with 4 setae; posterodistal corner of carpus with slender setae, some weakly pectinate; propodus stout, subtriangular, palmar margin with 3 robust setae, some distally notched; posterior margin of dactylus dentate. Gnathopod 2 (Fig. 4B) with subquadrate coxa, bearing setae on anterior margin and anterodistal corner, width 1.6 times as long as depth; posterior margin of basis with 3 setae; posterodistal corner of carpus with slender setae, some weakly pectinate; propodus stout, subchelate, palmar margin with 7 robust setae, some distally notched; posterior margin of dactylus dentate.
Pereopod 3 (Fig. 4C) with subquadrate coxa bearing setae on anterior margin and anterodistal corner, width 1.6 times as long as depth; anterior and posterior margins of basis with 2 and 4 setae, respectively; merus, carpus, and propodus in length ratio of 1.0: 0.7: 0.8; posterior margin and submargin of dactylus each with seta (Fig. 4D). Pereopod 4 (Fig. 4E) with subquadrate coxa bearing setae on anterior to ventral corner, width 1.76 times as long as depth; anterior and posterior margins of basis each with 2 and 3 setae; merus, carpus, and propodus in length ratio of 1.0: 0.8: 0.9; posterior margin and submargin of dactylus each with seta (Fig. 4F). Pereopod 5 (Fig. 4G) with weakly bilobed coxa bearing setae on anterior to posterior lobes; anterior and posterior margins of basis with 2 and 4 setae, respectively; merus, carpus, and propodus in length ratio of 1.0: 0.7: 1.0; anterior margin of dactylus with seta (Fig. 4H). Pereopod 6 (Fig. 4I) with weakly bilobed coxa bearing setae on posterior lobe; anterior and posterior margins of basis with 3 setae, respectively; merus, carpus, and propodus in length ratio of 1.0: 0.7: 0.9; anterior margin of dactylus with seta (Fig. 4J). Pereopod 7 (Fig. 4K) with subtriangular coxa, bearing seta on posteroproximal corner; anterior and posterior margins of basis with 3 and 4 setae, respectively; merus, carpus, and propodus in length ratio of 1.0: 0.9: 1.1; anterior margin of dactylus with seta.
Coxal gills (Fig. 4B, E, G, I) on gnathopod 2 and pereopods 3–6; sternal gills absent. Brood plates (Fig. 4B, C, E) slender, with numerous setae, on gnathopod 2 and pereopods 3–5.
Peduncle of pleopod 1 (Fig. 5A) anterodistal corner with seta; peduncles of pleopod 2 and 3 (Fig. 5B, C) lacking marginal and distal setae. Pleopods 1–3 with paired retinacula, and lacking bifid setae (clothes-pin setae) on inner basal margin of inner ramus; pleopods 1–3 inner ramus 3-, 3-, and 2-articulate; pleopods 1–3 outer ramus 3-, 3-, and 2-articulate (Fig. 5A–C).
Uropod 1 (Fig. 5D) with basofacial seta on peduncle; inner ramus 0.86 times as long as peduncle, inner margin with robust seta, outer margin bare, basal part with slender seta; outer ramus 0.65 times as long as inner, marginally bare. Uropod 2 (Fig. 5E) with inner and outer rami; inner ramus 1.30 times as long as peduncle; outer ramus 0.60 times as long as inner ramus; inner and outer rami marginally bare. Uropod 3 (Fig. 5F) with peduncle 0.32 times as long as outer ramus, with 3 robust and 1 slender setae; inner ramus absent; outer ramus 2-articulate, proximal article with robust setae, terminal article 0.38 times as long as proximal article, with 3 distal setae.
Telson (Fig. 5G) length 1.3 times as long as wide, cleft for 1.45% of length, each telson lobe with 2 lateral penicillate setae, 1 apical robust and 1 apical penicillate seta.
Male paratype (NNIBRIV69643): Antenna 1 (Fig. 6A, B) 0.42 times as long as body length, primary flagellum 9-articulate, 1 aesthetasc on some articles. Antenna 2 (Fig. 6C) 0.61 times as long as antenna 1; flagellum 0.76 times as long as peduncular articles 4 and 5 combined, consisting of 4 articles, first 2 of which with calceoli (Fig. 6D).
Gnathopod 1 (Fig. 6E) with coxa width 2.0 times as long as depth; palmar margin with 5 robust setae in 2 rows, some distally notched. Gnathopod 2 (Fig. 6F) with coxa width 1.46 times as long as depth; palmar margin with 9 robust setae in 2 rows, some distally notched.
Uropod 1 (Fig. 6G) with basofacial seta on peduncle; inner ramus 0.85 times as long as peduncle, outer margin with robust seta, inner margin bare, basal part with slender seta; outer ramus 0.73 times as long as inner ramus, marginally bare. Uropod 2 (Fig. 6H) with inner ramus 0.89 times as long as peduncle, inner and outer margins with 3 and 2 robust setae, respectively; outer ramus 0.88 times as long as inner ramus, with 4 outer marginal robust setae. Uropod 3 (Fig. 6I) with peduncle 0.3 times as long as outer ramus; inner ramus absent; outer ramus 2-articulate, proximal article with robust setae, terminal article 0.26 times as long as proximal article, with 3 distal setae.
Telson (Fig. 6J) length 1.5 times as long as width, subtriangular, not cleft.
Distribution. Known only from the type locality.
Etymology. The specific name is an adjective derived from the name of river (Seomjin River) where the new species inhabiting.
Remarks. Pseudocrangonyx seomjinensis sp. nov. is morphologically most similar to P. daejeonensis Lee et al., 2018 in having 1) small body size (about 4.0 mm), 2) male antenna 2 with calceoli, 3) inner rami of pleopods without bifid setae on inner margin, 4) uropod 1 and 2 outer ramus marginally bare, and 5) uropod 3 terminal article longer than adjacent robust setae. However, the new species is distinguished from P. daejeonensis by the following features (features of P. daejeonensis in parentheses): 1) ventral margin of epimeral plate 1 without (with) seta, 2) pereopod 7 carpus posterior margin with (without) robust seta, 3) female uropod 2 inner ramus without (with) robust seta, 4) male uropod 2 outer ramus with 4 (without) outer margin robust setae, and 5) male uropod 2 outer ramus end almost reach (shorter than) inner ramus.
description: Published as part of Lee, Chi-Woo & Min, Gi-Sik, 2024, Two new species of Pseudocrangonyx (Amphipoda: Pseudocrangonyctidae) from the hyporheic zones in South Korea, pp. 249-265 in Zootaxa 5433 (2) on pages 252-256, DOI: 10.11646/zootaxa.5433.2.5, http://zenodo.org/record/10954120