Pseudocrangonyx seomjinensis, Lee & Min, 2024

Lee, Chi-Woo & Min, Gi-Sik, 2024, Two new species of Pseudocrangonyx (Amphipoda: Pseudocrangonyctidae) from the hyporheic zones in South Korea, Zootaxa 5433 (2), pp. 249-265 : 252-256

publication ID	https://doi.org/ 10.11646/zootaxa.5433.2.5
publication LSID	lsid:zoobank.org:pub:AE99AF6B-787F-4E48-8DD3-F8B0ADD3A887
DOI	https://doi.org/10.5281/zenodo.10954103
persistent identifier	https://treatment.plazi.org/id/5F17DD49-0931-4E8C-A999-1D704F6C817B
taxon LSID	lsid:zoobank.org:act:5F17DD49-0931-4E8C-A999-1D704F6C817B
treatment provided by	Plazi
scientific name	Pseudocrangonyx seomjinensis
status	sp. nov.

Treatment

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 View FIGURE 2 , 3–6 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 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. GoogleMaps

Paratypes: NNIBRIV69643, 1 male, BL 3.3 mm, NNIBRIV69641, 1 female, BL 3.9 mm; collection data same as for holotype GoogleMaps .

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 View FIGURE 2 ) 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 View FIGURE 2 ). Ventral margin of urosomite 1 without setae ( Fig. 2A View FIGURE 2 ). Ventral margin of epimeral plate 1 without seta, posteroventral corner rounded with seta ( Fig. 2A View FIGURE 2 ); ventral and posterior margins of plate 2 each with seta, posteroventral corner rounded with seta ( Fig. 2A View FIGURE 2 ); ventral and posterior margins of plate 3 each with seta, posteroventral corner rounded without seta ( Fig. 2A View FIGURE 2 ).

Antenna 1 ( Fig. 3A View FIGURE 3 ) 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 View FIGURE 3 ) 2-articulate, terminal article with 3 setae and 1 aesthetasc; primary flagellum 9- articulate, 1 aesthetasc on some articles. Antenna 2 ( Fig. 3C View FIGURE 3 ) 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 View FIGURE 3 ) with rounded anterior margin, bearing fine setae. Mandibles (Female paratype, Fig. 3E, F View FIGURE 3 ) 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 View FIGURE 3 ) with broad outer lobes with fine setae, mandibular process of outer lobe rounded apically; inner lobes indistinct. Maxilla 1 ( Fig. 3H View FIGURE 3 ) 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 View FIGURE 3 ) with oblique inner row of 2 setae on inner plate. Maxilliped ( Fig. 3J View FIGURE 3 ) 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 View FIGURE 4 ) 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 View FIGURE 4 ) 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 View FIGURE 4 ) 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 View FIGURE 4 ). Pereopod 4 ( Fig. 4E View FIGURE 4 ) 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 View FIGURE 4 ). Pereopod 5 ( Fig. 4G View FIGURE 4 ) 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 View FIGURE 4 ). Pereopod 6 ( Fig. 4I View FIGURE 4 ) 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 View FIGURE 4 ). Pereopod 7 ( Fig. 4K View FIGURE 4 ) 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 View FIGURE 4 ) on gnathopod 2 and pereopods 3–6; sternal gills absent. Brood plates ( Fig. 4B, C, E View FIGURE 4 ) slender, with numerous setae, on gnathopod 2 and pereopods 3–5.

Peduncle of pleopod 1 ( Fig. 5A View FIGURE 5 ) anterodistal corner with seta; peduncles of pleopod 2 and 3 ( Fig. 5B, C View FIGURE 5 ) 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 View FIGURE 5 ).

Uropod 1 ( Fig. 5D View FIGURE 5 ) 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 View FIGURE 5 ) 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 View FIGURE 5 ) 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 View FIGURE 5 ) 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 View FIGURE 6 ) 0.42 times as long as body length, primary flagellum 9-articulate, 1 aesthetasc on some articles. Antenna 2 ( Fig. 6C View FIGURE 6 ) 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 View FIGURE 6 ).

Gnathopod 1 ( Fig. 6E View FIGURE 6 ) 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 View FIGURE 6 ) 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 View FIGURE 6 ) 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 View FIGURE 6 ) 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 View FIGURE 6 ) 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 View FIGURE 6 ) 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.