Pseudocrangonyx villosus, Jung & Kim & Kim & Yoon, 2020

Jung, Tae Won, Kim, Jong Guk, Kim, Min-Seop & Yoon, Seong Myeong, 2020, Five new subterranean amphipods of the genus Pseudocrangonyx from Korea (Crustacea, Amphipoda, Pseudocrangonyctidae), ZooKeys 970, pp. 1-50 : 1

Pseudocrangonyx villosus sp. nov. Figs 17 , 18 , 19 , 20 , 21

Korean name.

Teol-son-dong-gul-yeop-sae-u, new

Type locality.

Ansanangul Cave, Beolcheon-ri, Danseong-myeon, Danyang-gun, Chungcheongbuk-do, South Korea; 36°52'10"N, 128°17'00"E.

Material examined. Type material. Holotype: 1 female, 12.4 mm, NIBRIV0000862811. Paratypes: 2 specimens, NIBRIV0000872413. All type materials were collected on 17 Mar 2002 by YG Choi.

Etymology.

The specific name originates from the Latin word villosus meaning hairy. This name refers to the more setose bases of pereopods 3 and 4 compared to other pseudocrangonyctids.

Diagnosis.

Antenna 1, 1.61 × as long as body; 1st-3rd peduncular articles length ratio of 1.00: 0.86: 0.64. Antenna 2 peduncles moderate. Mandibles eight raker setae present on both sides. Maxilla 1 inner lobe with seven plumose setae on apical margin; palp with nine robust setae along distomedial to apical margins, with one oblique row of seven setae subdistally. Maxilla 2 with one oblique row of ten plumose setae on surface. Gnathopods 1 and 2 each possessing carpus with two rastellate setae, respectively. Pereopods 3 and 4 basis more setose on both margins. Pereopods 5-7 basis slightly elongate. Pereopod 5 carpus and propodus with rows of elongate setae medially. Pereopod 6, 1.24 × as long as pereopod 5. Pereopod 7 merus, carpus and propodus stout. Sternal gills present from pereonites 2 to 5 (1+1+1+1 in formulae). Epimeral plates 2 ventral margin with three setae anteriorly, posterodistal corner slightly notched bearing one elongate seta. Epimeral plates 3 posterior margin with eight setae, posterodistal corner slightly notched bearing one elongate seta, ventral margin with four submarginal setae anteriorly. Uropod 1 inner ramus with three elongate simple setae on ventral margin subproximally. Telson 0.71 × as wide as long, cleft for 35% of length.

Description.

Holotype female: Body (Fig. 17A ) approximately 12.4 mm long.

Head (Fig. 17B ) as long as pereonite 1; rostrum reduced, with three minute setae; lateral cephalic lobe anteriorly expanded, apex rounded, slightly dilated anteroventrally; antennal sinus not deep; eye absent.

Antenna 1 (Fig. 17C ) 0.61 × as long as body; 1st-3rd peduncular articles length ratio of 1.00: 0.86: 0.64; 1st article stout, posterior margin with simple setae only; accessory flagellum bi-articulate, last article very reduced; flagellum 1.32 × as long as peduncles, composed of 23 articles, calceoli absent, aesthetascs present from 16th to last articles.

Antenna 2 (Fig. 17D ) 0.59 × as long as antenna 1; antennal cone developed, apex rounded; 4th peduncular article margins parallel, 0.25 × wider than long, posterior margin with one row of setae in the middle and one elongate seta subdistally, 5th article 0.95 × as long and 0.61 × as wide as 4th article, three calceoli present on medial surface; flagellum composed of nine articles, 1.05 × as long as 5th peduncular article, single calceoli present from 1st to 5th articles medially, aesthetascs absent.

Upper lip (Fig. 17E ) rounded, apex slightly produced apically, covered with minute setae, not notched.

Lower lip (Fig. 17F ) inner lobes indistinct; outer lobes covered with minute setae; mandibular processes developed.

Mandible (Fig. 17G, H ) incisor 5-dentate on both sides; lacinia mobilis tri-cuspidate (two of them finely dentate and one small, produced upwards) on right and 5-dentate on left side; eight raker setae present on both sides; molar process columnar, triturative, without plumose setae on both sides; palp tri-articulate; 2nd article convex and with 18 setae medially; 3rd article subfalcate, as long as 2nd article, lined with 27 setae from medial margin to apex, with six setae laterally.

Maxilla 1 (Fig. 17I ) inner lobe subrhomboid, with seven plumose setae on apical margin; outer lobe with seven dentate robust setae; palp bi-articulate, 2nd article apex exceeding apical setae of outer plate, with nine robust setae along distomedial to apical margins, with one oblique row of seven setae subdistally.

Maxilla 2 (Fig. 17J ) inner lobe slightly shorter but wider than outer lobe, with one oblique row of ten plumose setae on surface and two rows of simple setae on apical margin; outer lobe apical margin with two rows of simple setae.

Maxilliped (Fig. 18A ) inner lobe subrectangular, apex rounded, with six subdentate robust setae mediodistally and with seven plumose setae apically and subapically; outer lobe elongate semicircular, as long as 2nd palp article, with six plumose setae on apical margin and six dentate robust setae on mediodistal margin; palp composed of four articles; 2nd article with many setae on medial margin; 3rd article slightly dilated distally, 0.63 × as long as 2nd article; 4th article falcate, 0.59 × as long as 3rd article, apical setae 0.71 × as long as 4th article.

Gnathopod 1 (Fig. 18B ) coxa subrectangular, 1.43 × wider than long, anterodistal corner somewhat produced, with six setae marginally, ventral margin a little convex, posterior margin slightly humped proximally; basis obtuse trapezoidal, posteriorly expanded, 0.51 × wider than long, lined with elongate simple setae posteriorly, anterior margin without setae; ischium 0.26 × as long as basis, with small anterior lobe; carpus 0.56 × as long as basis, with two pairs of robust setae on anterior margin, carpal lobe not developed, apex rounded with two rastellate setae and many simple or serrate setae; propodus subovate, 1.32 × as long and 1.48 × as wide as basis, posterior margin with four robust setae successively increasing distally, palm irregular, defined by largest lateral seta of posterior margin, finely serrated, lined with ten robust setae medially; dactylus as long as palm, inner margin toothed, outer margin with four setae, unguis developed.

Gnathopod 2 (Fig. 18C ) 1.10 × as long as gnathopod 1; coxa 1.13 × as long as that of gnathopod 1, 1.22 × wider than long, anterior and ventral margins not produced, rounded, lined with 15 setae, posterior margin humped proximally; basis somewhat expanded posteroproximally, 0.34 × wider than long, lined with elongate simple setae posteriorly, anterior margin without setae; ischium 0.14 × as long as basis, with small anterior lobe; carpus 0.56 × as long as basis, with two clusters of robust setae on anterior margin, carpal lobe not developed, broader than that of gnathopod 1 margin, weakly crenulate, with two rastellate setae and many simple or serrate setae; propodus trapezoidal, 1.00 × as long and 1.54 × as wide as basis, anterior margin slightly convex, posterior margin 0.57 × as long as anterior margin, lined with seven clusters of elongate setae, with two defining robust setae distally; palm irregular, finely serrated, lined with 12 medial and 14 lateral robust setae; dactylus as long as palm, inner margin toothed, outer margin with three setae, unguis developed.

Pereopod 3 (Fig. 19A ) coxa subrectangular, 1.19 × wider than long, slightly humped posteroproximally, ventral margin a little concave, with eleven setae anteriorly and four setae at posteroventral corner; coxal gill subovate; basis expanded, 0.69 × as wide and 3.05 × as long as coxa, width longest at proximal 1/3 and gradually diminished distally, margins lined with setae but posterior ones longer than anterior ones; ischium 0.16 × as long as basis; merus anterodistally expanded, 0.30 × wider than long, 0.49 × as long as basis, anterodistal corner produced, apex blunt; carpus not expanded, 0.37 × as long as basis; propodus, 0.42 × as long as basis, linear; dactylus 0.32 × as long as propodus, unguis developed.

Pereopod 4 (Fig. 19B ) similar to pereopod 3; merus, carpus and propodus slightly longer than those of pereopod 3.

Pereopod 5 (Fig. 20A, B ) coxa bilobate, anterior lobe larger than posterior lobe, expanded ventrally (1.00 × as long as wide), margin rounded, lined with 13 simple setae; posterior lobe with three setae posteriorly; coxal gill subovate; basis expanded, subrectangular, slightly expanded, 0.43 × wider than long, anterior margin slightly convex, lined with two single robust setae and four clusters of robust and simple setae, posterior margin lined with 28 simple setae, distal corner produced forming an angle; merus posterodistally expanded, 0.37 × as wide and 0.76 × as long as basis, with three clusters of simple setae on anterior margin and one robust seta and two clusters of robust setae on posterior margin; carpus not expanded, 0.79 × as long as basis, with three setal clusters on medial surface anteriorly and two robust setal clusters on lateral surface posteriorly; propodus linear, as long as carpus, anterior margin with four setal clusters (longest seta of distal cluster slightly exceeding end of propodus) and one pair of locking robust setae distally, posterior margin with five clusters of simple setae, with one cluster of simple and robust setae at distal corner; dactylus 0.26 × as long as propodus, unguis developed.

Pereopod 6 (Fig. 20C ) 1.24 × as long as pereopod 5; coxa bilobate, anterior lobe 0.59 × as long as that of pereopod 5, with three setae ventrally, posterior lobe narrow, expanded backward, with two setae posteriorly; basis expanded, subrectangular, slightly expanded, 1.16 × as long and 1.07 × as wide as that of pereopod 5, 0.40 × wider than long, with three single and four clusters of setae on anterior margin, with 16 setae on posterior margin, posterodistal corner produced forming an angle, but weaker than that of pereopod 5; merus posterodistally expanded, 0.48 × as wide and 0.89 × as long as basis, with four anterior and four posterior setal clusters; carpus not expanded, 0.83 × as long as basis, with four setal clusters on medial surface anteriorly and three setal clusters on lateral surface posteriorly; propodus linear, as long as carpus, anterior margin with four setal clusters (longest seta of distal cluster not exceeding end of propodus) and one pair of locking robust setae distally, posterior margin with one single seta and three clusters of simple setae and one distal cluster of elongate setae; dactylus 0.27 × as long as propodus, unguis developed.

Pereopod 7 (Fig. 20D ) 0.93 × as long as pereopod 6, but width slightly thicker universally; coxa unilobed, subtriangular, 0.82 × as long as that of pereopod 6, posteriorly expanded with three setae at posterior corner, with one seta on ventral margin; basis expanded, subrectangular, as long and wide as that of pereopod 6, posterodistal expansion weaker than those of pereopods 6 and 7; merus posterodistally expanded, 0.67 × as wide and 0.77 × as long as basis, with two setal clusters anteriorly and one single robust seta and two setal clusters posteriorly; carpus as long as merus, rectangular, not narrowed, 0.24 × as wide as long; propodus linear but thicker than that of pereopod 6, 1.10 × as long as carpus, anterior margin with four setal clusters (without elongate setae) and one pair of locking robust setae distally, with three clusters of simple setae posteriorly; dactylus 0.30 × as long as propodus, unguis developed.

Oostegites (Fig. 19C-F ) present from gnathopod 2 to pereopod 5, narrow, with marginal seta, shortest in that of pereonite 5.

Sternal gills (Fig. 21A ) present from pereonites 2 to 5 (1+1+1+1 in formulae), narrower than oostegites, similar to each other in length.

Epimeral plate 1 subquadrate, a little produced posteroventrally, ventral margin without setae, posterior margin with seven setae, posterodistal corner slightly notched bearing one elongate seta. Epimeral plate 2 subquadrate, slightly larger than epimeron 1, ventral margin with three setae anteriorly, posterior margin with nine setae, posterodistal corner slightly notched bearing one elongate seta. Epimeral plate 3 posterior margin with eight setae, posterodistal corner slightly notched bearing one elongate seta, ventral margin with four submarginal setae anteriorly (Fig. 21B ).

Pleopod 1 (Fig. 21C ) peduncle with one pair of retinaculae mediodistally and one pair of simple setae laterodistally, with one seta on lateral margin; outer ramus 1.55 × as long as peduncle, composed of 15 articles; inner ramus 1.74 × as long as peduncle, composed of 13 articles (coalesced 1st article as long as proximal three articles of outer ramus combined).

Pleopod 2 (Fig. 21D ) peduncle 1.10 × as long as that of pleopod 1, with one pair of retinaculae mediodistally and one pair of simple setae laterodistally, margins without setae; outer ramus 1.33 × as long as peduncle, composed of 14 articles; inner ramus 1.10 × as long as outer ramus, composed of twelve articles (coalesced 1st article with suture, as long as proximal three articles of outer ramus combined).

Pleopod 3 (Fig. 21E ) 0.92 × as long as pleopod 2; peduncle 0.98 × as long as that of pleopod 2, with one pair of retinaculae mediodistally and one pair of simple setae laterodistally, with one pair of setae on lateral margin; outer ramus 1.18 × as long as peduncle, composed of twelve articles; inner ramus 1.15 × as long as outer ramus, composed of twelve articles (1st coalesced article reaching middle of 2nd article of outer ramus).

Uropod 1 (Fig. 21F ) peduncle with one basofacial seta, with four marginal robust setae and one distal robust seta dorsolaterally, with one marginal robust seta and one distal robust seta dorsomedially; outer ramus 0.53 × as long as peduncle, with one robust seta dorsomedially and two robust setae dorsolaterally, apical cluster composed of five robust setae; inner ramus 1.36 × as long as outer ramus, with four robust setae dorsomedially and two robust setae dorsolaterally, apical cluster composed of seven robust setae and one sensory seta, with three elongate simple setae on ventral margin subproximally.

Uropod 2 (Fig. 21G ) 0.68 × as long as uropod 2; peduncle 0.50 × as long as that of uropod 1, with two marginal setae and one pair of distal setae dorsolaterally, with one distal seta dorsomedially; outer ramus 0.78 × as long as peduncle, with two robust setae dorsolaterally, apical cluster composed of five robust setae; inner ramus 1.48 × as long as outer ramus, with three robust setae dorsomedially and two robust setae dorsolaterally, apical cluster composed of seven robust setae and one sensory seta.

Uropod 3 (Fig. 21H ) uniramous, 0.86 × as long as uropod 1; peduncle short, 0.57 × as long as uropod 2, with one minute seta on medial margin and one robust seta mediodistally, with one setal cluster on laterodistal margin; ramus 3.24 × as long as peduncle, bi-articulate, proximal article gradually diminished in width, with six clusters of setae laterally and five clusters of setae medially (longest seta of distal cluster exceeding distal article ramus), distal article 0.08 × as long as proximal article, with three elongate simple setae apically.

Telson (Fig. 21I ) 0.71 × as wide as long, cleft for 35% of length, each lobe with one pair of penicillate setae dorsally, and one penicillate seta and four robust setae on apex.

Remarks.

Pseudocrangonyx villosus sp. nov. is distinguished from other Korean pseudocrangonyctids such as P. asiaticus , P. coreanus , P. concavus sp. nov., P. crassus sp. nov., P. daejeonensis , P. gracilipes sp. nov., P. joolaei , P. minutus sp. nov., and P. villosus sp. nov. in that antenna 1 is longer than half length of the body and the 2nd peduncular article is 0.89 times as long as the 1st peduncular article. In addition, maxilla 1 has seven plumose setae on the inner lobe, and a row on the inner lobe of maxilla 2 is composed of ten plumose setae. Both gnathopods have two rastellate setae on the carpus; each basis of pereopods 3 and 4 is more setose along the margins while the bases of pereopods 5-7 are more elongate than those of other Korean pseudocrangonyctids mentioned above. Finally, the sternal gills are present in pereonites 2 to 5 (1+1+1+1 in formulae) and the posterodistal corners of all epimeral plates are notched ( Uéno 1934, 1966, Lee et al. 2018, 2020).

Figures

Figure 17. Pseudocrangonyx villosus sp. nov. Holotype: female, NIBRV 0000862811, 12.4 mm, from Ansanan Cave, South Korea. A habitus B head C antenna 1 D antenna 2 E upper lip F lower lip G right mandible H left mandible I maxilla 1 J maxilla 2.

Figure 18. Pseudocrangonyx villosus sp. nov. Holotype: female, NIBRV 0000862811, 12.4 mm, from Ansanan Cave, South Korea. A maxilliped B gnathopod 1 C gnathopod 2.

Figure 19. Pseudocrangonyx villosus sp. nov. Holotype: female, NIBRV 0000862811, 12.4 mm, from Ansanan Cave, South Korea. A pereopod 3 B pereopod 4 C-F oostegites of gnathopod 2 - pereopod 5.

Figure 20. Pseudocrangonyx villosus sp. nov. Holotype: female, NIBRV 0000862811, 12.4 mm, from Ansanan Cave, South Korea. A pereopod 5 B coxal gill of pereopod 5 C pereopod 6 D pereopod 7.

Figure 21. Pseudocrangonyx villosus sp. nov. Holotype: female, NIBRV 0000862811, 12.4 mm, from Ansanan Cave, South Korea. A sternal gills B epimeral plates and urosomites C pleopod 1 D pleopod 2 E pleopod 3 F uropod 1 G uropod 2 H uropod 3 I telson. Abbreviations: Ep, epimeral plate; Pn, pereonite; sg, sternal gill; ir, inner ramus; and or, outer ramus.