Peramphithoe chujaensis, Kim, Young-Hyo, Hong, Soon-Sang, Conlan, Kathleen E. & Lee, Kyung-Sook, 2012

Kim, Young-Hyo, Hong, Soon-Sang, Conlan, Kathleen E. & Lee, Kyung-Sook, 2012, The genus Peramphithoe Conlan & Bousfield, 1982 from Korean waters (Crustacea: Amphipoda: Ampithoidae), Zootaxa 3400, pp. 1-19 : 6-11

publication ID	https://doi.org/ 10.5281/zenodo.211185
DOI	https://doi.org/10.5281/zenodo.5667753
persistent identifier	https://treatment.plazi.org/id/7F3EEF60-FFC8-FF83-07FA-FF60FDCCFB50
treatment provided by	Plazi
scientific name	Peramphithoe chujaensis
status	sp. nov.

Treatment

Peramphithoe chujaensis View in CoL sp. nov.

(Korean name: Chu-ja-do-cham-yeop-sae-u, new) (figs 3–6)

Type material. Holotype, adult male, 10.9 mm, (appendages on one slide), cat no. NIBRIV0000246630, Sangchujado Is., Jeju-si, Korea, 33° 57ʹ 51ʺN, 126° 17ʹ 11ʺE; 15 November 2008 (Y.H. Kim) by SCUBA diving at 6 m in depth. Paratypes, 1 Ƥ, 10.7 mm, dissected (appendages on one slide), NIBRIV0000246631, other data same as Holotype; 1 adult Ƥ, 6.8 mm, CMNC 2012-0012, other data same as holotype; and the remaining paratypes (15 juveniles, 3.2–5.8 mm), DKU 201204, in the collection of the first author.

Type locality. Sangchujado Is., Jeju-si, Korea.

Etymology. The species name is derived from the type locality, Chujado Island located off the south coast of Korea.

Diagnosis. Head as long as wide. Eye circular, medium. Epimeral plate 2 quadrate posteroventrally, epimeral plate 3 subquadrate posteroventrally. Antenna 1 peduncular article 1 subequal in length to article 2, flagellum elongate, more than 3 x as long as peduncle. Antenna 2 less than half length of antenna 1, with plumose setae ventrally (male only). Lower lip, medial lobe of outer lobe as long as lateral lobe. Maxilla 1 inner plate with 1 subapical seta. Maxilla 2 inner plate subequal in length to outer. Maxilliped outer plate extending beyond end of palp article 2. Gnathopod 1 carpus subequal to propodus. In male, gnathopod 2 propodus dilated proximally, about 0.7 x as wide as long, palm excavate. In male, pereopods 5–7 meri and carpi strongly expanded. In female, gnathopod 2 propodus, pereopods 5–7 meri and carpi rectangular, ordinary. Uropod 3 peduncle more than twice the length of rami.

Description. Male, holotype. Body (figs 3, 4A) 10.9 mm long; head as long as wide, subequal in length to pereonites 1–2 combined; circular eye occupying lateral cephalic lobes; pereon and pleon smooth; Epimeral plates 1–3 ( Fig. 4 View FIGURE 4 B) without ventral seta or spine, epimeral plate 2 quadrate posteroventrally, epimeral plate 3 roundedquadrate posteroventrally, prominently concave midposteriorly.

Antenna 1 ( Fig. 4 View FIGURE 4 C) less setose than antenna 2, about 0.7 x as long as body length, length ratio of peduncular articles 1–3 = 1.00: 0.92: 0.28, article 1 with 2 ventral and 3 distoventral spinules; flagellum 37-articulate, 3.52 x as long as peduncle; accessory flagellum absent.

Antenna 2 ( Fig. 4 View FIGURE 4 D) setose, short, about 0.4 x as long as antenna 1; length ratio peduncular articles 3–5 = 1.00: 2.50: 2.14; ventral margins of peduncular articles 3–5 and flagellum with transverse rows of plumose and simple setae; flagellum 13-articulate, 0.61 x as long as peduncle.

Lower lip ( Fig. 4 View FIGURE 4 E) inner lobe ovate; outer lobe tripartite, medial lobe subequal in length to lateral lobe, both lobes pubescent apically.

Right mandible ( Fig. 4 View FIGURE 4 F) incisor with 9 blunt teeth; lacinia mobilis with 7 tiny crenulated teeth; molar truncate, fully triturating; accessory setal row of 11 setae between lacinia mobilis and molar; palp well developed, triarticulate, article 2 1.28 x as long as distal one, with one submarginal seta; article 3 with 8 pinnate unequal setae on distal margin; left mandible similar to right one, but lacinia mobilis 9 dentate, more distinct and more pointed than that of the right one.

Maxilla 1 ( Fig. 4 View FIGURE 4 G) inner plate subtriangular, with subapical seta; outer plate with 10 sclerotized spine-teeth (3 simple, 2 bifid and 6 denticulate) apically; palp biarticulate, distal article with 1 simple and 3 tricuspidate spines apically.

Maxilla 2 ( Fig. 4 View FIGURE 4 H) inner plate subequal in length but more slender than outer one, apical and inner margins with row of pinnate setae; outer plate with pinnate setae on apical and apicolateral margins.

Maxilliped ( Fig. 4 View FIGURE 4 I) inner plate developed, lateral and apical submargins with pinnate setae, apical margin with 1 spine on right, 2 on left; outer plate subovate, extending beyond end of palp article 2, inner margin with 1 longitudinal row of conical, serrated teeth, distal half of outer margin with slender setiform teeth and setae; palp 4-articulate, article 1 short, with 3 simple setae apically, article 2 1.33 x as long as article 3, with a row of pinnate setae on inner margin, article 4 0.68 x as long as article 3, with inner marginal surface covered by tiny setules; unguis acute, well developed.

Gnathopod 1 ( Fig. 5 View FIGURE 5 A) coxa subrectangular, with 4 simple setae posterodistally; carpus subequal in length to propodus, posterior margin slightly rounded with unequal simple setae; propodus subrectangular, palm transverse, straight, defined by 1 small spine; dactylus falcate, with 1 penicillate seta anteroproximally; length ratio of articles 2–7 = 1.00: 0.24: 0.37: 0.59: 0.61: 0.30.

Gnathopod 2 ( Fig. 5 View FIGURE 5 B) coxa similar to coxa 1, with 5 unequal setae on distal margin; basis subrectangular, with long setae posteriorly; carpus subtriangular, rounded posterior lobe setaceous; propodus large, about 0.7 x as wide as long, subequal in length to basis, distal part narrower than proximal; palm excavate, curved concavely, with densely long to short setae marginally; dactylus falcate, with 1 penicillate seta anteroproximally, row of setules on medial margin, 0.83 x as long as propodus.

Pereopod 3 ( Fig. 5 View FIGURE 5 C) coxa subrectangular, ventral margin smooth, truncated, with 6 setae posterodistally; basis expanded, with row of simple setae posteriorly; merus widening anteriorly, anterodistal corner protruding; dactylus falcate, with 1 penicillate seta anteroproximally; length ratio of articles 2–7 = 1.00: 0.25: 0.47: 0.41: 0.38: 0.19.

Pereopod 4 similar to pereopod 3, but coxa ( Fig. 5 View FIGURE 5 D) slightly wider than coxa 3.

Pereopod 5 ( Fig. 5 View FIGURE 5 E) coxa bilobate, dorsodistal protruding lobe with 2 feeble spines; basis expanded, subequal in length to width, anterior margin with 1 proximal spine and several groups of setae, posterovental lobe slightly protruding, with 1 spine; merus subtriangular, strongly expanding distally; carpus subquadrate, expanded, 1.05 x as long as wide; propodus comparatively more slender than carpus, posterior margin with a row of 5 robust spines and 2 subdistal spines; length ratio of articles 2–7 = 1.00: 0.35: 0.68: 0.76: 0.76: 0.24.

Pereopod 6 ( Fig. 5 View FIGURE 5 F) basis weakly expanded, 1.61 x as long as wide, with 1 spine posterodistally; merus and carpus expanded, subequal in length; propodus narrow, subrectangular, posterior margin with 5 robust spines and triad spines subdistally; length ratio of articles 2–7 = 1.00: 0.25: 0.45: 0.49: 0.76: 0.21.

Pereopod 7 ( Fig. 5 View FIGURE 5 G) similar to pereopod 6, but longer and wider; carpus subequal in length and 3.2 x as wide as to propodus; length ratio of articles 2–7 = 1.00: 0.29: 0.68: 0.70: 0.73: 0.20.

Uropod 1 ( Fig. 5 View FIGURE 5 H) peduncle 1.1 x as long as inner ramus, bearing enlarged distoventral spur, with 5 dorsolateral (2 proximal spines missing), 7 dorsomedial spines and a row of basofacial setae; outer ramus slightly shorter than inner one.

Uropod 2 ( Fig. 6 View FIGURE 6 A) peduncle subequal in length to outer ramus, ventral spur short and slightly pointed, with 3 dorsolateral and 3 dorsomedial spines; outer ramus slightly shorter than inner one, both rami with 2 rows of spines, and a cluster apically.

Uropod 3 ( Fig. 6 View FIGURE 6 B) peduncle more than twice the length of rami, with 3 groups of lateral setae, a row of 11 ventral setae laterally, duad and triad spines mediodistally; both rami subequal in length, outer ramus bearing 2 hooked terminal spines, inner one apically setose and with one small spine.

Telson ( Fig. 6 View FIGURE 6 C) fleshy, subtriangular, wider than deep, posterodistal apex truncate and bulging, with simple or penicillate setae submarginally.

Female, paratype. Body ( Fig. 6 View FIGURE 6 D) length 10.7 mm, morphologically similar to male in shape, including gnathopod 1, which is not sexually dimorphic, subchelate. Antenna 2, gnathopod 2 and pereopods 5-7 sexually dimorphic. Antenna 2 lacking plumose setae ventrally. Gnathopod 1 ( Fig. 6 View FIGURE 6 E), carpus subequal in length to propodus. Gnathopod 2 ( Fig. 6 View FIGURE 6 F), carpus subtriangular and shorter than carpus of gnathopod 1; propodus similar in shape to but wider than propodus of gnathopod 1; palm steeply oblique. Pereopods 5–7 (figs 6G–I), meri and carpi not expanded but ordinary rectangular in form.

Variation. Unfortunately, only one mature male specimen was collected in the present study so that it is impossible to judge how much variation may occur during the mature stage in male. Body length at maturity of male is 10.9 mm, female 6.8-10.7 mm, because the 6.8 mm female (CMNC 2012-0012) was found brooding offspring. In these 2 mature females, gnathopod 1 to pereopod 7 ratio of article lengths are similar to each other. The mature female, 6.8 mm, however, pereopods 5–7 bases slightly wider than those of large female (10.7 mm long); pereopods 5–7 propodi with a row of 4, 5, and 4 spines along posterior margins, respectively, while 5, 6, and 4 spines in the large female; uropods 1–2 peduncles with 5 and 3 dorsolateral spines, while 6 and 3 in the large female; uropods 1–2 outer rami with 6 and 5 outer spines, while 7 and 5 in the large female. On the other hand, small juveniles (4.2–5.8 mm), antenna 1 has a flagellum of 17–30; antenna 2 a flagellum of 9–13 articles; pereopods 5–7 propodi with a row of 3–4, 4, 3–4 spines posteriorly; uropods 1–2 peduncles with 3–4 and 2 dorsolateral spines; uropods 1–2 rami with 3–5 and 3–4 outer spines.

Remarks. Among the species of genus Peramphithoe , only 3 other species have some degree of enlargement or broadening of pereopods 5–7 in the male: P. fa l s a Barnard, 1932, P. s p u r i a Krapp-Schickel, 1978 and P. p a r m e rong Poore & Lowry, 1997. However, male of P. chujaensis sp. nov. has a concave palm in the gnathopod 2 and ventral plumose setae on the antenna 2. These conditions do not occur in its congeners.

Molecular data. CO1 gene sequences (GenBank accession numbers JN575621 View Materials – JN575622 View Materials ) were obtained from two specimens. Sequence alignment was straightforward without any insertion or deletion. Intra-specific variation of the CO1 gene sequence of P. chujaensis sp. nov. ranged 0.4%, while inter-specific variation ranged from a low of 9.1% ( P. chujaensis sp. nov. and P. namhaensis ) to a high of 12.1% ( P. chujaensis sp. nov. and P. t e a) (Figure 12, Table 2 View TABLE 2 ).