Cephalopisella namhaensis, Choi & Kim & Kim, 2025

Choi, Jae-Hong, Kim, Kyung-Won & Kim, Young-Hyo, 2025, First record of the family Eriopisidae (Crustacea, Malacostraca, Amphipoda) from Southern Sea, Korea with description of one new species, Zootaxa 5722 (1), pp. 135-144 : 137-142

Cephalopisella namhaensis sp. nov.

(Korean name: Nam-hae-ppyo-jok-teok-yeop-sae-u, new)

( Figs. 2–5 )

Type material. Holotype, adult male, 3.4 mm, cat no. NIBRIV0000863933, Witdombae-do Island , Baekil-ri , Gwaeok-myeon, Goheung-gun, Jeollanam-do, Korea, 34°40′41″N, 127°26′58″E, 20 June 2017, collected by Y.H. Kim. Paratypes, adult female, 4.6 mm, cat no. NIBRIV0000928203, data same as holotype. The remaining paratypes ( 16 males, 3.0– 3.9 mm, 19 females, 3.6–4.6 mm, DKUAMP202503) in the collection of the corresponding author .

Additional material examined. 1 male, 7 females, So-do Island, Jangdo-ri, Beolgyo-eup , Boseong-gun , Jeollanam-do, 34°47′37″N, 127°28′32″E, Y.H. Kim, by SCUBA diving, 21 June 2017 ; 7 males, 12 females, Hyo-do Island, Jangdo-ri, Beolgyo-eup , Goheung-gun , Jeollanam-do, 34°46′52″N, 127°28′26″E, Y.H. Kim, by SCUBA diving, 21 June 2017 ; 3 females, Jin-do Island, Jangdo-ri, Beolgyo-eup , Boseong-gun , Jeollanam-do, 34°42′19″N, 127°25′51″E, Y.H. Kim, by SCUBA diving, 21 June 2017 ; 5 females, Chwi-do Island, Dolsan-eup, Yeosu-si , Jeollanam-do, 34°40′17″N, 127°42′41″E, Y.H. Kim, by SCUBA diving, 11 July 2018 ; 2 females, Geoje-do Island, Geoje-si , Gyeongsangnam-do, 34°53′08″N, 128°47′58″E, Y.H. Kim, by SM grab, 26 September 2021 ; 1 female, Geoje-do Island, Geoje-si , Gyeongsangnam-do, 34°53′06″N, 128°50′13″E, Y.H. Kim, by SM grab, 26 September 2021 ; 1 male, Geomun-do Island, Geomun-ri, Samsan-myeon , Yeosu-si , Jeollanam-do (continental shelf in the Southern Sea ), 34°05′35″N, 127°39′45″E, Y.H. Kim, by SM grab, 17 August 2022 ; 2 females, Geomun-do Island, Geomun-ri, Samsan-myeon , Yeosu-si , Jeollanam-do (continental shelf in the Southern Sea ), 33°51′30″N, 127°42′15″E, Y.H. Kim, by SM grab, 17 August 2022 .

Etymology. The specific epithet namhaensis originates from the Korean word “Nam-Hae”, meaning the South Sea, after the southern Korean coast in which the species was discovered.

Description. Holotype adult male, NIBRIV0000863933.

Body ( Figs. 2A , 3A ) dorsally smooth. Head (Fig, 3B) subrectangular, cephalic lobe produced anteroventrally, with a notch distally, ventral margin with a small notch; eye invisible in alcohol; epimeral plate 1 ( Fig 3C ), posteroventral corner acutely pointed, with 6 setae ventrally; epimeral plate 2, posteroventral corner acutely pointed, setose anteroventrally, with 2 setae ventrally; epimeral plate 3, posteroventral corner produced upward, distally pointed acutely, posterior margin convex, with 4 minute setae anteroventrally and 3 setae ventrally.

Antenna 1 ( Fig. 3D ) elongate; peduncular article 1 armed with 1 penicillate and 3 small robust setae dorsally, with 1 robust seta ventrally; peduncular article 2 subrectangular, with 2 dorsal and 1 ventral simple setae; peduncular article 3 short, with 2 dorsal and 2 ventral setae; length ratio of peduncular article 1–3 = 1.00: 0.92: 0.29; flagellum elongated, 15-articulate, x 1.47 peduncle in length, each article with setae distally, terminal article minute, with 4 apical setae; accessory flagellum short, uni-articulate.

Antenna 2 ( Fig. 3E ) shorter than antenna 1, gland corn bluntly pointed; peduncular article 3 short, with 1 seta ventrodistally; peduncular article 4 elongated, with 2 setae ventrally; peduncular article 5 with 2 dorsal and 1 ventral setae; length ratio of peduncular article 3–5 = 1.00: 2.23: 1.83; flagellum 5-articulate, each article with setae distally, terminal article with 4 setae distally.

Upper lip ( Fig. 3F ) laterally produced, covered with patch of pubescence apically.

Lower lip ( Fig. 3G ) well developed, inner lobes well defined, with patch of pubescence apically, outer lobe medially setulose, mandibular lobes produced, narrowing laterally.

Left mandible ( Fig. 3H ), incisor with 3 teeth; lacinia mobilis bifid, both part with 3 blunt teeth; accessory setal row absent; molar triturative; palp 3-articulate; article 1 short, unarmed; article 2 with 2 simple setae; article 3 slender, with 2 lateral and 3 distal simple setae; length ratio of articles 1–3 = 1.00: 2.35: 3.53.

Right mandible ( Fig. 3I ) similar to left one.

Maxilla 1 ( Fig. 3J ), inner plate small, with 2 plumose and 1 robust setae apically; outer plate with 7 dentate setae apically; palp biarticulate, distal article expanded, with 9 robust setae apically.

Maxilla 2 ( Fig. 3K ), inner plate subrectangular, with row of simple setae apically and 1 robust seta near the apical margin; outer plate broader than inner plate, with row of simple setae apically.

Maxilliped ( Fig. 3L ), inner plate subrectangular, about half length of outer plate, with 10 setae apically; outer plate broad, with 1 robust seta posteriorly and row of conical teeth medially; palp 4-articulate, article 1 subrectangular, unarmed; article 2 subrectangular, with unequal simple setae exteriorly; article 3 slightly dilated, with simple setae distally; article 4 falcate, with 1 small robust and 1 simple setae near the nail; length ratio of articles 1–4 = 1.00: 2.67: 1.13: 1.17.

Gnathopod 1 ( Fig. 4A ) subchelate; coxa small, subtrapezoidal, notched anteriorly, with 1 small seta on notch; basis subrectangular, widening distally, with 2 anterior and 4 posterior long setae, and 2 long setae on posterodistal corner; merus, densely pubescent posteriorly, with 4 long setae posterodistally; carpus slightly swollen posteriorly, with unequal setae on posterior margin; propodus subtriangular, with 3 long setae anterodistally; palm oblique, longer than posterior margin, with row of robust setae on palmar margin; dactylus slender, falcate, already fitting palm, with 1 seta distally; length ratio of basis to dactylus = 1.00: 0.26: 0.31: 0.69: 0.72: 0.62.

Gnathopod 2 ( Fig. 4B ) subchelate, similar to gnathopod 1, but coxa, with rounded anterior corners and notched anterior and posteriorly, each notch with 1 small seta; carpus subtriangular, with produced posterodistal lobe, densely pubescent posterodistally; propodus subtriangular, anteroproximal margin slightly concave; palm oblique, with row of unequal robust setae and 2 simple setae, palmer corner with 3 robust setae; dactylus falcate, not reaching palmer corner; length ratio of basis to dactylus = 1.00: 0.19: 0.25: 0.54: 0.63: 0.45.

Pereopod 3 ( Fig. 4C ), coxa small, with rounded corners and notched anterior and posteriorly, each notch with 1 small seta; basis subrectangular, with 1 simple seta posteriorly; merus subrectangular, widening distally, with 2 robust setae on anterodistal corner and 4 setae on posterior margin; carpus with 1 robust seta on anterodistal corner and 3 long and 3 stiff setae on posterior margin; propodus slender, with 2 setae on anterior corner and 3 simple setae on posterior margin; dactylus falcate; length ratio of basis to dactylus = 1.00: 0.16: 0.66: 0.44: 0.48: 0.41.

Pereopod 4 ( Fig. 4D ) similar to pereopod 3, but coxa smaller than that of pereopod 3; length ratio of basis to dactylus = 1.00: 0.20: 0.77: 0.50: 0.67: 0.55.

Pereopod 5 ( Fig. 4E ), coxa bilobate, anterior lobe slightly protruding downward, anterior margin with 3 teeth, accompanied by short setae, posterior lobe notched, with 1 short seta; basis subrectangular, anterior margin with 5 robust setae, posterior margin with 5 teeth, accompanied by short setae; merus, with 5 anterior and 2 posterior robust setae; carpus and propodus subrectangular, slender; dactylus slender, with 1 seta anterodistally; length ratio of basis to dactylus = 1.00: 0.19: 0.49: 0.56: 0.47: 0.32.

Pereopod 6 ( Fig. 4F ) similar to pereopod 5, but each article elongate; coxa anterior margin with 2 teeth, and with 1 robust and 1 short setae, posterior lobe notched, with 1 robust seta; basis border than that of pereopod 5, posterior margin serrate, with row of simple setae; length ratio of basis to dactylus = 1.00: 0.19: 0.50: 0.63: 0.67: 0.33.

Pereopod 7 ( Fig. 4G ) elongate; coxa unilobate, with 1 robust seta anteriorly; basis moderately broad, anterior margin with row of robust setae, posterior margin serrate, with row of simple setae, posterior lobe slightly protruding downward; merus widening proximally, with 3 anterior and 4 posterior robust setae; carpus and propodus subrectangular, slender; dactylus slender; length ratio of basis to dactylus = 1.00: 0.17: 0.42: 0.61: 0.69: 0.32.

Uropod 1 ( Fig. 4H ), peduncle subrectangular, length 1.04 x inner ramus, with 3 dorsolateral, 5 dorsomedial, 2 dorsodistal and 1 basofacial robust setae; inner ramus slender, length 1.04 x outer ramus, with 2 dorsal and 5 apical robust setae; outer ramus with 2 dorsal and 4 apical robust setae.

Uropod 2 ( Fig. 4I ), peduncle short, length 0.65 x inner ramus, with 2 dorsodistal robust setae; inner ramus length 1.16 x outer ramus, with 3 dorsal and 4 apical robust setae; outer ramus with 2 dorsal and 4 apical robust setae.

Uropod 3 ( Fig. 4J ), peduncle short, length 0.36 x outer ramus, with 3 robust setae on ventrodistal corner; inner ramus scale-like, short, length 0.20 x outer ramus, with 1 dorsal and 1 apical robust setae; outer ramus bi-articulated, proximal article elongate, with 1 dorsal, 4 ventral and 5 apical robust setae, distal article short, length 0.31 x proximal article, with 3 apical robust setae.

Telson ( Fig. 4K ) deeply cleft (80 %), each lobe apically pointed, with 2 simple and 1 robust setae apically.

Paratype, adult female, cat no. NIBRIV0000928203.

Body ( Fig. 2B , 5A ) about 4.6 mm long, similar to male in shape, but with brood plates on pereopods 2–6.

Gnathopod 1 ( Fig. 5B ) similar to that of male; length ratio of basis to dactylus = 1.00: 0.26: 0.37: 0.67: 0.67: 0.56.

Gnathopod 2 ( Fig. 5C ) subchelate, similar to that of male, but propodus ovate; length ratio of basis to dactylus = 1.00: 0.18: 0.36: 0.55: 0.59: 0.45.

Variation. Five adult males and five adult females from the paratype specimens were examined to assess intraspecific morphological variation. All examined specimens consistently exhibited the diagnostic characters described for the species. No notable differences were observed in key features, including the anteroventral corner of the cephalic lobe; the posterior margin and posteroventral corner of epimeral plate 3; the lateral projection of the upper lip; the number of posterior setae on article 3 of the mandibular palp; and the posteroventral lobe of the basis of pereopod 7 ( Table 1). These distinguishing features remained stable across all individuals, indicating no significant morphological variation within the species.

Remarks. Cephalopisella namhaensis sp. nov. resembles C. propagatio ( Imbach, 1967) from Nha-Trang, Vietnam, in having notched cephalic lobe and indistinct sexual dysmorphism in the male and female gnathopods 1 and 2. However, C. namhaensis sp. nov. can be distinguished from C. propagatio based on the characters listed in Table 1 and the following features (different character states of C. propagatio in brackets): (1) antenna 1, peduncular article 1 shorter than article 2 (vs. longer than article 2); (2) cephalic lobe of head blunt, not covering gland corn of peduncular article 2 of antenna 2 (vs. produced, covering gland corn); (3) mandibular palp, article 3 with two long setae posteriorly (vs. bare); and (4) epimeral plate 3 with posterolateral upturned acute process (vs. with produced acute process distally).

The occurrence of Cephalopisella propagatio s.l. was also documented by Ren (2012) from the lower Yangtze River and the Gulf of Liaodong in China. However, morphological differences were found between C. propagatio s.l. as described by Ren (2012) from China and the original description of C. propagatio by Imbach (1967) from Vietnam by the following features (different characters of C. propagatio from Vietnam in brackets): (1) cephalic lobe blunt, not covering gland corn of peduncular article 2 of antenna 2 (vs. produced, covering gland corn); (2) upper lip, lateral projection apically round (vs. apically acute); (3) mandibular palp, article 3 posterior margin with three setae (vs. without setae); and (4) epimeral plate 3, posteroventral corner truncate upward (vs. smoothly produced distally). Consequently, C. namhaensis sp. nov. collected from Korean waters shows closer morphological affinity to the geographically proximate C. propagatio s.l. from China than to those originally described from Vietnam. However, C. namhaensis sp. nov. can also be distinguished from C. propagatio s.l. as described by Ren in the following features: (1) antenna 1, peduncular article 2 slightly shorter than peduncular article 1 (vs. longer than peduncular article 1); (2) upper lip, lateral projection acutely produced (vs. bluntly produced); and (3) mandibular palp, article 3 with two lateral setae (vs. with three lateral setae).

In general, Cephalopisella namhaensis sp. nov. is very similar to C. propagatio s.l. from Chinese waters as described and figured by Ren (2012). However, since our Korean specimens show minor differences from the Chinese specimens described by Ren (2012) and we have not had the opportunity to examine Ren’s material, we cannot confidently determine whether they are the same species. Therefore, we decided not to synonymize these two species and leave them as separate species.

Distribution. Korea.

Figures

FIGURE 2. Cephalopisella namhaensis sp. nov., A, male, 3.4 mm, habitus; B, paratype, female, 4.6 mm, habitus. Scale bars: A, B = 1.0 mm.

FIGURE 3. Cephalopisella namhaensis sp. nov., holotype, adult male, 3.4 mm cat no. NIBRIV0000863933: A, habitus; B, head, lateral view; C, epimeral plates 1–3; D, antenna 1, medial view; E, antenna 2, medial view; F, upper lip; G, lower lip; H, left mandible; I, right mandible; J,maxilla 1; K, maxilla 2; L, maxilliped. Scale bars: A, D, E = 0.5 mm, B = 0.2 mm, C = 0.3 mm, F–L = 0.1 mm.

FIGURE 4. Cephalopisella namhaensis sp. nov., holotype, adult male, 3.4 mm cat no. NIBRIV0000863933: A, gnathopod 1; B, gnathopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, pereopod 7; H, uropod 1; I, uropod 2; J, uropod 3; K, telson, dorsal view. Scale bars: A–G = 0.2 mm, I–K = 0.1 mm.

FIGURE 5. Cephalopisella namhaensis sp. nov., paratype, adult female, 4.6 mm, cat no. NIBRIV0000928203: A, habitus; B, gnathopod 1; C, gnathopod 2. Scale bars: A = 1.0 mm, B, C = 0.3 mm.