Peramphithoe eoa (Brüggen, 1907), Bruggen, 1907

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 : 11-15

Peramphithoe eoa (Brüggen, 1907)

(Korean name: Gin-son-ga-lac-cham-yeop-sae-u, new) (figs 7–9)

Amphithoe eoa Brüggen, 1907: 481 , figs 4–5 (cited from Gurjanova, 1938). — Gurjanova, 1938: 345, figs 46–46a. — 1951: 881, figs 615a–b. — Barnard, 1954: 27, pls 25–26. — Tzvetkova, 1967: 186.

Peramphithoe eoa . — Conlan & Bousfield, 1982: 60.

Material examined. 1 3, Geojin, Gosung-gun, 24 February 2005 (Y.H. Kim), by fishing net; 4 specimens, Gajin, Gosung-gun, 14 March 2006 (Y.H. Kim), by fishing net; 1 Ƥ, Gajin, Gosung-gun, 24 February 2007 (Y.H. Kim), by fishing net.

Type locality. Vladivostok, Russian Far Eastern seas.

Diagnosis. Head as long as wide. Eye small, round. Epimeral plates 2–3 subquadrate posteroventrally. Antenna 1 elongate, peduncular article 1 subequal to article 2, flagellum elongate, more than twice the length of peduncle. Antenna 2 about half length of antenna 1, peduncular article 4 subequal in length to article 5, flagellum slightly longer than article 5. Lower lip outer lobe tripartite, medial lobe shorter than lateral lobe. Maxilla 1 inner plate with 3 pinnate setae subapically. In male, gnathopod 1 carpus subequal to propodus. Gnathopod 2 propodus massive, narrowing distally, posterior margin straight; dactylus elongate, longer than propodus. In female, gnathopod 1 propodus slightly longer than carpus. Gnathopod 2 propodus elongate-ovate, palm oblique. Uropod 3 peduncle more than twice the length of rami.

Description. Adult male: Body length 19.3 mm, comparatively large-sized species. Head (figs 7, 8A) 1.5 x as long as pereonite 1. Lateral cephalic lobe slightly angular. Eye small, round, located close to lateral cephalic lobe. Antenna 1 weakly setose, very long, slightly shorter than the total body length; peduncular article 1 stouter than and nearly as long as article 2; peduncular article 3 short, 0.26 x as long as article 2, bearing 1 or 2 spines ventrodistally; flagellum very long, 2.85 x as long as peduncle. Antenna 2 0.55 x as long as antenna 1; peduncular articles 1–3 short, article 4 slightly longer than article 5; flagellum 25-articulate, 1.20 x as long as peduncular article 5.

Epimera ( Fig. 8 B) without seta or spine on ventral margins, curved ventrally.

Lower lip ( Fig. 8 C) inner lobe pubescent apically; outer lobe tripartite, medial lobe shorter than lateral lobe, both lobes densely pubescent apically.

Mandible ( Fig. 8 D) incisor and lacinia mobilis dentate, with 9 blunt teeth, respectively; molar truncate, more or less protruding; accessory setal row of 13 setae between lacinia mobilis and molar; palp well developed, triarticulate, proximal article short, distal article 1.38 x as long as article 2, with apical pinnate setae.

Maxilla 1 ( Fig. 8 E) inner plate relatively small, with 3 pinnate setae subapically; outer plate with 10 sclerotized simple or irregularly serrate spine-teeth; palp biarticulate, distal article with 7 conical spines and 3 pinnate setae.

Maxilla 2 inner plate slightly smaller than outer one, both plates distomarginally setose.

Gnathopod 1 ( Fig. 8 F) coxa subquadrate, bearing simple setae posterodistally; basis 1.26 x as long as merus and carpus combined, with long setae posteromarginally; propodus subequal to carpus, palm transverse, with 1 medial spine; dactylus falcate, with 1 penicillate seta anteroproximally.

Gnathopod 2 ( Fig. 8 G) coxa D-shaped, roundly curved anteromarginally, with unequal setae on posterodistal margin; basis subrectangular, narrowing proximally, with long simple setae posteromarginally, 1.49 x as long as merus and carpus combined; propodus very large, massive, 1.31 x as long as basis, tapering distally, posterior margin straight, palm obscure; dactylus very long, lacking penicillate seta anteroproximally, 1.17 x as long as propodus, apical portion extending beyond propodus and curved upwards.

Pereopod 3 ( Fig. 9 A) coxa subquadrate, with unequal setae on ventrodistal margin; basis 1.63 x as long as merus and carpus combined, both margins slightly bulging, posterior margin with long setae; merus 1.18 x as long as carpus, anterodistal part more or less extending toward carpus; subequal in width to length ratio of carpus and propodus; dactylus falcate, with 1 penicillate seta anteroproximally.

Pereopod 5 ( Fig. 9 B) basis subcircular, relatively plump, 0.89 x as wide as long, 1.24 x as long as merus and carpus combined, with 4 spines on anteromedial margin, simple setae distal half of anterior margin; merus wider and 1.08 x longer than carpus; propodus bearing a row of spines, narrower and 1.45 x longer than carpus.

Pereopod 6 ( Fig. 9 C) coxa bilobate, anterior lobe roundly protruding downward; basis ovate, with a row of spines on anterior margin; propodus 1.38 x as long as carpus, with a row of spine-setae; dactylus falcate, with 1 penicillate seta anteroproximally; length ratio of articles 2–7 = 1.00: 0.26: 0.67: 0.55: 0.76: 0.26.

Uropod 1 ( Fig. 9 D) peduncle 1.87 x as long as inner ramus, with enlarged distoventral spur, 5 dorsolateral, 5 dorsomedial spines, and a row of basofacial setae laterally; outer ramus 0.84 x as long as inner one, rami bearing two rows of spines on both margins.

Uropod 2 ( Fig. 9 E) similar in structure but smaller than uropod 1, distoventral spur relatively short, peduncle 1.27 x as long as rami, with 3 dorsolateral and 2 dorsomedial spines; both rami subequal in length. Uropod 3 ( Fig. 9 F) peduncle cylindrical, 2.31 x as long as outer ramus, bearing 3 groups of lateral setae, 2 groups of small spines distally; outer ramus bearing 2 hooked terminal spines, inner ramus with 2 medial spines and small spines and setae apically; both rami subequal in length.

Telson ( Fig. 9 G) subtriangular, more or less distally truncated, 1.44 x as wide as long, with 5 or 6 lateral setae, 1 or 2 simple and 1 plumose penicillate seta on each submarginal margin.

Female. Body length 18.5 mm, similar to male in shape, but carpus of gnathopod 1 ( Fig. 9 H) shorter and stouter than that of male, carpus to dactylus of gnathopod 2 ( Fig. 9 I) showing sexual dimorphism; gnathopod 1, propodus slightly longer than carpus, gnathopod 2, palm of propodus oblique. Pereopod 7 ( Fig. 9 J) slender, coxa small, subrectangular, length ratio of articles 2–7 = 1.00: 0.29: 0.70: 0.56: 0.78: 0.46.

Remarks. Peramphithoe eoa (Brüggen, 1907) has morphologically closest affinity to P. baegryeongensis Kim & Kim, 1988 . However several morphological differences are found between P. e o a and P. baegryeongensis : 1) the length of antenna 1 of P. e o a relatively longer than P. baegryeongensis ; 2) the inner plate of maxilla 1 of P. e o a bearing 3 setae, while 1 seta in P. baegryeongensis ; 3) in male, the posterior margin of propodus of gnathopod 2 of P. eoa rather straight, while concave in P. baegryeongensis ; 4) in male, dactylus of gnathopod 2 of P. e o a very long, longer than propodus, reach the middle portion of merus, while shorter than propodus in P. baegryeongensis . This species is distributed in the temperate north Pacific.

Molecular data. CO1 gene sequences (GenBank accession numbers JN575623 – JN575624 ) were obtained from two specimens. Sequence alignment was straightforward without any insertion or deletion. Intra-specific variation of the CO1 gene sequence of the species ranged 0.1%, while inter-specific variation ranged from a low of 10.7% (P. e o a and P. namhaensis ) to a high of 13.5% (P. e o a and P. t e a) ( Figure 12 , Table 2 ).

Distribution. North Pacific: Korea (east coast), Japan, Russia, Canada, US.

Figures

FIGURE 8. Peramphithoe eoa (Brüggen, 1907), male, 19.3 mm, Gajin, Gosung-gun, Korea: A, head; B, pleonites; C, lower lip; D, mandible; E, maxilla 1; F, gnathopod 1; G, gnathopod 2. Scale bars = 2.0 mm (A, B), 1 mm (F, G), 0.4 mm (C – E).

FIGURE 9. Peramphithoe eoa (Brüggen, 1907), male, 19.3 mm, Gajin, Gosung-gun, Korea: A, pereopod 3; B, pereopod 5; C, pereopod 6; D. uropod 1; E, uropod 2; F, uropod 3; G, telson; Peramphithoe eoa (Brüggen, 1907), female, 18.5 mm, Gajin, Gosung-gun, Korea: H, gnathopod 1; I, gnathopod 2; J. pereopod 7. Scale bars = 1.0 mm (A – C, H – J), 0.4 mm (D – F), 0.1 mm (G).

FIGURE 12. Neighbor-joining tree of the five Korean species of peramphithoids with Ampithoe valida the outgroup, based on 657 base pairs of mtCO 1 gene. Values at nodes indicate bootstrap values above 50 %.