Guernea jejuensis Kim, Hendrycks & Lee, 2011, sp. nov.
Creators: name: Kim, Young-Hyo
name: Hendrycks, Ed A.
name: Lee, Kyung-Sook
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Dexaminidae
Guernea
Guernea jejuensis

description: Guernea jejuensis sp. nov.
(Korean Name: Je-ju-but-eun-kko-ri-yeop-sae-u, new) (Figs. 2 B, 6–10)
Type material. Holotype, adult male, 2.6 mm, (appendages on one slide), cat no. NIBRIV0000240789, Seongsanpo, Jejudo Is., 33° 28ʹ 25ʺN, 126° 56ʹ 0 6ʺE, 6 May 1994, (B.J. Kang), collected from light trap on bottom, depth 5 m. Paratypes, 1 Ƥ, 2.5 mm, dissected (appendages on one slide), NIBRIV0000240790, other data same as holotype; 2 adult 3, CMNC 2011-0183 other data same as holotype; 1 adult 3, 2.4 mm, dissected (appendages on one slide), 1 3, 2.3 mm, DKU cat no. 201101, other data same as holotype, and the remaining paratypes (23 3, 22 Ƥ) in the collection of the first author.
Additional material examined: 4 3, Hanlim, Jejudo Is., 11 August 1998; 2 3, Sewha, Jejudo Is., 12 August 1998.
Etymology. The species name is derived from the type locality, Jejudo Island located off the south coast of Korea.
Diagnosis. Antenna 1, peduncular article 2 rather slender, about 3/4 length of article 1; maxilla 1, inner plate small, lacking apical seta, palp uniarticulate; gnathopod 2 (male), carpus elongate, 1.6 x length of propodus; pereopod 5, merus broad, 0.5 x as wide as long; urosomite 1 lacking dorsal elevation; urosomites 2–3 extending anteriorly far beyond end of urosomite 1.
Description. Holotype, adult male, 2.6 mm, cat no. NIBRIV0000240789.
Body (Figs. 2 B, 6A) strongly chitinized; cephalon subequal in length to pereonites 1–3 combined; rostrum short, lateral cephalic lobe triangular, narrowly rounded; eye large, rounded, composed of numerous ommatidia, slightly bulging.
Pleonites (Fig. 6 B) weakly carinate; epimeron 1 with anterior sinus, slightly produced anteroventrally, with 2 small setae, posteroventral corner rounded; epimeron 2 rounded ventrally, with 3 small setae; epimeron 3 anteroventrally rounded, ventral margin straight, with 3 ventral and 2 posteroventral setae, posteroventral corner quadrate.
Urosomite 1 (Figs. 6 B, 10A–B) about 0.8 x as long as following urosomite, lacking dorsal keel, appearing separate from the following urosomite in dorsal view; urosomites 2–3 sloped posteriorly, isosceles triangularly shaped in dorsal view, anterodorsal portion shallowly notched, anteriorly extending far beyond end of urosomite 1, shallowly fluted between lateral ridges.
Antenna 1 (Fig. 6 C) subequal in length to cephalon and pereonites 1–4 combined; length ratio of peduncular articles 1–3 = 1.00: 0.69: 0.27, peduncular article 1 slightly convex posteriorly, with 2 thin, long simple setae and numerous setular tufts; peduncular article 2 slender, with 4 clusters of setae and 1 penicillate seta posteriorly; accessory flagellum vestigial, uniarticulate, with 1 simple seta and 1 tiny aesthetasc; flagellum 9-articulate, with 1 or 2 marginal aesthetascs.
Antenna 2 (Fig. 6 D) slightly shorter than half body length; peduncular articles 1–3 short, gland cone well developed, peduncular article 4 slightly longer and stouter than peduncular article 5, with numerous setular tufts anteriorly; flagellum 18-articulate.
Lower lip (Fig. 6 E) inner lobes broadly rounded, outer lobes with 1 shoulder tooth apically; both lobes pubescent apically.
Left mandible (Fig. 6 F) incisor smooth, broad, weakly bifurcate; lacinia mobilis blunt, weakly 5-dentate; molar process well developed, protruding, strongly sclerotized; accessory spines or setae lacking.
Right mandible (Fig. 6 G) smooth, similar to left one; incisor smooth, rounded; lacinia mobilis weakly bifid; molar process with 1 pappose seta.
Maxilla 1 (Fig. 6 H) inner plate small, triangular, without apical seta; outer plate with 7 tooth-like spines (simple, bifid and denticulate) apically; palp uniarticulate, slightly extending over apex of outer plate, apically with 2 simple setae and small tooth.
Maxilla 2 (Fig. 6 I) inner plate rounded apically, shorter than outer one, medial and apical margins with 4 simple setae; outer plate with 4 simple setae apically and 1 sub-apical short seta on lateral margin.
Maxilliped (Fig. 6 J) inner plate small, with 2 apical setae; outer plate large, extending beyond end of palp article 2, medial margin with 5 setae and 6 conical teeth; palp 4-articulate, article 2 about half as long as palp, medial margin with 2 rows of setae, article 3 about 0.4 x as long as article 2, distal article falcate, shorter than article 3.
Gnathopod 1 (Fig. 7 A) coxa elongate-ovate, anterior and ventral margins with 5 feeble setae; basis, strongly curved proximally, anterior margin with 4 short setae and 1 median long seta, posterodistal margin with 1 long seta; merus tapering distally, about 1.5 x as long as ischium, with 3 setae posterodistally; carpus gradually widening, about 1.3 x as long as propodus, posterior margin with 6 spines; propodus subrectangular, medial face with an angled row of 5 setae, palm obliquely inclined, about 0.6 x as long as ventral margin, with tiny unequal setules marginally, delimited by 3 spines distally; dactylus fitting palm, with distinct tooth on inner margin.
Gnathopod 2 (Fig. 7 B) slender, uniform in width; coxa 2 similar to coxa 1; basis elongate, rectangular, subequal in length to carpus and propodus combined, with 5 short setae anteriorly, 1 long setae posteriorly; carpus elongate, 1.63 x as long as propodus, posteriorly with clusters of simple setae; propodus subrectangular, medial face with an angled row of 4 setae, palm oblique, delimited by 4 spines distally; dactylus fitting palm.
Pereopod 3 (Fig. 7 C) slender, linear; coxa 3 wider than coxa 2, with 5 feeble setae ventrally; posterior margin of carpus with row of 5 spines; length ratio of articles 2–7 = 1.00: 0.29: 0.73: 0.40: 0.37: 0.18.
Pereopod 4 similar to pereopod 3.
Pereopod 5 (Fig. 7 D) coxa bilobate, subequal in length and width, posterior lobe strongly protruding downward; basis pear-shaped, about 1.5 x as long as merus, margins with tiny setae; merus slightly broadened, about half as wide as long, gradually widening distally, anteroventral corner with 2–3 spines; carpus to dactylus slender, length ratio = 1.00: 0.85: 0.51.
Pereopod 6 (Fig. 7 E) coxa small, subrectangular, with rounded corners, weakly bilobate; basis about 0.8 x as wide as long, posterior margin convex, strongly expanded, tapering distally; merus slightly broad, about 1.8 x as wide as carpus; length ratio of articles 4–7 = 1.00: 0.95: 0.69: 0.34.
Pereopod 7 (Fig. 7 F) coxa subrectangular, slightly deeper than wide, posterior margin convex, gently curved; basis greatly expanded posteriorly, anterior margin nearly straight, posterior margin rounded, subequal in length to the following articles combined; merus broadened, widening distally, anterior margin with rows of plumose setae and spines, posterior margin with 3 plumose setae and 1 distal seta; carpus, about 0.8 x as long as merus, anterior margin with rows of plumose setae and spines, posterior margin with 4 plumose setae and 1 slender seta apically.
Uropod 1 (Fig. 7 G) peduncle 2.3 x length of rami, with 2 dorsolateral robust spines, 1 medial spine, 5 basofacial plumose setae and 1 apicomedial spine; rami subequal, outer ramus with 3 dorsolateral and 2 unequal apical spines.
Uropod 2 (Fig. 7 H) peduncle about 1.9 x as long as outer ramus, with 4 dorsolateral robust spines and 1 apicomedial seta; outer ramus slightly shorter than inner one, with 3 robust dorsolateral spines, 1 medial spine and 2 unequal spines apically; inner ramus with 1 apicolateral and 1 apical spine.
Uropod 3 (Fig. 7 I) slightly longer than uropod 2; peduncle stout, subequal in length to inner ramus, with apicolateral robust spine; outer ramus slightly shorter than inner one, lateral margin with 2 robust spines, medial margin with 4 plumose setae and 2 feeble setae apically; inner ramus with row of 8 plumose setae on medial margin and 2 feeble setae on lateral margin.
Telson (Fig. 6 K) subtriangular, gradually narrowing distally, about 1.3 x as long as wide, deeply cleft, dorsal surface of each lobe with a pair of tiny penicillate setae and row of 3–4 cuticular pores, lateral margins of both lobes with 6–7 simple setae and 1 penicillate seta, apically with long simple seta.
Paratype, adult female, 2.5 mm, cat no. NIBRIV0000240790.
Body (Fig. 8 A) similar to male, but body less compressed, eye smaller, antennae 1–2 shorter, especially antenna 2; pleonites narrower than those of male, cephalon as long as pereonites 1–2 combined.
Antenna 1 (Fig. 8 B) about 2.7 x as long as cephalon; length ratio of peduncular articles 1–3 = 1.00: 0.58: 0.26, peduncular article 1 with 2 tiny unequal penicillate setae posterodistally; accessory flagellum very small, with 1 simple seta and 1 tiny aesthetasc apically; flagellum 6-articulate.
Antenna 2 (Fig. 8 C) short, about 0.7 x as long as antenna 1; gland cone of peduncular article 2 elongate, extending far beyond end of peduncular article 3; flagellum 3-articulate, subequal in length to peduncular article 5.
Gnathopod 1 (Fig. 8 D) slightly broader than that of male; carpus prominently shorter than that of male, subequal in length to propodus.
Gnathopod 2 (Fig. 8 E) broader than that of male; basis elongate, subequal in length to following articles combined; carpus about 1.36 x as long as propodus, these articles shorter than those of male; palm of propodus not as strongly oblique as male, palmar corner with 3 spines.
Pereopods 5–7 (Figs. 9 A–9C) nearly similar to those of male.
Uropod 1 (Fig. 9 D) peduncle about 1.7 x as long as rami, with 1 dorsolateral and apicomedial spine, and 4 basofacial plumose setae; rami subequal in length, outer ramus with 1 lateral and 1 apicolateral spines, with 2 unequal spines apically.
Uropod 2 (Fig. 9 E) peduncle about 1.4 x as long as rami, rami subequal in length, outer ramus with 2 dorsolateral and 2 distal spines.
Uropod 3 (Fig. 9 F) peduncle slightly longer than outer ramus, with apicolateral robust spine; outer ramus about 0.8 x as long as inner one, with 1 robust spine laterally and 2 feeble setae apically; inner ramus with 5 subdistal setae.
Telson (Fig. 9 G) similar to male in form, except each lobe with less marginal setae.
Remarks. This new species resembles Guernea minor Ishimaru, 1987 distributed in Japanese waters, in having similar mouthpart structure and broadened merus of pereopod 5. However, the new species is distinguished from G. minor (different characters of G. minor in brackets) by the following: 1) urosomite 1 without dorsal keel (vs posterior half produced dorsally into thin and high crest); 2) the anterodorsal portion of urosomites 2–3 placed above urosomite 1 (vs not extended toward urosomite 1); 3) peduncular articles of antennae 1–2 elongate, especially peduncular article 2 of antenna 1 rectangular, much longer than wide (vs rather stout, peduncular article 2 of antenna 1 quadrate, slightly longer than wide); 4) in male, carpus of gnathopod 2 elongate, about 1.63 x as long as propodus (vs short, about 1.4 x as long as propodus).
In adult specimens of G. jejuensis, the anterodorsal portion of urosomites 2–3 is slightly notched while this notch is lacking in juveniles (2.1 mm, female). The dorsal ridges are also continued backward in juveniles. Moreover, the indentation of the dorsal plane of urosomites 2–3 is shallower than those of adult specimens. Distribution. Korea (Jejudo Is.).
description: Published as part of Kim, Young-Hyo, Hendrycks, Ed A. & Lee, Kyung-Sook, 2011, The genus Guernea Chevreux, 1887 from Korean waters (Crustacea: Amphipoda: Dexaminidae), pp. 1-25 in Zootaxa 3104 on pages 10-16, DOI: 10.5281/zenodo.204467