Guernea jejuensis, Kim, Young-Hyo, Hendrycks, Ed A. & Lee, Kyung-Sook, 2011

Kim, Young-Hyo, Hendrycks, Ed A. & Lee, Kyung-Sook, 2011, The genus Guernea Chevreux, 1887 from Korean waters (Crustacea: Amphipoda: Dexaminidae), Zootaxa 3104, pp. 1-25 : 10-16

publication ID	https://doi.org/ 10.5281/zenodo.204467
DOI	https://doi.org/10.5281/zenodo.6191766
persistent identifier	https://treatment.plazi.org/id/1E0187EC-FFC4-FFE4-FF6D-F99FB16CC94E
treatment provided by	Plazi
scientific name	Guernea jejuensis
status	sp. nov.

Treatment

Guernea jejuensis View in CoL sp. nov.

(Korean Name: Je-ju-but-eun-kko-ri-yeop-sae-u, new) ( Figs. 2 View FIGURE 2. A 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 View FIGURE 2. A 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 6 E) inner lobes broadly rounded, outer lobes with 1 shoulder tooth apically; both lobes pubescent apically.

Left mandible ( Fig. 6 View FIGURE 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 View FIGURE 6 G) smooth, similar to left one; incisor smooth, rounded; lacinia mobilis weakly bifid; molar process with 1 pappose seta.

Maxilla 1 ( Fig. 6 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 8 D) slightly broader than that of male; carpus prominently shorter than that of male, subequal in length to propodus.

Gnathopod 2 ( Fig. 8 View FIGURE 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 View FIGURE 9 A–9C) nearly similar to those of male.

Uropod 1 ( Fig. 9 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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.).