Guernea nullispina Hirayama 1985
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 nullispina

description: Guernea nullispina Hirayama, 1985
(Korean Name: Min-ga-si-but-eun-kko-ri-yeop-sae-u, new) (Figs. 2 D, 14–15)
Guernea (Prinassus) nullispina Hirayama, 1985, p. 18, figs. 134–136.
Material examined. 24 3, Anpo, Yeosu-si, 20 March 2004; 1 3, Doyang, Goheung-gun, 7 July, 2005; 4 3, Yonggipo, Baengnyeongdo Is., 12 July 2006; 2 3, Yongdong-ri, Goheung-gun, 22 June 2008.
Type locality. Tomioka Bay, Kyushu, Japan.
Description. Male. Body (Figs. 2 D, 14A) slender, small, about 2.7 mm long, strongly chitinized; cephalon slightly longer than pereonites 1–2 combined; eye small, round, black; lateral cephalic lobe round, produced forward; pereonites smooth; pleonite 1 (Fig. 14 B) broader than pleonites 2 and 3, with 1 ventral and 2 anterodistal setae; pleonite 2 subequal in width to pleonite 3, ventral margin rounded, with 6–7 setae; urosomite 1 with characteristic strong dorsal carina, gradually rising dorsodistally well beyond end of urosomite 1.
Antenna 1 (Fig. 14 C) length ratio of peduncular articles 1–3 = 1.00: 0.52: 0.26, peduncular article 1 widest in middle, about 0.6 x as long as wide, distal half of ventral margin with long setular tufts; flagellum 7-articulate, shorter than peduncle, with slender aesthetascs ventrally.
Antenna 2 (Fig. 14 D) elongate, slightly shorter than body length; peduncular articles 1–3 short, peduncular article 4 convex ventromedially, 1.60 x as long as article 5, with numerous setular tufts dorsally; flagellum slender, elongate, about 4 x as long as peduncle, more than 26-articulate.
Lower lip (Fig. 14 E) inner lobes well developed, as long as outer; outer lobes subquadrate, apical margin flat, with fine pubescence.
Mandible (Figs. 14 F–G) similar to each other, subtriangular; incisor broad, smooth and blunt; lacinia mobilis medium, left bidentate, right tridentate; molar prominent, well developed.
Maxilla 1 (Fig. 14 H) inner plate small, lacking apical seta; outer plate with 7 tooth-like spines apically; palp biarticulate, distal article slightly shorter than proximal, with 2 simple setae apically and slender acute tooth.
Maxilla 2 (Fig. 14 I) inner plate medium, apical margin with 3 setae; outer plate about twice length of inner one, with 1 seta laterally and 6 setae apically.
Maxilliped (Fig. 14 J) inner plate very small, with 2 unequal setae apically; outer plate large, broad, not reaching end of palp article 2, medial margin with 7 setae and 4 spine-teeth distally; palp 4-articulate, medial margins with fine setae; article 2 elongate, 1.29 x as long as article 1, 2.30 x as long as article 3; article 4 0.45 x as long as article 3, with long claw apically.
Gnathopod 1 (Fig. 14 K) coxa slender, elongate-ovate, with 1 long seta and 2 short setules apically; basis elongate, 1.22 x as long as carpus and propodus combined, curved and narrowing proximally, with 2 setae anteriorly, 1 long seta posterodistally; ischium 0.66 x as long as merus, with 1 posterodistal seta; merus with 6 simple setae posterodistally; carpus widening distally, 1.66 x as long as merus, anterior margin with 2 strong setae, with 4 simple, 3 pinnate setae ventrally; propodus subequal in length to carpus, anterior margin about twice length of posterior; palm oblique, with fine unequal setules marginally, defined by 4 spines on palmar corner; dactylus falcate, about half length of propodus, with distinct tooth on inner margin.
Gnathopod 2 (Fig. 15 A) similar to gnathopod 1, but basis proximally straight not curved, carpus and propodus thin, narrower and longer than those of gnathopod 1; carpus 1.39 x as long as propodus.
Pereopod 3 (Fig. 15 B) coxa subquadrate, with rounded corners, ventral margin with 4 setae; basis rectangular, subequal in length to merus–carpus combined, anterior margin with 7 long setae; merus 1.56 x as long as carpus, with long setae on both margins; carpus slightly shorter than propodus, with 6 long setae ventrally; propodus 1.46 x as long as dactylus.
Pereopod 4 similar to pereopod 3.
Pereopod 5 (Fig. 15 C) coxa bilobate, posterodistal lobe large, round, broadly expanded ventrally; basis subovate, somewhat pear-shaped, gradually narrowing proximally, 0.75 x as wide as long, anterior margin curved, with row of 17 short pinnate setae, posterior margin straight, with 6 fine setules; merus 1.15 x as long as and about 2.5 x as wide as carpus, with 4 pinnate setae anteriorly, 4 short pinnate setae posteriorly and 1 spine posterodistally; carpus slender, subequal in length to propodus, with 2 posteromedial and 2 posterodistal spines; dactylus falcate, about half length of propodus.
Pereopod 6 (Fig. 15 D) coxa subovate, weakly bilobate, anterior lobe small, posterior lobe large, with 1 ventral setule; basis anterior margin straight, proximoposterior margin broadly expanded, narrowing strongly distally, proximal width about 2.9 x as wide as distal; merus 1.13 x as long as carpus, with pinnate setae on both margins; propodus 1.07 x as long as carpus, with 3 anteromedial setae; dactylus slender, long, 0.68 x as long as propodus.
Pereopod 7 (Fig. 15 E) coxa semicircular, ventral margin broadly convex; basis anterior margin straight, greatly expanded posteriorly, 0.81 x as wide as long; merus comparatively thick, 0.57 x as wide as long, with rows of pinnate setae on both margins, spines on anterior margin, 1 spine posterodistally; carpus as long as propodus, with rows of pinnate setae, small spines on anterior margin, pinnate setae posteriorly, long slender spine posterodistally; dactylus about half length of propodus.
Uropod 1 (Fig. 15 F) peduncle 1.61 x as long as outer ramus, with 2 dorsolateral, 2 dorsomedial, 2 basofacial and 1 apicomedial spine; outer ramus slightly longer than inner, with 2 apical spines of unequal length; inner ramus with 1 long spine apically.
Uropod 2 (Fig. 15 G) peduncle 1.49 x as long as outer ramus, with 4 dorsolateral and 1 apicomedial spine; outer ramus slightly longer than inner, both with long spines apically.
Uropod 3 (Fig. 15 H) peduncle stout, slightly longer than outer ramus, slightly shorter than inner one, with 1 distal spine; inner ramus longer than outer, with row of long pinnate setae.
Telson (Fig. 15 I) gradually rounded and slightly narrowing distally, length about 1.4 x width, deeply cleft (89%), lobes with long pinnate or penicillate setae apically and subapically.
Distribution. Japan (Kyushu), Korea (west and south coasts).
Remarks. The shape of the dorsal process of urosomite 1 is a unique and characteristic feature for the genus Guernea. Our specimens are in good agreement with the original description of Hirayama (1985), as it pertains to urosomite 1. However several morphological differences are found between our specimens and Hirayama’s: 1) maxilla 1 palp biarticulate (nonarticulated in original description); 2) maxilla 2 inner lobe with 3 apical setae (2 setae in original description); 3) uropod 3 peduncle slightly longer than outer ramus, slightly shorter than inner one (peduncle shorter than rami in original description); 4) uropod 3 inner ramus slightly longer than outer (both rami equal in length in original description). These slight differences (except the biarticulate palp) are deemed insufficient to warrant the erection of a new species for our material at this time, especially as we have not examined Hirayama’s type material for the condition of the maxilla 1 palp.
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 21-24, DOI: 10.5281/zenodo.204467