Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016

Heo, Jun-Haeng & Kim, Young-Hyo, 2021, A new species of the genus Opisa Boeck, 1876 (Crustacea, Amphipoda, Opisidae) and a new record for Opisa takafuminakanoi from the East Sea, South Korea, ZooKeys 1015, pp. 99-113 : 99

Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016

Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016: 335, figs 1,2.

Material examined.

Male, 8.8 mm, NIBRIV0000880624 and female, 8.7 mm, NIBRIV0000880625, South Korea: Namae Port, Yangyang-gun, Gangwon-do, 37°56'32"N, 128°47'12"E, Y.H. Kim, 21 December 2007. The remaining specimens (two males, three females), same station data as description specimens.

Diagnosis.

Lateral cephalic lobe rounded. Mouthparts forming subquadrate bundle. Antenna 1, callynophore well developed; flagellum short, calceoli absent. Antenna 2, flagellum elongated, calceoli absent. Upper lip, epistome normal. Mandible, molar setose, left lacinia mobilis vestigial. Maxilla 1, outer plate with 11 dentate spine-teeth in an 8/3 crown arrangement. Gnathopod 1 enlarge, palm strongly concave, with unequal simple setae, defined by 2 robust setae subapically. Uropods 1-2, each ramus without notch. Uropod 3, outer ramus biarticulate, longer than inner ramus. Telson cleft.

Description.

Adult male: body (Figs 5A , 6A ) 8.8 mm long, dorsally smooth. Lateral cephalic lobe rounded. Eye large, reniform, black. Epimeron 1 with rounded-quadrate posteroventral corner; epimeron 2 posteroventral corner right angled; epimeron 3 subquadrate. Urosomite 1 with mid-dorsal depression and dorsal carina.

Antenna 1 (Fig. 6B ) short, 1.71 × head; peduncular article 1 much longer than peduncular articles 2-3 combined, with a row of 9 penicillate setae dorsally; length ratio of peduncular articles 1-3 = 1.00: 0.31: 0.25; flagellum 10-articulate, 0.86 × shorter than peduncular articles, with 2-field callynophore, calceoli absent; accessory flagellum 5-articulate, article 1 slightly elongated.

Antenna 2 (Fig. 6C ) slender and elongated; peduncular article 4 shorter than peduncular article 5, with a row of small setae dorsally, 2 penicillate setae dorsodistally, 6 simple setae distally, 2 penicillate setae and 2 unequal simple setae ventrodistally; peduncular article 5 rectangular, with a row of simple setae dorsally and a cluster of long simple setae, 2 penicillate setae ventrally, 1 long simple and 1 penicillate setae ventrodistally; flagellum 48-articulate, calceoli absent.

Gnathopod 1 (Fig. 6D ) strongly chelate, enlarge; coxa rounded anterodistally; basis subrectangular, slightly bulge distally; ischium 0.32 as long as basis, unarmed; carpus 1.25 × ischium; propodus enlarge, strong, developed posteriorly, palm strongly concave, with unequal simple setae on palmar margin, defined by 2 robust setae subapically, 1.80 × carpus; dactylus stout, strongly curved.

Gnathopod 2 (Fig. 6E ), coxa (Fig. 6F ) subrectangular, slightly widening distally, width 0.51 × length; basis slender, elongated, with 1 simple anterodistal seta; ischium elongated, slightly shorter than carpus, with 3 anterior and 1 posterodistal setae; merus 0.58 × ischium, with patch of setules posteriorly and 3 unequal simple setae posterodistally; carpus elongated, 0.49 × basis, anterior and posterior margins covered with setules and with distal unequal group of setae, posterior margin slightly convex; propodus short, length 1.86 × width, subquadrate, surface covered by setules, with cluster of setae anterodistally, palm oblique, defined by 2 tiny blunt robust setae posterodistally; dactylus falcate, short.

Pereopod 3 (Fig. 6G ), coxa similar to that of gnathopod 2, but slightly more widening distally, width 0.60 × length; basis slender, with 2 simple setae distally; ischium short, 0.25 × basis, with 2 unequal simple setae posterodistally; merus subequal in length to carpus, slightly produced anterodistally, with 1 simple anterodistal seta and 7 unequal simple setae posteriorly; carpus subrectangular, with 1 simple anterodistal seta, 3 clusters of unequal posterior setae, and 2 simple setae posterodistally; propodus subrectangular, subequal in length to carpus, with a paired setae on posterior margin and 1 robust seta posterodistally; dactylus falcate, with 1 penicillate seta anteriorly.

Pereopod 4 (Fig. 6H ) similar to pereopod 3 except coxa broadened, posterior margin excavate, posterodistal lobe produced, truncate, corner rounded.

Pereopod 5 (Fig. 7A ), coxa large, with rounded corners, bilobate, posteroventral lobe developed, width 1.24 × length; basis subcircular, length 0.90 × width, posteriorly expanded, margin serrate, posteroventral lobe broadly rounded, anterior margin with a row of robust setae; merus expanded posteriorly, anterior margin with 3 simple setae and 4 robust setae, posterior margin with 3 simple setae; carpus 0.62 × merus, anterior margin with 2 robust setae and 1 simple seta distally, posterior margin with 1 robust seta distally; propodus rectangular, 1.50 × carpus, anterior margin with 2 robust setae; dactylus falcate, with 1 penicillate seta posteriorly.

Pereopod 6 (Fig. 7B ), coxa bilobate, anterior lobe small, posterior lobe strongly protruding downward; basis subquadrate, posterior margin weakly serrate, posteroventral lobe broadly rounded, anterior margin slightly concave, with 6 robust setae; merus slightly expanded posteriorly, anterior margin with 2 long simple setae and 1 small robust seta, posterior margin with 2 robust setae; carpus 0.75 × merus, anterior margin with 3 simple setae and 3 robust setae, posterior margin with 1 robust seta distally; propodus rectangular, 1.42 × carpus, anterior margin with 2 robust setae and 1 simple seta distally; dactylus falcate, with 1 penicillate seta posteriorly.

Pereopod 7 (Fig. 7C ) similar to pereopod 6, but coxa unilobate; basis much broader than that of pereopod 6, posterior margin broadly expanded.

Uropod 1 (Fig. 7D ), peduncle subrectangular, 0.86 × outer ramus, with a row of dorsolateral robust setae, 3 dorsomedial and 1 apicolateral robust setae; inner ramus with 2 lateral and 1 medial robust setae, outer ramus slightly longer than inner one, with 2 lateral robust setae.

Uropod 2 (Fig. 7E ), peduncle slightly longer than outer ramus, with 3 dorsolateral and 2 dorsomedial robust setae; inner ramus unarmed, unconstricted, subequal in length to outer one; outer ramus with 1 lateral robust seta.

Uropod 3 (Fig. 7F ), peduncle short, 0.61 × outer ramus, with 2 dorsomedial, 1 dorsolateral, and 3 ventrodistal robust setae; outer ramus biarticulate, 1.09 × inner ramus, proximal article with 5 plumose setae along inner margin and 1 lateral robust seta, each margin with 1 robust seta distally; distal article short, 0.19 × proximal one; inner ramus nearly reach base of distal article of outer ramus, outer margin with 9 plumose setae, inner margin unarmed.

Telson (Fig. 7G ) elongated, length 2.25 × width, cleft 87% of its length, dorsolaterally each lobe with 2 small robust setae and 2 unequal penicillate setae, apically with 1 stout seta and 1 penicillate seta.

Adult female: body (Figs 5B , 7H ) about 8.7 mm long. Head similar to that of male except more rounded lateral cephalic lobe.

Antenna 1 (Fig. 7I ) stout, similar to that of male except peduncular article 1 with 1 penicillate seta dorsally and 2 penicillate setae ventrally; flagellum 8-articulate, calceoli absent; accessory flagellum 5-articulate, article 1 slightly elongated.

Antenna 2 (Fig. 7J ) slender, much shorter than that of male, peduncular articles 4-5 shorter than those of male; flagellum 7-articulate, calceoli absent.

Remarks.

Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016 is similar to O. eschrichtii ( Krøyer, 1842) in terms of the following characteristics: 1) epimeron 3 round and smooth posteriorly; 2) gnathopod 1 enlarged, with strongly arched dactylus; 3) gnathopod 1, without “palisade” palmar robust setae; 4) coxa 5 longer than length of basis; and 5) uropod 3, rami with plumose setae. However, O. takafuminakanoi is distinguished from O. eschrichtii by a vestigial lacinia mobilis on the left mandible, the developed posterior lobe of coxa 5, and the unarmed inner ramus of uropod 2. Our specimens are consistent with the original description provided by Narahara-Nakano et al. (2016).

Distribution.

Japan, South Korea (East Sea).

Figures

Figure 5. Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016 A adult male, NIBRIV 0000880624, 8.8 mm, habitus B adult female, NIBRIV 0000880625, 8.7 mm, habitus. Scale bars: 1.0 mm (A, B).

Figure 6. Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016, adult male, NIBRIV 0000880624, 8.8 mm A habitus B antenna 1 C antenna 2 D gnathopod 1 E gnathopod 2 F coxa 2 G pereopod 3 H pereopod 4. Scale bars: 1.0 mm (A), 0.2 mm (B, C), 0.4 mm (D-H).

Figure 7. Opisa takafuminakanoi Narahara-Nakano, Kakui & Tomikawa, 2016, adult male, NIBRIV 0000880624, 8.8 mm A pereopod 5 B pereopod 6 C pereopod 7 D uropod 1 E uropod 2 F uropod 3 G telson. Adult female, NIBRIV 0000880625, 8.7 mm H habitus I antenna 1 J antenna 2. Scale bars: 0.4 mm (A-C), 0.2 mm (D-G, I-J), 1.0 mm (H).