Cyproidea okinawensis, Ariyama, Hiroyuki, 2016

Ariyama, Hiroyuki, 2016, Five species of the family Cyproideidae (Crustacea: Amphipoda) from Japan, with the description of a new genus and two new species, Zootaxa 4097 (3), pp. 301-331 : 309-313

Cyproidea okinawensis sp. nov.

[Japanese name: Okinawa-hoteiyokoebi, new] ( Figs 7–11 )

Material examined. Holotype: female (OMNH-Ar-9951), 5.0 mm, point "Red beach", Kin Bay, Kin Town, Okinawa Prefecture, 26°26'24"N, 127°54'36"E, 3 m in depth, sandy bottom, using SCUBA, 13 December 2014, coll. N. Shirakawa. Paratypes: 2 ovigerous females (OMNH-Ar-9952–9953), 4.5, 4.3 mm, same data as holotype; 2 ovigerous females (OMNH-Ar-9954–9955), 4.2, 4.0 mm, 5 m, 6 December 2014, other data same as holotype.

Description. Female [based on holotype, 5.0 mm (OMNH-Ar-9951), paratype, 4.5 mm (OMNH-Ar-9952) for lower lip, and paratype, 4.3 mm (OMNH-Ar-9953) for mandibles]. Body ( Fig. 7 ) oval; head longer than pereonite 1, eyes relatively small, diameter 35% length of head; pereonites 4–5 long, posteroventral corners of pereonites 5– 7 protruded; coxa 5 barely reaching posteroventral corner of pereonite 6; pleonites 1–3 each with dorsolateral ridge extending to urosomite 1; urosome slender.

Antenna 1 ( Fig. 8 A, A1) short, with ratio of lengths of peduncular articles 1–3 1:1.4:0.6, tooth of article 2 occupying quarter of whole length; accessory flagellum vestigial, with 3 setae; primary flagellum with 7 articles, articles 2, 3, 5, 6 each with 1 aesthetasc at distal end, respectively. Antenna 2 ( Fig. 8 B) short, with ratio of lengths of peduncular articles 3–5 1:1.8:1.5; flagellum with 3 articles.

Upper lip ( Fig. 8 C), ventrolateral margins with short setae. Mandible ( Fig. 8 D, D1, E, E1), incisor bearing 6–7 cusps, left lacinia mobilis fan-shaped, distal margin serrated, right lacinia mobilis lacking, number of both accessory blades 6 (paratype, 4.3 mm) or 10 (holotype, 5.0 mm); palp article length ratio 1:1.3: 1.1 in right, article 2 without setae, tip of article 3 with a long seta. Lower lip ( Fig. 8 F) wide; inner lobes indistinct; anteromedial surfaces of outer lobes setose, each with 1 round and 1 truncate projections on corner, mandibular processes small. Maxilla 1 ( Fig. 8 G, G1 – 2), inner plate rounded, with 4 setae on tip; mediodistal corner of outer plate projected, distal margin with 7 robust setae, medial margin bearing 5 robust setae; distal end of palp projected in middle, with 3 minutely-serrated robust setae and 3 robust setae (+1 additional spine in left). Maxilla 2 ( Fig. 8 H), inner plate shorter and wider than outer, terminal ends of both plates each with a few setae, dorsodistal surfaces of both plates setose. Maxilliped ( Fig. 8 I, I1 – 2), inner plate truncate, mediodistal corner with 2 robust setae dorsally; outer plate with 2 distal robust setae, mediodistal margin serrated; palp articles 1 – 2 with 3 and 6 setae, respectively, article 3 covered with short setae dorsally, article 4 slender.

Gnathopod 1 ( Fig. 9 A, A1), coxa roundish pentagonal; basis long, slightly curved posteriorly; posterodistal corner of ischium not projected; merus short; carpus long, posterodistal corner slightly protruded, bearing 3 long setae, posteromedial surface covered with thin setae; propodus long, about 1.5 times as long as carpus, palm with many acute denticles, anteromedial surface covered with thin setae; dactylus long, slightly curved, posteroproximal margin bearing 1 long and 6 short acute spines. Gnathopod 2 ( Fig. 9 B, B1) stouter than gnathopod 1; coxa trapezoidal; posterodistal corner of ischium strongly projected, with several setae; merus short; posterodistal projection of carpus longer than carpus proper, bearing 4 medial setae, posteromedial surface covered with thin setae; propodus relatively wide, palm with many blunt denticles; dactylus strongly flexed at a point of one fourth, gradually narrower, posteroproximal margin bearing 10 denticles.

Pereopod 3 ( Fig. 9 C), coxa triangular, anterior margin rounded, posterior margin slightly concave, posteroproximal corner with small projection, posteroventral corner with small medial hollow; basis and merus – propodus long. Pereopod 4 ( Fig. 9 D), coxa extremely wide, swollen posteriorly, anterior margin slightly convex, with small projection on anteroventral corner, ventral margin also slightly convex, posteroproximal corner a little projected; basis and merus – propodus long. Pereopod 5 ( Fig. 9 E, E1), coxa lanceolate, width about 2.8 times of length, anterior margin with small hollow, posterior end pointed; basis and merus – propodus long. Pereopod 6 ( Fig. 9 F, F1) slightly shorter than pereopod 5; coxa roundish trapezoidal; basis and merus – propodus long. Pereopod 7 ( Fig. 9 G) almost same length as pereopod 6; coxa roundish trapezoidal; basis and merus – propodus long.

Pleonal epimera ( Fig. 10 A), each with oblique lateral ridge (short in epimeron 1); epimera 1–2 projected bluntly and epimeron 3 rounded each on posteroventral corner; all ventral margins bare. Pleopods ( Fig. 10 B – D), pleopod 3 a little shorter than pleopods 1–2; peduncles of pleopods 2–3 bearing a few setae; inner and outer rami with 10, 9, 9 and 11, 11, 12 articles in pleopods 1 – 3, respectively. Uropods ( Fig. 10 E – G), peduncle and both rami without robust setae, but bearing minute denticles; peduncle of uropod 1 long, both rami about 0.8 times as long as peduncle; uropod 2 86% length of uropod 1, both rami 94% as long as peduncle; uropod 3 short, 64% length of uropod 1, peduncle relatively short, inner ramus about 1.3 times as long as peduncle, outer ramus almost same length as peduncle. Telson ( Fig. 10 G) ovoid, breadth about 0.6 times of length, without setae. Male unknown.

Coloration in life ( Fig. 11 ). Eyes red; dorsolateral surfaces from head to pereonite 7 with many brown and white pigments, ventral surfaces of pereonites and whole of pleonite 1 white; anteroproximal part of coxa 3 white, with several red pigments, anteroproximal and anteroventral parts of coxa 4 white, posteroproximal part of coxa 4 with black and red pigments.

Etymology. Referring to the type locality.

Remarks. Cyproidea okinawensis sp. nov. has the gnathopod 2 with both of a posterodistally-projected ischium and a long flexed dactylus. Only two species of Cyproidea , C. liodactyla and C. robusta Ren, 2006 collected from China, have such a gnathopod 2. However, this new species is different from C. liodactyla in the smaller eyes, the narrower coxa 5 and the coloration. Although the coloration of C. robusta resembles (milk white, with points of darkish-brown pigments), this species can be distinguished from C. robusta by the ovoid telson (pointed in C. robusta ).

Distribution. Japan: only Kin Town in Okinawa Prefecture ( Fig. 1 ).

Habitat. Sandy bottom, 3–5 m in depth.

Figures

FIGURE 1. Map showing collecting sites of the examined specimens.

FIGURE 7. Cyproidea okinawensis sp. nov. Holotype, female (OMNH-Ar- 9951), 5.0 mm. Habitus, lateral view.

FIGURE 8. Cyproidea okinawensis sp. nov. All except for D 1, E 1 and F, holotype, female (OMNH-Ar- 9951), 5.0 mm; D 1, E 1, paratype, female (OMNH-Ar- 9953), 4.3 mm; F, paratype, female (OMNH-Ar- 9952), 4.5 mm. A, left antenna 1, lateral view; A 1, accessory flagellum of left antenna 1, medial view; B, left antenna 2, lateral view; C, upper lip, posterior view; D, left mandible, ventral view; D 1, incisor, lacinia mobilis and accessory blades of left mandible, medial view; E, right mandible, dorsal view; E 1, incisor and accessory blades of right mandible, medial view; F, lower lip, ventral view; G, right maxilla 1, ventral view; G 1, distal part of right maxilla 1, ventral view, normal setae omitted; G 2, distal part of left maxilla 1 palp, dorsal view, normal setae omitted; H, left maxilla 2, dorsal view; I, right maxilliped, ventral view; I 1, distal part of outer plate of right maxilliped, ventral view, normal setae omitted; I 2, distal part of inner plate of right maxilliped, ventral view. Scale: A – B, 0.25 mm; C – I, 0.22 mm; A 1, 0.125 mm; D 1, E 1, G 1 – 2, I 1 – 2, 0.11 mm.

FIGURE 9. Cyproidea okinawensis sp. nov. Holotype, female (OMNH-Ar- 9951), 5.0 mm. A – B, left gnathopods 1 – 2, lateral views; A 1, palm and dactylus of left gnathopod 1, lateral view; B 1, posterodistal projection of carpus, palm and dactylus of left gnathopod 2, lateral view, thin setae omitted; C – G, left pereopods 3 – 7, lateral views; E 1, left gill and oostegite on coxa 5, lateral view; F 1, left gill on coxa 6, lateral view. Scale: A – G, E 1, F 1, 0.5 mm; A 1, B 1, 0.25 mm.

FIGURE 10. Cyproidea okinawensis sp. nov. Holotype, female (OMNH-Ar- 9951), 5.0 mm. A, right pleonal epimera 1 – 3, lateral view; B, left pleopod 1, anterior view; C, left pleopod 2, posterior view; D, left pleopod 3, posterior view; E, left uropod 1, dorsomedial view; F, left uropod 2, medial view; G, urosomite 3, telson and left uropod 3, dorsal view. Scale: A, E – G, 0.69 mm; B – D, 0.5 mm.

FIGURE 11. Cyproidea okinawensis sp. nov. Not-collected individual. Type locality, 6 April 2015, photography by N. Shirakawa.