Capropodocerus tagamaru Matsumoto & Kajihara & Kakui 2023, sp. nov.

Capropodocerus tagamaru sp. nov.

[New Japanese name: Kaizoku-warekara-doronomi]

Figs 1A, 2–4

Diagnosis. Length ratio of antenna 1 peduncle to flagellum 2.19. Gnathopod 2 palm with slightly convex margin bearing two proximal triangular projections. Mid-posterior triangular projection on gnathopod 2 dactylus absent. Length ratio of basis to merus of pereopod 3 1.72.

Etymology. The specific name is a noun in apposition referring to Tagamaru, the mythical pirate and king of the ogres in the Kumano Sea.

Type material. Holotype. Male, ICHUM6354; TR/ V Seisui-maru, Stn. 10, Kumano Sea, northwestern Pacific (33°59.32′ N 136°56.58′ E to 34°00.02′ N 136°56.32′ E), 800–775 m depth, biological dredge; collected 10 November 2017 by Yu Matsumoto and Keiichi Kakui.

Description. Body (Figs 1A, 2A–C) 4.96 mm long, translucent when alive. Head 0.64 mm long; eye distinct, round, red when alive. Pereonites 1–7 0.76 mm, 0.72 mm, 0.72 mm, 0.32 mm, 0.23 mm, 0.19 mm, 0.27 mm long, respectively. Pereonites 1–3 cylindrical; pereonite 1 longer than wide, suture visible laterally; pereonite 2 as long as wide, spherical in dorsal view, with small lateral projection; pereonite 3 longer than wide, suture visible laterally, with small lateral projection. Pereonites 4–7 similar, depressed, wider than long, with small lateral projection; pereonite 5 with dorsal simple seta. Pleonites 1–3 similar. Urosome with three segments.

Antenna 1 (Fig. 2D, D 1) 2.97 mm long, longer than antenna 2. Peduncle with three articles, 2.03 mm long (articles 1–3 0.35 mm, 0.87 mm, and 0.81 mm long, respectively); all articles with several dorsal simple setae and several ventral setulate setae; article 1 with one dorso-subproximal and one ventrodistal plumose setae; article 3 with dorsodistal plumose seta. Accessory flagellum (Fig. 2D 1) small, as long as wide, with two distal simple setae. Flagellum with three articles, 0.93 mm long (articles 1–3 0.56 mm, 0.20 mm, 0.17 mm long, respectively); articles 1 and 2 each with two dorsal simple setae and several ventral setulate setae; article 3 with three simple setae and distal plumose seta.

Antenna 2 (Fig. 2E, E 1) 2.86 mm long. Peduncle with five articles (articles 1 and 2 incompletely fused), 2.09 mm long; articles 1 and 2 with evident antennal gland cone directed ventrodistally; article 3 with ventral setulate setae; articles 4 and 5 with dorsal simple setae, ventral setulate setae, and one dorsal and two ventral plumose setae. Flagellum with three articles, 0.77 mm long; article 1 with dorsal simple setae and ventral setulate setae; article 2 with three dorsal, one dorsodistal, and one ventral simple setae and two ventrodistal thick, bifurcate setae; article 3 (Fig. 2E 1) tiny, with four distal simple setae.

Upper lip (Fig. 2F) with weak mid-ventral hollow and fine setae on distal surface, other portion lost. Epistome (Fig. 2G) produced anteriorly, with fine setae on distal surface. Mandibles (Fig. 2H, H 1, I, I1) with incisor bearing five (left) or six (right) cusps; lacinia mobilis with four (left) or three (right) cusps; subdistal region with one (left) or two (right) accessory blades and three (left) or one (right) plumose setae; molar with plate-like structure bearing pectinate margin. Palp with article 1 lacking setae; article 2 with medial setulate setae; article 3 distally expanded, with setulate setae in distal half. Lower lip (Fig. 3A) with well-developed inner lobes; distal regions of inner and outer lobes covered with fine setae, other parts broken. Maxilla 1 (Fig. 3B) with vestigial inner plate bearing distal fine setae; outer plate with nine distal robust setae (two bifurcate, seven simple). Palp with article 1 lacking setae; article 2 with four distal robust serrate setae (one broken, partly missing) and three subdistal setulate setae. Maxilla 2 (Fig. 3C) with inner and outer plates having distal setulate setae and covered with fine setae. Maxillipeds (Fig. 3D, D 1, 2) with inner plate bearing three short robust setae and several setulate setae; outer plate with three ventral setulate setae and three medial and three distal robust setae (one bifurcate, three biserrate, two simple). Palp with four articles: article 1 with mediodistal setulate seta; article 2 with medial row of setulate setae; article 3 with distal setulate setae; article 4 distally serrated, with lateral setulate seta in proximal region, and one setulate, two serrate, and one robust serrate setae in medio-distal region.

Gnathopod 1 (Fig. 3E, E 1) transverse, 1.15 mm long; basis, ischium, merus, carpus, propodus, dactylus 0.31 mm, 0.10 mm, 0.08 mm, 0.22 mm, 0.28 mm, 0.16 mm long, respectively. Coxa with slight lateral projection and two simple setae.Basis with two simple setae. Ischium with two simple and two setulate setae. Merus with one anterodistal and seven posterodistal simple setae and posterodistal setulate seta. Carpus with posterolateral shield-like expansion and one anterodistal, one lateral, 12 posterior, four medial, and five mediodistal simple setae. Propodus expanded distally, 1.10 times longer than wide, with posterolateral and posteromedial rows of simple setae, anteromedial row of simple setae, and two anterior, five anterodistal simple setae; palmar margin slightly convex, smooth, with row of simple setae and two posterolateral and one posteromedial robust setae. Dactylus slightly curved posteriorly, with several anterior fine setae and posterior row of simple setae.

Gnathopod 2 (Fig. 3F, F 1) subchelate, 2.92 mm long; basis, ischium, merus, carpus, propodus, dactylus 0.90 mm, 0.13 mm, 0.18 mm, 0.23 mm, 0.88 mm, 0.60 mm long, respectively. Coxa not laterally projecting. Basis with anterodistal simple seta. Ischium without setae. Merus rounded, without setae. Carpus expanded distally, with four distal simple setae. Propodus expanded distally, 1.36 times as long as wide, with several anteromedial, two anterodistal, and several lateral simple setae; palmar margin slightly convex, humped distally, with 13 lateral and 12 medial rows of small robust setae, posteromedial larger robust seta, several simple setae, and two proximal triangular projections (one larger than other). Dactylus curved posteriorly, without setae.

Pereopod 3 (Fig. 4A) 1.38 mm long, with length ratio of basis, ischium, merus, carpus, propodus, and dactylus 1.00:0.29:0.58:0.67:0.98:0.72. Coxa weakly pointed laterally. Carpus with one anterodistal and one posterodistal simple setae. Propodus with three anterior and three posterior simple setae and plumose seta. Dactylus with two anterior simple setae. Pereopods 4–7 (Fig. 4B–E) similar to pereopod 3, 1.43 mm, 1.59 mm, 1.52 mm, and 1.51 mm long, respectively; length ratio of basis, ischium, merus, carpus, propodus, and dactylus 1.00:0.33:0.58:0.67:0.96: 0.72 in pereopod 4, 1.00:0.35:0.65:0.77:1.40:1.00 in pereopod 5, 1.00:0.36:0.61:0.62:1.25: 0.90 in pereopod 6, and 1.00:0.44:0.71:0.77:1.44: 1.07 in pereopod 7.

Pleopods 1–3 (Fig. 4F–H) 0.85 mm, 0.84 mm, 0.76 mm long, respectively; all similar. Peduncle with two (pleopods 1 and 2) or one (pleopod 3) mediodistal coupling hooks. Each article of both inner and outer rami with pair of distal setulate setae.

Uropod 1 (Fig. 4I) biramous. Peduncle with two dorsolateral and one dorsodistal simple setae. Inner ramus with three dorsolateral simple setae and terminal robust seta. Outer ramus 2.25 times as long as inner ramus, with dorsolateral simple seta, and terminal robust seta. Uropod 3 (Fig. 4I) uniramous, uniarticulate, without setae.

Telson (Fig. 4J) entire, linguiform, with paired simple setae.