Agathotanais misakiensis, Kakui & Kohtsuka, 2015

Kakui, Keiichi & Kohtsuka, Hisanori, 2015, Two New Shallow-water Species of Agathotanais (Crustacea: Tanaidacea) from Japan, Species Diversity 20 (1), pp. 45-58 : 46-51

publication ID	https://doi.org/ 10.12782/sd.20.1.045
DOI	https://doi.org/10.5281/zenodo.4734056
persistent identifier	https://treatment.plazi.org/id/D26E879D-845A-FFDE-E94D-6AA5FA90523E
treatment provided by	Felipe
scientific name	Agathotanais misakiensis
status	sp. nov.

Treatment

Agathotanais misakiensis View in CoL sp. nov.

[New Japanese name: Misaki-kubire-tanaisu]

( Figs 2–9 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

Material examined. Holotype. Female , ZIHU-4948, BL 3.88, CW 0.53, 4 slides and 1 vial, RV Rinkai-maru , off Misaki , Sagami Sea, North Pacific Ocean, 35°06.086′N, 139°34.232′E to 35°05.807′N, 139°34.089′E, 238–291 m depth, 19 February 2014, coll. by K. Kakui. GoogleMaps

Allotype. Male, ZIHU-4949, BL 2.79, CW 0.41, 4 slides and 1 vial, same collection data as for holotype.

Paratypes. 10 females: ZIHU-4950, BL 3.37, CW 0.47, 4 slides and 1 vial; ZIHU-4951, BL 3.17, CW 0.45, 4 slides and 1 vial; ZIHU-4952, 3 slides and 1 vial; ZIHU-4953, 4 slides and 1 vial; ZIHU-4954, BL 3.12, CW 0.41, 1 vial (body and detached antennule and antenna); ZIHU-4955, BL 3.18, CW 0.44, 1 vial (body and detached antennule and pereopod); ZIHU-4956, BL 3.12, CW 0.44, 1 vial (body and detached antennule); ZIHU-4957, BL 3.03, CW 0.40, 1 vial (body and detached antennule); ZIHU-4958, 1 SEM stub and 1 vial; ZIHU-4959, BL 3.08, CW 0.43, 1 SEM stub. 3 males: ZIHU-4960, BL 2.66, CW 0.38, 1 vial (body and detached antennule); ZIHU-4961, BL 2.68, CW 0.39, 1 vial (body and detached antennule); ZIHU-4962, BL 2.72, CW 0.39, 1 vial (body and detached antennule). 4 females (including 2 anterior parts) and 4 males, ZIHU-4963, 1 vial. ZIHU-4960: RV Rinkai-maru, 35°07.084′N, 139°34.000′E to 35°07.112′N GoogleMaps , 139°34.146′E, 258– 211 m depth, 23 January 2014, coll. by H. Kohtsuka. ZIHU-4950–3, 4958, 4959, 4963: same collection data as for holotype GoogleMaps . ZIHU-4954–4957, 4961, 4962: RV Rinkai-maru, 35°07.301′N, 139°33.365′E to 35°07.327′N, 139°32.978′E, 250–493 m depth, 24 February 2012, coll GoogleMaps . by M. Shimomura.

Diagnosis. Body narrow (BL/CW more than 6.50); cephalothorax length longer than CW; length/width of pereonites 3 and 4 0.90–1.00 and 0.95–1.10, respectively; pleonites narrower than pereonite 6; pleonites 1 and 2 without ventral keel. Antennular article 3 1.80–2.05 (female) or 2.20–2.60 (male) times as long as antennular article 2. Antenna with one article. Fixed finger with one ventral simple seta. Basis of pereopods 1–6 lacking dorsal small spines. Carpus of pereopods 1–3 with one dorsodistal simple seta; that on carpus of pereopod 2 short (shorter than two-thirds of propodus length). Dactylus of pereopods 1–3 naked. Carpus and propodus of pereopods 4–6 with two and three distal spiniform setae, respectively, but lacking ventral small spines. Uropod with one articulation between basal article and tip.

Etymology. The specific name is an adjective referring to the type locality.

Description of females. Based primarily on holotype, with some observations from paratype ZIHU-4950.

Body ( Figs 2A, a View Fig 1 View Fig , C, 8 View Fig , 9 View Fig ) cylindrical, 7.35 times as long as wide, pitted and setulate on cephalothorax and pereon (e.g., Fig. 8A, B View Fig ). Cephalothorax 0.15 times as long as BL, 1.20 times as long as wide, oval in dorsal view; rostrum triangular; eye lobes absent; posterior region with shallow median ventral groove (cf. Fig. 8A View Fig ). Length ratio of pereonites 1–6 1.00: 1.20: 1.20: 1.20: 1.20: 0.90; length/width of pereonites 1–6 0.75, 0.95, 1.00, 1.05, 1.05, and 0.85, respectively. Pleon setulate, 0.15 times as long as BL. Pleonites 0.75 times as wide as pereonite 6, 0.60 times as wide as CW, all wider than long, similar in shape; segmental articulations posterior to articulation between pereonites 5 and 6 all obscure (cf. Fig. 9A View Fig ); pleonite 5 with two pairs of lateral simple setae. Pleotelson setulate, 0.80 times as long as wide, as wide as pleonites; distal region with two pairs of simple setae and one pair of PSS; apical margin straight.

Antennule ( Fig. 3A View Fig ) as long as cephalothorax; length ratio of articles 1–3 1.00: 0.20: 0.40. Article 1 3.50 times as long as wide, with one dorsomedial and two distal simple setae, and several middle and distal PSS. Article 2 with two distal simple setae and one distal PSS. Article 3 with six distal simple setae, one distal PSS, and one distal aesthetasc. Antenna ( Fig. 3B View Fig ) uniarticulate, 0.15 times as long as antennule, bearing two distal simple setae.

Labrum ( Fig. 4A View Fig ) with fine distal setae as illustrated. Mandibles ( Figs 4B, C View Fig , 8C, D View Fig ) with membranous molar process bearing small distal projection. Lefl mandible’s incisor ( Figs 4B View Fig , 8C View Fig ) with blunt teeth; lacinia mobilis round, fused to body of mandible. Right mandible’s incisor ( Figs 4C View Fig , 8D View Fig ) with broad triangular apex. Labium ( Fig. 4D View Fig ) with one pair each of lateral setulate projections and distal setulate rounded projections. Maxillule ( Fig. 4E, e View Fig 1 View Fig ) with palp bearing two setae; endite with nine spiniform setae. Maxilla ( Fig. 4F View Fig ) naked. Maxillipeds ( Fig. 4G View Fig ) with domed, cordate bases, each bearing one simple seta at insertion of palp; distal regions of bases separated, covered by fine setae, with one pair of simple setae. Palp article 1 naked; article 2 with two simple setae and one plumose seta; article 3 with one simple seta and two plumose setae; article 4 with one outer subdistal simple seta and five distal setulate setae. Epignath ( Fig. 4H View Fig ) narrow, curved, with one terminal seta.

Cheliped ( Fig. 3E View Fig ) with basis bearing small outer ventroproximal process ( Fig. 3E View Fig , arrow; Fig. 8A View Fig , arrow); portion proximal to process inserted into ventral surface of posterior region of cephalothorax. Merus with one ventral simple seta. Carpus 3.00 times as long as wide, with one dorsodistal simple seta and slight ventromedial projection bearing two simple setae. Chela 1.15 times as long as carpus, 3.00 times as long as wide; propodal palm 1.30 times as long as fixed finger, with one inner simple seta, and one simple seta at insertion of dactylus; fixed finger with one simple seta on ventral margin and two outer simple setae, one arched spiniform seta, and one distal projection on cutting surface; dactylus as long as fixed finger, with two spiniform setae on cutting surface.

Pereopods 1–6 cylindrical, setulate, with length ratio of 1.10:1.00: 1.00: 0.90: 0.85: 0.95. Pereopod 1 ( Fig. 5A, a View Fig 1 View Fig ) 0.23 times as long as BL, with length ratio of basis, ischium, merus, carpus, propodus, and dactylus-unguis 3.6 5: 0.25: 1.00: 1.55: 1.95: 1.65. Basis without dorsal spines. Ischium with one ventral simple seta. Merus with two ventral simple setae. Carpus with one dorsodistal and two ventrodistal simple setae. Propodus with one ventro-subdistal simple seta, one dorso-subdistal seta, and inner distal row of complex spiniform setae ( Fig. 5a View Fig 1 View Fig ). Dactylus and unguis subequal in length, naked. Pereopod 2 ( Fig. 5B, b View Fig 1 View Fig ) with length ratio of articles from basis to dactylus-unguis 4.50: 0.25: 1.00: 1.60: 2.10: 1.80; similar to pereopod 1, except merus with just one ventral simple seta. Dorsodistal simple seta of carpus short (shorter than two-thirds propodus length). Pereopod 3 ( Fig. 5C, c View Fig 1 View Fig ) with coxa bearing one simple seta. Length ratio of articles from basis to dactylusunguis 4.45: 0.20: 1.00: 1.70: 2.00: 1.70; similar to pereopod 2, except basis with one dorsal and one ventral PSS, merus with two ventral simple setae, and carpus with one inner distal simple seta. Pereopod 4 ( Fig. 5D View Fig ) with length ratio of articles from basis to dactylus-unguis 4.00:0.30: 1.00: 1.70: 1.85: 1.00. Basis with one dorsal and two ventral PSS. Ischium with two ventral simple setae. Merus with two ventral simple setae. Carpus with one outer and one inner simple setae and two ventrodistal spiniform setae. Propodus with three distal spiniform setae. Dactylus naked. Unguis with row of short setae. Pereopod 5 ( Fig. 5E View Fig ) with coxa naked. Length ratio of articles from basis to dactylus-unguis 4.20: 0.20: 1.00: 1.25: 1.05:1.45; similar to pereopod 4 except basis with just one ventral PSS. Pereopod 6 ( Fig. 5F View Fig ) with length ratio of articles from basis to dactylus-unguis 3.95: 0.25: 1.00: 1.20: 1.00: 1.25; similar to pereopod 5.

Pleopods absent.

Uropod ( Figs 5G View Fig , 9 View Fig ) with exopod fused to basal article, slight, not expanded laterally, bearing two simple setae. Endopod fused to basal article, but with one distal articulation ( Fig. 9a View Fig 1 View Fig , arrow) between ‘proximal’ and ‘distal’ articles; proximal article with two PSS; distal article with five simple setae and two PSS.

Description of males. Based on the allotype.

Body ( Fig. 2B, b View Fig 1 View Fig , D) similar to female but slightly stouter (6.85 times as long as wide) and with relatively shorter pereonite 6 and wider pleonites. Pereonites 1–6 with length ratio of 1.00: 1.15: 1.15: 1.15: 1.15: 0.70; length/width of pereonites 1–6 0.70, 0.90, 0.95, 1.00, 1.00, and 0.55, respectively. Pleon length 0.2 times BL. Pleonites 0.80 times as wide as pereonite 6, 0.70 times as wide as CW; articulations evident between all segments. Pleotelson narrower than pleonites.

Antennule ( Fig. 3C View Fig ) as long as cephalothorax, thicker than that of female; length ratio of articles 1–3 1.00: 0.20: 0.55. Articles 1–3 similar to those of female, except article 3 with groove in middle region. Antenna ( Fig. 3D View Fig ) similar to that of female but relatively longer (0.25 times as long as antennule).

Mouthparts ( Fig. 6 View Fig ) similar to those of female.

Cheliped ( Fig. 3F View Fig ) similar to that of female, except propodal palm with two inner simple setae, and dactylus with one inner proximal simple seta.

Pereopods 1–6 ( Fig. 7 View Fig A–F) with length ratio of 1.15: 1.05: 1.00: 0.95: 1.00: 1.00; pereopod 1 0.25 times as long as BL. Pereopods similar to those of female, except: merus of pereopods 1 and 3 with just one ventral simple seta; carpus of pereopod 2 with just one inner distal simple seta.

Pleopods ( Fig. 7G View Fig ) all similar. Basal article naked. Endo- and exopods fused to basal article; endopod with six distal and one inner subdistal spiniform setae; exopod with eight distal spiniform setae.

Uropod ( Fig. 7H View Fig ) similar to that of female, except proximal article with three PSS.

Variation. BL/CW 7.00– 7.55 in females (n =7), 6.85– 6.95 in males (n =4). Length/width of pereonites 3 and 4 0.90–1.00 and 0.95–1.10, respectively. Relative length of antennular article 3 to article 2 1.80–2.05 in females, 2.20–2.60 in males. Measurement data for these three characters listed in Table 1 View Table 1 .

Chelipedal basis with one dorsal simple seta in four paratypes. Chelipedal carpus with one dorsomedial simple seta in four paratypes. Merus of pereopod 2 with two ventral simple setae in three paratypes. Carpus of pereopod 2 with one inner distal simple seta in three paratypes and allotype. Basis of pereopod 4 with two ventral PSS in three paratypes and allotype.

Maxillular endite with nine spiniform setae in holotype, allotype and one paratype, and 10 in three paratypes.

Distribution. So far known only from type locality, at depths of 211– 493 m.

Remarks. Agathotanais misakiensis sp. nov. is the tenth species described in this genus. In having an articulation between the uropodal basal article and the tip of the endopod, this species closely resembles A. ghilarovi Kudinova-Pasternak, 1989 . The former differs from the latter (see Kudinova-Pasternak 1989) in having shorter pereonites (especially pereonites 3 and 4: length/width of both pereonites is about 1.00 in A. misakiensis but about 1.50 in A. ghilarovi ); narrower pleonites (pleonites narrower than pereonite 6 in A. misakiensis but as wide as pereonite 6 in A. ghilarovi ); a shorter antennular article 3 (in A. misakiensis , 1.80–2.05 times longer than article 2 in females, 2.20–2.60 times longer in males; comparable values for A. ghilarovi 3.05 in females and 3.35 in males); and the setation of the merus and carpus of pereopod 4 (in A. ghilarovi , the merus has four ventral setae, and the carpus lacks ventral setae).