Agathotanais toyoshioae, 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 : 51-55

publication ID	https://doi.org/ 10.12782/sd.20.1.045
publication LSID	lsid:zoobank.org:pub:A2A079DE-33AB-4918-A08D-95DCB4DF55F8
DOI	https://doi.org/10.5281/zenodo.4734058
persistent identifier	https://treatment.plazi.org/id/81D19B69-CE05-407B-959F-14FF10CDE9AB
taxon LSID	lsid:zoobank.org:act:81D19B69-CE05-407B-959F-14FF10CDE9AB
treatment provided by	Felipe
scientific name	Agathotanais toyoshioae
status	sp. nov.

Treatment

Agathotanais toyoshioae View in CoL sp. nov.

[New Japanese name: Toyoshio-kubire-tanaisu] ( Figs 10–14 View Fig View Fig View Fig View Fig View Fig )

Material examined. Holotype. Female with developed oostegites but lacking eggs or embryos, ZIHU-4964, BL 2.25, CW 0.30, 7 slides and 1 vial, TRV Toyoshio-maru , Genkai Sea, Sea of Japan, 34°04.911′N, 129°58.444′E to 34°04.891′N, 129°58.479′E, 95 m depth, 26 May 2014, coll. by S. Ohtsuka. GoogleMaps

Diagnosis. Body narrow (BL/CW more than 6.50); cephalothorax longer than CW; length/width of pereonites 3 and 4 1.05 and 1.15, respectively; pleonites narrower than pereonite 6 (pleonite width 0.65 times pereonite-6 width, 0.45 times CW); pleonites 1 and 2 with ventral keel. Antennular article 3 2.35 (female) times as long as antennular article 2. Antenna with one article. Fixed finger with one ventral simple seta. Basis of pereopods 1–6 with 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 one and three distal spiniform setae, respectively but lacking ventral small spines. Uropod with no articulation between basal article and tip.

Etymology. The species is named afler TRV Toyoshiomaru, the ship from which the type specimen was collected.

Description of female. Body ( Figs 10 View Fig , 14 View Fig ) cylindrical, 7.50 times as long as wide, pitted and setulate on cephalothorax and pereon (cf. Fig. 14 View Fig ). Cephalothorax 0.15 times as long as BL, 1.30 times as long as wide, acorn-shaped in dorsal view; rostrum rounded; eye lobes absent; posterior region with shallow median venral groove ( Fig. 14A View Fig ). Pereonites 1–6 with length ratio of 1.00: 1.20: 1.20: 1.30: 1.30: 1.00; length/width of pereonites 1–6, 0.75, 0.95, 1.05, 1.15, 1.20, and 1.05, respectively. Pleon setulate, 0.15 times as long as BL. Pleonites 0.65 times as wide as pereonite 6, 0.45 times as wide as CW, all wider than long, similar in shape; segmental articulations posterior to that between pereonites 5 and 6 all obscure; pleonites 1 and 2 each with ventral keel; pleonites 3 and 4 slightly narrower than others; pleonite 5 with one pair of lateral simple setae. Pleotelson setulate, 0.80 times as long as wide, wider than pleonites; distal region with two pairs of simple setae; apical margin straight.

Antennule ( Fig. 11A View Fig ) 1.10 times as long as cephalothorax; length ratio of articles 1–3 1.00: 0.15: 0.35. Article 1 thick proximally, with one dorsomedial and two distal simple setae, several middle and distal PSS, and several small spines. 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. 11B View Fig ) uniarticulate, 0.20 times as long as antennule, bearing two distal simple setae.

Labrum ( Fig. 12A View Fig ) with fine distal setae as illustrated. Mandibles ( Fig. 12B, C View Fig ) with membranous molar process bearing small distal projection. Lefl mandible’s incisor ( Fig. 12B View Fig ) with blunt teeth; lacinia mobilis triangular, fused to body of mandible. Right mandible’s incisor ( Fig. 12C View Fig ) with blunt teeth. Labium ( Fig. 12D View Fig ) with one pair each of lateral and distal setulate projections. Maxillule ( Fig. 12E, e View Fig 1 View Fig ) with palp bearing two setae; endite with 10 spiniform setae. Maxilla ( Fig. 12F View Fig ) naked. Maxillipeds ( Fig. 12G 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 three simple setae; article 3 with two plumose setae; article 4 with five distal simple setae. Epignath ( Fig. 12H View Fig ) narrow, curved, with one simple terminal seta.

Cheliped ( Fig. 11C View Fig ) with basis bearing small outer ventroproximal process; portion proximal to process inserted into ventral surface of posterior region of cephalothorax. Merus with one ventral simple seta. Carpus 2.15 times as long as wide, with slight ventromedial projection bearing two simple setae, and one dorsomedial and one dorsodistal simple setae. Chela 1.05 times as long as carpus, 2.15 times as long as wide; propodal palm 1.30 times as long as fixed finger, with one inner and one outer simple setae at insertion of dactylus; fixed finger with one simple seta on ventral margin and two outer simple setae, one arched spiniform seta, one distal projection, and several small spines 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 1.20: 1.10: 1.00: 0.95: 1.05: 1.05. Pereopod 1 ( Fig. 13A, a View Fig 1 View Fig ) 0.20 times as long as BL, with length ratio of articles from basis to dactylus-unguis 3.70: 0.25: 1.00: 1.40: 1.95: 1.65. Basis with dorsal small 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 and inner distal row of spiniform setae ( Fig. 13a View Fig 1 View Fig ). Dactylus and unguis subequal in length, naked. Pereopod 2 ( Fig. 13B, b View Fig 1 View Fig ) with coxa bearing one dorsal simple seta. Length ratio of articles from basis to dactylus-unguis 3.65: 0.25:1.00: 1.35: 1.80: 1.55; similar to pereopod 1, except carpus with just one ventral simple seta. Dorsodistal simple seta on carpus short (shorter than two-thirds propodus length). Pereopod 3 ( Fig. 13C, c View Fig 1 View Fig ) with length ratio of articles from basis to dactylusunguis 3.70: 0.25: 1.00: 1.30: 1.95: 1.65; similar to pereopod 2. Pereopod 4 ( Fig. 13D View Fig ) with naked coxa. Length ratio of articles from basis to dactylus-unguis 4.35:0.25: 1.00: 1.15: 1.05: 2.00. Basis with one dorsal and two ventral PSS, and dorsal small spines. Ischium with two ventral simple setae. Merus with two ventral simple setae. Carpus with one inner simple seta and one ventrodistal spiniform seta. Propodus with three distal spiniform setae. Dactylus naked. Unguis with row of short setae. Pereopod 5 ( Fig. 13E View Fig ) with length ratio of articles from basis to dactylus-unguis 4.90: 0.30: 1.00: 1.40: 1.30: 2.35; similar to pereopod 4, except basis with two dorsal PSS. Pereopod 6 ( Fig. 13F View Fig ) with length ratio of articles from basis to dactylus-unguis 4.45: 0.30: 1.00: 1.50: 1.20: 2.25; similar to pereopod 5, except basis with one dorsal and one ventral PSS.

Pleopods absent.

Uropod ( Fig. 13G View Fig ) with exopod fused to basal article, slight, not expanded laterally, bearing two simple setae. Endopod fused to basal article, with four simple setae and four PSS.

Distribution. So far known only from type locality.

Remarks. Agathotanais toyoshioae sp. nov. is the eleventh species described in this genus. Seven congeners similarly have a uniarticulate antenna and uropods without articulations between the basal article and the tip. Among these, A. toyoshioae most closely resembles A. spinipoda Larsen, 1999 in having: 1) all pleonites narrower than pereonite 6; 2) a short dorsodistal simple seta on the carpus of pereopod 2 (shorter than two-thirds of the propodus length); and 3) the carpus and propodus of pereopods 4–6 with one and three distal spiniform setae, respectively. Agathotanais toyoshioae differs from A. spinipoda in having 1) narrower pleonites (i.e., pleonite width 0.65 times width of pereonite 6 and 0.45 times CW in A. toyoshioae , but 0.75 times and 0.65 times respectively in A. spinipoda ); 2) a ventral keel on pleonites 1 and 2; 3) the bases of pereopods 1–6 with dorsal small spines; and 4) no ventral small spines on the carpus and propodus of pereopods 4–6 (see Larsen 1999b).