Leptognathia bamberi Larsen & Shimomura, 2007, n. sp.

Leptognathia bamberi n. sp.

(Figs 6 and 7)

Material examined. Holotype, non-ovigerous female (KMNH IvR 700.171), Station 12, 31°14.28’N, 131°32.68’E, 367– 254 m, shell sand, East of Cape Toi, Miyazaki, 29 May 2006. Paratype, 1 female (KMNH IvR 700.172) (dissected), Station 2, 31°11.45’N, 131°28.78’E, 223 m, shell sand, East of Cape Toi, Miyazaki, 23 May 2006.

Diagnosis. Female. Mandibular molars sharply decrease in width midlength. Pereopod 4–6 meral and carpal spiniform setae short (less than 20 % of article length). Uropods shorter than pleotelson, endopod articles subequal, exopod uniarticulated and shorter than first endopod article.

Etymology. The species is named in honor of Dr. R. Bamber, tanaidacean expert.

Description (body of holotype, appendages of dissected paratype).

FEMALE.

Body (Fig. 6 A, B). Body length 1.2 mm. Dorso-ventrally flattened, 6.25 times as long as broad.

Cephalothorax. Marginally longer than combined length of pereonites 1 and 2. Eyes absent but weak traces of eye-lobes persist.

Pereonites. All wider than long.

Pleon. About 0.25 times as long as total body length. All pleonites subequal; bearing small pleopods. Pleotelson longer than combined length of three pleonites.

Antennule (Fig. 6 C). As long as cephalothorax. Article 1 as long as rest of antennule combined, with one simple and three short setulated setae. Article 2 shorter than half the length of article 1, with two simple distal setae. Article 3, longer than half of article 2, with two simple distal setae. Article 4 as long as article 2, with four long and one tiny simple distal setae.

Antenna (Fig. 6 D). 0.8 times as long as antennule. Article 1 naked, wider than other articles. Article 2 longer than article 3, with one dorsal seta. Article 3 longer than article 1, with one dorsal seta. Article 4 longer than other articles and with medial fusion line, with three simple distal setae. Article 5 shorter than article 2, with one simple distal seta. Article 6 minute, with four distal setae.

Mouthparts. Labrum (Fig. 7 A) smoothly curved, rounded. Mandibles molar S-shaped, pointed and longer than incisor. Left mandible (Fig. 7 C) lacinia mobilis as long as incisor and with pointed apex; incisor as lacinia mobilis. Right mandible (Fig. 7 B) incisor pointing outwards, broad and with many small tubercles. Labium (Fig. 7 D) with two lobes, naked. Maxillule (Fig. 7 E) short, endite with eight distal spiniform setae; palp with two terminal setae. Maxilla (Fig. 7 F) ovoid, without features. Maxilliped (Fig. 7 G) basis with one seta at palp insertion. Endites as wide as basis, with one inner distal seta. Palp article 1 naked; article 2 with two setae on inner margin; article 3 with three setae on inner margin; article 4 with three setae on inner margin and one on outer margin. Epignath not recovered.

Cheliped (Fig. 7 H). Basis shorter than carpus, divided unequally by sclerite, naked. Merus with one ventral seta. Carpus shorter than propodus including fixed finger, with one ventral and two dorsal setae. Propodus with two setae between dactylus and fixed finger. Fixed finger with two ventral setae and three on inner margin, with few small distal denticles on inner margin. Dactylus as long as fixed finger.

Pereopod 1 (Fig. 7 I). Longer than other pereopods. Coxa with one seta. Basis longer than three succeeding articles combined, with one dorsomedial setulated seta. Ischium with one ventral seta. Merus as long as carpus, widening distally, naked. Carpus longer than half the length propodus, with one dorsodistal seta. Propodus longer than half the length of basis, with one ventral and one dorsodistal seta and dorsal spine. Dactylus and unguis shorter than propodus and not fused. Unguis longer than dactylus.

Pereopod 2 (Fig. 7 J). As pereopod 1 except: merus with one small spiniform ventral seta; carpus with two small distal spinifom setae.

Pereopod 3 (Fig. 7 K). As pereopod 2 except: basis with additional long ventrodistal plumose seta; propodus without dorsal seta.

Pereopod 4 (Fig. 7 L). Coxa partly fused with somite. Basis marginally thicker than in pereopods 1–3, with one dorsomedial setulate seta. Ischium with one ventral seta. Merus with two spiniform setae. Carpus with one simple and two spiniform distal setae. Propodus ventral margin with two spiniform distal setae, dorsally with one seta and spine. Dactylus and unguis shorter than propodus. Unguis shorter than dactylus.

Pereopod 5 (Fig. 7 M). As pereopod 4 except: basis with ventromedial setulated seta (broken in illustration); propodus with two spiniform distal setae on both margins.

Pereopod 6 (Fig. 7 N). As pereopod 5 except: basis with both ventral and dorsal setulated setae; carpus with three distal spiniform and one simple setae.

Pleopods (Fig. 6 E). Small but well developed, both rami with gap between proximal and other setae. Endopod with ten plumose setae. Exopod with seven plumose setae.

Uropods (Fig. 7 O). Including basal article almost half as long as pleotelson. Basal

article with one seta. Endopod with two articles of subequal length; article 1 with two distal setae; article 2 with five distal setae. Exopod longer than half of first endopod article, with one simple distal seta.

Remarks. This species is the only species of Leptognathia sensu stricto recorded from the Pacific. It can be separated from L. gyreae, L. manca, L. breviremis, and L. glandiceps by the short uropods (shorter than pleotelson) and from L. vitjazi, L. longa, and L. breviremoides by the presence of an obvious fusion line on antenna article 3 and by its short spiniform carpal setae on pereopods 4–6.