Leptognathiopsis langi Kudinova-Pasternak 1970, comb.nov.

Leptognathiopsis langi (Kudinova-Pasternak, 1970) comb.nov.

Figures 4–6

Leptognathia langi Kudinova-Pasternak, 1970: 359 –360, fig.12.

Material examined. 1 non-ovigerous female (KMNH IvR 500.176), station TD-7, 38°47.93’– 38°45.87’N 144°08.07’– 144°07.89’E, 7340–7433 metres, 30 September 2001. 1 non-ovigerous female (right uropod missing), (partly dissected; KMNH IvR 500.177), station XR-7, 42°12.87’– 42°12.10’N 145°33.93’– 145°32.05’E, 3853–3858 metres, 17 September 2001. 2 ovigerous females (KMNH IvR 500.178), station TD- 4, 39°27.08’– 39°29.15’N 143°37.79’– 143°38.52’E, 3272–3146 metres, 26 September 2001.

Diagnosis. Leptognathiopsis with long, deflexed, apical process on pleotelson. Uropod basis and rami slender.

Redescription of non-ovigerous female.

Body (Fig. 4 A). Slender, 6.7 times as long as broad, weakly tapering posteriorly, length 1.75–1.98 mm (1.6 mm, Kudinova-Pasternak 1970).

Carapace. Fairly stout, 1.2 times as long as broad, with rounded rostrum and convex lateral margins, shorter than pereonites 1–2 together.

Pereonites. With weakly convex lateral margins. Pereonite 1 slightly narrower posteriorly. Pereonites 1–6 0.51, 0.89, 0.94, 0.9, 0.76, and 0.52 times as long as broad, respectively.

Pleon (Fig. 4 B). Short, 13% of total body length, epimera with marginal seta generally aligned close to edge, sternal profile shallow.

Pleotelson (Figs 4 D–E). As long as three and a half preceding pleonites, with long, deflexed, acuminate apical process, with two setae and two sensory setae.

Antennule (Fig. 4 F). 0.8 times as long as carapace, overlapped by rostral margin at base. Article 1 half of total antennule length, 2.2 times as long as broad, with disto-outer seta and three more proximal sensory setae. Article 2 1.6 times as long as broad, with one inner and outer setae and one sensory setae. Article 3 short, as long as broad, with inner seta almost as long as article. Article 4, shorter than article 2, with one aesthetasc and one short and four long setae.

Antenna (Fig. 4 G). Six-articled, 0.8 times as long as antennule. Article 3 with dorsal seta. Article 4 3.75 times as long as broad, with distal sensory seta and three terminal setae. Article 5 with terminal seta. Article 6 small, with about five terminal setae.

Mouthparts. Labrum (Fig. 5 A) rounded, hood-shaped, distally setose. Labium (Fig. 5 B) lobes with small apical notch. Maxilla (Fig. 5 C) tongue-shaped. Mandible (Fig. 5 D) incisor with about four cusps, lacinia mobilis (left mandible) strong, slightly tapering, molar tapering, with about seven apical spines, medial two longer than others. Maxillule (Fig. 5 E) endite with at least five terminal spiniform setae (some concealed). Maxilliped (Figs 5 F–G) with bases unfused distally, and seta near palp articulation, endites unfused, with medial process and lateral setae on distal margin; palp article 2 with three inner and one outer setae, article 3 as long as article 2, with two long and one shorter, setae; article 4 with five terminal setae.

Cheliped (Figs 5 H–I). Attached via posterior sclerite. Basis with long posterior free process. Merus with ventral seta. Carpus 1.75 times as long as broad, without shield, with two unequal ventral setae, and one proximal and one distal dorsal seta. Propodus and spine longer than carpus, 2.3 times as long as broad, with three unequal spiniform setae on inner face and one outer seta near base of dactylus. Fixed finger with three rounded teeth on incisive margin, three outer setae and two ventral setae. Dactylus with inner seta.

Pereopod 1 (Fig. 6 A). Larger than pereopods 2–3. Coxa annular, with seta. Basis shorter than succeeding articles together, 3.9 times as long as broad. Ischium with seta almost half as long as merus. Merus with short inner seta and long outer spiniform seta that over-reaches carpus. Carpus rectangular, stout, shorter than merus, with two, dorsal and ventral, spiniform setae that reach end of propodus, and with few ventral spinules. Propodus longer than merus, with ventral spinules and ventro-distal spiniform seta longer than dactylus. Dactylus and unguis shorter than propodus, unguis with spatulate tip.

Pereopod 2 (Fig. 6 B). Similar to pereopod 1 but shorter. Basis with two (sensory?) setae. Carpus with one long, one medium and one short spiniform setae. Ventro-distal spiniform seta of propodus as long as dactylus. Pereopod 3 (Fig. 6 C). Similar to pereopod 2, but smaller. Basis without sensory setae. Dactylus with accessory seta (perhaps present on pereopods 2–3).

Pereopod 4 (Fig. 6 D). Without obvious coxa. Basis slightly longer than in pereopod 3, four times as long as broad. Ischium with two unequal setae. Merus with two ventral spiniform setae. Carpus rectangular, longer than merus, 2.7 times as long as broad, with three unequal spiniform seta and one rod-like seta. Propodus longer than carpus, with two ventro-distal spiniform setae and one dorso-distal spiniform seta. Dactylus and unguis together longer than propodus, dactylus with spinulose ventral margin.

Pereopod 5 (Fig. 6 E). Similar to pereopod 4, but basis with two sensory setae.

Pereopod 6 (Fig. 6 F). Similar to pereopods 4–5 but propodus with two dorso-distal spiniform setae.

Pleopod (not figured). Present, similar to those of preparatory male of L. attenuata.

Uropod (Fig. 4 H). Long and slender, as long as pleotelson and two and a half preceding pleonites. Basal article 2.7 times as long as broad, as long as exopod. Exopod one-articled, as long as article 1 of endopod, eight times as long as broad, with one seta at halfway point, one short and one long terminal setae. Endopod two-articled, article 1 five times as long as broad, with two sensory setae, article 2 as long as article 1, with one distal seta, two sensory setae and four terminal setae.

Ovigerous female. Generally as above but with oostegites, length 1.58–1.66 mm.

Remarks. The very similar habitus, mouthparts and general cheliped, pereopod and uropod morphology indicate a close relationship of Leptognathiopsis langi with the only other congeneric species, L. attenuata. The abysso-hadal L. langi is, however, characterized by the strong pleotelson projection and more slender uropods. Leptognathia langi is now removed from the list of doubtful (incertae cedis) species of Leptognathia given by Larsen & Shimomura (2007).

Distribution. Kurile-Kamchatka Trench and Japan Trench, 3146–7433 metres (this study), 6675–6710 metres (Kudinova-Pasternak 1970).