Araphura macrobelone Błażewicz-Paszkowycz, Bamber & Cunha, 2011, sp. nov.

Araphura macrobelone sp. nov.

Figs 1–3

Type material. 1Ƥ, Holotype (Reg. No. BMNH.2010.291), 5ƤƤ paratypes (BMNH.2010.292-296), Station CA 546, Captain Arutyunov mud-volcano, 35º39.692’N 07º20.046’W, 1345 m depth, Mud-breccia and gas-hydrate, TV-grab, 0 6.08.2004, coll. MRC.

Other records. 1 specimen, Stn CA 393, Captain Arutyunov mud-volcano, 35º39.740’N 07º19.942’W, 1327 m depth, mud breccia, TV-grab, 09.07.2002; 1 specimen, Stn Ki 528, Kidd mud-volcano, 35º25.304’N 06º43.972’W, 489 m depth, mud breccia and H2S, TV-grab, 03.08.2004; 8 specimens, Stn CA 547, Captain Arutyunov mud-volcano, 35º39.701’N 07º20.037’W, 1344 m depth, mud breccia and gas-hydrate, TV-grab, 06.08.2004; 5 specimens, Stn CA 548, Captain Arutyunov mud-volcano, 35º39.708’N 07º20.034’W, 1345 m depth, mud breccia and H2S, Kasten corer, 06.08.2004; 3 specimens, Stn Ki 560, Kidd mud-volcano, 35º25.306’N 06º43.976’W, 498 m depth, mud-breccia, Boxcorer, 08.08.2004; all coll. MRC.

Description of female: body (Fig. 1 A, B) attenuate, holotype 2.9 mm long, 11.5 times as long as wide. Cephalothorax subrectangular, 1.8 times as long as wide, twice as long as pereonite 1, narrowing towards anterior, naked, small rostrum present, eyes absent. Pereonites mostly about as wide as long, naked; pereonites 1 and 5 subequal in length, pereonites 2 to 4 subequal in length, 1.2 times as long as pereonite 1, pereonite 6 shortest, 0.85 times as long as pereonite 5 (all pereonites respectively 1.1, 0.9, 0.85, 0.9, 0.86 and 1.2 times as wide as long). Each pleonite 4 times as wide as long and bearing pleopods. Pleotelson semicircular, as long as last three pleonites together, 0.85 times as long as anterior width, naked.

Antennule (Fig. 2 A) proximal article 2.3 times as long as wide, as long as distal three articles together, subdistally with single simple seta and three penicillate setae; second article twice as long as wide, half as long as first article, with simple outer, subdistal seta; third article compact, half as long as second article, with single simple distal seta; fourth article (flagellum) as long as third article, slender, distally with five simple setae and one aesthetasc.

Antenna (Fig. 2 B) of six articles, proximal three articles compact, subequal in length, second and third articles with dorsodistal seta; fourth article longest, as long as first three articles together, with fusion-line in proximal half and adjacent penicillate seta, distally with two simple setae and tuft of penicillate setae; fifth article one-third as long as fourth, with single distal seta; sixth article shortest, one third as long as fifth, with five distal setae.

Labrum (Fig. 2 C) hood-shaped, hirsute distally. Left mandible (Fig. 2 D) incisor process with narrow, crenulated distal margin; lacinia mobilis small, as long as incisor, distally crenulated; pars molaris pointed, distally trifurcated, slightly bent down. Labium (Fig. 2 H) m-shaped, with microtrichia laterodistally. Maxillule (Fig. 2 E) endite with eight distal spines and finely setulose outer distal edge, palp (Fig. 2 Eʹ) slender, with two distal setae. Maxilla (Fig. 2 F) linguiform, naked. Maxilliped (Fig. 2 I) palp first article naked, second article with one outer and three inner setae, third article with two longer and two shorter inner setae, fourth article with three subdistal and three distal setae; basis fused, with single, simple seta about half as long as endites; endites not fused, distally with two fine outer spinules and conspicuous single oval tubercle towards inner corner. Epignath (Fig. 2 G) talon-shaped, distally pointed.

Cheliped (Fig. 2 J) with elongate rounded, naked basis, merus subtriangular with single ventral seta, overlapping half of ventral margin of carpus; carpus twice as long as wide, with two midventral, one dorsodistal and one dorsoproximal setae; propodus comparatively short (1.35 times as long as wide), fixed finger with two ventral setae, three setae on crenulate cutting edge; dactylus naked.

Pereopod 1 (Fig. 3 A) coxa with seta; basis slender, 3.3 times as long as wide, naked; ischium compact, with single ventral seta; merus as long as carpus, and ventrodistally with single fine seta and slender simple spine; carpus distally with seta and slender spine with fine marginal denticulations in distal half; propodus 1.7 times as long as carpus, with ventral subdistal seta; dactylus with proximal seta, distinct, slender unguis twice as long as dactylus and with lanceolate tip, both together longer than propodus. Pereopod 2 (Fig. 3 B) similar to pereopod 1, basis four times as long as wide; merus distally with single fine seta, slender simple spine, and denticulate spine; carpus with three distal denticulate spines; propodus 1.3 times as long as carpus; dactylus without seta, together with longer unguis 1.1 times as long as propodus. Pereopod 3 (Fig. 3 C) similar to pereopod 2, but merus without denticulate spine, carpus with two distal spines.

Pereopod 4 (Fig. 3 D) similar to pereopod 2, basis 3.2 times as long as wide; ischium with two ventral setae; merus shorter than carpus, merus with two denticulate spines, carpus distally with four denticulate spines and one simple seta; propodus with two ventrodistal and one dorsodistal denticulate spines; dactylus almost twice as long as unguis, both together 1.1 times as long as propodus. Pereopod 5 (Fig. 3 E) as pereopod 4, but without dorsodistal spine on propodus (possibly broken off in preparation). Pereopod 6 (Fig. 3 F) as pereopod 4, but propodus with two dorsodistal spines.

Pleopods (Fig. 3 G) all alike, with naked basis, rami with plumose setae: endopod with single dorsal and ventral subdistal setae and six distal setae, exopod longer than endopod, without separated ventroproximal seta, five ventral setae and 11 distal setae.

Uropod (Fig. 3 H) uniramous, without exopod; outer projection of basis about half as long as proximal endopod segment, and with three distal setae; endopod of two segments, proximal segment more than twice as long as distal segment and distally with single simple and paired penicillate setae; distal segment with one simple subdistal seta, distally with four simple and one penicillate setae.

Male unknown.

Etymology. from the Greek makros – long, and belone (f.) – a needle, in reference to the unguis on pereopod 1 and spines on all pereopods being unusually long.

Remarks. the overall morphology of the present species, and notably the antennae, antennules, mouthparts, pereopod spination and the uropod basis, are broadly typical of Araphura, as defined by Bird & Holdich (1984) and Sieg & Dojiri (1989). Recently, Larsen et al. (2009: 4) presented a key to adult females of this genus; A. macrobelone sp. nov. keys out to couplet 8, thence to A. higginsi Sieg & Dojiri, 1989 (from the western North Atlantic coast at 20 to 200 m depth) or the generotype, A. brevimanus (Lilljeborg, 1864) (from European North- Atlantic coasts and the Mediterranean, at 22 to 1110 m depth), with both of which species it shares the presence of eight distal spines on the maxillule endite.

Araphura macrobelone differs from A. higginsi in that the proximal uropod endopod segment is more than twice as long as the distal segment (less than twice as long in A. higginsi, see Sieg & Dojiri 1989, p.133, for significance of this feature); A. macrobelone differs from A. brevimanus (its geographically closest congener) in having only a fusion-line in the proximal half of article 4 of the antennule, rather than the suture found in A. brevimanus (see Sieg & Dojiri 1989, fig. 8), and in the second pereonite being more than 1.5 times as long as the first in A. brevimanus (1.2 times in both A. macrobelone and A. higginsi); finally, A. macrobelone differs from both of these species in the proportionately greater length of the spines on the pereopods, and of the dactylus and unguis of pereopod 1, for which the species is named.

The lack of a male in this material is not surprising, as male Araphura have only rarely been reported, and undoubtedly die immediately after reproduction; Brady (in Norman & Brady 1909) recorded males of Araphura brevimana; Sieg and Dojiri (1989) refer to unspecified subadult males; Larsen et al. (2009) describe the male of A. arvedlundi Larsen & Araújo-Silva, 2009 in Larsen et al. 2009.

The species was collected from the Captain Arutyunov mud-volcano (type-locality), in the deep-water field within the Portuguese margin, at depths from 1327 to 1345 m, and from the Kidd mud-volcano in the El Arraiche field on the Moroccan margin, at depths from 489 to 498 m, on muddy-substrata with gas-hydrate or hydrogen sulphide present.