Collettea longipleona Blażewicz-Paszkowycz & Larsen, 2005, sp. nov.

Collettea longipleona sp. nov. (Figs. 5–6)

Diagnosis. Female. Pereonite 2 longer that pereonite 1. Pereonite 6 almost as long as pereonite 5. Pleon marginally longer than pereon. Pleonites long, about two­thirds as long as wide. Pleotelson longer than last three pleonites. Antenna article 4 without fusion line. Maxilliped endite with one distal seta only. Cheliped fixed finger with several prominent pointed denticles. Cheliped dactylus as long as fixed finger. Uropods short, not protruding beyond apex of pleotelson; endopod uni­articulated.

Male. Unknown.

Material examined. Non­ovigerous female holotype, body length 3.5 mm (ZMH­K 40911): Polarstern Cr. PS61/141­10; 58°25.08'­ 58°24.93' S, 25°0.77'­ 25°0.95' W; depth 2313­ 2281 m, 23 Mar 2002. Paratypes: 1 non­ovigerous female dissected (ZMH­K 40912), same locality as holotype.

Etymology. Named to reflect the elongate pleon of this species (Latin: longus = long + pleona = pleon in feminine form).

Description. Adult female. Body (Fig. 5 A) 11 times as long as broad. Cephalothorax longer than combined length of pereonites 1 and 2. Eye lobes present but without visual pigment. Pereonites 1–3 wider than long. Pereonite 2 longer than pereonite 1. Pereonite 4 as long as wide. Pereonites 5 and 6 longer than wide. Pleon long, about 40% of total body length. All pleonites subequal. Pleotelson longer than combined length of three pleonites.

Antennule (Fig. 5 B). As long as cephalothorax, with five articles. Article 1 as long as rest of antennule combined, with one distal seta. Article 2 shorter than article 4, with two simple distal setae. Article 3 shorter than article 2, with two simple and one setulose distal setae. Article 4 length less than half the length of article 1, with five simple distal setae. Article 5 minute and partly obscured under extension of article 4, with one simple seta and one aesthetask.

Antenna (Fig. 5 C). As long as antennule. Article 1 fused to the body, naked. Article 2 twice as long as article 3, with one simple distal seta. Article 3 as long as article 1, with one distal seta. Article 4 longer than two preceding articles combined, with two simple distal setae, no trace of fusion line. Article 5 shorter than article 2, with one distal simple seta. Article 6 minute with four distal setae.

Mouthparts. Labrum (Fig. 5 D) flat and setulose. Mandible molar process longer than incisor and relatively broad with few denticles and group of small spines. Left mandible (Fig. 5 E) lacinia mobilis broad and larger than incisor, with three denticles; incisor with four denticles. Right mandible (Fig. 5 F) incisor with three denticles. Labium (Fig. 5 I) with one pair of naked lobes. Maxillule (Fig. 5 G) endite with eight distal spiniform setae. Palp not recovered. Maxilla not recovered. Maxilliped (Fig. 5 H) basis much wider than endite, rectangular. Each endite with two subdistal setae and one tubercle process distally. Palp article 1 smooth; article 2 with three inner setae; article 3 with four inner setae; article 4 with five inner and one outer seta. Epignath not recovered.

Cheliped (Fig. 6 A). Basis divided unequally by sclerite attached distally, shorter than carpus, naked. Merus naked. Carpus as long as propodus inclusive fixed finger, with two dorsal setae. Propodus with row of setae at dactylus insertion. Fixed finger with ventral and three inner setae, with several (about nine) prominently pointed denticles on inner margin. Dactylus as long as fixed finger.

Pereopod 1 (Fig. 6 B). Coxa naked. Basis longer than three succeeding articles combined, naked. Ischium with one ventral seta. Merus shorter than carpus, widening distally, with one small spiniform ventro­distal seta. Carpus three­quarters the length of propodus, with three spiniform setae of which at least one is serrated. Propodus almost half as long as basis, with three spiniform distal setae of which at least one is serrated, and dorsal spine. Dactylus and unguis of subequal length and combined shorter than propodus. Dactylus with small seta at unguis insertion. Unguis with uneven spatulate tip.

Pereopod 2 (Fig. 6 C). As pereopod 1 except: propodus with one ventral spiniform seta and dorsal spine. Dactylus naked.

Pereopod 3 (Fig. 6 D). As pereopod 2 except: dactylus with small seta at unguis insertion.

Pereopod 4 (Fig. 6 E). As pereopod 3 except: basis with two setulate ventro­medial setae. Merus with two serrated spiniform ventro­distal setae. Carpus with four serrated spiniform setae and one simple distal setae. Propodus with two serrated spiniform ventrodistal setae and dorsal spine. Dactylus and unguis combined longer than propodus, subequal.

Pereopod 5 (Fig. 6 F). As pereopod 4 except: basis and ischium naked.

Pereopod 6 (Fig. 6 G). As pereopod 4 except: carpus with only three serrated spiniform setae and one simple distal setae.

Pleopods. No pleopods in female.

Uropods (Fig. 6 H). Short (not protruding apex of pleotelson). Protopod as long as endopod, naked. Endopod uni­articulated, with four long, simple setae and two small setulate distal setae. Exopod about half as long as endopod, with two small simple setae and one long distal seta.

Distribution. Species known only from type locality, atlantic sector of Southern Ocean, out of Weddell Sea at the depth range 2313­ 2281 m.

Remarks. Collettea longipleon n. sp., as well as C. arnaudi (Shiino), C. cylindrata (G. O. Sars), and C. cylindratoides Larsen, is distinguishable from most other colletteids by the pleon being subequal to pereon in length, but C. longipleona has, in contrast to the last three species, an uniarticulated uropodal endopod, and only one ventral setae on the fixed finger of the cheliped.