Collettea lilliputa, Blażewicz-Paszkowycz, Magdalena & Larsen, Kim, 2005

Blażewicz-Paszkowycz, Magdalena & Larsen, Kim, 2005, New species of the genus Collettea Lang, 1973 (Peracarida: Tanaidacea, Colletteidae) from the Antarctic., Zootaxa 1085, pp. 1-19 : 8-12

C. lilliputa n. sp. ( Figs. 3 , 4 )

Diagnosis. Female. Pereonite 1 shorter than pereonite 2. Pereonites 2 and 3 subequal. Pereonite 6 almost as long as pereonite 5. Pleon shorter than pereon. Pleonites long, about three­quarters of the width. Pleotelson short, shorter than two pleonites combined. Antenna article 4 without fusion line. Maxilliped endite with one tuberculous distal process. Cheliped fixed finger with two large pointed denticles. Cheliped dactylus as long as fixed finger. Uropods long, about half as long as pleotelson; endopod biarticulated.

Male. As female but with thicker antennule article 1 and small pleopods (not dissected).

Material examined. Juvenile male holotype, body length 1.5 mm (ZMH­K­40913). Polarstern Cr. PS61/046­7, 60°38.12' S, 53°57.49' W, depth 2893.2 m, 30 Jan 2002; Paratypes: 1 non­ovigerous female dissected, 1 non­ovigerous female, 1 manca II, 3 males (ZMH­K­40914), same locality as holotype.

Etymology. Named to reflect the small size of the species (Lilliput – the native population of one of the countries in Swift’s Gulliver’s Travels).

Description. Adult female. Body 12 times as long as broad. Cephalothorax as long as combined length of pereonites 1­2. Eye lobes present but without visual pigment. Pereonites 1 and 2 wider than long. Pereonite 3 square. Pereonites 4–6 longer than wide. Pleon long, more than 35% of total body length; all pleonites subequal. Pleotelson shorter than combined length of three pleonites.

Antennule ( Fig. 3 C). As long as cephalothorax. With four articles. Article 1 longer than rest of antennule combined, with one simple, one subdistal setae, and four pinnate setae. Article 2 as long as article 4, with one simple and two pinnate distal setae. Article 3 shorter than article 2, with two simple distal setae. Article 4 length less than one third the length of article 1, with five long simple setae, one small pinnate seta, and two aesthetascs.

Antenna ( Fig. 3 D). Two­thirds the length of antennule, with 6 articles. Article 1 fused to body, naked. Article 2 twice as long as article 3, with one robust distal seta. Article 3 shorter than article 5, square, with one robust distal seta. Article 4 longer than other articles, with one medial pinnate seta, two simple and one pinnate distal setae, no trace of fusion line. Article 5 shorter than article 2, with one distal simple seta. Article 6 minute with two long and one tiny distal setae.

Mouthparts. Labrum and labium not recovered. Left mandible molar process longer than incisor and relatively broad with few blunt and many pointed distal denticles ( Fig. 3 E), lacinia mobilis in the shape of a single blunt spine, as long as incisor; incisor with five blunt denticles. Right mandible not recovered. Maxillule ( Fig. 3 F) endite with ten distal spiniform setae, two of which are bifurcate. Palp not recovered. Maxilla not recovered. Maxilliped ( Fig. 4 A) basis wider than endite, triangular. Endites with one subdistal seta and one distal tuberculous process, outer corner with small setule. Palp twisted during dissection, article 1smooth; article 2 with two inner setae; article 3 with four inner setae; article 4 with five inner setae (one short, four long) and one outer seta. Epignath not recovered.

Cheliped ( Fig. 4 B). Basis divided unequally by sclerite attached distally, shorter than carpus, naked. Merus with one ventral seta. Carpus shorter than propodus including fixed finger, with one ventral and two small dorsal setae. Propodus naked, fairly robust (length/ width ratio 1.45). Fixed finger with one ventral and three inner setae and with two large pointed denticles on inner margin. Dactylus as long as fixed finger, naked.

Pereopod 1 ( Fig. 4 C). Coxa naked. Basis as long as combined length of ischium, merus, carpus, and half of propodus, naked. Ischium with one ventral seta. Merus shorter than carpus, widening distally, naked. Carpus less than half as long as propodus, with two small distal setae. Propodus two­thirds as long as basis, with one dorsal and one ventral spiniform small subdistal setae and two dorsal spines distally. Dactylus and unguis combined shorter than propodus. Dactylus shorter than unguis.

Pereopod 2 ( Fig. 4 D). As pereopod 1, except carpus with one spiniform ventro­distal seta. Propodus two­thirds as long as basis, with one dorsal and one ventral spiniform subdistal setae and dorsal spine. Dactylus with tiny spine or setule at unguis insertion.

Pereopod 3 ( Fig. 4 E). As pereopod 2, except ischium naked. Propodus with one spiniform ventral seta, one simple dorsal seta, and several small distal setules.

Pereopod 4 ( Fig. 4 F). Coxa naked. Basis naked and as long as combined length of ischium, merus, and carpus. Ischium with one ventral seta. Merus shorter than carpus, with two spiniform setae. Carpus with three spiniform and one simple seta. Propodus with one ventral and two dorsal spiniform setae and dorsal spine. Dactylus and unguis of subequal length, combined longer than propodus.

Pereopod 5 ( Fig. 4 G). As pereopod 4, except ischium naked. Propodus with one dorsal spiniform seta and dorsal spine.

Pereopod 6 ( Fig. 4 H). As pereopod 5, except carpus with two spiniform and one simple setae. Propodus with two dorsal and two ventral spiniform setae.

Pleopods. No pleopods on female.

Uropods ( Fig. 4 I). Long (more than half as long as pleotelson). Protopod shorter than first endopod article, naked. Endopod with two articles; article 1 with one simple and one setulose distal setae; article 2 as long as exopod, with three simple and two small setulose distal setae. Exopod about one­third as long as endopod first article, with one long distal seta.

Juvenile male. Body ( Fig. 3 A, B) as female except: 12 times as long as broad. Pleon long, more than 30% of total body length. All pleonites subequal, with pleopods. Pleopods without setae.

Distribution. The species have been found only at type locality: north­western part of Weddell Sea, at 2893 m. depth.

Remarks. Collettea lilliputa n. sp., as well as C. elongata Larsen , C. rotundicaudata Kudinova­Pasternak and C. humbolti Hansen , all have a relatively short carapace which is subequal in length (or shorter) to pereonites 1 and 2 combined. The new species can, however, be distinguished from C. elongata on the relatively short pleon, which is subequal in length to the combined length of pereonites 4–6 in C. lilliputa and longer than the combined length of pereonites 3–6 in C. elongata . Moreover C. lilliputa has only one ventral seta on the cheliped fixed finger, and the uropod exopod is shorter than half of endopod proximal article. Also the combined length of the pleonites in C. lilliputa , is almost 3 times as long as the pleotelson. Those characters allow immediately distinguish the new species from C. rotundicaudata which has two setae on the fixed finger and combined length of pleonites is subequal to pleotelson. The third species of Collettea with a relatively short carapace is C. humbolti . In contrast to C. lilliputa the pleon in that species is much shorter than half the length of the pereon and it has strong spiniform setae on pereopod 3.

The long uropods (longer than half pleotelson length), the two bifurcate setae in maxillule, and the feeble body structure in C. lilliputa and C. minima are unique characters within Collettea and possibly indicate that a separate genus is warranted for these two species. This will be tested in a phylogenetic in preparation by the authors.

Figures

FIGURE 3. Collettea lilliputa n. sp. A, B, male holotype: dorsal and lateral view; female paratype: C, antennule; D, antenna; E, left mandible; F, maxillule. Scale bar: 1 mm for A, B; 0.1 mm for C, D; 0.01 mm for E, F.

FIGURE 4. Collettea lilliputa n. sp. female paratype: A, maxilliped. B, cheliped; C – H, pereopods 1 – 6, respectively; I, uropod. Scale bar: 0.1 mm.