Collettea longisetosa, Larsen, Kim, 2011

Larsen, Kim, 2011, Tanaidaceans (Crustacea) from the Central Pacific Manganese Nodule Province. I. The genera Collettea, Robustochelia and Tumidochelia, ZooKeys 87, pp. 19-41 : 21-25

Collettea longisetosa sp. n. Figs 13

Material examined.

Holotype male (MNHN-Ta1029) SUB-CStation MAC 3 #43, 07/06-2004, 13°42.3490'N, 131°29.9940'W, depth> 4000 m.

Diagnosis male.

Body 19 times longer than broad. Antenna article 4 without fusion line. Maxilliped endite with small inner process. Cheliped propodus with setulose inner ridge; fixed finger with multiple prominent sharply pointed processes. Cheliped dactylus not longer than fixed finger. Heavy armament with spiniform setae on all pereopods. Pleopods uniramous and strongly elongated; endopod with four long (longer than antennule) plumose setae. Uropods long (0.3 times pleotelson length), endopod biarticulated.

Etymology.

Named to reflect the long setae of the pleopods.

Description.

Adult male, 2.9 mm (body and appendages of holotype).

Body (Fig. 1A) strongly elongated, 19 times as long as broad.

Cephalothorax longer than combined length of pereonite 1 and 2.

Pereon. Pereonites 1 and 2 wider than long. Pereonites 3-6 longer than wide.

Pleon long (about 75% as long as rest of body). All pleonites subequal, bearing long uniramous setae.

Pleotelson as long as combined length of three pleonites.

Antennule (Fig. 1B) with four articles, terminal article fused with article 4 and creating a dorsal projection. As long as cephalothorax. Article 1 marginally shorter than rest of antennule, with two setulated distal setae. Article 2 shorter than article 4, with one simple and two setulated distal setae. Article 3 half as long as article 4, with one simple distal seta. Article 4 half as long as article 1, with five simple distal setae and one short but wide aesthetasc.

Antenna (Fig. 1C) length 0.8 times length of antennule. Article 1 naked and fused to the cephalon. Article 2 elongated and widening distally, with one robust dorsodistal seta. Article 3 shorter than article 2, with one robust dorsodistal seta. Article 4 longer than other articles, with one medial setulose seta but without recognizable fusion line, with one simple and two setulated distal setae. Article 5 longer than article 2, with one simple distal seta. Article 6 minute with four distal setae.

Mouthparts: Labrum (Fig. 2A) acorn-shaped, with finely setulose apex. Mandibular molarwith very wide basis, tapering into a small crushing area with five-six terminal spines. Left mandible (Fig. 2B) incisor with two indiscrete distal denticles, lacinia mobilis prominent but simple. Right mandible (Fig. 2C) incisor wide, with two distal denticles. Labium (Fig. 2D) with medially setulose projections and finely setulose apex.Maxillule (Figure 2E) endite with ten spiniform distal setae and dorsal setulation. Palp longer than endite, with two long terminal setae. Maxilla (Fig. 2F) acorn. Maxilliped (Fig. 2G) basis with one small simple seta. Endites with small inner distal process and fine outer setulation. Palp article 1 smooth. Article 2 with three outer setae. Article 3 with three finely setose setae. Article 4 with four finely setose and one simple distal setae. Epignath (Fig. 2H) longer than maxillule endite, with finely setose inner margin but naked apex.

Cheliped (Fig. 3A) basis divided unequally by sclerite, marginally shorter than carpus. Merus triangular with one ventral seta. Carpus longer than propodus including fixed finger, with two small simple ventromedial setae and one small simple seta dorsoproximal and dorsodistal. Propodus with setulose inner ridge, with two robust setae, with one simple outer seta at dactylus insertion; fixed finger with multiple prominent sharply pointy processes and three inner seta and one ventral seta arising from a prominent tubercle; with ventral ridge terminating in unguis. Dactylus with conspicuous inner seta, row of setules and one inner spine.

Pereopod 1 (Fig. 3B) coxa with one simple seta. Basis fairly robust, shorter than three succeeding articles together, naked. Ischium with one robust simple seta. Merus shorter than carpus, widening distally, with one simple ventrodistal seta. Carpus shorter than dactylus, with one spiniform and two simple distal setae. Propodus more than half as long as basis, with three spiniform subdistal setae, row of scales and dorsal spine. Dactylus and unguis combined shorter than propodus. Unguis with subdistal ventral expansion at exit of spinning gland.

Pereopod 2 (Fig. 3C) as pereopod 1 except: basis with medioventral setulated seta, merus with one spiniform distal seta, propodus with two spiniform and one simple subdistal setae and dorsal spine; ventral margin with row of spines.

Pereopod 3 (Fig. 3D) as pereopod 2 except basis naked.

Pereopod 4 (Fig. 3E) coxa indistinct. Basis with two dorsoproximal setulated setae. Ischium with regular simple ventral seta. Merus with two spiniform ventrodistal setae. Carpus with four spiniform (two of which are finely serrated) and one bone-shaped distal setae. Propodus as long as carpus, with three spiniform distal setae. Dactylus and unguis combined longer than propodus, not fused, and without spinning gland exit.

Pereopod 5 (Fig. 3F) as pereopod 4 except basis with one medioventral setulated seta.

Pereopod 6 (Fig. 3G) as pereopod 4 except basis naked. Propodus with four spiniform distal setae.

Pleopods (Fig. 1D) uniramous and strongly elongated. Basal article shorter than endite, naked. Endopod with four long (longer than antennule) sparsely plumose setae.

Uropod (Fig. 1E) basal article shorter than exopod, naked. Endopod with two articles subequal length articles; article 1 with two setulated distal setae; article 2 with one long subdistal, four long simple and two setulated distal setae. Exopod longer than endopod article 1, with one medial and two unequally length distal setae.

Remarks.

It is hard to compare Collettea longisetosa and other Collettea species given that it is a male and most other species are described from females only. The sexual dimorphism of Collettea , know from the species, which have described male ( Collettea minima (Larsen, 2000) Collettea elongate (Larsen, 2002) and Collettea lilliputa ( Błażewicz-Paszkowycz & Larsen, 2005) indicate only minor differences between the sexes in the antennule and absence of pleopods in the females. The remarkable uniramous pleopods and their equally remarkable setae of this species separate it from any other male described.

A similar armament of the cheliped fixed finger with its strong inner serration and transverse row of inner setae/setules is also seen in Collettea subtilis Kudinova-Pasternak, 1981 and Collettea rotundicauda Kudinova-Pasternak, 1983, but none of these species have the ventral fixed finger setae arising from a tubercle or the prominent dactyli seta. Furthermore in the case of Collettea subtilis the pereonites 2-5 are of similar size and in Collettea rotundicauda the antennule is much more robust (despite being a female, which usually have slender antennules than male), a shorter antennule article 4, and a shorter pleon. The powerful setae of the pereopods is also recorded from Collettea longipleona Błażewicz-Paszkowycz & Larsen, 2005, but this species have shorter and uniarticulated uropod. Another important feature of this species is the ischial setae on the pereopods 1-3, which are much more robust than usually seen in tanaidacean ischial setae. The crushing area of the mandibular molar, while not exactly pointed, is unusual small compared to what is seen in other species of Collettea. However, the long pleotelson still indicate that the species belong to Collettea , or to a new genus if/when Collettea is spilt into several genera. The only other genus that show some similarities, like the elongated body, cheliped structure and species with variable mandibular molar width, is Filitanais Kudinova-Pasternak, 1973 but the pleon is too short and the pleotelson too long in the new species to fit the diagnosis of that genus.