Armaturatanais atlanticus, Larsen & Błażewicz-Paszkowycz & Cunha, 2006

Larsen, Kim, Błażewicz-Paszkowycz, Magdalena & Cunha, Marina R., 2006, Tanaidacean (Crustacea: Peracarida) fauna from chemically reduced habitats-the lucky strike hydrothermal vent system, mid-atlantic ridge, Zootaxa 1187, pp. 1-36 : 27-30

Armaturatanais atlanticus n. sp. ( Figs. 9–11 )

Material examined

Holotype: non­ovigerous female ( ZMUC CRU­4908 ), inside the vent field, 37°17.438’ N, 32º16.599’ W, 1685 m, RV Prof. Logachev, TV­assisted grab, TTR­10, station AT­265­GR, August 2000, body length, 1.6 mm . Paratypes, 2 non­ovigerous female, 1 manca ( ZMUC CRU­4909 ), same data. Other material: 1 female, 37º17.275’ N, 32º16.525’ W, 1704 m, RV Prof. Logachev, TV­assisted grab, TTR­10, station AT­250­ GR, August 2000 . 5 females, 2 mancae, 37º17.300’ N, 32º16.563’ W, 1709 m, RV Prof. Logachev, TV­assisted grab, TTR­12, station AT­436­GR, August 2002 .

Diagnosis

Female. Antennule article 2 shorter than half of article 1; article 3 more than half as long as article 2. Right mandibular incisor smooth; left mandibular lacinia mobilis with few dorsal denticles. Chelipedal dactylus naked. Pereopods longer than pleon. Pereopods 4–6 dactylus naked; unguis of same with simple apex.

Etymology Named after the Atlantic distribution of this species.

Description

Adult female. Body length 1.95 mm.

Body ( Fig. 9A ). Dorso­ventrally flattened, 7.5 times as long as broad.

Cephalothorax. Longer than combined length of pereonites 1 and 2. Eyes and eyelobes absent.

Pereonites. Pereonites 1–3, 5 and 6 wider than long. Pereonite 4 as wide as long.

Pleon. About 0.3 times as long as total body length. All pleonites subequal; bearing small pleopods and one thick lateral seta. Pleotelson as long as combined length of four pleonites, apex acorn­shaped in lateral view, and with uropods extending from a depression.

Antennule ( Fig. 9B ). As long as cephalothorax. Article 1 as long as rest of antennule combined, with three simple and three short pinnate distal setae. Article 2 shorter than half the length of article 1, partly covering article 3 on inner margin, with three simple distal setae. Article 3, longer than half of article 2, naked. Article 4 longer than article 2, with four relatively thick simple distal setae.

Antenna ( Fig. 9C ). Almost as long as antennule. Article 1 naked, wider than other articles. Article 2 shorter than article 4, naked. Article 3 shorter than article 2, naked. Article 4 longer than other articles and with medial fusion line, with four simple distal setae. Article 5 shorter than article 2, with two simple distal setae. Article 6 minute, with four short setae and 1 aesthetasc.

Mouthparts. Labrum not recovered. Mandibular molar broad and longer than incisor, with terminal ring of several small denticles (not illustrated). Left mandible ( Fig. 10B ) lacinia mobilis longer than incisor and with curved apex; incisor with four blunt dorsal denticles. Right mandible ( Fig. 10A ) incisor fairly short, smooth, and narrow. Labium ( Fig. 10C ) with two lobes with lateral cluster of setules. Maxillule ( Fig. 10D ) endite with nine distal spiniform setae; palp not recovered. Maxilla not recovered. Maxilliped ( Fig. 10E ) endites as wide as basis, with one distal seta. Palp article 1 naked; article 2 with two setae on inner margin; article 3 with two setae on inner margin; article 4 with three setae on inner margin and one on outer margin. Epignath ( Fig. 10F ) tapering in distal direction but without terminal seta, apex naked.

Cheliped ( Fig. 11A ). Basis shorter than carpus, divided unequally by sclerite attached distally on basis. Merus naked. Carpus as long as propodus including fixed finger, with two ventral, one dorsomedial, and one dorsodistal setae. Propodus with three setae between dactylus and fixed finger. Fixed finger with two ventral setae and three on inner margin, with several small distal denticles on inner margin. Dactylus as long as fixed finger.

Pereopod 1 ( Fig. 11B ). Coxa naked. Basis longer than three succeeding articles combined, with one ventromedial seta. Ischium with one ventral seta. Merus shorter than carpus, widening distally, naked. Carpus longer than half the length propodus, with two dorsodistal setae. Propodus longer than half the length of basis, with one ventral and one dorsodistal seta and dorsal spine. Dactylus and unguis shorter than propodus and not fused. Unguis longer than dactylus.

Pereopod 2 ( Fig. 11C ). As pereopod 1 except: coxa with one seta. Basis with dorsal seta. Merus with one small ventral seta.

Pereopod 3 ( Fig. 11D ). As pereopod 2 except: basis naked and carpus setae stout. Propodus with distal setules.

Pereopod 4 ( Fig. 11E ). Coxa naked. Basis thicker than in pereopods 1–3, with one ventromedial pinnate seta. Ischium naked. Merus with two spiniform setae. Carpus with one simple and three spiniform distal setae. Propodus ventral margin with small scattered setules, with two spiniform distal setae and dorsal spine. Dactylus and unguis shorter than propodus. Unguis shorter than dactylus.

Pereopod 5 ( Fig. 11F ). As pereopod 4 except: ischium with one seta. Carpus with three spiniform distal setae. Propodus with two spiniform distal setae but apparently without setules.

Pereopod 6 ( Fig. 11G ). As pereopod 5 except: carpus with three distal spiniform and one simple setae. Propodus with three distal and one subdistal spiniform setae.

Pleopods ( Fig. 10G ). Biramous, endites longer than basal article, elongated with five simple setae on endopod and six simple setae on exopod. Setae restricted to distal edge only. No gap between proximal seta and other setae on either endite.

Uropods ( Fig. 10H ). Including basal article almost half as long as pleotelson. Basal article naked. Endopod with two articles of subequal length; article 1 naked; article 2 with one short and four long distal setae. Exopod half as long as first endopod article, with one short and one long simple distal seta.

Remarks

This species is easily separated from A. trispinipodus by the pereopods 4–6 dactylus being naked and the unguis being a single spine, and from A. minipodus by the short antennular article 2 (shorter than half or article 1), by the long pereopods, and by the uropodal exopod not reaching endopod article 2.

Figures

FIGURE 9. Armaturatanais atlanticus n.sp. A, holotype, lateral view; B, antennule; C, antenna. Scale bars: A = 1 mm. Others 0.1 mm.

FIGURE 10. Armaturatanais atlanticus n.sp. A, right mandible; B, left mandible; C, labium; D, maxillule, endite; E, maxilliped; F, epignath; G, pleopod; H, uropod. Scale bars 0.1 mm.

FIGURE 11. Armaturatanais atlanticus n. sp. A, cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pereopod 6. Scale bars = 0.1 mm.