Armaturatanais Larsen, 2005

Larsen, Kim, 2006, Tanaidacea (Crustacea; Peracarida) from chemically reduced habitats-the hydrothermal vent system of the Juan de Fuca Ridge, Escabana Trough and Gorda Ridge, northeast Pacific, Zootaxa 1164, pp. 1-33 : 21-24

Genus Armaturatanais Larsen, 2005

Diagnosis of female (modified from Larsen 2005)

Body slightly dorso­ventrally flattened. Cuticle heavily calcified. Pleotelson acornshaped in lateral view. Antennule with four articles. Antenna with six articles and fusion line on article 4. Mandibles small; molar fairly broad with flat distal crushing area surrounded by small denticles Maxilliped endites without denticles, processes or flat setae.

Pereopods 1–3 merus and carpus without spiniform setae. Pereopods and pleopods attached on the inner side of the lateral shield. Pereopods with coxa; dactylus and unguis not fused to a claw; pereopods 1–3 unguis longer than dactylus; pereopods 4–6 dactylus longer than unguis. Pleopods present in female, with simple or plumose setae. Uropods biramous, endopod with two articles; exopod with one article.

MALE. Pleon marginally longer than in female. Antennular article 3 shorter than in female and without fusion line. Functional mouthparts retained. All pleonites bearing pleopods with plumose setae, pleopods larger than in female.

Gender. Masculine.

Type species Armaturatanais minipodus Larsen, 2005 .

Remarks

Species of this genus were recently discovered from the Gulf of Mexico ( Larsen 2005) and from the Mid­Atlantic Ridge ( Larsen et al. in press). Its systematic position is not yet resolved.

The large cephalothorax of the species described below is somewhat similar to Cryptocopoides Sieg, 1976 , but the following characters differ from Sieg’s (1976) diagnosis: body lateral margins straight, lacking hyposphenia. Pleopods display a gap between proximal seta and other setae on both endites, only endopod with outer setae.

Armaturatanais trispinipodus n. sp.

( Figs. 11 , 12 )

Material examined

Holotype non­ovigerous female ( FMNH # 12530 ), sample 6148, 54°22,181’E 150°20,561’W, depth 1190 m, Sta. 3438, Patton­Murray Seamount, associated with basalt rock . Paratypes: 1 female ( FMNH # 6148 ), same locality . 1 female, sample 7670. 2 females, sample 12490. 1 female, sample 12519.

Diagnosis of female

Antennular article 3 less than half as long as article 2. Mandibular incisors/lacinia mobilis with several dorsal denticles. Chelipedal dactylus naked. Pereopods 4–6 dactylus with two spines and unguis of same trifurcate.

Male. Unknown.

Etymology This species is named after the diagnostic trifurcated unguis of the pereopods 4­6. Description

FEMALE, body length 1.9 mm.

Body ( Fig.11A ). Slightly dorso­ventrally flattened, 5.8 times longer than broad.

Cephalothorax. Longer than combined length of pereonites 1–3. Eyes and eye­ lobes absent.

Pereonites. All wider than long.

Pleon. About 0.25 times total body length. All pleonites subequal; lateral edge of dorsal shield extending almost all the way down to the ventral surface. Pleotelson longer than combined length of three pleonites. Pleotelson covered by dorsal plate.

Antennule ( Fig. 11B ). Shorter than cephalothorax. Article 1 longer than rest of antennule combined, with two simple setae. Article 2 shorter than half the length of article 1, with one simple distal seta. Article 3 shorter than half of article 4, with one simple distal seta. Article 4 shorter than article 2, with one tiny simple and four relatively thick simple distal setae.

Antenna ( Fig. 11C ). Almost as long as antennule. Article 1 naked. Article 2 longer than article 5, with one robust dorsal seta. Article 3 shorter than article 2, with one robust dorsal seta. Article 4 longer than other articles and with medial fusion line, with one medial simple and two distal setae. Article 5 longer than article 1, with two simple distal setae. Article 6 minute, with one short and one long seta and one aesthetasc.

Mouthparts. Labrum ( Fig. 11D ) hood shaped, naked. Mandibular molar process broad and longer than incisor, with terminal ring of several small denticles. Left mandible ( Fig. 11E ) lacinia mobilis as long as incisor and with several dorsal denticles; incisor with several dorsal denticles. Right mandible ( Fig. 11F ) incisor with several dorsal denticles. Labium ( Fig. 11G ) with two simple lobes, naked. Maxillule ( Fig. 11H ) endite with eight distal spiniform setae of which at least two are serrated; palp broken but of typical shape with two long distal setae. Maxilla not recovered. Maxilliped ( Fig. 11I ) endites narrower than basis, naked. Palp article 1 naked; article 2 with two inner and one outer setae; article 3 with two inner setae; article 4 with five inner and one outer setae. Epignath not recovered.

Cheliped ( Fig. 11J ). Basis divided almost equally by sclerite, shorter than carpus, naked. Merus with one ventral seta. Carpus as long as propodus inclusive fixed finger, with one ventral and two dorsal setae. Propodus with three setae near dactylus insertion. Fixed finger with two ventral setae and three on inner margin, with two small distal denticles on inner margin. Dactylus as long as fixed finger.

Pereopod 1 ( Fig. 12A ). Coxa with one seta. Basis longer than three succeeding articles combined, naked. Ischium with one ventral seta. Merus shorter than carpus, widening distally, with one simple ventrodistal seta. Carpus longer than half the length propodus, with one ventral and two dorsodistal setae. Propodus marginally longer than half the length of basis, with one ventral and one robust dorsodistal seta and dorsal spine. Dactylus and unguis combined shorter than propodus and not fused to a claw. Unguis longer than dactylus.

Pereopod 2 ( Fig. 12B ). As pereopod 1 except: basis with one ventromedial bipinnate seta. Carpus with one ventral and one dorsal seta.

Pereopod 3 ( Fig. 12C ). As pereopod 2 except: coxa and basis naked. Merus with one ventral and one dorsal seta.

Pereopod 4 ( Fig. 12D ). Coxa naked. Basis thicker than that of pereopods 1–3, naked. Ischium with one ventral seta. Merus with one spiniform seta. Carpus with four spiniform distal setae. Propodus with three robust distal setae and dorsal spine. Dactylus and unguis shorter than propodus not fused. Dactylus with two dorsal spines. Unguis shorter than dactylus, with trifurcate apex.

Pereopod 5 ( Fig. 12E ). As pereopod 4 except: basis with three bipinnate setae medially. Merus with two spiniform setae. Carpus with two spiniform and one simple distal setae. Propodus with three robust distal setae and dorsal spine.

Pereopod 6 ( Fig. 12F ). Similar to pereopod 5 except: basis and ischium naked. Propodus with four robust distal setae and dorsal spine.

Pleopods ( Fig. 12G ). Biramous, basal article less than half the length of endites. E ndopod with one outer and six inner plumose setae, gap between proximal seta and other setae. Exopod with 11 inner plumose setae, gap between proximal seta and other setae.

Uropods ( Fig. 12H ). Including basal article longer than half of pleotelson. Basal article with one seta. Endopod with two articles of subequal length; article 1 naked; article 2 with one short and five long distal setae. Exopod almost as long as first endopod article, with one short and one long simple distal seta.

Remarks

This species differs from the other species of this genus by the dorsal denticles of the mandibular incisors and lacinia mobilis, the naked chelipedal dactylus, and the spinose dactylus and unguis of pereopods 4–6. A key to the genus is given in Larsen et al. (in press).

Acknowledgments

I thank Dr. J. R. Voight and the crew of Atlantis and Alvin for the opportunity to participate in the collection of this material on the August­September Cruise to the Northeast Pacific Ridges. The expedition was funded by the National Science Foundation grant DEB­ 0 103690 to J. R. Voight. Thanks are extended to the Department of Zoology’s Marshall Field Fund, for supporting collection of additional material off Oregon and the Alvin cruise to the Patton­Murray Seamount. I also thank Dr. J. R. Voight and Dr. T. Wolff for commenting on an early draft of this paper and thank the Zoological Museum of Copenhagen for providing workspace and use of facilities.

Figures

FIGURE 11. Armaturatanais trispinipodus, female. A) Holotype, lateral view; B) Antennule; C) Antenna; D) Labrum; E) Left mandible; F) Right mandible; G) Labium; H) Maxillule; I) Maxilliped; J) Cheliped. Scale bar A 1 mm, scale bars B–I 0.25 mm.

FIGURE 12. Armaturatanais trispinipodus, female. A) Pereopod 1; B) Pereopod 2; C) Pereopod 3; D) Pereopod 4; E) Pereopod 5; F) Pereopod 6; G) Pleopod; H) Uropod. Scale bars 0.25 mm.