Tanaidacean (Crustacea: Peracarida) fauna from chemically reduced habitats the lucky strike hydrothermal vent system, mid-atlantic ridge

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1 Zootaxa : 1 36 (2006) Copyright 2006 Magnolia Press ISSN (print edition) ZOOTAXA ISSN (online edition) Tanaidacean (Crustacea: Peracarida) fauna from chemically reduced habitats the lucky strike hydrothermal vent system, mid-atlantic ridge KIM LARSEN 1, MAGDALENA BŁAîEWICZ-PASZKOWYCZ 2 & MARINA R. CUNHA 3 1 Invertebrate Department, Zoological Museum, University of Copenhagen,Universitetsparken 15, 2100 Copenhagen, Ø, Denmark. tanaids@hotmail.com 2 Institute for Polar Biology and Oceanobiology, University of Lodz, Banacha 12/16, Lodz , Poland. magdab@biol.uni.lodz.pl 3 Centro de Estudos do Ambiente e do Mar, Departamento de Biologia, Universidade de Aveiro, Aveiro, Portugal. mcunha@bio.ua.pt Table of contents Abstract... 2 Introduction... 2 Material and methods... 3 Systematics... 3 Suborder Tanaidomorpha Sieg, Family Colletteidae Larsen & Wilson, Genus Leptognathiella Hansen, Leptognathiella fragilis n. sp Family Leptocheliidae Lang, Genus Mesotanais Dollfus, Mesotanais styxis n. sp. (Figs. 3, 4)...10 Family Nototanaidae Sieg, Genus Obesutanais n. gen Obesutanais sigridae n. sp. (Figs. 5, 6)...16 Genus Typhlotanais G. O. Sars, Typhlotanais incognitus n. sp. (Figs. 7, 8)...21 Family Indet Genus Armaturatanais Larsen, Key to the species of Armaturatanais Armaturatanais atlanticus n. sp. (Figs. 9 11)...27 Discussion Acknowledgments...32 Literature cited...33 Appendix 1. Previously described or undescribed species found on MAR...35 Accepted by N. Bruce: 23 Feb. 2006; published: 28 Apr

2 ZOOTAXA Abstract The tanaidacean fauna from the hydrothermal vents in the Lucky Strike Field on the Mid-Atlantic Ridge is examined. The material reveals species belonging to the genera Agathotanais, Apseudes, Leviapseudes, Sphyrapus, Armaturatanais, Leptognathiella, Mesotanais, Pseudotanais and Typhlotanais. One new typhlotanaid genus, Obesutanais, and five new species, Armaturatanais atlanticus, Obesutanais sigridae, Mesotanais styxis, Leptognathiella fragilis, and Typhlotanais incognitus, are described. Key words: Tanaidacea, Hydrothermal vents, Lucky Strike vent field, Mid-Atlantic Ridge, Armaturatanais, Leptognathiella, Mesotanais, Obesutanais, Typhlotanais Introduction This is the second in a series of taxonomic papers on the tanaidaceans from chemically reduced habitats (hydrothermal vents, cold seeps, mud-volcanoes) from around the world. The previous paper (Larsen 2006) dealt with the fauna of the Juan de Fuca Ridge. This contribution documents the fauna of the hydrothermal vents of the Lucky Strike Field on the Mid-Atlantic Ridge (MAR). Only two species (Leptognathia ventralis Hansen, 1913 and Typhlotanais sp.) have previously been recorded from the MAR hydrothermal vents (Desbruyères & Segonzac 1997). In this study, the tanaid fauna of the Lucky Strike hydrothermal vent field on the MAR is examined and the new taxa described. The recently collected specimens of tanaids are the first record of the families Agathotanaidae, Colletteidae, Leptocheliidae and Pseudotanaidae from hydrothermal vents in the Atlantic. Although many differences in faunal composition and abundance between individual vents and different distance to the vent opening have been revealed by studies on vent communities (Grassle & Petrecca 1994; Wolff 2005), the sampling effort has been focused in the most active areas close to the vent openings and chimney walls where steep gradients of temperature and chemistry occur. On the other hand, the sample collection is frequently directed to large-sized organisms that can be easily seen during submersible dives or ROV operations. During geological surveys carried out in August 2000, and August 2002 by a joint program of the Geological and Mining Institute of Portugal, Moscow State University and University of Aveiro, Portugal. Over 100 different taxa were retrieved and the fauna collected yielded not only the most typical vent species but also a variety of vagrant or background organisms (Cunha et al. 2001, 2003). Small crustaceans accounted for about 50% of the species richness and included eleven tanaidacean species Magnolia Press LARSEN ET AL.

3 Material and methods Samples were collected during geological surveys carried out in August 2000 (cruise TTR-10), and August 2002 (cruise TTR-12), onboard the RV Prof. Logatchev (Training Through Research program, IOC-UNESCO). A TV-assisted grab was used to sample the Lucky Strike segment and vent field. The location of samples inside the vent field was predetermined and based on data (ROV Jason images) obtained during the cruise LUSTRE A TV-assisted grab was used to locate different types of rocks allowing a minimally destructive sampling procedure. Macro-invertebrates were picked from the surface of the rocks or sorted from sieved sediments and rock washings. Samples were preserved in 70% ethanol. Station data are given in Table 1. Dissections were conducted using chemically sharpened Wolfram (Tungsten) wire needles working under a Nikon SNZ800 dissection microscope. Observations and illustrations were made using a Zeiss Axiolab compound microscope. Body descriptions are made from the designated holotypes, while appendages are described from dissected paratypes. Terminology follows Larsen (2003a). Type specimens are held at the collection at the Zoological Museum of Copenhagen (ZMUC). Additional specimens are kept in the reference collection at the Biological Research Collection, Universidade de Aveiro, Portugal. Previously described or undescribed species found on MAR are listed in appendix 1. ZOOTAXA Systematics Suborder TANAIDOMORPHA Sieg, 1980 Family COLLETTEIDAE Larsen & Wilson, 2002 Genus Leptognathiella Hansen, 1913 Leptognathiella Hansen, 1913 Leptognathia Lang, 1968 Leptognathiella Bird & Holdich, 1984 Diagnosis Female (after Bird & Holdich 1984 and Larsen 2005). Relatively small (rarely over 2 mm in length. Body elongated. Pleon and pleotelson short (never longer than combined length of three last pereonites). Antennule with four or five articles; article 2 frequently with dorsal projection overlapping basal part of article 3. Antenna with five or six articles. Molar thin with few terminal spines. Maxilliped endite often with medial, frequently triangular, process. Chelipeds attached via sclerite. Pereopods 1 3 often stout, with or without coxa; ischical setae longer than merus; meral spiniform setae as long as carpus. TANAIDACEAN 2006 Magnolia Press 3

4 ZOOTAXA Pereopods 4 6 without coxa and not stouter than pereopods 1 3; dactylus and unguis not fused. Pleopods absent or present with simple setae only. Uropods longer than pleotelson, biramous; rami with one or two articles. Male: pleon and pleotelson longer than female often longer than combined length of two last pereonites (but barely so). Pleopods present with simple setae only. Type species Leptognathiella abyssi Hansen, Gender Feminine. Remarks This genus is represented by seven species including the one described below. The genus appears to be restricted to the Atlantic or Gulf of Mexico. A key to the genus has been given by Larsen (2005). Leptognathiella fragilis n. sp. (Figs. 1, 2) Material examined Holotype: non-ovigerous female (ZMUC CRU-4912), inside the vent field, N, 32º W, 1718 m, RV Prof. Logachev, TV-assisted grab, TTR-12, station AT-428-GR, August Paratypes: 1 female, (ZMUC CRU-4913), same data. 1 female (dissected), same data. Other material: 1 female, 37º N, 32º W, 1709 m, RV Prof. Logachev, TV-assisted grab, TTR-12, station AT-436-GR, August Diagnosis Female. Body fairly elongate relative to most other species of the genus (length:width ratio 9.5). Cephalothorax as long as combined lengths of first two pereonites. Pereopods 1 3 carpus and propodus without small ventral spines. Uropods twice as long as pleotelson but shorter than combined pleon; basal article shorter than pleotelson and biarticulated exopod half as long as first endopod article. Male: unknown. Etymology. Named after the fragile cuticle of this species. Description Adult female. Body length 1.3 mm. Body (Fig. 1A). 9.5 times as long as broad Magnolia Press LARSEN ET AL.

5 TABEL 1. Station data for the samples yielding tanaids (in some cases the bad condition of the specimens prevented an accurate identification). The active chimneys or vent sites closest to each sampling location are referred in brackets using the names given during French and American cruises (see Desbruyres et al. 2001). ZOOTAXA Station Taxa Latitude Longitude AT-250-Gr Pseudotanais vulsella 37 o N 32 o W Armaturatanais atlanticus AT-252-Gr Pseudotanais vulsella 37 o N 32 o W AT-255-Gr Tanaid undetermined 37 o N 32 o W AT-256-Gr Apseudes grossimanus 37 o N 32 o W AT-260-Gr Tanaid undetermined 37 o N 32 o W AT-265-Gr Leptognathia sp. Obesutanais sigridae Pseudotanais vulsella Armaturatanais atlanticus 37 o N 32 o W AT-267-Gr Obesutanais sigridae 37 o N 32 o W AT-271-Gr Obesutanais sigridae 37 o N 32 o W Pseudotanais vulsella AT-272-Gr Tanaid undetermined 37 o N 32 o W AT-273-Gr Obesutanais sigridae 37 o N 32 o W Pseudotanais vulsella AT-278-Gr Pseudotanais vulsella 37 o N 32 o W AT-279-Gr Pseudotanais vulsella 37 o N 32 o W AT-280-Gr Apseudes grossimanus Leviapseudes hanseni Sphyrapus malleolus Mesotanais styxis 37 o N 32 o W AT-425-Gr Sphyrapus malleolus 37 o N 32 o W AT-428-Gr Agathotanais ingolfi Leptognathiella fragilis Mesotanais styxis Typhlotanais incognitus Pseudotanais vulsella 37 o N 32 o W AT-436-Gr Leptognathiella fragilis Mesotanais styxis Leptognathia sp. Pseudotanais vulsella Armaturatanais atlanticus 37 o N 32 o W to be continued. TANAIDACEAN 2006 Magnolia Press 5

6 ZOOTAXA TABLE 1 (continued). Station Depth (m) Lithology Location AT-250-Gr 1704 Volcanic: hyaloclastic rocks SE area (Tour Eiffel) near active chimneys AT-252-Gr 1673 Volcanic: high vesicularity lava SE area (Y3) near active chimneys AT-255-Gr 1680 Hydrothermal slab SE area AT-256-Gr 1668 Hydrothermal slab SE area at the periphery of the field AT-260-Gr 1690 Sulfide rubble NW area AT-265-Gr 1685 Volcanic: hyaloclastic rocks SE area (Y3) near active chimneys AT-267-Gr 1710 Sulfide chimney: low temperature, inactive SE area (Fantôme) AT-271-Gr 1712 Sulfide chimney: low temperature, active AT-272-Gr 1710 Sulfide chimney: high temperature, inactive NW area (Nuno), diffuse venting NW area (Elisabeth) AT-273-Gr 1675 Sulfide rubble SE area (Y3), near active chimney AT-278-Gr 1655 Sulfide rubble SE area AT-279-Gr 1703 Volcanic: high vesicularity lava SE area (Y3) AT-280-Gr 1750 Volcanic: massive lava Outside the vent field AT-425-Gr 2072 Volcanic: massive lava Outside the vent field AT-428-Gr 1716 Hydrothermal slab SE area (Chimiste) near active chimney AT-436-Gr 1709 Hydrothermal slab SE area (Chimiste) near active chimney Cephalothorax. As long as combined lengths of pereonites 1 and 2. Eyelobes absent. Pereonites. Pereonites 1, 2 and 6 wider than long. Pereonite 3 longer than wide. Pereonites 4 and 5 as wide as long. Pleon. Short (less than 0.25 times as long as total body length). All pleonites subequal. Pleotelson as long as combined length of two pleonites, apex blunt. Antennule (Fig. 1B). Longer than cephalothorax. Article 1 as long as rest of antennule, with two simple distal and three pinnate subdistal setae. Article 2 shorter than half of article 1, with two simple- and three pinnate distal setae. Article 3 shorter than article 4, with two simple distal setae. Article 4 about as long as article 2, with one aesthetasc, four simple, and one tiny setae, all distal. Antenna (Fig. 1C). 0.7 times as long as antennule. Article 1 not broader than following articles, naked. Article 2 longer than article 5, naked. Article 3 longer than other articles, Magnolia Press LARSEN ET AL.

7 with fusion line, with one simple seta proximal to fusion line and two distal simple setae. Article 4 longer than article 1, with one distal seta. Article 5 minute, with two long thick distal setae. Mouthparts. Labrum (Fig. 1D) slightly pointed, naked. Mandibular molar pointed and longer than incisor, with small distal spines. Right mandible (Fig. 1E) incisor slender and terminating in a small spine. Labium not recovered. Maxillule (Fig. 1F) with eight spiniform terminal setae. Maxilla (Fig. 1G) slightly elongated and naked. Maxilliped (Fig. 1H) endites apparently naked, narrower than basis; palp article 1 naked; article 2 and 3 with three setae on inner margin; article 4 only half as wide as article 3, with four setae. Epignath not recovered. Cheliped (Fig. 1I). Basis divided unequally by sclerite, shorter than carpus. Merus triangular with one ventral seta. Carpus longer than propodus including fixed finger, with two ventral setae. Propodus with one seta near dactylus insertion on inner margin. Fixed finger with two ventral setae, three on inner margin, and with four prominent sharp denticles on inner margin. Dactylus as long as fixed finger. Pereopod 1 (Fig. 2A). Coxa naked. Basis as long as three succeeding articles combined, naked. Ischium apparently naked (see remarks). Merus shorter than carpus, widening distally, with one stout ventrodistal seta. Carpus longer than half of propodus, with two stout distal setae. Propodus longer than half the length of basis, with one ventrodistal spiniform seta. Dactylus and unguis subequal, combined shorter than propodus and not fused to a claw. Pereopod 2 (Fig. 2B). As pereopod 1 except: coxa and basis each with one seta. Pereopod 3 (Fig. 2C). As pereopod 1 except: merus with two setae. Propodus with tiny ventrodistal setules. Pereopod 4 (Fig. 2D). No apparent coxa. Basis naked, longer than three succeeding articles. Ischium with one long ventral seta (almost as long as merus). Merus with two spiniform distal setae. Carpus with three stout and one small simple distal setae. Propodus with three stout distal setae. Dactylus and unguis shorter than propodus, dactylus more than twice as long as unguis. Pereopod 5 (Fig. 2E). As pereopod 4 except: basis with one ventromedial pinnate seta. Pereopod 6 (Fig. 2F). Described from holotype. As pereopod 5 except carpus with three stout distal setae. Pleopods (Fig. 2G). Small, rather stout. All pairs similar. Each endite armed with five short simple distal setae only. Uropods (Fig. 2H). Twice as long as pleotelson but shorter than entire pleon. Basal article shorter than pleotelson. Endopod with two articles of subequal length, article 1 with one distal seta, article 2 with two long and three simple distal setae. Exopod half as long as endopod article 1, with two articles of subequal length; article 1 naked; article 2 with one prominent and one small distal seta. ZOOTAXA TANAIDACEAN 2006 Magnolia Press 7

8 ZOOTAXA FIGURE 1. Leptognathiella fragilis n. sp. A, holotype, lateral view; B, antennule; C, antenna; D, labrum; E, right mandible; F, maxillule, endite; G, maxilla; H, maxilliped; I, cheliped. Scale bars: A = 1 mm. Others = 0.1 mm Magnolia Press LARSEN ET AL.

9 Remarks. This species is rather similar to L. subaequalis Hansen, 1913 and L. clivicola Bird & Holdich, 1984 but can be distinguished from the first by a biarticulated uropodal exopod and from the latter by the cheliped denticles and by the uropodal exopod only being as long as half of first endopod article. The medial and frequently triangular process on the distal edge of the endite of the maxilliped is reported as a stable character for this genus by Larsen (2005). This structure was not found in this species and this makes genus designation rather weak. However, due to the small size of this species and the poor condition of the material, the lack of maxilliped process might be an artefact. The ischial setation is described as diagnostic by Bird & Holdich (1984) and seems to be a good character for the genus. However, these setae are fragile and it is often not possible to determine whether they have been broken off or never been present. ZOOTAXA FIGURE 2. Leptognathiella fragilis n. sp. A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, pleopod; H, uropod. Scale bar = 0.1 mm. TANAIDACEAN 2006 Magnolia Press 9

10 ZOOTAXA Family LEPTOCHELIIDAE Lang, 1973 Genus Mesotanais Dollfus, 1897 Diagnosis (modified from Sieg & Heard 1989) Female. Eyelobes present but without visual pigment. Antennule with three articles. Antenna with six articles; article 2 and 3 with spiniform dorsal setae. Mandibles well developed with broad molar. Labium with two pairs of lobes. Maxilliped basis and endites not fused; endites with two or three short, flat, unequal-sized setae, basis with one or two long simple setae near palp insertion. Chelipeds attached via sclerite. Pereopod 1 almost twice as long as following pereopods; dactylus and unguis combined longer than propodus, combined dactylus and unguis on other pereopods shorter than propodus. Pereopods 1 3 with coxa; dactylus/unguis not fused. Pereopods 4 6 without coxa; basis thicker than pereopods 1 3, dactylus/unguis incompletely fused to an elongated claw. Pleopods present and well developed, with plumose setae. Uropods biramous; exopod biarticulated; endopod with three or more articles. Male (after Sieg & Heard 1989). Only known from one incomplete specimen of M. vadicola (Sieg & Heard 1989). Habitus as female except the carapace is longer and the pleon is wider. Antennule with seven articles and with multiple aesthetascs. Cheliped basis enlarged (rest of chelipeds are missing in only known specimen). Remarks This genus is similar to other genera in the family Leptocheliidae but can be separated by the lack of eyes. Previously, the setation of the maxilliped basis was supposed to be stable in this genus but Mesotanais styxis n. sp. conflicts with this character and displays only one such seta. Another leptocheliid genus (Heterotanais) is diagnosed by having only one of these setae, but this genus is diagnosed with eyes. Type species Mesotanais dubius Dollfus, 1897; by monotypy. Gender Masculine. Mesotanais styxis n. sp. (Figs. 3, 4) Material examined Holotype: non-ovigerous female (ZMUC CRU-4910), south of the vent field, N, 32º W, 1750 m, RV Prof. Logachev, TV-assisted grab, TTR-10, station AT-280-GR, August Paratypes:1 non-ovigerous female (ZMUC CRU-4911), Magnolia Press LARSEN ET AL.

11 same data. 1 non-ovigerous female (dissected), same data. Other material: 2 non-ovigerous females, 1 manca III, inside the vent field, 37º N, 32º W, 1718 m, RV Prof. Logachev, TV-assisted grab, TTR-12, station AT-428-GR, August non-ovigerous female, 2 (half) non-ovigerous females, 37º N, 32º W, 1709 m, RV Prof. Logachev, TV-assisted grab, TTR-12, station AT-436-GR, August ZOOTAXA Diagnosis Female. Antennule without long (almost as long as antennule) setae. Maxilliped basis with only one distal seta. Uropodal endopod with four articles. Etymology This species is named after the mythological subterranean River Styx separating the world of the living from the underworld, due to the collection sites at another such river (the vent plume). Description Female. Body length 1.85 mm. Body (Fig. 3A, B). Seven times as long as broad. Cephalothorax. Shorter than combined length of Pereonite 1 and 2. Eyelobes present, no visual pigmentation. Pereonites. Pereonite 1 and 6 wider than long. Pereonite 2 square. Pereonites 3 5 slightly longer than wide. Pleon. Very short (only 15% of total body length). Pleonites marginally wider than pereonites, all with pleopods and with one robust lateral seta on each margin. Pleotelson longer than combined length of last two pleonites (in lateral view). Antennule (Fig. 3C). Long (as long as combined length of cephalothorax and pereonite 1. With three articles; article 1 longer than rest of antennule combined, with three simple medial and five simple distal setae; article 2 one-third as long as of article 1, with two simple distal setae; article 3 about half length of article 1, with three long, two short simple distal setae and one aesthetasc. Antenna (Fig. 3D). Three-quarters length of antennule. With six articles; article 1 not broader than following articles, naked; article 2 shorter than article 5, with one spiniform dorsodistal seta and one simple seta on each distal margin; article 3 shorter than article 2, with one spiniform dorsodistal seta; article 4 longer than other articles, with one simple and one pinnate medial seta and eight distal setae; article 5 slightly longer than half of article 4, with one distal seta; article 6 minute, distally with three long simple setae and two short setae. Mouthparts. Labrum (Fig. 3E) setose and with flat apex. Mandibles (Fig. 3F H) large and well developed; molar broad and twisted relative to incisor, longer than incisor. Left mandible (Fig. 3F) lacinia mobilis larger than incisor, with several distal denticles on TANAIDACEAN 2006 Magnolia Press 11

12 ZOOTAXA upper margin; incisor with tapering apex without denticles. Right mandible (Fig. 3G & H) incisor with tapering apex and serration on both margins. Labium (Fig. 3I) consisting of two pairs of lobes, outer lobe setose on distal margin, inner lobes apparently naked. Maxillule (Fig. 3J) with nine spiniform terminal setae, several distal setules and row of setae proximally on inner margin of endite shaft; palp (Fig. 3K) shorter than endite and with two distal setae. Maxilla not recovered. Maxilliped (Fig. 4A) endites small and narrow, with three rounded, flat, short setae (middle one with irregular distal edge). Basis with only one long simple seta at palp insertion. Palp article 1 naked; article 2 with one outer seta, four short medial setae, and four long distal setae (of which at least one is serrated) on inner margin; article 3 with multiple inner setae of variable thickness, (of which several are serrated); article 4 with six distal inner and one outer setae. Epignath not recovered. Cheliped (Fig. 4B). Basis shorter than carpus, naked, attached via anterior sclerite. Merus with one ventral seta. Carpus shorter than propodus including fixed finger, with three ventral and two dorsal setae. Propodus elongated and with several setae at dactylus insertion. Fixed finger with two ventral setae and three setae on inner margin and with conspicuous denticles on inner margin. Dactylus as long as fixed finger and naked. Pereopod 1 (Fig. 4C). Almost twice as long as pereopods 3 6. Coxa with one seta. Basis longer than three following articles combined, naked. Ischium naked. Merus as long as carpus, rectangular and naked. Carpus less than half as long as propodus, with three simple distal setae. Propodus longer than half of basis, with three simple dorso-subdistal setae, one minute ventro-subdistal seta and without apparent dorsal spine. Dactylus and unguis combined longer than propodus and not fused. Dactylus with one simple dorsal seta. Unguis shorter than dactylus. Pereopod 2 (Fig. 4D) Coxa with one seta. Basis longer than three following articles combined. Ischium with one ventral seta. Merus widening distally, with one ventral distal seta. Carpus three-quarters length of propodus, with three minute distal setae. Propodus shorter than merus and carpus combined, with one ventral and two simple subdistal setae and without apparent dorsal spine. Dactylus and unguis shorter than propodus, not fused. Dactylus naked. Unguis shorter than dactylus. Pereopod 3 (Fig. 4E). As pereopod 2 except: coxa naked. Basis with one dorsoproximal seta. Merus with two simple distal setae. Carpus with two simple distal setae. Propodus with one subdistal seta on each margin. Pereopod 4 (Fig. 4F). Without coxa. Basis marginally thicker than on pereopods 1 3, with one dorsoproximal pinnate seta. Ischium with one ventral seta. Merus as long as carpus, with two spiniform ventral setae. Carpus with three spiniform distal setae. Propodus shorter than combined length of merus and carpus, with dorsomedial pinnate seta, one ventral and three dorsal spiniform and one stout distal setae. Dactylus and unguis incompletely fused to a slender claw, shorter than propodus. Pereopod 5 (Fig. 4G). As pereopod 4 except: ischium naked. Propodus with one Magnolia Press LARSEN ET AL.

13 dorsodistal stout seta, and one ventral and two dorsal spiniform distal setae. Pereopod 6 (Fig. 4H). As pereopod 5 except: basis naked. Ischium with one seta. Carpus with two spiniform and one simple distal setae. Propodus with five spiniform and two stout dorsodistal setae ZOOTAXA FIGURE 3. Mesotanais styxis n. sp. A, holotype, dorsal view; B, holotype, lateral view; C, antennule; D, antenna; E, labrum; F, left mandible; G, right mandible, incisor; H, right mandible, molar; I, labium; J, maxillule, endite; K, maxillule, palp; L, pleopod. Scale bars: A & B = 1 mm. others = 0.1 mm. TANAIDACEAN 2006 Magnolia Press 13

14 ZOOTAXA FIGURE 4. Mesotanais styxis n.sp. A, maxilliped; B, cheliped; C, pereopod 1; D, pereopod 2; E, pereopod 3; F, pereopod 4; G, pereopod 5; H, pereopod 6; I, uropod. Scale bars = 0.1 mm Magnolia Press LARSEN ET AL.

15 Pleopods (Fig. 3L). Well developed. Basal article with one plumose seta (setulation not illustrated). Exopod with seven outer and one inner plumose setae. Endopod with eleven outer plumose setae, gap between proximal seta and other setae. Uropods (Fig. 4I). Biramous, more than half as long as pleon. Basal article naked. Exopod biarticulated, longer than first endopod article; article 1 with one distal seta, article 2 with two distal setae. Endopod with four articles, all with distal setae; most articles also with pinnate setae. Remarks. This new species can be separated from all other species of Mesotanais by the presence of only one seta at the maxilliped bases. Furthermore, the new species differs from M. vadicola Sieg & Heard, 1989 by a slender, almost straight cheliped and from M. longisetosus Sieg & Heard, 1989 by the absence of long antennular setae. From M. elongatus Sieg & Bird, 1989 it differs by having three short flat maxillipedal endite setae and from M. dubius Dollfus by the simple shape of the right mandibular incisor, the lack of maxilliped basal simple setae, and by the two meral spiniform setae on pereopods 5 and 6. The incomplete fusion of dactylus and unguis of the pereopods 4 6 is also seen in M. vadicola and M. longisetosus and, although not described, has been illustrated to vary within the individuals (Sieg & Bird 1989: 177, fig. 8). This species is also unique in the having a four-articulated uropodal endopod, but this character has shown to be dependent on ontogeny in many species (Larsen 2005) which is also the case in the family Leptocheliidae (Masunari 1983; Bird & Bamber 2000). ZOOTAXA Family NOTOTANAIDAE Sieg, 1976 Genus Obesutanais n. gen. Diagnosis Body habitus short and stout (almost pseudotanaid-like) with a wide head. Body tapering off posteriorly. Pleon curved ventrally. Antennule with long setae on article 1. Mandibular molar with few distal spines. Maxilliped endite with one distal tubercule. Pereopods all with many setules and cuticular scales. Pereopods 2 and 3 merus with one seta as long as or longer than carpus; carpus with a long seta (almost as long as propodus). Pereopods 4 6 without ornamented process (clinging process); unguis bifurcate. Pleopod setation restricted to the distal end (except for the endopod proximal seta); large gap between endopod proximal seta and other setae; long (more than half the length of endopod). Uropod endopod with two incompletely fused articles (pseudo-uniarticulate); endo- and exopod with thick specialized terminal setae; exopod unarticulated, almost as long as endopod. Type species Obesutanais sigridae n. sp., here designated. TANAIDACEAN 2006 Magnolia Press 15

16 ZOOTAXA Etymology Name alluding to the fat body (Latin: obesus = fat). Remarks The typhlotanaid component of the family Nototanaidae is overburdened and heterogenous. The genus Typhlotanais alone contains 56 species and is currently under revision (B»aïewicz-Paszkowycz personal communication). Several genus-level typhlotanaid groups can be recognized, but the new genus differs from these in a number of characters. The pleopod setation being restricted to the distal end and the relatively large gap between the proximal seta and the other setae, are unique to the new genus. The maxilliped endites have only one distal process while most typhlotanaids have two, although they may be of different size. The long meral and carpal setae of the pereopods 2 and 3 are also a unique character. Members of the genera Typhlotanais G.O. Sars, 1882 and Peraeospinosus Sieg, 1986 have pereopods 4 6 shortened, thick and, in their natural position, curved upwards as an adaptation to clinging inside tubes. The outer margin of merus and carpus of such legs contribute to this clinging apparatus (which in most Typhlotanais sensu lato consists of processes of various size), being covered with hooks and numerous short setae or well calcified spines. Obesutanais has no such processes but the clinging apparatus is formed by a pair of spines on both merus and carpus and numerous short setae and well calcified spines that are arranged in combs. One other species, listed as Typhlotanais sp., was found in a hydrothermal vent habitat (Larsen 2005) also belongs in this new genus and three additional from the North Atlantic are under description (Bird & B»aïewicz-Paszkowycz personal communication). Obesutanais sigridae n. sp. (Figs. 5, 6) Material examined Holotype: ovigerous female (ZMUC CRU-4904), inside the vent field, N, 32º W, 1685 m, RV Prof. Logachev, TV-assisted grab, TTR-10, station AT-265-GR, August Paratypes: 1 ovigerous female, 1 non-ovigerous female, 1 manca (ZMUC CRU-4905), same data. 1 non-ovigerous female (dissected), same data. Other material: 1 female, 37º N, 32º W, 1710 m, RV Prof. Logachev, TV-assisted grab, TTR- 10, station AT-267-GR, August female, 37º N, 32º W, 1675 m, RV Prof. Logachev, TV-assisted grab, TTR-10, station AT-273-GR, August Diagnosis Female. Pereonite 6 three-quarters length of pereonite 5. Pereopods long (longer than pleon). Antennule article 3 without spiniform setae. Pereopods 4 6 dactylus and unguis partly fused but not into a claw. Uropods longer than pleotelson Magnolia Press LARSEN ET AL.

17 Etymology Named in honour of our close friend, Mrs. Sigrid Dawn Hart, editor of Gulf and Caribbean Research. ZOOTAXA Description Female. Body length 1.2 mm. Body (Fig. 5A, B). Very stout, only about 3 times as long as broad, tapering in distal direction. Cephalothorax. As long as combined length of pereonites 13. Eyelobes absent. Pereonites. All wider than long and progressively narrower posteriorly towards the pleotelson. Pereonite 1 shortest, pereonite 4 longest. Pleon times as long as total body length. All pleonites subequal in length but tapering in width posteriorly. Pleotelson longer than combined length of two pleonites. Antennule (Fig. 5C). Marginally shorter than cephalothorax. Article 1 longer than rest of antennule, with six relatively long simple setae and three groups of pinnate distal setae. Article 2 only 0.2 times as long as article 1, with two simple distal setae. Article 3 twice as long as article 2, with one pinnate and seven simple distal setae. Antenna (Fig. 5D). Almost as long as antennule but only one-third as wide. Article 1 not broader than following articles, naked. Article 2 longer than article 3, with one dorsodistal seta. Article 3 shorter than article 2, with one dorsodistal seta. Article 4 longer than other articles, with four dorsodistal setae and proximal setules. Article 5 as long as article 2 with one simple distal seta. Article 6 minute, with five setae. Mouthparts. Labrum (Fig. 5E) flat and with several setules. Mandibular molar broad and longer than incisor, with terminal ring of blunt denticles interrupted by small group of proximal spines. Left mandible (Fig. 5F G) lacinia mobilis longer than incisor, with multiple denticles; incisor broad, with two denticles. Right mandible (Fig. 5H & I) incisor with three denticles. Labium not recovered. Maxillule (Fig. 5J) endite with eight distal spiniform setae; palp not recovered. Maxilla not recovered. Maxilliped (Fig. 5K) basis apparently without setae at palp insertion. Endites almost as wide as basis, with two setae and one inner distal process. Palp article 1 naked; article 2 with three finely serrated inner setae and one simple outer seta; article 3 with two finely serrated and two simple inner setae; article 4 with five finely serrated inner setae and one simple outer seta. Epignath not recovered. Cheliped (Fig. 6A). Basis divided unequally by small sclerite attached proximally, shorter than carpus, with one seta near sclerite insertion. Merus with one ventral seta. Carpus longer and wider than propodus including the fixed finger, with three ventral setae, two small dorsal setae and setules along the entire dorsal margin. Propodus with one seta by dactylus insertion. Fixed finger with two ventral setae and three on inner margin, and several prominent denticles on inner margin. Dactylus as long as fixed finger. Pereopod 1 (Fig. 6B). Longer than other pereopods. Coxa with one simple seta. Basis longer than three succeeding articles combined, with two dorsal setae and multiple dorsal TANAIDACEAN 2006 Magnolia Press 17

18 ZOOTAXA setules. Ischium with one ventral seta. Merus as long as carpus, widening distally, with one tiny ventrodistal seta and setules and cuticular scales. Carpus 0.8 times as long as propodus, with four simple distal setae and scattered setules and cuticular scales. Propodus half as long as basis, with three dorsal and one ventral subdistal setae. Dactylus and unguis shorter than propodus and not fused to a claw, of subequal length. Pereopod 2 (Fig. 6C). As pereopod 1 except: ischium naked. Merus with two simple distal setae, one of which is longer than carpus. Carpus with two long (almost as long as propodus), two small, and one spiniform distal setae. All articles except propodus, with multiple setules and cuticular scales. Pereopod 3 (Fig. 6D). As pereopod 1 except: basis with only one dorsal seta. Carpus with two short, one long, and one short spiniform setae. Propodus with small ventrodistal spiniform seta, two simple dorsodistal setae and dorsal spine, with setules only on proximal part. Dactylus with one simple distal seta. Pereopod 4 (Fig. 6E). Basis 3 times as wide as in pereopods 1 3, longer than three succeeding articles combined, with several scattered setules. Ischium with two ventral setae. Merus longer than carpus, widening distally, and with one spiniform distal seta and scattered setules and cuticular scales. Carpus two-thirds as long as propodus, with one spiniform seta and cuticular scales. Propodus with serrated dorsal margin, with one dorsodistal seta, dorsal spine, and two spiniform ventral setae. Dactylus and unguis incompletely fused to a claw and combined shorter than propodus. Dactylus with ventral serration longer than ungius. Unguis with bifurcate tip (not visible on illustration due to appendage orientation). Pereopod 5 (Fig. 6F). As pereopod 4 except: basis with one setulose dorsal seta and scattered setules. Carpus with two multifurcate spiniform setae and cuticular scales. Propodus with dorsomedial setulose seta. Pereopod 6 (Fig. 6G). As pereopod 4 except: carpus two-thirds as long as propodus, with one simple seta, three spiniform setae and cuticular scales. Propodus half as long as length of basis, with three dorsodistal setae, dorsal spine, and two spiniform ventral setae. Pleopod (Fig. 6H). Basal article naked. Exopod with one outer and seven inner plumose setae, no gap between proximal seta and others. Endopod with 11 simple inner setae, large gap between proximal seta and others. Uropods (Fig. 5L). Basal article shorter than first endopod pseudoarticle, naked. Endopod with two partly fused articles, shorter than pleotelson; article 1 with two pinnate distal setae; article 2 with four distal simple setae and one thick specialized seta. Exopod uniarticulated, three-quarters as long as endopod, with one medial seta and one simple and one thick specialized distal seta. Remark Specimens were found in very heavy tubes consisting of densely packed mud particles. This species is quite common and abundant in other Lucky Strike-MAR samples Magnolia Press LARSEN ET AL.

19 ZOOTAXA FIGURE 5. Obesutanais sigridae n.sp. A, holotype, dorsal view; B, holotype, lateral view; C, antennule; D, antenna; E, labrum; F, left mandible, incisor and lacinia mobilis; G, left mandible, molar; H, right mandible, molar; I, right mandible, incisor; J, maxillule; K, maxilliped; L, uropod. Scale bars: A D, K 0.1 mm. E J 0.01 mm. TANAIDACEAN 2006 Magnolia Press 19

20 ZOOTAXA FIGURE 6. Obesutanais sigridae n.sp. A, cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5; G, pereopod 6; H, pleopod. Scale bars 0.1 mm Magnolia Press LARSEN ET AL.

21 Genus Typhlotanais G. O. Sars, 1882 Diagnosis Female (modified after G.O. Sars 1882). Body almost completely cylindrical. Cephalothorax wider than pereon. Antennule with three articles. Antenna with five or six articles. Molar broad with several terminal denticles. Maxilliped basis partially fused, endites not fused; distal edge with lateral process. Chelipeds ventrally attached via sclerite. Pereopods 1 3 walking type, with coxae; merus and carpus with simple setae only. Pereopods 4 6 clinging type, with or without coxae, merus and carpus with at least one spiniform seta, usually with clinging process, dactylus and unguis fused. Pleopods present, with simple or plumose setae. Uropods biramous; endopod and exopod with one or two articles. ZOOTAXA Remarks It is the opinion of these authors that the genus Typhlotanais and its most closely allied genera (Obesutanais, Peraeospinosus, Paratyphlotanais, Typhlotanaoides, and Meromonakantha), although likely to constitute a monophyletic taxon, are so intermingled and poorly defined that only a thorough phylogenetic analysis can resolve the systematics of this group. Such a systematic revision of the typhlotanaids is currently in preparation (B»aïewicz-Paszkowycz & Bird personal communication). Therefore the diagnosis given above should be considered as only provisional. Typhlotanais incognitus n. sp. (Figs. 7, 8) Material examined Holotype: non-ovigerous female (ZMUC CRU-4906), inside the vent field, N, 32º W, 1718 m, RV Prof. Logachev, TV-assisted grab, TTR-12, station AT-428-GR, August 2002, body length 1.05 mm. Paratypes, 1 non-ovigerous female in poor condition (ZMUC CRU-4907), same data. 1 non-ovigerous female (dissected), same data. Diagnosis, female. Carapace oval (1.25 times as long as wide), narrowing anteriorly. All pereonites wider than long. Pereonites 1 3 clearly separated. Pereonites 2 5 with rounded margins. Chelipeds basis do not reach the edge of pereonite 1, wide groove at the cheliped insertion. Mandible molar with ring of terminal blunt denticles. Maxillule with eight spines distally; one of them bifurcated. Chela shorter than carpus. Pereopods 4 6 not stouter than pereopods 1 3; dactylus and unguis fused but not into a claw, not bifurcate. Uropods longer than pleotelson; endopod and exopod with two articles and almost subequal length. TANAIDACEAN 2006 Magnolia Press 21

22 ZOOTAXA Etymology Named after inconspicoulous characters of this species. Description Female. Body length 1.5 mm. Body (Fig. 7A, B). Cylindrical, about 6 times as long as broad. Cephalothorax. Longer than combined length of pereonites1 and 2. Narrowing anterior, rounded posteriorly. Eyelobes absent. Pereonites. All wider than long. Pereonite 1 shortest. Pereonite 5 longest. Pleon. Marginally wider than pereon, short (including pleotelson about 20% of total body length). All pleonites subequal, carrying pleopods. Pleotelson shorter than combined length of two pleonites, apex smoothly rounded. Antennule (Fig. 7C). As long as cephalothorax. Article 1 longer than rest of antennule and four times as wide as article 3, with several setules along both margins and four simple distal setae. Article 2 less than 0.25 times as long as article 1, with one simple distal seta. Article 3 more than twice as long as article 2, with one pinnate and six simple distal setae. Antenna (Fig. 7D). Three-quarters length of antennule and one-quarter as wide as proximal part of antennule. Articles 1 and 2 broken but not broader than following articles. Article 3 marginally longer than article 6, with one minute dorsal seta. Article 4 longer than other articles, with three simple and two pinnate dorsodistal setae. Article 5 more than twice as long as article 3, with one distal seta. Article 6 minute, with five distal setae. Mouthparts. Labrum (Fig. 7E) flat and with several setules. Mandibular molar broad and longer than incisor, with terminal ring of denticles. Left mandible (Fig. 7F) lacinia mobilis longer than incisor, in shape of a single spine; incisor broad, with two denticles. Right mandible not recovered. Labium (Fig. 7G) with inner and outer processes, both with a few setules. Maxillule (Fig. 7H) endite with eight distal spiniform setae, one of which is bifurcate; palp not recovered. Maxilla not recovered. Maxilliped (Fig. 8A) basis with one long seta at palp insertion. Endites with inner medial and outer distal processes and two setae, almost as wide as basis. Palp article 1 naked; article 2 with one outer and three inner setae, one of which is serrated; article 3 with four inner setae; article 4 with one outer and five inner setae. Epignath not recovered. Cheliped (Fig. 8B). Basis divided unequally by small sclerite attached to the proximal part of basis, shorter than carpus. Merus with one ventral seta. Carpus longer and wider than propodus including fixed finger, with three ventral and two small dorsal setae. Propodus with two setae at dactylus insertion. Fixed finger with two ventral setae and three on inner margin, with two visible denticles on inner margin. Dactylus longer than fixed finger. Pereopod 1 (Fig. 8C). Coxa with one simple seta. Basis longer than three succeeding articles combined, with three setae. Ischium with one seta. Merus as long as carpus, widening distally, with two distal setae. Carpus three-quarters length of propodus, with four distal setae. Propodus longer than half of basis, with three robust distal setae Magnolia Press LARSEN ET AL.

23 Dactylus and unguis shorter than propodus, not fused to a claw. Dactylus shorter than unguis. ZOOTAXA FIGURE 7. Typhlotanais incognitus n.sp. A, holotype, lateral view; B, holotype, dorsal view; C, antennule; D, antenna; E, labrum; F, left mandible; G, labium; H, maxillule; I, uropod. Scale bars 0.1 mm. TANAIDACEAN 2006 Magnolia Press 23

24 ZOOTAXA FIGURE 8. Typhlotanais incognitus n.sp. A, maxilliped; B, cheliped; C, pereopod 1; D, pereopod 2; E, pereopod 3; F, pereopod 4; G, pereopod 5; H, pereopod 6; I, pleopod. Scale bars 0.1 mm Magnolia Press LARSEN ET AL.

25 Pereopod 2 (Fig. 8D). As pereopod 1 except: basis naked. Carpus half as long as propodus. Propodus with two dorsodistal setae and one ventral spiniform seta. Pereopod 3 (Fig. 8E). As pereopod 2 except: basis with one dorsal seta. Carpus with three simple distal setae. Dactylus longer than unguis. Both dactylus and unguis stouter than that on pereopods 1 and 2. Pereopod 4 (Fig. 8F). Coxa not present. Basis twice as wide as on pereopods 1 3, with one simple and one setulose ventromedial seta. Ischium with one seta. Merus with one spiniform distal seta and cuticular scales. Carpus with one simple dorsodistal seta, one ventrodistal spiniform seta, and two tubercles covered with minute spines (clinging apparatus). Propodus with two ventrodistal spiniform setae, one dorsodistal robust seta and dorsal spine. Dactylus and unguis shorter than propodus and incompletely fused into an elongate claw. Unguis with simple apex, shorter than dactylus. Pereopod 5 (Fig. 8G). As pereopod 4 except: merus with two ventrodistal setae. Carpus with one tubercle covered with minute spines and one simple and one spiniform distal seta. Pereopod 6 (Fig. 8H). As pereopod 5 except: basis naked. Propodus with three dorsodistal setae. Pleopod (Fig. 8I). Basal article naked. Exopod with one outer and seven inner plumose setae (setulation not illustrated). Endopod with twelve inner plumose setae, large gap between proximal seta and other setae. Uropods (Fig. 7I). Basal article shorter than first endopod article, naked. Endopod with two articles, longer than pleotelson; article 1 with one simple and two pinnate distal setae; article 2 with five distal setae. Exopod with two articles, article 1 with one medial seta; article 2 with one short simple and one long thick specialized distal seta. ZOOTAXA Remarks Typhlotanais incognitus n. sp. somewhat resembles Typhlotanais vaiabilis Hansen, 1913 from the deep North Atlantic. These species display a number of shared characters such as: the same habitus (oval head, slim body and clearly separated pereonites 1 3); similar mandible molar; a slim cheliped basis not reaching pereonite 1; relatively slim pereopods 4 6 which have simple-tipped unguis; uropodal endites biarticulated. Typhlotanais incognitus however differs from T. variabilis possessing a cheliped propodus shorter than carpus and a distal seta on pereopod 4 and 5 propodus which is only reaching halfway of dactylus. In contrast the chela of T. variabilis is clearly longer than the carpus while the distal setae on pereopod 4 and 5 propodus reaches beyond the unguis. To some extent, a similar habitus can be observed in Typhlotanais mucronatus Hansen, However, this species has an elongated antennule equipped with especially long terminal setae and a bifurcated unguis of pereopod 4 6. TANAIDACEAN 2006 Magnolia Press 25

26 ZOOTAXA Family Indet Genus Armaturatanais Larsen, 2005 Diagnosis Female (modified from Larsen 2005). Body slightly dorso-ventrally flattened. Cuticle heavily calcified. Pleotelson acorn-shaped 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 and pleopods attached on the inner side of the lateral shield. Pereopods with coxa; Pereopods 1 3 merus and carpus without spiniform setae; dactylus and unguis not fused to a claw; 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. Alle pleonites bearing pleopods with plumose setae, pleopods larger than in female. Gender Masculine. Type species Armaturatanais minipodus Larsen, 2005 (by monotype). Remarks. This genus was only recently described from the Gulf of Mexico (Larsen 2005) and yet another species, A. trispinipodus Larsen, 2006 was recently described from the hydrothermal vent system at the Juan de Fuca Ridge. The systematic position of this genus is not yet resolved. Key to the species of Armaturatanais 1. Pereopods 4 6 dactylus and unguis trifurcate...a. trispinipodus Pereopods 4 6 dactylus naked and unguis in the shape of a single spine Antennular article 2 short (shorter than half of article 1). Uropodal exopod not reaching endopod article 2...A. atlanticus n. sp. Antennular article 2 long (longer than half of article 1). Uropodal exopod reaching endopod article 2...A. minipodus Magnolia Press LARSEN ET AL.

27 Armaturatanais atlanticus n. sp. (Figs. 9 11) Material examined Holotype: non-ovigerous female (ZMUC CRU-4908), inside the vent field, N, 32º W, 1685 m, RV Prof. Logachev, TV-assisted grab, TTR-10, station AT-265-GR, August 2000, body length, 1.6 mm. Paratypes, 2 non-ovigerous female, 1 manca (ZMUC CRU-4909), same data. Other material: 1 female, 37º N, 32º W, 1704 m, RV Prof. Logachev, TV-assisted grab, TTR-10, station AT-250- GR, August females, 2 mancae, 37º N, 32º W, 1709 m, RV Prof. Logachev, TV-assisted grab, TTR-12, station AT-436-GR, August ZOOTAXA 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). Dorso-ventrally 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 acorn-shaped 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. TANAIDACEAN 2006 Magnolia Press 27