During two IceAGE expeditions, a large collection of Tanaidacea was gathered from the shelf down to the slope (213−2750 m) in six areas off Iceland—the Irminger Basin, the Iceland Basin, the Norwegian Sea, the Denmark Strait, the Iceland-Faroe Ridge, and the Norwegian Channel. In this collection, members of the family Pseudotanaidae were most numerous component. We examined 40 samples collected with different gears (e.g., EBS, VVG. GKG), in which 323 pseudotanaid individuals were counted and covered a total depth from 213.9 to 2746.4 m. Morphological identification of the material has revealed the presence of five species: Akanthinotanais cf. longipes, Mystriocentrus biho sp. n. Pseudotanais misericorde sp. n., P. svavarssoni sp. n., and P. sigrunis sp. n. The description of the four new species has been presented in the paper and a rank of the subgenus Akanthinotanais is elevated to a genus rank. A large group of morphologically almost identical specimens, similar with P. svavarssoni sp. n. from a wide depth range and from various areas off Iceland was discriminated to species by applying morphometric methods; one distinct species (P. svavarssoni sp. n.) and complex of presumably cryptic species the species was discovered. Based on current data and literature records, similarity among fauna of Pseudotanaidae was assessed with applying Bray–Curtis formula. As results, potential zoogeographic regions in the North Atlantic have been distinguished. . . . . . . Keywords Tanaidacea Pseudotanaidae Pseudotanais Mystriocentrus Akanthinotanais New species Zoogeography . . IceAGE Iceland North Atlantic Introduction Scotland Ridge hampers the interaction between two water masses: the warm water originated in the southern part of Iceland is located at the junction of the Mid-Atlantic Ridge North Atlantic, and the polar water from the Arctic Ocean and Greenland–Scotland Ridge (Logemann et al. 2013.) The (Logemann et al. 2013; Jochumsen et al. 2016). The warm submarine ridges play an essential role in the oceanic circula- and saline Atlantic water flows northwards in the near- tion and distribution of water masses, and hence, in the distri- surface layer via the Reykjanes Ridge, to continue northern- bution of marine fauna (Asthorsson et al. 2007;Brixand most as the North Icelandic Irminger Current north-west of Svavarsson 2010; Schnurr et al. 2014). The Greenland– Iceland, and over the Iceland-Faroe Ridge east of Iceland (Asthorsson et al. 2007). The cold Arctic water is transported south, partly in the near-surface layer along the Greenland This article is registered in ZooBank under: urn:lsid:zoobank.org:pub: F65EDFAB-7032-44B2-9484-06EDD56B87D8. coast (the East Greenland Current), and in part as a bottom current carrying a very cold and dense water from the Nordic This article is part of the Topical Collection on Biodiversity of Icelandic Sea down to the south off Iceland (Perkins et al. 1998;Hansen Waters by Karin Meißner, Saskia Brix, Ken M. Halanych and Anna Jazdzewska. and Osterhus 2000). Since the water masses below the thresh- old of the Ridge are separated (Jochumsen et al. 2016), bio- Communicated by S. Brix logical processes and species composition of faunas in basins located on both sides of the Ridge are thought to be different * Aleksandra Jakiel email@example.com (Gislason and Astthorsson 2004; Astthorsson et al. 2007). The specific oceanography of waters surrounding Iceland renders the region an important field laboratory in which to Department of Invertebrate Zoology and Hydrobiology, University of Łódź, Banacha 12/16, 90-237 Łódź, Poland investigate diversity, distribution, and migration of the marine 860 Mar Biodiv (2018) 48:859–895 fauna. The Icelandic marine Animals Genetic and Ecology the Norwegian coast (Sars 1882)and P. affinis Hansen, 1887 (IceAGE) project aimed to understand how underwater phys- from the Kara Sea (Hansen 1887). Hansen (1913) added new ical structures (e.g., submerged ridges) and non-physical bar- records of the previously known species and described three riers (e.g., currents, temperature, salinity) affect the distribu- new species (P. abyssi Hansen, 1913; P. oculatus Hansen, tion of benthic organisms (Brix et al. 2014). Traditional taxo- 1913, and P. longipes Hansen, 1913) from off Iceland and nomic methods as well as modern approaches to biodiversity Greenland. The wide distribution of those species in arctic, research (ecological modeling and molecular species discrim- subarctic, and boreal regions was subsequently reported by ination) have been studied for such groups as Isopoda, numerous authors (e.g., Sars 1896;Greve 1965a, b, c:along Tanaidacea, Ophiuroidea, and Mollusca (Brix, 2011; the Norwegian coast; Stephensoen 1937: off Greenland, Błażewicz-Paszkowycz et al. 2014; Khodami et al. 2014; Iceland, and Faroe). The number of pseudotanaid species Mikkelsen and Todt 2014; Schnurr and Malyutina 2014; known in the North Atlantic remained unchanged for the next Todt and Kocot 2014). Benthic samples collected from an 60 years until two further species (P. jonesi Sieg, 1977, P. extensive depth range (117−2750 m), at different localities similis Sieg, 1977) were described by Sieg from the Bay of around Iceland, providing an opportunity to test if, and to what Biscay (Sieg 1977). Furthermore Sieg (1977) proposed split- extent, topographic and oceanographic barriers (i.e., ridges, ting genus Pseudotanais to two subgenera: Akanthinotanais currents) influence the distribution, community structure, (A.)and Pseudotanais (P.). and diversity of benthic organisms. In a series of papers describing results of BIOGAS, The Tanaidacea (Peracarida, Malacostraca) are small ma- GASCOR, and EPI VI programmes, Bird and Holdich (1985, rine crustaceans commonly occurring in diverse benthic hab- 1989a, b) highlighted the high biodiversity of pseudotanaids in itats. As they are brooders and have no planktonic larvae, their the depth range of 1100–4800 m in the North Atlantic, mainly mobility is low, and thus their dispersal ability is considered to west of Great Britain and in the Bay of Biscay. They erected be limited (Błażewicz-Paszkowycz et al. 2012, 2014). Tanaids two new genera—Mystriocentrus Bird and Holdich, 1989a and may reach high densities (Larsen 2005); under specific envi- Parapseudotanais Bird and Holdich, 1989b, and described elev- ronmental conditions (i.e., depth), they were found to be more en species, namely Mystriocentrus serratus Bird and Holdich, abundant than amphipods, isopods, or mysids (Bamber 2005). 1989a; Parapseudotanais abyssalis Bird and Holdich, 1989b; Although the interest in the tanaidacean fauna has been ob- Pseudotanais (P.) corollatus Bird and Holdich, 1989a; P.(P.) served to increase during the last decade (e.g., Bamber 2012; colonus Bird and Holdich, 1989b; P.(P) denticulatus Bird and Błażewicz-Paszkowycz et al. 2013; Drumm and Bird 2016), Holdich, 1989a; P.(P.) falcicula Bird and Holdich, 1989b; P. the taxon still remains inadequately known. Over 1300 of the (P) longispinus Bird and Holdich, 1989a; P.(P.) scalpellum species described so far represent some 2–3% of their estimat- Bird and Holdich, 1989b; P.(P.) spatula Bird and Holdich, ed diversity (Błażewicz-Paszkowycz et al. 2012). 1989a; P.(P.) spicatus Bird and Holdich, 1989b;and P.(P.) The IceAGE cruises carried out in 2011 and 2013 (Brix vulsella Bird and Holdich, 1989a. Finally, one more species, et al. 2013) provided an opportunity to obtain a large collec- P.(P.) falcifer Błażewicz-Paszkowycz and Bamber, 2011 from tion of tanaidaceans and the family Pseudotanaidae Sieg, 1976 a mud volcano off Norway, was added to the list (Błażewicz- accounted for a substantial part of it (unpublished data of the Paszkowycz and Bamber 2011). authors). The family is widespread in the world’s ocean, and Our aims in this work were to (1) assess, based on literature its members being encountered within a wide depth range: data and new records from the IceAGE project, the diversity from 0.5toover7000m(BirdandHoldich 1989a; and distribution of the Pseudotanaidae in the North Atlantic, Błażewicz-Paszkowycz et al., 2012; Pabis et al. 2015). understood as the area north of 40° N (Dinter 2001); (2) de- Pseudotanaids have been reported from different habitats, scribe new species belonging to the family; and (3) based on e.g., hard bottom, algae, coral reefs, cold seeps, mud volcanos, current data and literature records to assess the similarity and hydrothermal vents (Bird 1999;Błażewicz-Paszkowycz among fauna of Pseudotanaidae in various region of The and Bamber 2011;Larsen, 2012;Stępień unpublished data). North Atlantic to pinpoint potential zoogeographic regions. So far, 51 species have been described and 21 species have While working on the IceAGE collection, we found a large been recorded in the North Atlantic (Fig. 2). Lilljeborg (1864) group of morphologically almost identical specimens from all was the first to report on pseudotanaids, although the family the basins off Iceland where the samples were collected (the would be established in 1976 by Sieg (1976). Lilljeborg de- Iceland and Irminger Basins, Denmark Strait, Norwegian Sea, scribed Pseudotanais forcipatus (Lilljeborg 1864)as Tanais Iceland-Faroe Ridge and the Faroe-Shetland Channel) from a forcipatus from the Swedish coast. Almost 20 years later, Sars wide depth range. Considering the low mobility of the (1882)erected thegenus Pseudotanais and synonymized the Tanaidacea (they are tube-building brooders without plank- species of Lilljeborg. Moreover, the list of North Atlantic tonic stage) and the presence of geographic barriers around pseudotanaids was supplemented by records of P. Iceland (i.e., submarine ridges, a complex current system), we macrocheles Sars, 1882 and P. lilljeborgi Sars, 1882 from hypothesize that those morphologically almost identical Mar Biodiv (2018) 48:859–895 861 individuals found in different environmental regimes are dis- (MNAW). Upon reaching the Faroe-Shetland Ridge, SIC turns tinct species. To test the hypothesis, we attempted to discrim- to the south-east to flow along the ridge and to open out into the inate between the species (which are presumably a cryptic Faroe Current. The south-eastern Icelandic slope (at a depth of species complex) using a morphometric approach. 500–1100 m) is bathed by the anticlockwise current, made up by the Norwegian Sea Deep Water (NSDW) (Malmberg and Valdimarsson 2003). This water mass, called here the Iceland– Study area Scotland Overflow Water (ISOW), crosses the Iceland–Faroe Ridge, passes the Iceland Basin, and continues into the Iceland lies at the junction of the Mid-Atlantic Ridge (MAR) Irminger Basin (Meißner et al. 2014). and the Greenland–Scotland Ridge (GSR) (Logemann et al. Thedeep part (deeperthan1500m)ofthe IrmingerBasin is affected by ISOW as well as by the Denmark Strait Overflow 2013). As a result of the topography, the oceanic area around Iceland is divided into four basins (Fig. 1). The Iceland and Water (DSOW), which passes though the Denmark Strait and flows south along the Greenland slope) and the Labrador Sea Irminger Basins, located south of the island to the east and west, respectively, are separated by the Reykjanes Ridge, an exten- Water (formed in the Labrador Sea) (Malmberg 2004;Meißner et al. 2014)(Fig. 1). The shallower part of the Basin remains sion of MAR (Malmberg and Valdimarsson 2003). The two basins are bounded by the Greenland–Iceland Sill (Denmark under the influence of the Irminger Current (IC), which trans- ports MNAW along the Reykjanes Ridge. IC flows north along Strait) to the west and by the Iceland–Faroe Ridge to the East (Malmberg and Valdimarsson 2003). The northern and north- the slope (Logemann et al. 2013). Upon reaching the Denmark Strait, IC turns south to flow along the Greenland slope. eastern basins are the Iceland Sea and the Norwegian Sea, re- spectively (Malmberg and Valdimarsson 2003), the former be- The Denmark Strait is, in part, affected by MNAW ing split into two parts by the Kolbeinsey Ridge. transported by an IC branch, the North Icelandic-Irminger Current (NIIC) flowing north along the Icelandic shelf edge The area south of Iceland is primarily affected by the Atlantic water masses (Fig. 1). The southern and south-eastern shelf is (Meißner et al. 2014). A cold-water mass [i.e., the Arctic Polar Water (APW, DSOW)] flows along the East Greenland shelf bathed by the South Icelandic Current (SIC) that flows north and north-east and transports the Modified North Atlantic Water and slope. Fig. 1 Study area and location of sampling station (yellow dots) in the N East Greenland Curent, EIC East Icelandic Current, IC Irminger Current, Atlantic during IceAGE expeditions. Red lines: warm currents (branches NIIC North Icelandic Irminger Current, SIC South Icelandic Current; after of North Atlantic Current); blue lines: cold currents of arctic origin; Hansen and Osterhus (2000) and Ostmann et al. (2014) dashed lines: surface currents; not-dashed lines: deep sea current. EGC 862 Mar Biodiv (2018) 48:859–895 The north and north-eastern areas experience mixing of sev- The material has been deposited in the Universität Hamburg eral water masses (Meißner et al. 2014). NICC transports the Zoological Museum Center of Natural History (CeNak) Atlantic water which loses heat here. In addition, shallow areas (Germany) (Table 2). are affected by the Norwegian Sea Arctic Intermediate Water, deeper parts being influenced by NSDW (Fig. 1). East of the Measurements Kolbeinsey Ridge, NIIC and the Arctic Water form the East Icelandic Current (EIC) which bathes the north-eastern conti- We applied a morphometric analysis to strengthen the identifi- nental slope to eventually reach the northern flank of the cation of the most numerous and widely distributed circum- Iceland-Faroe Ridge. EIC is underlain by the North Icelandic Icelandic species of the genus Pseudotanais (described as Jet, a cold undercurrent which flows west, within the depth P. svavarssoni, sp. n. see below). Ovigerous females and neutri range of 200–1000 m, to cross the Kolbeinsey Ridge and reach individuals (similar in size to ovigerous females) from each the northern part of the Denmark Strait. basin, with unbroken appendages and a complete blade-like spine, were selected for the analysis (Table 3). The measurements were made with a camera connected to the microscope (Nikon Eclipse Ci-L) and NIS-Elements View Material and methods software (www.nikoninstruments.com). The body width and the length of the carapace, pereonites, pleonites, and Samples pleotelson were measured on whole specimens. The length was measured along the axisofsymmetry, whereasthe This study is based on the pseudotanaid collection obtained width, perpendicular to the axis of symmetry, at the widest during two (2011 and 2013) IceAGE cruises on board the spot. As the pseudotanaid pleotelson is usually curved, it was RVs Meteor and Poseidon (Brix et al. 2014). The samples were often impossible to observe on a slide; therefore, instead of collected from the shelf down to the slope (213–2750 m) in six measuring the total body length, we took three measurements areas off Iceland, henceforth referred to as Bbasins^:the (i.e., the lengths of the carapace, total pereonites, and five Irminger Basin, the Iceland Basin, the Norwegian Sea, the pleonites). Thus, the body length is a sum of lengths of all Denmark Strait, the Iceland-Faroe Ridge, and the Norwegian the body segments without the pleotelson. Channel (Fig. 1). Appendages were measured (length and width) by measur- The pseudotanaid material was obtained with different sam- ing their articles on dissected specimens. A total of 173 char- pling devices: a Van Veen grab (VV), a Shipek grab (SG), a box acters and 29 specimens from four different Bpopulations^ corer (GKG), and an epibenthic sledge (EBS). It was sieved (with respect to regions and depth: Bpopulation 1^ (P1) from (500 μm mesh size) using chilled seawater, and preserved in the deep (~ 2000 m) part of the Norwegian Sea; Bpopulation 4% formaldehyde for morphological research; some individ- 2^ (P2) from the deep (~ 1300–1500 m) part of the southern uals were fixed in pre-cooled 96% undenaturated ethanol for basins: the Iceland and Irminger; Bpopulation 3^ (P3) from the molecular analyses (Riehl et al. 2014). For the purpose of this shallow (~ 200 m) part of the southern Irminger Basin; and work, the formaldehyde-treated samples were used only. Bpopulation 4^ (P4) from the shallow (~ 400–600 m) part of A total of 40 samples were examined, which yielded 323 the Iceland–Scotland Ridge (the Iceland–Faroe Ridge and the pseudotanaid individuals. Four samples were collected in the Norwegian Channel) was measured. For the statistical analy- Iceland Basin, 6 in the Irminger Basin, 6 in the Denmark Strait, sis, the following 42 characters/ratios were used: 11 in the Norwegian Sea, 5 in the Norwegian Channel, and 8 off the Iceland-Faroe Ridge (Table 1). (1) The combined carapace, pereonite, and pleonite length (CPP) Taxonomic description (2) The CPP to carapace length ratio (3) The CPP to pereonite-1 length ratio Representative females were dissected using chemically (4) The CPP to pereonite-2 length ratio sharpened tungsten needles; appendages were mounted in (5) The CPP to pereonite-3 length ratio glycerine on slides. Working drawings were prepared using (6) Length of CPP to pereonite-4 length a microscopeequippedwith a camera lucida; the publication- (7) Length of CPP to pereonite-5 length quality illustrations were prepared using a digital tablet and (8) The CPP to pereonite-6 length ratio Illustrator software (Coleman 2003). The morphological ter- (9) The combined pleonite length to pleon width ratio minology follows that proposed by Błażewicz-Paszkowycz (10) The antennule to carapace length ratio and Bamber (2011). The spatulate setae mentioned by Bird (11) The antennule to antennule article-1 length ratio and Holdich (1989a, b) are referred to as the sensory setae (12) The antennule ariticle-3 to article-2 length ratio (13) The antenna article-2 to article-2 distal spine length ratio here. Mar Biodiv (2018) 48:859–895 863 Table 1 Main characteristics of the sampling stations where Pseudotanaidae species were collected during IceAge cruises (according to Brix et al. 2012); (EBS epibenthic sledge, GKG box corer, SG Shipek grab, VV Van Veen grab) Cruise Area Station Gear Date Latitude [N] Longitude [W] Depth Temperature [°C] Salinity Oxygen [m] [μmol/kg] IceAge I Iceland Basin 963-1 EBS 28.08.2011 60° 02.73′ 21° 29.86′ 2746.4 2.65 34.99 258.38 IceAge I Iceland Basin 979-1 EBS 30.08.2011 60° 21.48′ 18° 08.24′ 2567.6 2.65 34.99 258.38 IceAge I Iceland Basin 1010-1 EBS 02.09.2011 62° 33.10′ 20° 23.71′ 1384.8 3.88 35.02 254.57 IceAge I Iceland Basin 1019-1 EBS 03.09.2011 62° 56.32′ 20° 44.61′ 913.6 5.29 35.08 242.79 IceAge I Irminger Basin 1043-1 EBS 05.09.2011 63° 55.46′ 25° 57.66′ 213.9 7.42 35.19 246.74 IceAge I Irminger Basin 1051-1 GKG 07.09.2011 61° 37.41′ 31° 22.11′ 2538.9 3.16 34.94 254.17 IceAge I Irminger Basin 1054-1 EBS 07.09.2011 61° 36.19′ 31° 22.60′ 2537.3 3.16 34.94 254.17 IceAge I Irminger Basin 1066 GKG 08.09.2011 62° 59.97′ 28° 04.78′ 1621.8 4.28 34.99 245.53 IceAge I Irminger Basin 1072-1 EBS 08.09.2011 63° 00.46′ 28° 04.09′ 1593.8 4.28 34.99 245.53 IceAge I Irminger Basin 1086-1 EBS 09.09.2011 63° 42.53′ 26° 23.05′ 698.1 6.19 35.09 231.52 IceAge I Denmark Strait 1116-1 GKG 14.09.2011 67° 12.82′ 26° 16.31′ 683.1 0.07 34.90 292.96 IceAge I Denmark Strait 1129-1 GKG 14.09.2011 67° 38.77′ 26° 44.78′ 320.6 0.70 34.62 290.90 IceAge I Denmark Strait 1132-1 EBS 14.09.2011 67° 38.48′ 26° 45.28′ 318.1 0.70 34.62 290.90 IceAge I Denmark Strait 1136-1 EBS 14.09.2011 67° 38.15′ 26° 45.99′ 315.9 0.70 34.62 290.90 IceAge I Denmark Strait 1141-1 GKG 15.09.2011 67° 50.22′ 23° 42.11′ 1241.6 − 0.66 34.91 278.77 IceAge I Denmark Strait 1148-1 EBS 15.09.2011 67° 50.79′ 23° 41.76′ 1248.8 − 0.66 34.91 278.77 IceAge I Norwegian Sea 1178-1 GKG 20.09.2011 67° 38.71′ 12° 10.10′ 1818.8 − 0.85 34.91 1818.80 IceAge I Norwegian Sea 1152-1 GKG 17.09.2011 69° 05.60′ 09° 56.01′ 2172.6 − 0.75 34.91 266.74 IceAge I Norwegian Sea 1155-1 EBS 17.09.2011 69° 06.89′ 09° 54.72′ 2203.8 − 0.75 34.91 266.74 IceAge I Norwegian Sea 1159-1 EBS 17.09.2011 69° 06.66′ 09° 55.02′ 2202.8 − 0.75 34.91 266.74 IceAge I Norwegian Sea 1166-1 GKG 19.09.2011 67° 35.28′ 06° 57.47′ 2401.8 − 0.82 34.91 271.26 IceAge I Norwegian Sea 1168-1 EBS 19.09.2011 67° 36.38′ 07° 00.08′ 2372.6 − 0.82 34.91 271.26 IceAge I Norwegian Sea 1184-1 EBS 20.09.2011 67° 38.63′ 12° 09.72′ 1819.3 − 0.85 34.91 1819.30 IceAge I Norwegian Sea 1188-1 GKG 21.09.2011 67° 04.32′ 13° 00.89′ 1580.6 − 0.74 34.90 269.25 IceAge I Norwegian Sea 1212-1 EBS 22.09.2011 66° 32.63′ 12° 52.48′ 317.2 1.36 34.84 291.81 IceAge I Norwegian Sea 1216-1 GKG 22.09.2011 66° 18.06′ 12° 22.38′ 730.8 −0.40 34.90 283.58 IceAge I Norwegian Sea 1219-1 EBS 22.09.2011 66° 17.34′ 12° 20.82′ 579.1 −0.40 34.90 283.58 IceAge II Norwegian Chanel 871-4 GKG 26.07.2013 62° 45.31′ 00° 54.09′ 1562.7 −0.78 34.91 298.34 IceAge II Norwegian Chanel 872-4 EBS 27.07.2013 63° 01.88′ 01° 29.91′ 1858.3 −0.79 34.91 295.35 IceAge II Norwegian Chanel 872-5 GKG 27.07.2013 63° 01.80′ 01° 27.05′ 1842 −0.79 34.91 295.35 IceAge II Norwegian Chanel 873-2 GKG 28.07.2013 61° 46.63′ 03° 52.38′ 835.1 −0.70 34.91 303.51 IceAge II Norwegian Chanel 873-6 EBS 28.07.2013 61° 46.52′ 03° 52.38′ 833.7 −0.70 34.91 303.51 IceAge II Iceland-Faroe Ridge 879-2 SG 31.07.2013 63° 06.02′ 08° 35.14′ 505.9 1.33 34.95 305.41 IceAge II Iceland-Faroe Ridge 879-5 EBS 31.07.2013 63° 06.10′ 08° 34.32′ 510.9 1.33 34.95 305.41 IceAge II Iceland-Faroe Ridge 880-2 EBS 31.07.2013 63° 23.36′ 08° 09.42′ 686.0 − 0.43 34.91 306.23 IceAge II Iceland-Faroe Ridge 880-3 GKG 31.07.2013 63° 24.79′ 08° 11.63′ 688.1 − 0.43 34.91 306.23 IceAge II Iceland-Faroe Ridge 881-4 EBS 01.08.2013 63° 34.66′ 07° 42.69′ 1043.6 − 0.57 34.91 303.94 IceAge II Iceland-Faroe Ridge 881-6 VV 01.08.2013 63° 38.50′ 07° 47.03′ 1073.4 − 0.57 34.91 303.94 IceAge II Iceland-Faroe Ridge 882-2 VV 02.08.2013 63° 25.01′ 10° 58.80′ 441.4 0.27 34.90 311.93 IceAge II Iceland-Faroe Ridge 882-5 EBS 02.08.2013 63° 25.04′ 10° 58.20′ 440.5 0.27 34.90 311.93 864 Mar Biodiv (2018) 48:859–895 Table 2 Distribution of species described during this study Area Station Depth Akanthinotanais Mystriocentrus Pseudotanais Pseudotanais Pseudotanais Pseudotanais Pseudotanaidae Total of [m] cf. longipes biho n.sp misericorde sigrunis n.sp svavarssoni svavarssoni indet individuals n.sp n.sp complex Iceland Basin 963-1 2746.4–– – 1 – 1 – 2 Iceland Basin 979-1 2567.6–– – – – 1 – 1 Iceland Basin 1010-1 1384.8 1 – 1 –– 3 – 5 Iceland Basin 1019-1 913.6 – 1 –– – 1 – 2 Irminger Basin 1043-1 213.9–– – – – 18 – 18 Irminger Basin 1051-1 2538.9–– – – – 1 – 1 Irminger Basin 1054–-1 2537.3 – 34 –– 2 – 9 Irminger Basin 1066 1621.8–– 1 –– – – 1 Irminger Basin 1072-1 1593.8–– – – – 2 – 2 Irminger Basin 1086-1 698.1–– – – – 1 – 1 Denmark Strait 1116-1 684.1–– – 1 –– – 1 Denmark Strait 1129-1 683.1–– – – – 1 – 1 Denmark Strait 1132-1 320.6–– – – – 3 – 3 Denmark Strait 1136-1 318.1–– – – – 2 – 2 Denmark Strait 1141-1 1241.6–– – – – 1 – 1 Denmark Strait 1148-1 1248.8–– – – – 5 – 5 Norwegian Sea 1178-1 1818.8–– – – – 2 – 2 Norwegian Sea 1152-1 2172.6–– – – 6 – 511 Norwegian Sea 1155-1 2203.8–– – – 1 –– 1 Norwegian Sea 1159-1 2202.8–– – – 127 –– 127 Norwegian Sea 1166-1 2401.8–– – – 2 –– 2 Norwegian Sea 1168-1 2372.6–– – – 49 –– 49 Norwegian Sea 1184-1 1819.3–– – – – 8 – 8 Norwegian Sea 1188-1 1580.6–– – – – 6 – 6 Norwegian Sea 1212-1 317.2–– – 4 – 9 – 13 Norwegian Sea 1216-1 730.8–– – 4 – 6 – 10 Norwegian Sea 1219-1 579.1–– – 2 – 5 – 7 Norwegian Chanel 871-4 1562.7–– – – – 2 – 2 Norwegian Chanel 872-4 1858.3–– – – – 3 – 3 Norwegian Chanel 872-5 1842–– – – – 1 – 1 Norwegian Chanel 873-2 835.1–– – – – 2 – 2 Norwegian Chanel 873-6 833.7–– – – – 1 – 1 Iceland-Faroe Ridge 879-2 505.9–– – – – 2 – 2 Iceland-Faroe Ridge 879-5 510.9–– – – – 3 – 3 Mar Biodiv (2018) 48:859–895 865 (14) The antenna article-3 to article-3 distal spine length ratio (15) The cheliped carpus length to width ratio (16) The cheliped basis to carpus length ratio (17) The cheliped propodus length to width ratio (18) The cheliped fixed finger length to propodus length ratio (19) The pereopod-1 basis length to width ratio (20) The pereopod-1 propodus to carpus length ratio (21) The pereopod-1 propodus to dactylus + unguis length ratio (22) The pereopod-1 unguis to dactylus length ratio (23) The pereopod-2 propodus to carpus length ratio (24) The pereopod-2 propodus to dactylus + unguis length ratio (25) The pereopod-2 propodus to blade-like spine length ratio (26) The pereopod-3 propodus to carpus length ratio (27) The pereopod-3 propodus to dactylus + unguis length ratio (28) The pereopod-3 propodus to blade-like spine length ratio (29) The pereopod-4 propodus to carpus length ratio (30) The pereopod-4 propodus to dactylus + unguis length ratio (31) The pereopod-4 propodus to blade-like spine length ratio (32) The pereopod-4 propodus to carpus distal seta length ratio (33) The pereopod-5 propodus to carpus length ratio (34) The pereopod-5 propodus to blade-like spine length ratio (35) The pereopod-4 propodus to carpus distal seta length ratio (36) The pereopod-6 propodus to carpus length ratio (37) The pereopod-6 propodus to dactylus + unguis length ratio (38) The pereopod-6 propodus to blade-like spine length ratio (39) The pereopod-6 propodus to carpus distal seta length ratio (40) The pleonite combined length to uropod basis and endopod combined length ratio (41) The uropod basis length to width ratio (42) The uropod exopod to endopod length ratio Statistical analysis The Kruskal–Wallis test with multiple post-hoc comparison (Statistica 10 software) was used to find out which of the ratios or characters determined significantly differentiate between the four Bpopulations^studied. The characters and ratios iden- tified by the test were used further to perform the principal component analysis (PCA) and analysis of similarity (ANOSIM). PCA is an ordination method in which samples (specimens here) regarded as points in a multi-dimensional space are projected onto a best fit plane (Clarke and Gorley 2006). Prior to the analysis, the data were normalized. ANOSIM (Clarke and Gorley 2006) was conducted to test for the degree and significance of differences between a priori determined groups (Bpopulations^)ofspecimens: ANOSIM calculates a test statistic (Global R) which equals 1 if all indi- viduals within a population are more similar to each other than to any individual in another population, and 0 if there is no difference between populations (Clarke and Gorley 2006). The relevant dissimilarity matrix was constructed using the normalized Euclidean distance. Table 2 (continued) Area Station Depth Akanthinotanais Mystriocentrus Pseudotanais Pseudotanais Pseudotanais Pseudotanais Pseudotanaidae Total of [m] cf. longipes biho n.sp misericorde sigrunis n.sp svavarssoni svavarssoni indet individuals n.sp n.sp complex Iceland-Faroe Ridge 880-2 686.0–– – – – 1 – 1 Iceland-Faroe Ridge 880-3 688.1–– – 1 –– – 1 Iceland-Faroe Ridge 881-4 1043.6–– – – – 1 – 1 Iceland-Faroe Ridge 881-6 1073.4–– – – – 1 – 1 Iceland-Faroe Ridge 882-2 441.4–– – 2 – 1 – 3 Iceland-Faroe Ridge 882-5 440.5–– – 2 – 9 – 11 Total 1 4 6 18 185 105 5 323 sum % 0.3 1.2 1.8 5.5 57 32.4 1.5 866 Mar Biodiv (2018) 48:859–895 Table 3 Morphological characters and proportion found in Pseudotanais svavarssoni sp. n. individials to be diffrentiated: P1—group of individuals from deep Norwegian Sea, P2—deep Southern Basins, P3—shallow Irminger Basin, P4—shallow Iceland-Faroe Ridge. H—value of Kruskal–Wallis test (df = 3; N = 29); probabilities; Z—multiple comparison value Group Variable (V1) combined (V2) length of (V3) length of (V4) length of (V5) length of (V6) length of cheliped (V7) length of length of carapace, pereopod-1 propodus pereopod-1 propodus pereopod-3 propodus pereopod-6 propodus carpus to width cheliped pereonites and to carpus lenght to dactylus + unguis to blade-like spine to distal seta on carpus propodus to width pleonites length length length P1 Measurements 1.21–1.74 2.28–2.53 1.15–1.29 1.41–1.75 2.62–6.42 1.78–2.15 1.47–1.63 Range 0.98–1.98 2.35–2.51 1.2–1.38 1.46–1.66 2.98–6.46 1.86–2.08 1.49–1.59 SD 0.5 0.08 0.09 0.1 1.24 0.11 0.05 P2 Measurements 1.45–1.57 2.48–2.58 0.99–1.28 1.4–1.58 1.48–4.79 1.33–1.73 1.38–1.51 Range 1.47–1.59 2.46–2.56 1.01–1.29 1.41–1.59 1.6–4.94 1.36–1.76 1.36–1.5 SD 0.06 0.05 0.14 0.09 1.67 0.20 0.07 P3 Measurements 1.38–1.59 1.78–2.19 0.86–1.06 1.21–1.45 2.98–4.4 1.53–2.01 1.36–1.98 Range 1.34–1.54 1.56–2.36 0.88–11.25–1.41 3.18–4.88 1.56–1.9 1.55–1.93 SD 0.1 0.11 0.06 0.08 0.85 0.17 0.19 P4 Measurements 0.76–1.75 1.77–2.61 0.78–0.95 1.12–1.62 1.66–3.88 1.55–1.97 1.45–2.01 Range 0.84–1.44 1.94–2.62 0.82–1.02 1.14–1.46 1.96–3.44 1.57–1.91 1.53–1.89 SD 0.3 0.34 0.10 0.16 0.74 0.17 0.18 Kruskal-Wallis H 13.33 13.52 20.01 15.52 9.25 13.92 10.36 p 0.004 0.003 0.0002 0.001 0.01 0.002 0.01 Multiple Groups G1 & G4 G1 & G3 G1 & G3 G1 & G3 G1 & G4 G1 & G2 G1 & G3 comparison Z 3.48 3.18 3.56 3.25 2.83 2.89 2.72 p 0.002 0.008 0.002 0.006 0.02 0.02 0.03 Mar Biodiv (2018) 48:859–895 867 Fig. 2 Distribution of the Pseudotanaidae species in the North Atlantic based on literature (present study not included): Bird and Holdich (1989a, b); Błażewicz-Paszkowycz and Bamber (2011); Bruce et al. (1963); [Dahl] in Sieg (1977); [Deboutteville (1960), Deboutteville et al. (1954)] in Sieg (1983); [Fee, Hatch] in Sieg (1977); Greve (1965a, b, c); Hansen (1887, 1913); Holdich and Bird (1986); Holdich and Jones (1983); Just (1970); Kruuse, Ryder, Wandel in Hansen (1913); Liljeborg (1864); Sars (1882, 1896); Stephensen (1937); Sieg (1977); [Vanhöffen, Kruuse, Ryder, Horring, Sars] in Hansen (1913); [Vanhöffen, R. Horring, H.J. Hansen, Sars, A.M. Norman, Stappers, Th. Scott] in Hansen (1913); see Table 4 868 Mar Biodiv (2018) 48:859–895 Fig. 2 (continued) Mar Biodiv (2018) 48:859–895 869 Fig. 3 Plot of principal component analysis based on seven morphometric characters (V1–7) of P. svavarssoni sp. n. and P. svavarssoni complex. List of character in Table 3 Similarities between the North Atlantic sites of pseudotanaids Fig. 3. The first and the second PC axes (PC1 and PC2) ex- were determined in multivariate analysis using the group-average plain 44 and 16% of the total variance, respectively. PC1 axis cluster and derived from the presence/absence-based Bray-Curtis similarity coefficient. In case of the species with particularly wide distribution (e.g., P. affinis, P. lilljeborgi, P. forcipatus), the re- cords from a type locality and/or vicinity of the type localities only were included to analysis. In this approach, all potentially erroneous records and the records of possible cryptic species were excluded. PCA, ANOSIM, and group-average clustering were run using the PRIMER v. 6 package (Clarke and Gorley 2006). Results Species composition The morphological approach adopted in this study allowed to identify five pseudotanaid species representing three genera: Akanthinotanais Sieg, 1977, Mystriocentrus Bird and Holdich, 1989b,and Pseudotanais Sars, 1882. The third genus yielded three species (including two new for science), Akanthinotanais and Mystriocentrus being represented by one species each. Species discrimination PCA run with the seven morphometric characters initially identified as significantly discriminating (Table 3) was applied to the most numerous pseudotanaid species (Pseudotanais svavarssoni sp. n.) and resulted in the first five PCs accounting for 90% of the total variation. Most of the variability in the Fig. 4 Mystriocentrus biho sp. n., female with oostegites (cat no…). a Dorsal view. b Lateral view. Scale: 0.1 mm seven characters is captured in the 2D projection plotted in 870 Mar Biodiv (2018) 48:859–895 Fig. 5 Mystriocentrus biho sp. n., preparatory female, paratype (cat no…). a Antennule. b Antenna. c Labrum. d Left mandible. e Right mandible. f Maxillule. g Maxilliped. h Details of maxilliped palp. Scale: 0.1 mm for a–b and 0.01 mm for c–h separated the specimens examined into two groups (A, B) The morphometric analysis confirmed morphological (Fig. 3). The group A consists of those individuals collected differences between groups of individuals collected from from deeper stations (> 1300 m) in the Irminger and Iceland different regions and depths. The differences, although Basins as well as the Norwegian Sea, the group B includes present, are detectable only with careful measurement of specimens found in shallow-water (< 800 m) samples from the the seven characters identified; therefore, the results indi- Iceland–Scotland Ridge and the Irminger Basin. cated the presence of at least two (but possibly four) cryp- Most variables decreased along the PC1 axis (from left to tic species. Moreover, as the strongest differences were right), the highest values being attained by characters V4, V1, observed between specimens from deep stations in the and V2 (Fig. 3, Table 3). An opposite trend (values increasing Norwegian Sea and all the other individuals (Table 3), along PC1) was shown by the V7 (chelae propodus length to we decided to choose a holotype for the newly described width ratio only). species (P. svavarssoni sp. n., see below) from those sta- ANOSIM showed significant morphometric differences tions. As the differences between the other three sets of (Global R = 0.68, p = 0.1%) between populations from the specimens (shallow stations in ISR, and Irminger Basin, regions examined. The highest differences were found be- deeper stations in the Irminger and Iceland Basins) were tween the specimens representing Bpopulation 1^ (deeper sta- less pronounced, we decided to retain them as the tions in the Norwegian Sea) and Bpopulation 3^ (shallow sta- Bsvavarssoni^ complex until genetic data would lend rea- tions in the Irminger Basin) (Global R = 0.88, p =0.1%) as sonable support to the presence of distinct species. well as between specimens from Bpopulation 1^ and Bpopulation 4^ (shallow stations in ISR) (Global R = 0.83; Taxonomic descriptions p = 0.1%). Significant, relatively high differences were also detected between specimens from Bpopulation 2^ (deeper sta- Family Pseudotanaidae Sieg 1976 tions in the Irminger and Iceland Basins) and Bpopulation 3^ Genus: Mystriocentrus Bird and Holdich, 1989a (Global R = 0.74; p = 0.5%) and between specimens from Diagnosis (amended after Bird and Holdich, 1989b): Bpopulation 1^ and Bpopulation 2^ (Global R =0.63, p = pereonite-2 similar in length or longer than pereonites 1 and 1%). Differences in morphometry between specimens from 3; antenna articles 1 and 2 with simple setae, and with thick- Bpopulation 3^ and Bpopulation 4^ were weaker (Global ened seta on article-6 (terminal); molar process acuminate and R = 0.33), but still significant (p =0.7%). simple; maxilliped endites fused, palp article-4 with thickened Mar Biodiv (2018) 48:859–895 871 Fig. 6 Mystriocentrus biho sp. n., preparatory female. a Cheliped. b Pereopod-1. c Pereopod-2. d Pereopod-3. e Pereopod-4. f Pereopod-5. g Pereopod-6. h Uropod. i Pleopod. Scale: 0.1 mm seta; cheliped propodus almost as long as wide (1−1.2 times as setae^ on merus and carpus (through which the genus re- long as wide), and small folds in distodorsal corner; chela ceived its name Bird and Holdich 1989a: 277) might not be forcipate, with serrate inner margin; pereopods 2−6with so robust generic character, although still valid for species blade-like spine on carpus. identification (see Remarks page 14). Type species: M. serratus Bird and Holdich, 1989a Mystriocentrus biho sp. n. Registered in ZooBank Species included: M. serratus Bird and Holdich, 1989b; M. under: urn:lsid:zoobank.org:act:0AED0F58-63D5-4524- biho,sp. n. A857-FE6EC2883162 Figs. 4, 5,and 6 Remarks: Until examination of the Pseudotanaids from Material examined: Holotype: Ovigerous female, ZMH IceAGE collection (present studies), the Mystriocentrus K-54850, St 1054-1, 61° 36.82′ N 31° 22.26′ W−61° 36.98′ was monotypic genus. Most of the diagnostic character N 31° 22.18′ W, depth 2545.7−2536.8 m, EBS, 07 Sep 2011. for genus given as by Bird and Holdich 1989a, b (e.g., Paratypes: neutrum (dissected), ZMH K-54852, St. 1019- relatively long pereonite-2, thickened seta on antennule 1, 62° 56.46′ N 20° 44.06′ W−62° 56,52′ N 20° 43,77′ W, article-6 and maxilliped palp article-4, forcipate seta with depth 916.1−909.4 m, EBS, 03 Sep 2011. serrate incisive margins and folds in distodorsal corner, and Two neutri, ZMH K-54851, St 1054-1, 61° 36.82′ N31° blade like spines on carpus of pereopods 2–6welldefine 22.26′ W−61° 36.98′ N 31° 22.18′ W, depth 2545.7 this genus so far. Observed in type species Bspatulate −2536.8 m, EBS, 07 Sep 2011. 872 Mar Biodiv (2018) 48:859–895 Fig. 7 Distribution of the Pseudotanaidae species collected during IceAGE cruises. Distribution of Pseudotanais affinis, P. corollatus, P. denticulatus,and P. lilljeborgi as in the Fig. 2 Diagnosis: Pereonite-2 similar in length to pereonite- Etymology: The name is composed of the first letters from 3; pereonite-3 clearly narrower, 0.8 times as wide as the last names of Graham J. Bird and David M. Holdich, who pereonite-4; maxilliped endites with small tubercles; pe- erected the genus Mystriocentrus. reopods 2–3 carpal blade-like spines long, 0.4 times as Description of ovigerous female: Body (Fig. 4)1.9 mm long as propodus. length, 3.8 times as long as wide. Carapace 18% of total Mar Biodiv (2018) 48:859–895 873 Antenna (Fig. 5b) article-1 fused, broken during dissection; article-2 1.5 times as long as wide, with seta on middle outer margin; article-3 1.3 times as long as wide, 0.8 times as long as article-2, with seta on proximal outer margin; article-4 four times as long as article-3, 6.3 times as long as wide, with two simple and one penicillate distal setae; article-5 3.4 times as long as wide, half times as long as article-4, with distal simple seta; article-6 vestigial, with one thickened, sensory seta and three simple setae distally. Mouthparts. Labrum (Fig. 5c) rounded, hood-shape, na- ked. Left mandible (Fig. 5d) incisor distal margin blunt and serrated, lacinia mobilis large and distally serrated; molar acuminate and simple. Right mandible (Fig. 5e) with incisor distal margin serrated; lacinia mobilis fussed to a small pro- cess. Maxillule (Fig. 5f) distally bent, with eight slender distal spines. Maxilliped (Fig. 5g, h) endites completely fused, distal edges with small tubercles and lateral margins finely setose. Palp article-1 and article-2 naked; article-3 with three and one short setae on inner margin; article-4 with one thickened seta (Fig. 5h) and four simple inner and distal setae and one outer seta. Cheliped (Fig. 6a) basis 1.6 times as long as wide; merus subtriangular, with simple midventral seta; carpus three times as long as wide, with two midventral setae, and with simple distodorsal seta; propodus (palm) as long as wide, small folds in distodorsal corner and small ventral seta; fixed finger 5.1 times as long as wide, 1.2 times as long as propodus, with serrated inner margin and three small inner setae; dactylus Fig. 8 Akanthinotanais cf. longipes, preparatory female. a Dorsal view. b simple with slightly serrated inner margin. Antennule. c Cheliped. Scale: 0.1 mm Pereopod-1 (Fig. 6) basis 5.7 times as long as wide, with simple dorsoproximal seta; ischium 0.4 times as long as wide, naked; merus 1.8 times as long as wide, 0.6 times as long as body length, subtriangular, 0.8 times as long as wide, with carpus, naked; carpus 2.7 times as long as wide, 0.6 times as simple setae on each anterio-lateral margin. Pereon 55% of long as propodus, naked; propodus 6.6 times as long as wide, total body length, pereonite-1, half times as long as with dorsoproximal and distodorsal seta; dactylus 0.1 times as pereonite-2; pereonite-2 0.9 times as long as pereonite-3; long as propodus, unguis 1.5 times as long as dactylus, togeth- pereonite-3, 0.8 times as wide as pereonite-4; pereonite-4 er 0.5 times as long as propodus. 1.2 times as long as pereonte-3; pereonite-5 similar in length Pereopod-2 (Fig. 6c) basis 5.5 times as long as wide, with and width to pereonite-4; pereonite-6 half times as long as two simple ventral setae and with two penicillate dorsoproximal pereonite-5; pereonites 0.1, 0.2, 0.3, 1.2, 1.2, and 0.3 times setae; ischium half times as long as wide, with simple seta; as long as broad, respectively. Pleon 17% of total body merus 1.5 timesaslongaswide, 0.9timesaslong ascarpus, length, with five similar in length pleonites, each 0.1 times with microtrichiae ventrally, spine and sensory seta as long as wide. Pleotelson 10% of body length; pleonites distoventrally; carpus twice as long as wide, 0.6 times as long together with pleotelson as long as pereonites 4−6com- as propodus, with simple distodorsal seta and blade-like bined length. distoventral spine (0.4 times as long as propodus); propodus Antennule (Fig. 5a) article-1 3.7 times as long as wide, with six times as long as wide, with distoventral spine; dactylus penicillate middle seta, one penicillate and one simple distal 0.2 times as long as propodus, unguis subequal propodus to- setae on outer margin; article-2 2.1 times as long as wide, half gether almost as long as half of propodus. times as long as article-1, with simple and penicillate distal Pereopod-3 (Fig. 6d) basis 3.5 times as long as wide, with setae on inner margin; article-3 3.5 times as long as wide, as one simple and one penicillate seta on ventral margin; ischium long as article-2, with one subdistal seta, tipped with one 0.3 times as long as wide, with simple ventral seta; merus 1.6 aesthetasc, one simple, one distally rounded, three distally times as long as wide, and 1.1 times as long as carpus, with furcate setae. sensory seta and spine distoventrally; carpus half as long as 874 Mar Biodiv (2018) 48:859–895 wide, and 0.6 times as long as propodus, with microtrichiae Diagnosis (after Sieg 1977): Pereopods without ventrally, small distodorsal seta and blade-like spine blade-like spines. distoventral spine (0.4 times as long as propodus); propodus Remarks: The Pseudotanaidae is a morphologically six times as long as wide, with one distoventral spine; dactylus consistent family with few autapomorphic characters 0.3 times as long as propodus, unguis 0.6 times as long as (Bird and Holdich, 1989a). Distinguished by Sieg dactylus, together 0.6 as long as propodus. (1977), two subgenera—Akanthinotanis (Sieg, 1977) Pereopod-4 (Fig. 6e) basis six times as long as wide, with and Pseudotanais (Sieg, 1977)—were seen by ventroproximal simple seta; ischium 0.6 times as long as wide, McLelland (2008) distinct enough to erect them as gen- with simple seta; merus 1.8 times as long as wide, 0.6 times as era or even subfamily. Although the research by long as carpus with simple distoventral seta; carpus five times McLelland unfortunately were never published, Bird as long as wide, subequal propodus, with blade-like spine and Larsen (2009) treated the two taxa as valid genera (broken) and spine distoventrally, and with sensory seta in their phylogenetic analyses adding in its result two distodorsally; propodus six times as long as wide, with two other genera Mystriocentrus Bird and Holdich, 1989b distoventral setae and long distodorsal seta; dactylus with and Parapseudotanais Bird and Holdich, 1989a. unguis half as long as propodus; unguis 0.2 as long as dactylus. The phylogenetic analysis is beyond the purpose of Pereopod-5 (Fig. 6f) as pereopods-4, but carpus with one this paper, but it is essential to mention that molecular sensory seta and one simple seta, on dorsal margin distally, markers approach ascertain Pseudotanais itself as not with one spine and with one blade-like spine ventral margin. monophyletic and highly diverse taxon (Jakiel and Pereopod-6 (Fig. 6g) similar to pereopod-4 but basis 3.7 Błażewicz, in preparation), that can be straightforwardly times as long as wide, carpus with one sensory seta, one sim- split into at least few new genera. Furthermore, the ple seta, one spine and one blade-like spine; propodus with same approach apparently demonstrated that four setae terminally. Akanthinotanais is not monophyletic with Pseudotanais Pleopoda (Fig. 6i) basal article 3.6 as long as wide, supporting McLelland proposition to treat them both as endopod 5.3 as long as wide, with four distal setae; exopod valid genera. 3.3 as long as wide, with eight distal setae. Uropod (Fig. 6h) basal article as long as wide, naked; exopod 1.7 times as long as basis, and as long as endopod article-1, with two articles, article-1 1.3 times as long as arti- cle-2, with distal seta, article-2 with one small subdistal and one strong distal setae; endopod 1.8 times as long as exopod, with two articles; article-1 1.2 times as long as article-2, with long simple seta distally on outer margin; article-2 with three long simple and two short penicillate setae distally. Distribution: M. biho sp. n. was recorded in Irminger and Iceland Basins at the depth range 913−2540 m (Fig. 7b). The new species is the second member of the genus Mystriocentrus, that is so far known only from the North Atlantic (Fig. 2b). Remarks: The Mystricentrus biho sp. n. can be recognized from the congener M. serratus Bird and Holdich, 1989a, b by the proportion of pereonites 2−3. In the new species, the pereonite-2 is similar in length to pereonite-3, but twice as long as pereonite- 3in M. serratus. Beside that, pereonite-3 is visibly narrower than rest of the pereonites (0.8 times as wide as pereonite-4) in the new species, but similar size in M. serratus. Additionally, M. biho. sp. n. has one sensory (spatulate) setae on merus and carpus of the pereopods 2−6, while in M. serratus one to three such setae present; blade-like spine on pereopods 2−3 carpus are clear- ly longer (0.4 times as long as propodus) in M. biho than in M. serratus (0.1−0.2 times as long as propodus). Finally, the new species can be distinguished by appearance of maxilliped endite that has small tubercles on the distal margin; the distal margin of maxilliped endites in M. serratus is smooth. Fig. 9 Pseudotanais misericorde sp. n., preparatory female. a Dorsal view. b Lateral view. Scale: 0.1 mm Genus Akanthinotanais Sieg, 1977 Mar Biodiv (2018) 48:859–895 875 Fig. 10 Pseudotanais misericorde sp. n., preparatory female. A antennule, B antenna, C left mandible, D right mandible, E maxillule endite, E’ maxillule palp, F maxilla, and G maxilliped. Scale: 0.1 mm for A-B and 0.01 mm for C–G Akanthinotanais cf. longipes conspecific with A. longipes. Only three akan- Fig. 8 thinotanaids known at present are blind, but only A. Material examined: one neutrum, ZMH K-54853, St. 1010- longipes is elongated (3.0 times as long as it is wide) 1, 62° 33.17′ N 20° 23.18′ W−62° 33.22′ N 20° 22.88′ W, and has a not-forcipate cheliped. Two other blind depth 1383.3−1387.8 m, EBS, 02 Sep 2011. akanthinotanaids Akanthinotanais gaussi (Vanhöffen, Distribution: Akanthinotanais longipes was described 1914) and Akanthinotanais similis (Sieg, 1977)have by Hansen (1913)from Ingolf Expedition (st. 78; 60° rather robust chela which is 2.0 and 2.5 times, respec- 37′ N 27° 52′ W, depth 364 m, temp. 4.5 °C) in the tively,as longasitiswide. Iceland Basin and so far it is the only known location Genus Pseudotanais G.O. Sars, 1882 of the species (Fig. 2c). Pseudotanais misericorde sp. n. In the IceAGE collection, the only specimen presumably Figs. 9, 10,and 11 conspecific with A. longipes was found in Iceland Basin at the Material examined: Holotype: neutrum, ZMH K-54854, depth 1387 m (Fig. 7b). St. 1054-1, 61° 36.82′ N 31° 22.26′ W−61° 36.98′ N 31° Remarks: As the only individual collected during the 22.18′ W, depth 2545.7−2536.8 m, EBS, 07 Sep 2011. IceAGE cruises was preserved in poor condition, its full Paratypes: neutrum (dissected), ZMH K-54855, St. 1010– identification and comparison of details with those of 1, 62° 33.17′ N 20° 23.18′ W−62° 33.22′ N 20° 22.88′ W, Akanthinotanais longipes (Hansen, 1913) was not possi- depth 1383.3−1387.8 m, EBS, 02 Sep 2011; three neutri (two ble. However, the absence of eyes, the presence of slen- dissected), ZMH K-54856, St. 1054–1, 61° 36.82′ N 31° der antennule and cheliped, and the absence of a blade- 22.26′ W−61° 36.98′ N 31° 22.18′ W, depth 2545.7 lik seta on pereopod-1 allowed us to regard it as −2536.8 m, EBS, 07 Sep 2011; neutrum ZMH K-54857, St. 876 Mar Biodiv (2018) 48:859–895 Fig. 11 Pseudotanais misericorde sp. n., preparatory female. a Cheliped. b Pereopod- 1. c Pereopod-2.d Pereopod-3. e Pereopod-4. f Pereopod-5. g Pereopod-6. h Uropod. i Pleopod. Scale: 0.1 mm 1066, 62° 59.97′ N028° 04.78′ W, depth 1621.8 m, GKG, 08 slightly wider than all other pleonites. Pleotelson 13% of total Sep 2011. body length pleonites together with pleotelson almost as long Diagnosis: Eyes absent. Pereonites 2−3 the same length. as pereonites 2–6combinedlength. Antennule article-1 six times as long as wide. Antenna articles Antennule (Fig. 10a) article-1 six times as long as wide, 2–3 with simple setae. Maxilliped molar pointed with upper with middle penicillate seta, one simple and two penicillate margin serrated. Maxilliped endites with conical tubercles. distal setae on inner margin and simple distal seta on outer Cheliped carpus 1.6 times as long as wide. Chela forcipate, margin; article-2 2.1 times as long as wide, with distal seta unguis, and dactylus distal spines inside bent. Pereopods 2−6 longer that article-3 on inner margin; article-3 just longer than blade-like spine slender and pointed. Uropod exopod two ar- article-2, with six distal setae: two simple and three distally ticulated, 0.8 times as long as endopod. trifurcate seta, one seta broken. Etymology: From Latin misericorde was called the long Antenna (Fig. 10b) shorter than antennule; article-1 fussed and narrow knife used in medieval for delivering a mercy with body; article-2 1.1 times as long as wide, with one seta on stroke. The name refers to the unusual shape of the blade- outer margin; article-3 1.5 times as long as wide, subequal to like spine on pereopods 2−6, that is long and pointed. article-2 with one seta on outer margin; article-4 3.5 times as Description of neutrum: Body (Fig. 9a, b) 1.8 mm; 5.0 long as article 3, 7.4 times longer than broad, with two simple timesaslong asbroad. Carapacealmostas long aspereonites and one penicillate setae distally; article-5 0.3 times as long as 1−3 and half of pereonite-4 combined, naked, lateral margin article-4, with one simple seta distally; article 6 vestigial, with gently rounded. Pereon 39% of total body length, pereonite-1 four simple setae distally. half as long as pereonite-2; pereonites 2 the same length and Mouthparts. Labium not observed. Left mandible pereonites 3, wilt lateral setae; pereonite-3 half as long as (Fig. 10c) incisor distal margin blunt and serrated, lacinia pereonite-4; pereonite-4 as long as pereonites-5; pereonite-5 mobilis large, and distally serrated; molar acuminate; right 1.2 times as long as pereonites-6, pereonites 0.1, 0.2, 0.2, 0.5, mandible (Fig. 10d) with incisor distal margin serrated; 0.5, and 0.4 times as long as broad, respectively (data for the lacinia mobilis fussed to a small process. Maxillule (Fig. 10e) distally bent, with eight spines and two setae holotype). Pleon 22.7% of total body length, pleonite-1 Mar Biodiv (2018) 48:859–895 877 distally, three fine setae subdistally on outer margin; endite (Fig. 10e’) with two distal setae. Maxilla (Fig. 10f) ovoid, naked. Maxilliped (Fig. 10g) endites completely fused except the most distal fragment, where they stay well separated; distal margin with two conical tubercles, each with visible distal hole, and finely setose lateral margins. Palp article-1 naked, article-2 with three inner setae (two long one short), article-3 with four inner setae (three long and one short), article-4 with and five simple inner and distal setae and one middle outer seta. Cheliped (Fig. 11a) basis 1.6 times as long as wide; merus subtriangular with single midventral seta; carpus 1.7 times as long as broad, with two midventral (long and short) setae; dorsal margin with simple submiddle distal seta not seen; che- la forcipate, propodus (palm) 1.3 times as long as wide and 0.9 times as long as fixed finger, with ventral seta and one seta near dactylus insertion; row of five small setae on inner sur- face; fixed finger with three seta, distal spine bent upward; dactylus simple as long as fixed finger, distal spine bent downward. Pereopod-1 (Fig. 11b) slender, basis 7.9 times as long as wide with two dorsoproximal setae (one broken); ischium naked; merus 2.3 times as long as wide, 0.2 times as long as basis, naked; carpus 3 times as long as wide 0.6 times as long Fig. 12 Pseudotanais svavarssoni sp. n., neutrum, holotype (cat no…), dorsal view. Scale: 0.1 mm as propodus, with fine distodorsal seta; propodus 7 times as long as wide, with two fine distal seta; dactylus 0.3 as long as propodus, with blade-like spine (0.4 times as long as propodus, dactylus 0.6 times as long as unguis; dactylus and propodus) and three setae distally (one serrate, two broken); unguis combined as long as propodus. propodus 5.2 times as long as wide, with two distoventral Pereopod-2 (Fig. 11c) basis 6.5 times as long as wide; simple setae, one subdistal penicillate seta and one dorsodistal ischium with simple seta; merus 1.5 times as long as wide, serrated, distally flatten seta; dactylus 1.4 times as long as 0.7 times as long as carpus, with two setae distally; carpus 2.7 unguis. times as long as wide, 0.7 times as long as propodus with two Pereopod-6 (Fig. 11g) basis 3.8 times as long as wide with setae and one blade-like spine, very slender spine (distally dorsoproximal seta (broken off); ischium with one seta (sec- broken) distally; propodus 8.3 times as long as wide with ond seta probably broken off); merus 2.1 times as long as plumose seta distally, ventral margin with microtrichiae; carpus with one distal seta (second seta probably broken unguis twice as long as dactylus, combined half as long as off); carpus 3.8 times as long as wide and 1.1 times as long propodus. as propodus, with three simple setae and one blade-like spine Pereopod-3 (Fig. 11d) similar to pereopod-2, but carpus (0.3 times as long as propodus), distally; propodus 4.8 times 2.6 times as long as propodus and propodus 5 times as long as long as wide with two simple distoventral setae, one simple as wide, without microtrichiae; blade-like spine on carpus 0.6 and one distally serrated, dorsodistal flatten setae; dactylus 5 times as long as propodus. times as long as unguis. Pereopod-4 (Fig. 11e) basis 3.3 times as long as wide, Pleopod (Fig. 11i) endopod 4.5 times as long as wide, naked; ischium with two setae; merus 0.2 times as long as with four distal setae; exopod four times as long as wide; 0.4 times as long as carpus, with two distal setae; carpus wide with seven distal setae. 4.5 times as long as wide, 1.2 times as long as propodus, with Uropod (Fig. 11h) basis naked; exopod 0.8 times as long as blade-like spine (0.4 times as long as propodus) and with three endopod, with two articles, article-1 0.8 times as long as arti- setae distally; propodus 6.2 times as long as wide, with two cle-2, article-2 with at least one distal seta (broken); endopod ventrodistal simple setae and dorsodistal seta broken; dactylus with two, subequal articles, article-2 with at least one subdistal twice as long as unguis. seta. Pereopod-5 (Fig. 11f) basis 3.4 times as long as wide; Distribution: P. misericorde was recorded in the Iceland ischium naked (setae probably broken off); merus 2.6 times and Irminger Basins (Fig. 7) at the depth range: from 1383 as long as wide, 0.5 times as long as carpus, with two distal setae; carpus 4.3 times as long as wide, 1.2 times as long as to 2545 m. 878 Mar Biodiv (2018) 48:859–895 Fig. 13 Pseudotanais svavarssoni sp. n., preparatory female. A antennule, B antenna, C labrum, D left mandible, E right mandible, F maxillule endite, F’ maxillule palp, G maxilla, H labium, I maxilliped, J epignath. Scale: 0.1 mm for A–B and 0.01 for C–J Remarks: Pseudotanais misericorde sp. n. represents the Material examined: Holotype: neutrum ZMH K-54858, group of blind pseudotanaids with a forcipate chela and 1168-1, 67° 36.38’ N007° 00.08′ W, depth 2372.6 m, EBS, exopod of the uropod almost as long as the endopod. These 19 Sep 2011. two characters delineate also Pseudotanais vulsella Bird and Paratypes: five neutri, one manca, ZMH K-54859, St. Holdich, 1989b and P. falcicula Bird and Holdich, 1989a, 1152-1, 69° 5.60′ N9° 56.01′ W, depth 2172.6 m, GKG, 17 both recorded in Porcupine Bank and Rockall Trough. Sep 2011; neutrum, ZMH K-54860, St. 1155-1, 69° 06.89′ N P. misericorde,as P. vulsella, has the same conical tuber- 009° 54.72′ W, depth 2203.8 m, EBS, 17 Sep 2011; 92 neutri, cles on distal margin of maxilliped endites but the new species 35 juvenile males, ZMH K-54861, St. 1159-1, 69° 06.66′ N can be distinguished from P. vulsella by slender blade-like 009° 55.02′ W, depth 2202.8 m, EBS, 17 Sep 2011; one carpal spines (Bblade^ part is much narrower than in all other neutrum, one juvenile male, ZMH K-54862, St.1166-1, 67° species). In P. falcicula tubercles in edge of the maxilliped 35.28′ N6° 57.47′ W, depth 2401.8 m, GKG, 19 Sep 2011; 43 endites are very small (Bird and Holdich, 1989b,Fig. 19g) neutri, (one dissected), five juvenile males ZMH K-54863, besides straight distal spines in chela dactylus and fixed finger, 1168-1, 67° 36.38′ N 007° 00.08′ W, depth 2372.6 m, EBS, what allow to comfortably distinguish it P. falcicula from the 19 Sep 2011. new species. Diagnosis: Eyes absent. Carapace, pereonites, and Pseudotanais svavarssoni sp. n. pleonites combined length range between 1.2 and 1.7 mm. Figs. 12, 13,and 14 Pereonite-1 the shortest. Antennule article-1 four times as long Mar Biodiv (2018) 48:859–895 879 Fig. 14 Pseudotanais svavarssoni sp. n., preparatory female. A cheliped, B pereopod- 1, C pereopod-2, D pereopod-3, E pereopod-4, F pereopod-5, G pereopod-6, H uropod, and I pleopod. Scale: 0.1 mm as wide. Antenna articles 2–3 with distal simple setae. Left pereonite-1, 0.4 times as long as pereonite-2; pereonite- mandible with two teeth. Maxilliped endites with small tuber- 2 0.9 times as long as pereonite-3; pereonite-3 0.6 times cles. Cheliped elongated, carpus 1.7–2.1 times as long as as wide as pereonite-4; pereonite-4 0.8 times as long as wide, propodus 1.4–1.6 times as long as wide. Pereopod-1 pereonte-5; pereonite-5 1.5 times as long as pereonite-6; propodus 2.2–2.5 times as long as carpus, propodus 1.1–1.3 pereonites 1−6: 0.1, 0.3, 0.3, 0.4, 0.5, and 0.4 times as times as long as combined length of dactylus and unguis. long as wide, respectively; pereonites 1, 4, and 5 with Pereopods 2−6 carpal blade-like spine well developed. one lateral seta on each margin. Pleon 18.8% of total Pereopod-3 propodus 1.4–1.7 times as long as blade-like body length, with five similar in length pleonites, each spine. Pereopod-6 propodus 2.6–6.4 times as long as distal 6.4 times as long as wide, with one seta on lateral carpal seta ratio. Females with pleopods. Uropod exopod margin. Pleotelson 6% of total body length; pleonites two articulated, 0.8 times as long as endopod. together with pleotelson almost as long as pereonite-2, Etymology: The species named after Jörundur two setae on pleotelson distal margin. Svavarsson, a professor in marine biology at the Antennule (Fig. 13a) article-1 4.0 times as long as wide, with University of Iceland, the great enthusiast of Icelandic long simple, and three midlength penicillate setae, and three nature and wonderful fellow on the land as well as on penicillate and long simple seta distally; article-2 2.2 times as the sea. long as wide, and 0.4 times as long as article-1, with one outer Description of neutrum: Body (Fig. 12) 1.7 mm long, over distal seta longer that article-3, one penicillate and one simple three times as long as wide. Carapace 18% of total body seta distally; article-3 1.2 times as long as article-2, with two length, subtriangular, naked. Pereon 58% of total body length, simple and four distally trifurcate and one aesthetasc, distally. 880 Mar Biodiv (2018) 48:859–895 Table 4 Geographical distribution of North Atlantic Pseudotanaidae species. * type localities/ 16: Stephensen 1937, 17: Delamare-Deboutteville 1960, 18: Bruce et al. 1963, 19: Greve 1965a, b, source of type localities; 1: Lillieborg 1864, 2: Sars 1882,3: Hansen 1887,4:Sars, 1869,5: Hansen c, 20: Just 1970, 21: Dahl in Sieg 1977, 22: Fee in Sieg 1977,23: HatchinSieg 1977,24:Sieg 1913, 6: Hansen H.J. in Hansen 1913, 7: Horring in Hansen 1913, 8: Kruuse in Hansen 1913,9: 1977, 25: Delamare-Deboutteville et al. 1955 in Sieg 1983, 26: Holdich and Jones 1983, 27: Bird Norman in Hansen 1913, 10: Ryder in Hansen 1913, 11: Sars in Hansen 1913, 12: Scott in Hansen and Holdich, 1989a, 28: Bird and Holdich, 1989b,29:Błażewicz-Paszkowycz and Bamber 2011, 1913, 13: Stappers in Hansen 1913, 14: Vanhoffen in Hansen 1913, 15: Wandel in Hansen 1913, 30: Vanhoffen in Sieg 1977, 31: Kudinova-Pasternak in Sieg 1977 Area Species/localities Latitude A. longipes A. similis Mystriocetrus Parapseudtanais P. abyssi P. affinis P. colonus P [N] serratus abyssalis corolatus Bay of Biscay South 44 –– – – – – – – Biscay Abyssal Plains 46 –– – – – – – – Bay of Biscay North 47 –– ++* –– +* – Roscoff/Bloscon 48 – + –– – – – – Porcupine Abyssal Plains 48–50 –– + –– – – – British coast Braden, Plymouth 50 –– – – – – – – Porcupine Seabight 50–51 –– + –– – – – Celtic and Armorican 50–51 –– – – – – – – Slope British coast Isle of Man 55 –– – – – – – – Feni Ridge 54–55 –– + –– – – – Rockall Trough 54–57 –– +* –– – – – Sweaden coast Sund 55 –– – – – – – – Sweaden coast Kategatt 56 –– – – – – – – British coast 56 –– – – – – – – Hebridean Slope 56–58 –– – – – – – – Sweaden coast Skagerrak 58 –– – – – – – – Sweaden coast Gullmar fiord 58 –– – – – – – – Norwey coast south of Bergen 60 –– – – – – – – Iceland coast Iceland Basin 60–63 –– – – – + –– Iceland coast Irminger Basin 60–63 +* –– – – – – – Norwegian coast 60–72 –– – – – – – – Norwey coast Trondheimfiord 63 –– – – – – – – Davis Strait 61–66 –– – – +* + – +* Iceland coast IF Ridge 63–64 –– – – – + –– Greenland coast Ameralik fiord 64 –– – – – – – – Greenland coast Angmasivik 64 –– – – – – – – Iceland coast Denmark Strait 65–67 –– – – – – – – Norwey coast vicinity of Nesna 66 –– – – – – – – Iceland coast Norwegian Sea 66–67 –– – – – + –– Iceland coast Iceland Sea 66–67 –– – – – + –– Norwey coast Raunefiord 67 –– – – – – – – Greenland coast Kap Dalton 69 –– – – – – – – Greenland coast Turner Sound 69 –– – – – – – – Norwey coast Balsfjord 69 –– – – – – – – Norwey coast vicinity of Malangen 69 –– – – – – – – Norwey coast Ullsfjord 69 –– – – – – – – Norwey coast Ramfiord 69 –– – – – – – – Finmark coast 69 –– – – – – – – Mar Biodiv (2018) 48:859–895 881 Table 4 (continued) Area Species/localities Latitude A. longipes A. similis Mystriocetrus Parapseudtanais P. abyssi P. affinis P. colonus P [N] serratus abyssalis corolatus close upon the frontiers of Russia Greenland coast Denmark Island 70 –– – – – – – – Greenland coast Karajak Fiord 70 –– – – – – – – Jan Mayen 70 –– – – – + –– Norwey coast vicinity of Kvalsund 70 –– – – – – – – Norwey coast vicinity of Kvaloy 70 –– – – – – – – Norwey coast Varanger Fjord 70 –– – – – + –– Greenland coast Forsblad fiord 72 –– – – – + –– Greenland coast Upernivik 72 –– – – – – – – Norwey coast Håkon Mosby 72 –– – – – + –– Mud Volcano Barents Sea 76 –– – – – – – – Norwey coast Spitsbergen 76–79 –– – – – – – – Greenland coast Jørgen Brønlund Fiord 82 –– – – – + –– Source 5 17, 24*, 25 28 28 5 3*, 5, 20, 29 27 27 Localities other than Antarktyka Kra Sea*; N Atlantic Alaska Source 30 31 Area P. denticulatus P. facifer P. falicula P. forcipatus P. jonesi P. lilieborgie P. longispinsus P. macrocheles P. oculatus P. scalpellum Bay of Biscay + –– – – – – – – – Biscay Abyssal Plains + – + –– – + –– – Bay of Biscay + – + –– – +* –– – Roscoff/Bloscon –– – – – – – – – – Porcupine Abyssal Plains + – + –– – + –– – British coast –– – – +* –– – – – Porcupine Seabight +* – + –– – + –– + Celtic and Armorican Slope + –– – – – – – – – British coast –– – – + –– – – – Feni Ridge + –– – – – – – – – Rockall Trough + – +* –– – + –– +* Sweaden coast –– – + –– – – – – Sweaden coast –– – + –– – – – – British coast –– – ++ –– – – – Hebridean Slope + –– – – – – – – – Sweaden coast –– – + –– – – – – Sweaden coast –– – +* –– – – – – Norwey coast –– – – – – – + –– Iceland coast –– – – – – – – – – Iceland coast –– – – – – – – – – 882 Mar Biodiv (2018) 48:859–895 Table 4 (continued) Area P. denticulatus P. facifer P. falicula P. forcipatus P. jonesi P. lilieborgie P. longispinsus P. macrocheles P. oculatus P. scalpellum Norwegian coast –– – + –– – – – – Norwey coast –– – + –– – – – – Davis Strait –– – – – – – – +* – Iceland coast –– – + – + –– – – Greenland coast –– – + –– – – – – Greenland coast –– – – – + –– + – Iceland coast –– – – – + –– – – Norwey coast –– – + –– – – – – Iceland coast –– – – – – – – – – Iceland coast –– – + – + –– – – Norwey coast –– – – – – – + –– Greenland coast –– – + – + –– – – Greenland coast –– – + –– – – – – Norwey coast –– – + –– – – – – Norwey coast –– – + –– – – – – Norwey coast –– – + –– – + –– Norwey coast –– – + –– – – – – Finmark coast –– – + –– – – – – Greenland coast –– – + – + –– – – Greenland coast –– – + – + –– – – Jan Mayen –– – – – + –– – – Norwey coast –– – + – + –– – – Norwey coast –– – + –– – – – – Norwey coast –– – – – +* – +* –– Greenland coast –– – – – – – – – – Greenland coast –– – – – – – – + – Norwey coast – +* –– – – – – – – Barents Sea –– – + – + –– + – Norwey coast –– – – – – – – + – Greenland coast –– – – – + –– – – Source 27* 29 28 1*, 5, 6, 7, 9, 11, 18, 24*, 26, 27 4*, 5, 7, 8, 10, 11, 28* 2*, 19 5*, 8, 10, 15, 28* 12, 13, 14, 16, 19, 21 14, 16, 19, 20, 28 22, 23, 24 Localities other than Franz Joseph Land N Atlantic Source 12 Area P. spatula P. spicatus P. vulsella A. cf. longipes Mystriocetrus biho n. sp P. misericorde nsp. P. sigrunis n sp. P. svavarrsoni n sp. P. svavarrsoni complex Bay of Biscay + + –– – – – – – Biscay Abyssal Plains –– – – – – – – – Bay of Biscay – + –– – – – – – Roscoff/Bloscon –– – – – – – – – Porcupine Abyssal Plains – + –– – – – – – Mar Biodiv (2018) 48:859–895 883 Table 4 (continued) Area P. spatula P. spicatus P. vulsella A. cf. longipes Mystriocetrus biho n. sp P. misericorde nsp. P. sigrunis n sp. P. svavarrsoni n sp. P. svavarrsoni complex British coast –– – – – – – – – Porcupine Seabight +* +* +* –– – – – – Celtic and Armorican Slope + – + –– – – – – British coast –– – – – – – – – Feni Ridge –– + –– – – – – Rockall Trough – ++ –– – – – – Sweaden coast –– – – – – – – – Sweaden coast –– – – – – – – – British coast –– – – – – – – – Hebridean Slope + – + –– – – – – Sweaden coast –– – – – – – – – Sweaden coast –– – – – – – – – Norwey coast –– – – – – – – – Iceland coast –– – – – – – – + Iceland coast –– – ++ + + – + Norwegian coast –– – – – – – – – Norwey coast –– – – – – – – – Davis Strait –– – – – – – – – Iceland coast –– – – – – + – + Greenland coast –– – – – – – – – Greenland coast –– – – – – – – – Iceland coast –– – – – – + – + Norwey coast –– – – – – – – – Iceland coast –– – – – – – – – Iceland coast –– – – – – ++ – Norwey coast –– – – – – – – – Greenland coast –– – – – – – – – Greenland coast –– – – – – – – – Norwey coast –– – – – – – – – Norwey coast –– – – – – – – – Norwey coast –– – – – – – – – Norwey coast –– – – – – – – – Finmark coast –– – – – – – – – Greenland coast –– – – – – – – – Greenland coast –– – – – – – – – 884 Mar Biodiv (2018) 48:859–895 Antenna (Fig. 13b) shorter than antennule; article-1 fussed with body, broken during dissection; article-2 1.1 times as long as wide, with spine on outer margin; article-3 as article- 2; article-4 8.0 times as long as wide, with five simple and one penicillate setae, distally; article-5 2 times as long as wide, 0.3 times as long as article-4, with simple distal seta; article-6 short, with five simple distal setae. Mouthparts. Labrum (Fig. 13c) rounded, hood-shape, na- ked. Left mandible (Fig. 13d) incisor margin irregularly ser- rated, lacinia mobilis large and irregularly serrated; molar acuminate with two serrated distal spines. Right mandible (Fig. 13e) with regularly serrated incisor, lacinia mobilis fussed to a small process; molar acuminate, with five serrated distal spines. Maxillule (Fig. 13f) distally bent, with nine distal setae and four subdistal fine setae on outer margin endite (Fig. 13f’) with two distal setae. Maxilla (Fig. 13g) suboval distally, proximal margin flattened, naked. Labium (Fig. 13h) simple (accessory lobe not seen), naked. Maxilliped (Fig. 13i) basis short, almost as long as wide with two simple proximal setae directed posteriorly to main axis of the body; endites partly fussed, distally separated, distal edge with one seta and a pair of small tubercles on each side, lateral margins finely setose. Palp article-1 naked; article-2 with three setae on inner margin and one seta on outer margin.; article-3 with three long and one short seta on inner margin; article-4 with five simple setae on inner distal margin and one seta on outer margin. Epignath (Fig. 13j) naked, linguiform. Cheliped (Fig. 14a) basis1.5 timesas longas broad;merus subtriangular, with midventral seta; carpus 2.0 times as long as broad, with two midventral setae, and with one subproximal and one distal setae on dorsal margin; chela not-forcipate, slender; propodus (palm) 1.9 times as long as wide, little shorter than fixed finger, and row of five serrated setae on inner side; fixed finger with three setae on cutting edge and one ventral seta, distal spine bent upward; dactylus as long as fixed finger with two seta on inner margin, with distal spine bent downward. Pereopod-1 (Fig. 14b) slender, coxa with simple seta; basis 6.7 times as long as wide, with two dorsoproximal and one distoventral setae; ischium with one seta, merus 2 times as long as wide, 0.8 times as long as carpus with short distoventral and long dorsoproximal setae; carpus 2.5 times as long as wide, 0.4 times as long as propodus, with two small distal setae; propodus 6.6 times as long as wide, naked; dactylus 0.3 times as long as propodus; unguis 1.8 times as long as dactylus, combined 0.9 times as long as propodus. Pereopod-2 (Fig. 14c) basis seven times as long as wide, with two simple and one penicillate seta dorsoproximally, one distoventral seta; ischium with small simple seta; merus 1.8 times as long as wide, 0.7 times as long as carpus, with simple and penicillate setae distoventrally; carpus 3.3 times as long as wide, 0.6 times as long as propodus, with two simple setae and long blade-like spine propodus 7 times as long as wide, with simple distal seta; numerous microtrichiae in distal half; Table 4 (continued) Area P. spatula P. spicatus P. vulsella A. cf. longipes Mystriocetrus biho n. sp P. misericorde nsp. P. sigrunis n sp. P. svavarrsoni n sp. P. svavarrsoni complex Jan Mayen –– – – – – – – – Norwey coast –– – – – – – – – Norwey coast –– – – – – – – – Norwey coast –– – – – – – – – Greenland coast –– – – – – – – – Greenland coast –– – – – – – – – Norwey coast –– – – – – – – – Barents Sea –– – – – – – – – Norwey coast –– – – – – – – – Greenland coast –– – – – – – – – Source 28* 28* 28 Localities other than N Atlantic Source Mar Biodiv (2018) 48:859–895 885 Table 5 Characters of the Baffinis,^ Bdenticulatus,^ and Blongisetosus^’ group Reference Antenna article Mandibles Pereopod-1 Pereopod-1 carpus Pereopods 2–3 Number of the Number of the 2–3 merus distodorsal merus distoventral pereonite bearing pleonite bearing distodorsal seta ornamentation ornamentation setae setae Affinis’ P. affinis Hansen 1886/87; Spines ? Long Short Spine 4–62,4,5 Ingolf st 25 (Davis Strait) P. scalpellum Bird and Holdich 1989 Spines Acuminate (4 spines) Long Short Spine and seta 1, 4–61,2 P. svavarssoni present study Spines Acuminate 2 spines Long Short Two long setae 1, 4, 5 1–5 sp. n. (slender) (L); 5 spines (R) (one serrated) Pseudotanais McLelland 2008 Spines Acuminate Absent Long Spine 1, 3–61–5 sp. P (3–5 spines) Denticulatus’ P. corollatus Hansen 1913,Sieg 1977 Spines Wide Short Short Two setae 0 0 P. denticulatus Bird and Holdich 1985 Spines Wide Short Short Spine and seta 1, 4–60 Pseudotanais McLelland 2008 Spines Wide Absent Short sp. A Longisetosus’ P. longisetosus Sieg, 1977 Spine and seta Acuminate (central Long Long Spine and seta 0 0 spine long) P. longispinus Bird and Holdich 1989a, b Spines Acuminate (central Long Long Spine and seta 0 0 spine long) P. nipponicus McLelland 2007 Spines Acuminate (central Long Long Spine and seta 1, 4–6 (dorso lateral), 5(2 pairs) spine long) 2–6 (antero-lateral), 4–5 (medio-lateral seta) P. spatula Bird and Holdich 1989a, b Spines Acuminate Long Long Spine and seta 1,3 0 Pseudotanais sp. O McLelland 2008 BStout Acuminate (one Long Long Spine and seta 3–61–5 spiniform spine long) seta^ L left, R right 886 Mar Biodiv (2018) 48:859–895 Fig. 15 Pseudotanais sigrunis sp. n. preparatory female, holotype (cat no…). a Dorsal view. b Lateral view. Scale: 0.1 mm dactylus 0.6 times as long as propodus, unguis 1.7 times as as long as propodus, blade-like spine 0.7 times as long as long as dactylus, together 0.9 times as long as propodus. propodus; propodus 7.3 times as long as wide. Pereopod-3 (Fig. 14d) similar to pereopod-2, but basis with Pereopod-4 (Fig. 14e) 4.1 times as long as wide, with pen- ventroproximal and ventrodistal simple setae; carpus 0.9 times icillate midventral seta; ischium with one short and one long Mar Biodiv (2018) 48:859–895 887 Fig. 16 Pseudotanais sigrunis sp. n. preparatory female. A antennule, B antenna, C labrum, D left mandible, D’ molar of left mandible, E right mandible, F maxillule endite, F’ maxillule palp, G maxilliped. Scale: 0.1 mm for A, B and 0.01 for C–F simple setae; merus 1.5 times as long as wide, 0.5 times as Uropod (Fig. 14h) basis naked; exopod 0.8 times as long as long as carpus, with one distoventral seta; carpus 3.3 times as endopod, with two articles, article-1 0.8 times as long as arti- long as wide, 0.9 times as long as propodus, dorsal margin cle-2, with distal seta, article-2 with at two distal setae; with microtrichiae, distodorsal sensory seta and distoventral endopod with two subequal articles, article-1 with one simple small spine and blade-like spine (0.4 times as long as and penicillate distal setae, article-2 with four long, two short propodus); propodus 6 times as long as wide, with distal mar- simple setae and one plumose seta terminally (Table 4). gin setose and dorsal margin with microtrichiae, short and Distribution: Pseudotanais svavarssoni sp. n. was repre- long ventrodistal setae and long (as long as propodus) peni- sented in Norwegian Sea, in the depth range 2172.6– cillate, distodorsally; dactylus 0.2 times as long as propodus, 2401.8 m (Fig. 7a). unguis 0.3 times as long as dactylus, combined 0.3 times as Remarks: Pseudotanais svavarssoni sp. n. with characters long as propodus. such as (1) spines on antenna articles 2−3, (2) acuminate mo- Pereopod-5 (Fig. 14f) similar to pereopod-4. lar, (3) long distodorsal seta on pereopod-1 merus, and (4) Pereopod-6 (Fig. 14g) similar to pereopod-4, but propodus elongated uropods, with exopod somewhat shorter than with additional longer seta. endopod, can be unequivocally regarded as representing the Pleopod (Fig. 14i) endopod 4.6 times as long as wide, with Baffinis^ group. It is distinguished from other members of the six distal setae; exopod 3.2 times as long as wide, with eleven group by (1) relatively slender spines on antenna articles 2−3 distal setae. (the spines are strong in P. affinis, P. scalpellum,and 888 Mar Biodiv (2018) 48:859–895 Fig. 17 Pseudotanais sigrunis sp. n., preparatory female. a Cheliped. b Pereopod-1. c Pereopod-2. d Pereopod-3. e Pereopod-4. f Pereopod-5. g Pereopod-6. h Uropod. i Pleopod. Scale: 0.1 mm Pseudotanais sp. P), (2) the presence of two setae on merus of Hansen’s collection, they concluded that the species Sieg the pereopods 2−3(the spinein P. affinis and P. scalpellum, (1977) identified and illustrated as P. affinis was hardly a and the spine and seta in Pseudotanais sp. P are relatively member of the Baffinis^ grouponaccountofits wide man- long), as well as a slender dactylus and unguis in the pereo- dible molar and the setae on antenna articles 2–3. As a pods 4−6 (see Table 5). result, they erected two new species: P. corollatus Bird The history of the Baffinis: group is quite convoluted (Bird and Holdich, 1989b to accommodate the former P. affinis and Holdich 1985, 1989a). The first species, Pseudotanais from the Davis Strait (Hansen 1913), and P. denticulatus affinis Hansen, 1887, was described from Kara Sea; it was for the former P. affinis from off the west coast of Great subsequently recognized, based on the Ingolf collection, in Britain and the Bay of Biscay (Bird and Holdich, 1989a). numerous locations, e.g., the Davis Strait, around Iceland, The presence of the wide mandible led Bird to assume that south of Jan Mayen, an East Greenland fjord (Hansen 1913; P. denticulatus and P. corollatus may come from the same Fig. 2b). Morphological differences between the specimens group of species, the Bdenticulatus.^ Another species that studied by Hansen (1913) were considered the intraspecific could be assigned to the group is Pseudotanaissp. A variation, although the eurytopic distribution of the species, (McLelland, 2008). Differences between the Baffinis^ and reported from both Bwarm^ (2.4–4.5 °C) and Bcold^ (0.4– the Bdenticulatus^ species-groups are listed in Table 5. 0.9 °C) areas over a relatively wide depth range (582 As emphasized by Bird and Holdich (1989b), we are far −2196 m) suggests a complex of (possibly) cryptic species. away from fully recognizing the complexity of the Baffinis^ Later on, the distribution range of the species was extended to species-group. Based on the existing knowledge, they provi- cover an area between off the British coasts down to the Bay sionally assigned three other species to the group: P. spatula of Biscay (Bird and Holdich, 1989b). Bird and Holdich, 1989a; P. scalpellum Bird and Holdich, The wide distribution and interspecific morphological 1989b;and P. longispinus Bird and Holdich, 1989a. variability of pseudotanaids was addressed by Bird and Although all those species are, most likely, phylogenetically Holdich, 1989a). Having conducted comprehensive mor- closely related to the Baffinis^ group (Jakiel unpublished da- phological studies which involved re-examination of ta), they may represent two separate evolutionary lines. The Mar Biodiv (2018) 48:859–895 889 manca (ZMH K-54815), St. 879-5, 63° 06.10′ N008° 34.32′ W, EBS, depth 510.9 m, 31 Jul 2013; neutrum (ZMH K-54816), St. 880-2, 63° 23.36′ N008°09.42′ W, depth 686 m, EBS, 31 Jul 2013; juvenile male, (ZMH K-54817), St. 881-4, 63° 34.66′ N 007° 42.69′ W, depth 1043.6 m, EBS, 01 Aug 2013; neutrum (ZMH K-54818), St. 881-6, 63° 38.50′ N 007° 47.03′ W, depth 1073.4 m, VV, 01 Aug 2013; ovigerous female, (ZMH K-54819), St. 882-2, 63° 25.01′ N 010° 58.80′ W, depth 441.4 m, VV, 02 Aug 2013; three neutri, four ovigerous females, two juvenile males, (ZMH K-54820), St. 882-5, 63° 25.04′ N 010° 58.20′ W, 440.5 m, EBS, 02 Aug 2013; neutrum, (ZMH K-54821), St. 963-1, 60° 2.72′ N 21° 29.52′ W−60° 2.73′ N 21° 29.86′ W; depth 2746 m, EBS, 29 Aug 2011; neutrum, (ZMH K-54822) , St. 979-1, 60° 20.87′ N 18° 8.52′ W−60° 20.72′ N 18° 8.60′ W, 2568.8−2571 m, EBS, 30 Aug 2011; three neutri, (ZMH K-54823) , St. 1010-1, 62° 33.17′ N 20° 23.18′ W−62° 33.22′ N 20° 22.88′ W, 1383.3–1387.8 m, EBS, 02 Sep 2011; neutrum, (ZMH K-54824), St. 1019-1, (62° 56.46′ N 20° 44.06′ W−62° Fig. 18 Morphological variability of the occurrence of the pleopods in different life stages in Pseudotanaid sigrunis sp. n. first (Pseudotanais longisetosus Sieg, 1977; P. longispinus Bird and Holdich, 1989a; P. nipponicus McLelland, 2007; P. spatula Bird and Holdich, 1989b;and Pseudotanais sp. O, McLelland, 2008) is defined by two autapomorphies: the pres- ence of a long seta on the merus and carpus of pereopod-1 and a few setae on the pereopod 1–3 basis. Members of the other line show a long seta only on the merus of pereopod-1 and few (if any) setae on the basis of pereopods 1–3. Further analysis of other Pseudotanais species with an acuminate mandible and the uropod exopod slightly shorter than the endopod sup- port distinguishing still one more species-group, the Blongisetosus.^ Differences between the Baffinis^ and Blongisetosus^ groups are listed in Table 5. Pseudotanais svavarssoni species complex Material examined: two neutri (ZMH K-54810), St. 871-4, 62° 45.31′ N 000° 54.09′ W, depth 1562.7 m, GKG, 26 Jul 2013; two neutri, one juvenile male (ZMH K-54811), St. 872-4, 63° 01.88′ N 001° 29.91′ W, EBS, depth 1858.3 m, 27 Jul 2013; manca (ZMH K-54812), St. 872-5, 63° 01.80′ N 001° 27.05′ W, depth 1842 m, GKG, 27 Jul 2013; two neutri (ZMH K-54813), St. 873-2, 61° 46.63′ N 003° 52.38′ W, depth 835.1 m, GKG, 28 Jul 2013; juvenile male, St. 873-6, Fig. 19 Dendrogram of similarity (Bray Curtis, average linkage 61° 46.52′ N003° 52.38′ W, depth 833.7 m, EBS, 28 Jul 2013; clustering method) of occurrence of Pseudotanaidae fauna in the North two neutri (ZMH K-54814), St. 879-2, 63° 06.02′ N 008° Atlantic based on both present study and literature data (see caption of 35.14′ W, depth 505.9 m, SG, 31 Jul 2013; two neutri, one Table 4) 890 Mar Biodiv (2018) 48:859–895 Fig. 20 Bathymetric distribution of the Pseudotanaidae species recorded in the N Atlantic from both the IceAGE collection and literature data. For literature data, see Table 4 caption 56.52′ N 20° 43.77′ W, depth 916.1−909.4 m, EBS, 03 Sep ovigerous females, (ZMH K-54836), St. 1184-1, 67° 38.63′ 2011; 15 neutri, three juvenile males, (ZMH K-54825), St. N 012° 09.72′ W, depth 1819.3 m, EBS, 20 Sep 2011; three 1043-1, 63° 55.53′ N 25° 57.54′ W−63° 55.62′ N 25° 57.36′ neutri females, two juvenile males, manca, (ZMH K-54837), W, depth 214.9−216.5 m, EBS, 05 Sep 2011; neutrum, (ZMH St. 1188-1, 67° 4.32′ N 13° 0.89′ W, depth 1580.6 m, GKG, K-54826), St. 1051-1, 61° 37.40′ N 31° 22.11′ W, 2547.5 m, 21 Sep 2011; seven neutri, two juveniles male (ZMH GKG, 07 Sep 2011; two neutri, (ZMH K-54827), St. 1054-1, K-54838), St. 1212-1, 66° 32.63′ N 012° 52.48′ W, depth 61° 36.82′ N31° 22.26′ W−61° 36.98′ N 31° 22.18’ W, 317.2 m, EBS, 22 Sep 2011; five neutri, juvenile male, 2545.7–2536.8 m, EBS, 07 Sep 2011; two neutri, (ZMH (ZMH K-54839), St. 1216-1, 66° 18.06′ N 12° 22.38′ W, K-54828), St. 1072-1, 63° 0.97′ N 28° 3.35′ W−63° 1.10′ N 730.8 m, GKG, 22 Sep 2011; 5 neutri, (ZMH K-54840), 28° 3.15′ W, depth 1564.2–1567 m, EBS, 09 Sep 2011; 1219-1, 66° 17.34′ N012° 20.82′ W, depth 579.1 m, EBS, neutrum, (ZMH K-54829), St. 1086-1, 63° 42.66′ N26° 22 Sep 2011. 22.78′ W−63° 42.78′ N 26° 22.54′ W, depth 688.4−680.3 m, Diagnosis: carapace, pereonites, and pleonites combined EBS, 09 Sep 2011; neutrum, (ZMH K-54830), St. 1129-1, 67° length 0.7–1.7 mm; cheliped carpus 1.3–2.0 times as long as 38.77′ N 26° 44.78′ W, depth 320.6 m, GKG, 14 Sep 2011; wide, propodus 1.3–2.0 times as long as wide; pereopod-1 three neutri, (ZMH K-54831), St. 1132-1, 67° 38.48′ N026° propodus 1.7–2.6 times as long as carpus, propodus 0.7–1.2 45.28′ W, 318.1 m, EBS, 14 Sep 2011; neutrum, ovigerous times as long as combined length of dactylus and unguis; female, (ZMH K-54832), St. 1136-1, 67° 38.06′ N 26° 46,19′ pereopod-3 propodus 1.1–1.6 times as long as blade-like W−67° 37.96′ N 26° 46.42′ W, depth 315.9 m, EBS, 14 Sep spine; pereopod-6 propodus 1.4–4.7 times as long as distal 2011; neutrum, (ZMH K-54833), St. 1141-1, 67° 50.22′ N23° carpal seta. 42.11′ W, depth 1241.6 m, GKG, 15 Sep 2011; four neutri, Distribution: P. svavarssoni species complex is widely rep- juvenile male, (ZMH K-54834), St. 1148-1, 67° 50.79′ N023° resented in the studied area and in the widest depth range 41.76′ W, depth 1248.8 m, EBS, 15 Sep 2011; neutrum male, (214–2746 m). It occurs in all investigated regions: Iceland- manca, (ZMH K-54835), St. 1178-1, 67° 38.72′ N 12° 10.10′ Faroe Ridge, Iceland Basin, Irminger Basin, Denmark Strait W, depth 1818.9 m, GKG, 20 Sep 2011; six neutri, two Norwegian Channel, and Norwegian Sea (Fig. 7a). Mar Biodiv (2018) 48:859–895 891 Pseudotanais sigrunis sp. n. spine; article-4 four times as long as wide and 2.5 times as Figs 15, 16,and 17 long as article-3, with one midlength penicillate seta and three Material examined: Holotype neutrum (ZMH K-54841); distal setae (one broken); article-5 4.2 times as long as wide St. 1216-1, 66° 1.06′ N 12° 22.38′ W, depth 730.8 m, 22 and 0.5 times as long as article-4, with one distal seta; article-6 Sep 2011. short, with three simple and one bifurcated distal setae. Two ovigerous female, (ZMH K-54842), St. 882-2, 63° Mouthparts: Labrum hood-shaped, weakly setose 25.01′ N 010° 58.80′ W, depth 441.4 m, 02 Aug 2013; one (Fig. 16c); left mandible (Fig. 16d) incisor margin weakly neutrum, ovigerous female, (ZMH K-54843), St. 882-5, 63° serrated, lacinia mobilis large and irregularly serrated; molar 25.04′ N010° 58.20′ W, depth 440.5 m, EBS02 Aug 2013; acuminate with four distal spines (Fig. 16d’). Right mandible manca (ZMH K-54844), St. 880-3, 63° 24.79′ N 008° 11.63′ (Fig. 16e) with regularly serrated incisor, lacinia mobilis W, depth 688.1 m, GKG, 31 Jul 2013; neutrum (ZMH fussed to a small process; molar not seen. Maxillule K-54845), St. 963-1, 60° 2.72′ N 21° 29.52′ W–60° 2.73′ N (Fig. 16f) tipped with seven spines and one seta; endite 21° 29.86′ W, depth 2746.4−2746 m, EBS, 29 Aug 2011; (Fig. 16f’) with two distal setae. Labium not observed. neutrum, (ZMH K-54846), St. 1116-1, 67° 12.82′ N 26° Maxilliped (Fig. 16g) endites distally separated, simple, with 16.31′ W, depth 683.1 m, GKG, 14 Sep 2011; three neutri, microtrichiae in distal corners; palp article-1 naked, article-2 ovigerous female, manca, (ZMH K-54847), St. 1212-1, 66° with two inner setae (short and log) and one outer seta; article- 32.63′ N012° 52.48′ W, depth 317.2 m, EBS, 22 Sep. 2011; 3 with four inner setae, article-4 with five simple inner and two neutri, manca, (ZMH K-54848), St. 1216-1, 66° 18.06′ N distal setae and one outer seta. Epignath not seen. 12° 22.38′ W, depth 730.8 m, GKG, 22 Sep 11; neutrum, Cheliped (Fig. 17a) basis 0.9 times as long as broad; merus ovigerous female, (ZMH K-54849), St. 1219-1, 66° 17.34′ triangular with midventral seta; carpus elliptical, 1.5 times as N 012° 20.82′ W, depth 579.1 m, EBS, 22 Sep 2011. long as wide, with two midventral setae and subproximal and Diagnosis: Eyes absent. Antennule article-1 four times as distal setae dorsally; chela not-forcipate, propodus (palm) 1.7 long as wide. Antenna article-2 with seta, article-3 with spine. times as long as wide, almost as long as fixed finger with two Mandible molar acuminate with four spines. Maxilliped endites ventral seta and row of three serrated setae on inner side; fixed simple. Cheliped robust, chela not forcipate; carpus 1.6 times as finger with three setae on cutting edge and one simple seta in long as wide; unguis and dactylus distal spines inside bent. near dactylus insertion; dactylus with dorsoproximal seta. Pereopods 2−6 carpal blade-like spine well developed. Pereopod-1 (Fig. 17b) basis 6.1 times as long as broad; Uropod exopod two articulated, as long as endopod article-1. ischium with simple seta; merus 1.5 times as long as wide, Etymology: The species named after Sigrún Haraldsdóttir, 0.7 times as long as carpus, naked; carpus 2.2 times as long as a great fellow during cruise IceAGE, who tirelessly helped in wide, 0.6 times as long as propodus, with one fine distodorsal seta; propodus 5.8 times as long as wide, with distoventral sorting of the benthic samples onboard. Description of neutrum: Body (Fig. 15) more than three seta; dactylus 0.3 times as long as propodus, unguis four times times as long as broad. Cephalothorax 22% of total body as long as dactylus; unguis and dactylus combined 1.3 times length subtriangular, with two pairs of lateral simple seta. as long as propodus. Eyes absent. Pereon 55% of total body length. Pereonite-1 Pereopod-2 (Fig. 17c) basis 5.4 times as long as wide with 0.6 times as long as pereonite-2; pereonite-2 0.7 times as long middle simple seta; ischium with simple seta; merus 2.1 times as pereonite-3; pereonite-3 0.6 times as long as pereonite-4; as long as wide, 1.1 times as long as carpus, with simple seta pereonites-4 0.7 times as long as pereonites-5; pereonites-5 and spine distoventrally; carpus 2.4 times as long as wide, 0.7 twice as long as pereonite-6; pereonites 0.1, 0.2, 0.3, 0.5, times as long as propodus with blade-like spine 0.4 times as 0.6, and 0.4 times as long as broad respectively (measure- long as propodus, one distodorsal seta and short distoventral ments for the holotype); pereonites 1–5 each with a pair of spine; propodus five times as long as wide, with serrated distal simple lateral setae. Pleonites 15% of total length, as long as spine; dactylus 0.2 times as long as propodus, unguis twice as pereonite-5. Pleotelson 8% of total length, as long as three long as dactylus, dactylus and unguis combined 0.6 times as pleonites combined length, with two pairs of distal seta. long as propodus. Antennule (Fig. 16a) article-1 3.7 times as long as wide, Pereopod-3 (Fig. 17d) similar to pereopod-2, but merus with outer medial and distal tufts penicillate (3–5) and simple with short spine and seta distoventrally; propodus three times (1–3) setae. Article-2 2.3 times as long as wide and 0.4 times as long as wide. as long as article-1 with short and long outer distal setae; Pereopod-4 (Fig. 17e) basis 5.1 times as long as wide, with article-3 as long as article-2, with one aestetasc, four simple, one simple seta midlength and one penicillate seta subdistally; three distally trifurcate and one broken seta. ischium with short and long setae; merus 1.6 times as long as Antenna (Fig. 16b) aricle-1 fussed with body, article-2 as wide, 0.6 times as long as carpus, with two serrated long as wide with one thin spine, article-3 1.4 times as long as distoventral setae; carpus 2.8 times as long as wide and 0.9 wide, and 1.2 times as long as article-2, with small distal times as long as propodus, with blade-like spine 0.3 times as 892 Mar Biodiv (2018) 48:859–895 long as propodus and three serrated spines distally; propodus proximal article of the endopod), the uropod endopod proximal 5.7 times as long as wide, with two distoventral serrated spines article being longer than the distal one. Moreover, the species and dorsodistal serrated seta; dactylus 0.3 times as long as shows long setae on articles 2–3 of the antenna. propodus, unguis 0.1 times as long as propodus, dactylus Sieg (1977) redescribed P. lilljeborgi using the Ingolf ma- and unguis combined 0.3 times as long as propodus. terial collected off Iceland and Jan Mayen Island by Hansen Pereopod-5 (Fig. 17f) similar to pereopod-4; propodus (1913); he disregarded Hansen’s note that the BIcelandic^ five times as long as wide, with one distodorsal penicillate specimens lacked eyes and their carapace shape differed from seta. that of the BNorwegian^ individuals (Hansen 1913,p. 27). In Pereopod-6 (Fig. 17g) similar to pereopod-4; but propodus addition, the P. lilljeborgi studied by Sieg (1977) showed short with one additional simple seta distally. setae on the antenna articles 2 and 3, and the exopod uropod Pleopoda (Fig. 17i) basal article as long as wide, 3.5 times somewhat longer than the endopod proximal article, while as long as wide, with five distal setae; exopod 1.9 times as they were apparently long in the type specimens. long as wide, with eight distal setae. The newly described Pseudotanais sigrunis sp. n. shows Uropod (Fig. 17h) basis naked; exopod 0.6 times as long as setae on the antenna articles 2–3 to be as short as those in P. endopod, with two articles; article-1 times as long as article-2 lilljeborgi studied by Sieg (1977), the exopod uropod being with one distal seta; article-2 with two setae (one broken); somewhat longer than the endopod proximal article. endopod two articles, article-1 with two distal setae; article-2 Therefore, we assume that the part of the Ingolf collection with two short and four long distal setae. studied by Sieg (1977) is conspecific with P. sigrunis. Distribution: P. sigrunis sp. n. was well represented in It is important to emphasize that all except one specimens IceAGE material. It was recorded at Iceland Faroe Ridge, in were found in relatively shallow areas (317–731 m) in nearly Norwegian Channel, Iceland Basin, Denmark Strait, and all the basins around Iceland, a single individual only being Norwegian Sea (Fig. 7b)at thedepth rangefrom317 to collected at a deeper station (2746 m, the Icelandic Basin). 731 m and 2746 m. Morphological analyses failed to reveal differences between the Bshallow^ and the Bdeep^ individuals. Nevertheless, we Morphology variables anticipate that molecular studies involving a larger collection of specimens should show whether (1) the Bshallow-water^ Some of the specimens of P. sigrunis sp.n.hadfullydeveloped and the Bdeep-water^ populations of the species are conspe- pleopods, while the others missed those appendages (4 with and cific rather than forming a complex of cryptic species, and (2) 13 without pleopods). This presence/absence of the pleopods other records of P. lilljeborgi (e.g., from off the northern part was irrespective to locality, depth, body size, and, in some cases, of Norway: vicinity of Kvalsund (Greve 1965a, c), Barents also to the life stage (Fig. 18), although all studied mancas (0.6 Sea (Strapper unpublished data), and East Greenland (Hansen −0.9 mm) apparently missed the pleopods. Pseudotanais 1913)) belong to the only one species. sigrunis sp. n. was a series of just 17, widely distributed speci- mens, what hampers further analysis and any reliable conclu- sion. If the studied individuals are really conspecific, we can hypothesize the presence and the absence of the pleopods can Discussion be rationalized by presence in the life-history a dispersal stage. Remarks: P. sigrunis sp. n. with a robust cheliped, acumi- The Pseudotanaidae are currently represented by 51 nominal nate mandible molar, and short, bi-articulated exopod on the species known worldwide (WoRMS 2018). In the North uropods is the most similar to Pseudotanais lilljeborgi Sars, Atlantic, the number of nominal pseudotanaid species known 1882. Two other species with also an acuminate molar and a at present is, together with the new species described in this regular (non-forcipate) chela (P. colonus Bird and Holdich, paper, 25 (Table 4). The IceAGE collection represented by 323 1989b and P. falcifer Błażewicz-Paszkowycz and Bamber, specimens was dominated by Pseudotanais svavarssoni sp. n. 2011) show a non-articulated exopod on the uropods. which accounted for 57% of the specimens examined, followed Pseudotanais lilljeborgi Sars, 1882 is a Pseudotanais with a by Pseudotanais sigrunis sp. n., Pseudotanais misericorde sp. wide geographic distribution (Fig. 2b) and numerous records in n., Mystriocentrus biho sp. n., and Akanthinotanais cf. the literature (e.g., Sars 1896;Hansen 1913;Greve 1965a, b, c; longipes, which made up 5.5, 1.8, 1.2, and 0.3% of all the Stephensen 1937;Just 1970; Bird and Holdich, 1989a), all re- identified specimens, respectively. Because of poor preserva- cords being confined to a relatively narrow depth range (139– tion condition, five specimens from the collection we studied 536 m). The species was described by Sars (1882) based on the could not be identified to the species level (Table 2). type material from Varangerfjord (northern part of Norway) and Most of those taxa have a limited zoogeographical range diagnosed as a non-forcipate member of the genus with eyes and (i.e., one, relatively well-defined basin) and a distinct bathy- a relatively short exopod on the uropod (not longer than the metric range (Fig. 19). The Bray-Curtis similarity-based Mar Biodiv (2018) 48:859–895 893 cluster analysis separated the different a priori designated Conclusion areas into groups based on the pseudotanaid faunas: In the IceAGE collection made in waters surrounding Iceland – Off the British coast: P. corollatus and P. jonesi (Irminger Basin, Iceland Basin, Norwegian Sea, Denmark – Off the Norwegian coast: P. macrocheles Strait, Iceland–Faroe Ridge, and Norwegian Channel), five spe- – High latitudes of the North Atlantic: P. oculatus cies of pseudotanaids were identified; four of them were new for – The Bay of Biscay and the Porcupine Abyssal Plain: P. science (Mystriocentrus biho sp. n., P. misericorde sp. n., abyssi, P. colonus, P. denticulatus, P. falcicula, P. P. sigrunis sp. n., and P. svavarssoni sp. n.). Apart from species longispinosus, P. scalpellum, P. serratus, A. similis, P. new to the knowledge, Akanthinotanais cf. longipes was col- spatula, P. spicatus,and P. vulsella lected from close place to type locality A. longipes Hansen, – Off Iceland: north—P. svavarssoni sp. n.; south—A. 1913 that is known only from that original location. One species longipes, M. biho sp. n., P. misericorde sp. n., P. that is probably complex of closely related species morpholog- svavarssoni complex ically was very similar with P. svavarssoni sp.n.The morpho- metric approach and analysis highlighted significant differences A separate group in the dendrogram was made up by between specimens collected in northern and southern Icelandic P. falcifer known from mud volcanoes off Norway basins; distinct differences were also apparent between speci- (Błażewicz-Paszkowycz and Bamber 2011). In addition, mens collected from shallow and deep waters. Molecular ap- the Kara Sea with the original locality of P. affinis proach is required to confirm our findings. Pseudotanaidae of produced a separate branch in the dendrogram. Three Iceland are currently represented by seven nominal species. species, namely P. forcipatus, P. affinis,and P. Distinguished in the analysis, zoogeographical regions are lilljeborgi, are particularly widely distributed, their range represented by distinct pseudotanaid fauna. Our results stay in extending from the high Arctic (the Barents Sea) to the contrast to the earlier observation for bivalves (Dijkstra et al. British coast of the North Sea (e.g., P. forcipatus)or 2009) or munnopsids (Schnurr et al. 2014). The wide distri- from Novaya Zemlya to the coasts of Norway and bution of these isopods in the North Atlantic and marine ba- Iceland to the west coast of Greenland (P. affinis and sins are rationalized by their efficient swimming abilities and P. lilljeborgi) (Table 4). potentially high ecological plasticity. The bathymetric range of N Atlantic pseudotanaids ex- Considering a restricted dispersal ability of pseudotanaids, the tends from the upper shelf down to 4800 m (Fig. 20), few North Atlantic could be divided into several zones, where distinct of them showing a narrow range (e.g., A. similis, P. species, or discrete group of species, are noted (see Fig. 19). For macrocheles, P. oculatus, P. jonesi, P. corollatus, P. example, some taxa are known only for the Bay of Biscay while colonus, P. abyssi). Unsurprisingly, all of those species P. oculatus werenotedinhighlatitudesintheNorthAtlantic, but have very narrow zoogeographical distribution and they P. macrocheles was collected from fiords along Norway coast. are often restricted to the type locality (Fig. 2). An excep- Four of the pseudotanaid species in the North Atlantic are tion is P. macrocheles that occurs only in Norwegian fjords widely distributed.P. affinis, P. macrocheles, P. lilljeborgi, (Fig. 2d). A few other pseudotanaids recorded in the North and P. forcipatus were noted in various marine basisn located Atlantic show a depth range extending from some hundred around Iceland, Norway, and Greenland. Those records need meters up to 2500 m (e.g., P. sigrunis sp.n., 317–731 m; P. to be re-examined, and it is highly probable that they represent svavarssoni sp. n., 2172–2401 m; M. biho sp. n.; 913– complex of sister (or cryptic) species. 2537 m; P. scalpellum, 2081–2634 m; P. falcifer,722– Acknowledgments We appreciate Captain Michael Schneider, the crew 1263 m; P. spatula, 1400–2200 m; P. vulsella, 1028– of R/V Meteor and Klaus Ricke with his crew of R/V Poseidon, the 1640 m; and P. misericorde, 1385, 1621, 2537 m) and have scientist participating in the IceAGE programs as well as pickers and a relatively narrow zoogeographical distribution (Figs. 2 sorters for their valuable help on and off board. We are thankful to Kelly Merrlin for language editions. We are grateful to two anonymous and 7). Five species (P. longispinus, P. spicatus, P. reviewers for comments and critiques that helped to improve this article. falcicula, M. serratus,and P. denticulatus) spans their This study was funded by the National Science Centre of Poland (grant bathymetric range over 3000 m, although the distribution number UMO-2014/13/B/NZ8/04702). is relatively narrow (Fig. 20). Two of them, P. denticulatus and P. serratus, show the widest depth range (around 3700 Funding This study was funded by Polish National Science Centre grant (UMO-2014/13/B/NZ8/04702). and 3100 m, respectively). Quite a wide depth range has beenalsofoundinthe P. svavarssoni complex (2500 m) Compliance with ethical standards and P. affinis (1700 m), accompanied by a wide zoogeo- graphical range (Fig. 7), in contrast to P. lilljeborgi and P. 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