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This paper presents an analysis of the literature data on the Subantarctic fauna of the benthic Myodocopida, including 97 species. The studied fauna is characterized by a high degree but a low level of endemism. The fauna is based on the species of common genera. Ostracods of the families Cylindroleberididae and Cypridinidae lead in the number of species and genera. With depth increase, species richness of ostracods, and the number of their genera decrease; taxonomic and bathymetric characteristics markedly change. Similarities between the Antarctic and Subantarctic faunas of Myodocopida are evident in the low diversity of species, in the high degree and low rank of endemism, and in the proportion of the number of species and genera in families. Differences between the faunas are defined by significant isolation, by the pattern of vertical distribution, and by the taxonomic structure of myodocopids. The Subantarctic fauna of Myodocopida is completely isolated from the boreal fauna and exceeds it in the number of species and genera but is comparable to the boreal fauna in the number of endemic species. Both faunas are characterized by a high degree but a low level of endemism. Species richness of these faunas depends on different families. With a depth increase the number of myodocopid species decreases in both faunas; myodocopids do not penetrate deeper than 5500 m.

The diverse deep-water ostracod fauna of the subclass Myodocopa in the North-Western Pacific includes about 52 benthic and pelago-benthic species and has a high degree of endemism, whereas the deep-water zone of the Far East seas is inhabited by an impoverished Pacific fauna of ostracods. The deep-sea ostracod fauna in a basin of the Sea of Okhotsk is poorer (16 species) than that in the North-Western Pacific because this sea is separated from the oceanic waters by the Kuril Ridge. The ostracod fauna of the Sea of Japan do not include any typical deep-water species compared to ostracod fauna of the adjacent regions. The ostracod fauna of the deep-sea zone in the North-Western Pacific consists mainly of pelago-benthic species of the subfamily Bathyconchoeciinae (Halocyprida). This paper presents descriptions of the Bathyconchoecetta gen. nov. and two new species of this subfamily.

A new species of halocyprid ostracod, Scottoecia villosa sp. nov., from the bathypelagic zone of the Kurile-Kamchatka Trench, is described and illustrated. This species is closely similar to S. foveolata (Deevey, 1968), but differs by the shape of the postero-dorsal corners of the carapace, the carapace sculpture, the number of secondary filaments on the first antenna, and the setae on the first endopodite segment of the maxilla. A key to the species of the genus Scottoecia is presented.

Plankto-benthic ostracods of the subfamily Bathyconchoeciinae constitute an extremely heterogeneous group of species, as well in body size, as well as in the shape and structure of carapace and limbs. At present, their fauna contains 35 known (described) species, belonging to four genera. Besides that, about 50 species with still open nomenclature were noted in the literature and have been found in material from our collections. A preliminary morphological analysis of the bathyconchoeciines allowed, in addition, to single out 13 species complexes (= putative genera). One of these genera is described herein as Bathyconchoecilla gen. nov., from the deep-sea zone of the Kurile-Kamchatka Trench. The new genus differs from other genera in this subfamily by the shape and sculpture of the carapace, the location of the left hook on the second antenna in the male, and the structure of the coxale and basale of the mandible and the endites of the maxilla.

Schornikovoecia eugenyi gen. et sp. nov. of the benthopelagic ostracods of the subfamily Bathyconchoeciinae is established and described, based upon samples collected in the deep-sea zones near the Kurile-Kamchatka Trench and in the Sea of Okhotsk (Kurile Hollow). Most of the specimens have been found at depths over 5000 m. The new genus differs sharply from the currently known genera Bathyconchoecia, Scottoecia, Bathyconchoecetta and Septemoecia of this subfamily in numerous ways: the singular sculpture; the form and structure of the glands on the carapace; the masticatory pad on the mandible; the arming of the fifth limb. The new genus is at present monospecific. Descriptions of the new genus and its new species S. eugenyi sp. nov. are presented.

The tribe Conchoeciini Chavtur & Angel, 2011, which was singled out by Chavtur and Angel (2011) from the subfamily Conchoeciinae Müller, 1912, is divided into the new Conchoeciina subtribe, including all species of the genera Conchoecia Dana, 1849 and Porroecia (Martens, 1979), and the “non-Conchoeciina” group, which includes all the remaining genera in other subtribes. The genus Conchoecia is subdivided into five genera - retaining Conchoecia and establishing four new genera, namely Macrochoecilla Chavtur, gen. nov., Lophuroecia Chavtur, gen. nov., Parvidentoecia Chavtur, gen. nov .and Hyalocoecia Chavtur, gen. nov.. Similarly, a new genus, Parthenoecia Chavtur, gen. nov., is split from the genus Porroecia. All species attributed to these new genera, which have been collected by numerous Russian expeditions in the North Pacific, are described. Keys to these genera and their species are provided.

In the waters of the subarctic structure of the Sea of Japan, the fauna of planktonic ostracods of the Halocyprididae family occurs within the oceanic zone of the sea. In contrast to halocypridids of other Far Eastern seas of Russia, this fauna is depauperated and isolated from the Pacific fauna. Deep-water species of halocypridids are absent; the only inhabitant of deep water is an interzonal eurytopic, Discoconchoecia pseudodiscophora (Rudjakov, 1962), which is found in the open part of the Sea of Japan from the surface to great depths. The maximum abundance of pelagic ostracods in the Sea of Japan was observed in the mesopelagic zone. The northern boundary of the distribution of tropical-subtropical species of halocypridid ostracods runs along 38°–40° N in the southern Sea of Japan and along the La Perouse Strait in the eastern part of the sea (based on the data for the 1970s–1980s). Benthic ostracods of the families Philomedidae and Cypridinidae (which are found in the meroplankton only during their spawning period) inhabit the neritic zone of the cold-water and warm-water parts of the Sea of Japan.

The structure of the epipelagic halocypridid ostracod fauna of the boreal zone of the northwestern Pacific has changed during the last 50–60 years. As a result, the frequency of occurrence and abundance of the traditionally most common cold-water species Discoconchoecia pseudodiscophora (Rudjakov, 1962) significantly decreased, while, in contrast, those of the previously rare and relatively warmth-loving Conchoecia sp. A increased to the level of common species. In 2009 and 2010, the position of the northern boundary of the Subarctic Front in this area in the period of biological spring already corresponded to its position at maximum water warming (biological summer) in the middle of the past century. Based on the ostracod distribution, the northern boundary of the Subarctic Front roughly corresponds to the position of a 10°C surface isotherm, and at the present time in the summer it lies further north than half a century ago.

An annotated check-list is given of Ostracoda species occurring deeper than 2000 m in the seas bordering Europe. The check-list is based on published data. The check- list includes 30 species. For each species synonymy, data on localities in European seas and general species distribution are provided. Station data are presented separately in the present thematic issue. How to cite this article: Chavtur V.G. 2014. Deep-sea fauna of European seas: An annotated species check-list of benthic invertebrates living deeper than 2000 m in the seas bordering Europe. Ostracoda // Invert. Zool. Vol.11. No.1. P.210-216.

Bathyconchoecia paulula pacifica Chavtur, 1977, from the Kurile-Kamchatka Trench is redescribed and raised to specific rank. Comparisons are made between this species and the other species in the B. paulula species complex. A key is given whereby the three species in the complex can be discriminated.

Spinacopia dietkeyseri, a new species of the family Sarsiellidae is described from the Southern Ocean (61°48.70' S-47°28.04' W to 61°48.57' S-47°28.19 W) from the depth of 1993-1999 m. It very close to S. mastix Kornicker, 1975, but differs in the ornamentation on the surface of the carapace and in the number of setae on the maxilla, 5supth/sup, 6supth/supand 7supth/suplimbs.

Skogsbergiella tetrathrix sp. nov. and S. species A, species of the family Cylindroleberididae are described from the Drake Passage (59°21.97´S - 60°4.27´W to 59°22.55´S - 60°4.01´W, depth 2372-2380 m) and Weddell Sea (75°49.9´S-27°31.7´W to 74°51.55´S-27°40.3´W, depth 467-475m) respectively. Skogsbergiella tetrathrix sp.nov. is very close to S. macrothrix Kornicker, 1975 but differs by greater size of carapace, 2-jointed rod-shaped organ, lesser number of setae on comb of fifth limb and teeth on combs of seventh limb, and absence of lateral eyes. S. species A is similar to S. skogsbergi Kornicker, 1971 and S. senex Kornicker, 1996 but differs in size and number of setae on the dorsal margin of mandibular basale and seventh limb.

The faunistic composition of pelagic ostracods of regions situated to the north and northwest of the d’Urville Sea (60°–65°S, 148°–136° and 136°–113°E) is largely similar to that of the area adjacent to the Somov Sea at the same latitudes. Alacia hettacra is the most abundant species here; Austrinoecia isocheira, Boroecia antipoda, and Obtusoecia antarctica are common species. The maximum abundance of pelagic ostracods is observed in the 100–200 m depth range; the largest contribution to it is contributed by A. hettacra. The number of species increases with increasing depth. The 64°–65°S region between 148° and 113° E is regarded as the northern boundary of the “Polar Antarctic zone.”

The study of materials collected by Russian expeditions and literature data showed that the pelagic ostracod fauna of the Somov Sea, which lies south of the Antarctic Divergence (AD), is an impoverished complex of the fauna of the Australian-New Zealand Antarctic sector. While to the north of the AD the ostracod fauna includes species introduced from waters of the subantarctic and tropical-subtropical structures, ostracods of the Somov Sea are mainly typical Antarctic species. To the north and south of the AD, ostracod abundance and species richness are highest in the depth range of 200–500 m (especially at 300–400 m). Austrinoecia isocheira is the most common species in the Somov Sea and Alacia hettacra in the adjacent northern region. The more southerly Ross Sea has harsher environmental conditions than the Somov Sea and its ostracod fauna is a more impoverished complex of mainly Antarctic species. Alacia belgicae and A. isocheira are the dominant species in the Ross Sea, with their highest abundances at 200–300 m depths. The proportion of A. hettacra in the Ross Sea taxocene decreases southwards. The taxonomical composition and biogeographical structure of ostracod faunas change in the AD region at the northern boundaries of both seas.

The study of the pelagic ostracod fauna of the Arctic Ocean based on materials collected by numerous Russian expeditions (1929–1993) and data from the literature showed the extreme poorness of the Arctic pelagic ostracod fauna, its mainly North Atlantic genesis and complete isolation from the Pacific fauna. Maximum ostracod abundance was observed in the epipelagic zone, and the greatest species diversity occurred in the relatively warm deep Atlantic layer throughout the year. To the north, east, and west of Franz Josef Land and Spitsbergen, the number of species and abundance indices of pelagic ostracods were decreased. In superficial water layers of the Central Arctic, maximum ostracod density and biomass were recorded in June and September. The best bioindicator of warm Atlantic water in the Arctic basin is Obtusoecia obtusata; and of cold polar water in the North Atlantic, Boroecia maxima.

Morphology of Halocypris inflata (Dana, 1853), H. pelagica Claus, 1890, Felia cornuta (Muller, 1906) and F. bicornis (Muller, 1906) is examined with North Pacific materials and compared with previous records. Complete synonymy and corrected distribution were given for these species. Halocypris angustifrontalis, new species is described in detail. It differs from known species of this genus by its very large size and the structure of the coxal segment of the mandible. Keys to all species of both genera are presented.

Halocypretta, a new genus of halocypridine ostracods in the subfamily Halocypridinae is proposed for H. parvirostrata, new species in the North Pacific and for H. striata (Muller, 1906) in the Indian ocean. New genus and species are described and illustrated. Keys to all genera of this subfamily and to all species of the new genus are presented.

Based on materials obtained during Soviet and Russian expeditions to the Arctic basin and adjacent Atlantic waters during the period from 1929–1993, as well as data from the literature, we examined the distribution range of the common deep-sea ostracod Boroecia maxima. This species occurs throughout the pelagic water column (down to 3000 m depth and below) and prefers low water temperatures (surface Arctic and intermediate water masses). During the year, at all depths, the ratio between age groups of B. maxima remains virtually unchanged. Breeding apparently continues year-round. During the polar night, B. maxima makes no migration into warm Atlantic water, where wintering predatory zooplankton occur in large numbers, and thus avoids grazing pressure.

This study is based on the material of myodocopid ostracodes of the family Philomedidae collected by the Russian Antarctic Polar Expeditions (1963–2007) and the Germany Expeditions on R/V “Polarstern” (1990–2002) from the continental shelf and upper slope near the Mawson and Davis stations, the Weddell Seas, the region of the South Shetland Islands near the Russian Polar station “Molodezhnaya” and adjacent waters. Eight philomedid species belonging to two genera were identified in these collections. Scleroconcha tuberculata sp. nov. is described and figured as a new species. Additional descriptions and figures for the species S. gallardoi Kornicker, 1971, Philomedes assimilis Brady, 1907, P. charcoti Daday, 1908 , P. heptatrix Kornicker, 1975 , P. rotunda Skogsberg, 1920 , P. orbicularis Brady, 1907 and P. tetrathrix Kornicker, 1975 are given. Keys for all species of the mentioned genera known from the Southern Ocean are presented. A list of sampling stations and species collected is provided in the Appendix 1.

We report new ostracod data (Family Cylindroleberididae) based on material collected during the German Expeditions onboard the research vessel “Polarstern” from bathyal and abyssal zones (sampling depth range from 1030 to 3963 m) in the Weddell and Scotia Seas and Drake Passage in 2002 and 2005. Four species belonging to four genera were identified in these collections. A new species, Synasterope pseudomystax , is illustrated and described. A first occurrence of an adult female is registered for Archasterope weddellensis (Kornicker, 1975). Additional description for Parasterope cf. styx Kornicker, 1975 is given. Description of Bathyleberis grossmani Kornicker, 1975 is supplemented with new data on the distribution. Additionally, keys for all species known for Antarctic waters are included.

Skogsbergiella tetrathrix sp. nov. and S . species A, species of the family Cylindroleberididae are described from the Drake Passage (59°21.97´S – 60°4.27´W to 59°22.55´S – 60°4.01´W, depth 2372–2380 m) and Weddell Sea (75°49.9´S–27°31.7´W to 74°51.55´S–27°40.3´W, depth 467–475m) respectively . Skogsbergiella tetrathrix sp.nov. is very close to S. macrothrix Kornicker, 1975 but differs by greater size of carapace, 2-jointed rod-shaped organ, lesser number of setae on comb of fifth limb and teeth on combs of seventh limb, and absence of lateral eyes. S . species A is similar to S. skogsbergi Kornicker, 1971 and S. senex Kornicker, 1996 but differs in size and number of setae on the dorsal margin of mandibular basale and seventh limb.

Morphologically similar Boroecia borealis and B. maxima are redescribed from the Central Arctic. Their morphological differences are minor but well defined. Their geographic and vertical distribution is studied based on an extensive body of materials collected by many expeditions in the Arctic Ocean during the period from 1929 to 1993 at the depth range of 0-4000 m. The comparison of the distribution of both species reveals that B. borealis prefers waters of subarctic structure in the Atlantic, and it inhabits waters in the relatively warm Atlantic layer in the Arctic. In contrast, B. maxima is a good indicator of cool Arctic waters. This species is also present in greater depths of the Northern Atlantic, where polar waters penetrate far towards the south.

The project ANDEEP was designed to fill gaps in the knowledge of the biodiversity of the Southern Ocean deep sea. Threeoceanographic cruises (ANDEEP I, II and III) were undertaken in 2002 and 2005 in the Atlantic Sector of the SouthernOcean. Hundreds of samples were collected from 40 stations with water depths ranging from 748 to 6,348 m. Investiga-tions were carried out on a broad range of taxa, including bacteria, meio-, macroand megafauna. Approximately 5000ostracods were collected, which included 29 specimens of Doloria (Dolorietta) subgen. nov.The subdivision of the genus Doloria Skogsberg, 1920 into two subgenera, Doloria (Doloria) and the novel subgenus Doloria (Dolorietta), is based on differences in the structures of the fifth limb, the armature of the sensory bristle on the5th segment of the antennula, and the number of bristles on the 4th endite of the sixth limb. Four new species in the newsubgenus were identified from the ANDEEP samples. The new subgenus and the four novel species are described andillustrated. Two of these new species are named Doloria (Dolorietta) antarctica sp. nov. and Doloria (Dolorietta) sextafiliformis sp. nov., but the other two species are left in open nomenclature (i.e. Doloria (Dolorietta) sp. nov. 1 and Doloria (Dolorietta) sp. nov. 2) because only juveniles were found in our material. Keys to the subgenera and species of Doloria are provided.

A new tribe of pelagic Ostracoda (Halocyprididae), the Metaconchoeciini, is established to encompass all the species formerly classified in the genus Metaconchoecia. All the remaining genera in the subfamily Conchoecinae are, therefore, assigned to another new tribe, the Conchoeciini. The original genus Metaconchoecia is subdivided into ten genera. Metaconchoecia is retained and nine new genera established namely: Austrinoecia, Clausoecia, Deeveyoecia, Juryoecia, Kyrtoecia, Muelleroecia, Nasoecia, Rotundoecia and Vityazoecia. Keys to these new genera and their component species are provided. Tables summarize the characters that most readily distinguish between the most closely related taxa. Appendices summarize the taxonomic characters and detailed size data for the majority of species that occur in the Atlantic and the North Pacific. A new species, Vityazoecia distoglandula, is described, which is designated as the type species of its genus.