Biogeography of deep-sea wood fall, cold seep and hydrothermal vent Ostracoda (Crustacea), with the description of a new family and a taxonomic key to living Cytheroidea

Deep-Sea Research II 111 (2015) 76–94

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Deep-Sea Research II journal homepage: www.elsevier.com/locate/dsr2

Biogeography of deep-sea wood fall, cold seep and hydrothermal vent Ostracoda (Crustacea), with the description of a new family and a taxonomic key to living Cytheroidea Ivana Karanovic a,b,n, Simone Nunes Brandão c a

Department of Life Science, College of Natural Science, Hanyang University, Seoul 133-791, South Korea Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, 7001 Hobart, Tasmania, Australia c Laboratório de Geologia e Geofísica Marinha e Monitoramento Ambiental-GGEMMA, Departamento de Geologia, Programa de Pós-Graduação em Geodinâmica e Geofísica, Universidade Federal do Rio Grande do Norte (UFRN), Campus Universitário Lagoa Nova s/n, Caixa-postal: 1596, CEP 59072-970 Natal, RN, Brazil b

art ic l e i nf o

a b s t r a c t

Available online 7 October 2014

Stimulated by finding a novel cytheroid ostracod in a piece of sunken wood retrieved from the sea-bed in the Kuril–Kamchatka Trench, we have reviewed all previously published data on ostracods from similarly ephemeral deep-sea habitats (wood falls, hydrothermal vents and cold seeps). These data are placed in the context of all data on living, deep-sea ostracods from other environments. We confirm previous authors' conclusions that faunas from these ephemeral habitats are similar at the generic level, and include elements common to shallow and deep habitats. However, at the species level, endemism varies from zero at cold seeps, to 35% in wood falls and 60% at hydrothermal vents, which is an indication of the relative longevity of these habitats. Non-endemic species occur also in oligotrophic, deep-sea sediments but not in shallow environments. This is in contradiction to previous assumptions that these ephemeral faunas share more species and with shallow habitats than genera with the oligotrophic, deep-sea sediments. We agree with previous authors that the dispersal strategy of wood fall, vent and seep ostracods includes hitchhiking and we propose that it also includes the ability to survive ingestion by larger, more motile animals. The homogeneity of the faunas from ephemeral habitats collected off the American continent is in stark contrast to the highly endemic fauna found in Northwestern Pacific. This suggests that the ostracods may have biogeographical patterns similar to those previously proposed for other groups of benthos. However, any proposal for a global biogeographical scheme for ostracod distributions will have to await far more comprehensive coverage from presently unstudied regions. Finally, we describe and name a novel species of ostracod from the wood fall collected at a depth of 5229 m in the abyss east to the Kuril–Kamchatka Trench, Northwestern Pacific; erecting a new family Keysercytheridae fam. nov. and a new genus, Keysercythere gen. nov., to accommodate it, and name it, Keysercythere enricoi sp. nov. We present a preliminary key to all Cytheroidea families for which living representatives have been described. & 2014 Elsevier Ltd. All rights reserved.

Key words: Deep sea Ostracoda Biogeography Taxonomy Keysercytheridae Pacific

1. Introduction The German–Russian expedition KuramBio (Kuril–Kamchatka Biodiversity Study) investigated the biodiversity of the meiofauna, macrofauna, and megafauna in the abyssal areas east to the Kurile Kamchatka Trench, Northwestern Pacific (Brandt and Malyutina, 2015; Brandt and Malyutina, 2012). On board of the German Research Vessel Sonne (SO 223), the KuramBIO cruise began and n Corresponding author at: Department of Life Science, College of Natural Science, Hanyang University, Seoul 133-791, South Korea. Tel.: þ82 10530951. E-mail addresses: [email protected] (I. Karanovic), [email protected] (S.N. Brandão).

http://dx.doi.org/10.1016/j.dsr2.2014.09.008 0967-0645/& 2014 Elsevier Ltd. All rights reserved.

finished in Busan, South Korea, on July 21th–September 7th, 2012 (for details see the cruise report Brandt and Malyutina, 2012). Many ostracods were collected during this expedition, but herein we focus on a novel taxon associated with a wood fall, and its broader implications. Deep-sea ostracod faunas have been relatively well studied in the North Atlantic (e.g., Alvarez Zarikian et al., 2009; Yasuhara et al., 2009, 2014), in the Mediterranean (e.g., Bonaduce et al., 1983; Harten van and Droste, 1988) and, to a lesser extent, in the Arctic (e.g., Cronin et al., 1991; Poirier et al., 2012) and Western Pacific Oceans (e.g., Boomer and Whatley, 1995; Jellinek and Swanson, 2003). However, the remaining regions, including the Indian Ocean, the Northeastern Pacific, and the equatorial and tropical

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Western Atlantic remain poorly sampled, so the biogeography of this group, which has important applied implications, remains incompletely studied. Most of the knowledge of deep-sea ostracods has been derived from fossils or empty valves (i.e., subrecent specimens), and very few studies have been made of ‘living’ specimens (i.e. specimens collected with soft parts (¼ limbs, and other organic parts)) and even fewer of these studies have been able to analyze ecological or macroecological patterns of the living ostracod fauna (e.g., Brandão, 2008, 2010; Brandão et al., in press). A contributing factor is the extremely low densities of living specimens (i.e. number of living specimens per m2) in the deep ecosystems (Brandão et al., in press), and the inadequacy of the sampling techniques. However the taxonomy and phylogeny of living ostracods have been addressed by Poulsen (1962), Schornikov (1975), Chavtur (1981), Brandão (2010), Karanovic and Brandão (2012) etc. In a Recent study, Brandão et al. (in press) concluded that abyssal regions underlying areas of low and high productivity of the Southern Polar Front seem to be supporting distinct ostracod assemblages. However, because so few samples were available, the authors considered their conclusions to be speculative. Brandão (2010) carried out a multivariate analysis on a large data set of ostracod data and environmental and geographical variables (temperature, salinity, phosphate, nitrate, silicate, latitude, longitude and depth) from the Atlantic sector of the Southern Ocean and concluded that depth was most important determining factor. In the Kuril–Kamchatka Trench, ostracod abundance seems to be higher than in other deep-sea regions, based on the high diversity in a single grab sample (Chavtur, 1981). From this single sample from a depth of 5240 m Chavtur (1981) described ten new Polycopidae species. Previously Schornikov (1975) had described another cytheroid ostracod Abyssocythereis vitjasi Schornikov, 1975, collected from 5200 m (Schornikov, 1975). However, these authors provided no information about the other ostracod species or their abundances in these grab samples. Hence there is an almost complete lack of information on the deep ostracod fauna inhabiting the Kuril–Kamchatka Trench. At the KuramBio station 12-05 (39143.47ʹN, 147110.11ʹE, 5229 m), a fragment of wood fall was retrieved by an Agassiz trawl which contained an unusual fauna (for details see Schwabe et al., 2015). This fauna included two ostracod species: a novel cytheroid species described below, and a single specimen of an unidentified bairdioid. The unusual morphological characters of the cytheroid and the current polyphyly of the Cytheroidea made it difficult to attribute the new species into any of the existing families. So we are erecting a new genus and a new family for this species. The genus is very closely allied to Aspidoconcha De Vos, 1953, a commensal with woodburrowing isopods of the genus Limnoria Leach, 1914 (De Vos, 1953) and so we also include Aspidoconcha in the new family. Some isopods were also collected during the KuramBio expedition, but no commensal ostracods were found on them. Wood containing Aspidococnha was washed ashore (De Vos, 1953) on the coast of The Netherlands; but our piece of wood, a relatively fresh piece of birch-like tree (Schwabe et al., 2015), was collected from a much deeper environment (5229 m). Ostracods have already been reported from sunken wood and majority of them also belong to Cytheroidea. The first records came from the experimental pieces of wood set out at several locations around Bahamas and Panama Basins, at depths ranging from 2000 to 4000 m (Maddocks and Steineck, 1987). These ostracod communities were quite rich with several species occurring on a single piece of wood and many of the same species occurred on several wood pieces as far apart as 1000 km. Maddocks and Steineck (1987) established the genus Xylocythere in the family Cytheruridae to accommodate several of these species. The superfamily Cytheroidea is by far the most diverse ostracod group, both in the number of living as well as Cenozoic and Mesozoic

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fossil species. Of the approximately 65,000 ostracod species and subspecies described so far, over two-thirds are Cytheroidea (Horne et al., 2002). The rich fossil record of this superfamily is not only the result of the great abundance an ubiquity of its species, but also their strongly calcified shells, which are often highly ornamented and have distinctive hinge structures, which fossilize well and are readily identified. At present not all 43 described families have known living species, and some families are highly diverse with many genera. For example, the Trachyleberididae Sylvester-Bradley, 1948 includes 153 accepted genera, the Bythocytheridae Sars, 1866 91 accepted genera, the Hemicytheridae Puri, 1953 69 accepted genera, the Cytheruridae Müller, 1894 39 genera, and the Loxoconchidae Sars, 1825 35 accepted genera (Kempf, 1986, 1988, 1994, 1995, 1996, 1997, 2000, 2002, 2004, 2008; for an overview see Brandão et al., 2014). However, the vast majority of cytheroid genera and species have been described on the basis of shell characters alone (although some of these taxa are Recent) and a large proportion of families are undoubtedly polyphyletic. The shells of cytheroids present far more systematic characters than other ostracod groups, but these characters are inadequate to explain the group's phylogeny and evolution, since co-evolution cannot be detected. The shells, however, provide a very useful indicator of the past climate conditions and is often used as a paleoenvironmental proxy (Börner et al., 2013). The chemophysical properties of the shell mirror the environment where the animal spent its life and are thus as plastic as the tolerance of the species is on certain conditions (Keyser, 2005; Keyser and Aladin, 2004). Cytheroids can be found living in almost all types of ecosystems, and are undoubtedly the most successful of all Recent ostracod groups. Their major diversity is in the marine environment, where they occupy a variety of habitats and inhabit depths ranging from shallow littoral to hadal. The group has colonized continental waters, but there they are subdominant to the Cypridoidea (Martens et al., 1998). However, the true ubiquitous nature of cytheroids is mirrored in freshwater as well, because one can find them from the hyporheic to deep zones of ancient lakes (Karanovic and Humphreys, 2014). Cytheroids are almost the only group of ostracods that live commensally on other crustaceans. Species of Entocytheridae Hoff, 1942 live exclusively on decapods crustacean, and both Xestoleberididae Sars, 1928 and Paradoxostomatidae Brady and Norman, 1889 include commensal species as well (see McKenzie, 1972).

2. Material and methods 2.1. Description of the novel wood-fall species The material described here was collected on September 1st at the station 12-05 of the KuramBio expedition (R. V. Sonne, 223rd Expedition). It was collected by an Agassiz trawl, trawled from 39143.47ʹN, 147110.11ʹE, 5229 m to 39142.54ʹN, 14719.51ʹE, 5217 m (for collection details see Schwabe et al. 2015). The ostracods specimens were loaned to one of us (IK) in a small glass vial containing 96% ethanol. They were identified on the basis of the morphologies of both their valves and soft parts. Most specimens were retained in ethanol both for preservation of soft parts and further DNA extraction. The soft parts of the dissected specimens have been retained on a glass slide in the CMC-10 mounting medium. Their valves were mounted on SEM stubs. One specimen with soft parts was critical point dried and mounted on a stub for analysis on a Scanning Electron Microscope (SEM). All drawings were prepared using a drawing tube attached to a Leica DMLS bright-field compound microscope with N-PLAN achromatic objectives.

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The Scanning Electron Micrographs (SEM) were taken with Hitachi S-4700 scanning electron microscope at Eulji University (Seoul). The studied specimens are deposited in the Crustacea collections of the Zoologisches Museum Hamburg (abbreviation ZMH K-) and of the Zoologische Staatssammlung München (abbreviation ZSMA), both in Germany. Abbreviations: A1, antennule, the first limb. A2, antenna, the second limb. H, height. L, length. Md, mandibula, or third limb. Mxl, maxillula, or fourth limb. KuramBio, Kuril–Kamchatka Biodiversity Study. L5, fifth limb. L6, sixth limb. L7, seventh limb. LV, Left Valve. RV, Right Valve. SEM, Scanning Electron Microscope. UR, uropodal rami (also known as furca). W, Width. ZMH K-, Crustacea collection of the Zoologisches Museum Hamburg. ZSMA, Zoologische Staatssammlung München in Munich (Germany). Here we use the term “Recent” (capital) to indicate the stratigraphical occurrence of a taxon, in contrast to fossil; and “Subrecent” for empty valves without soft parts (limbs, gut and other organic parts), but unfossilized. 2.2. Biogeographical Reviewreview Here we revised all papers on ostracods from hydrothermal vents, cold seeps and deep-sea wood-falls. Maps were made on the Ocean Data View (Schlitzer, 2012).

3. Taxonomic description Class Ostracoda Letreille, 1802 Subclass Podocopa Sars, 1866 Order Podocopida Sars, 1866 Suborder Cytherocopina Baird, 1850 Superfamily Cytheroidea Baird, 1850 Family Keysercytheridae fam. nov. Diagnosis: Shell surface smooth and sparsely covered with sensilla. Two types of pores present: normal pores, and sieve pores. Some surface pores carrying sensilla. Sieve pores are arranged in distinct patches, clearly visible even on the light microscope, giving an apparent look of coloration. These patches are clearly visible on the inner carapace surface, but on the outer surface they appear to be tiny openings (sieve pores). Carapace shape in lateral view is elliptical with medial portion inflated. Marginal pore canals are irregular, slightly denser anteriorly than posteriorly, sometimes branched, and being very short, vestibule sometimes present antero-dorsally. Muscular scar imprints consist of a vertical row of four scars and one, slightly crescent shaped, anterior scar. Several smaller scars present more dorsally to the main central muscle scar patterns. Inner calcified lamella relatively broad, both anteriorly and posteriorly. Hinge highly modified merodont with fine serrated median hinge on the LV and appropriate small groves on the RV. Anterior and posterior sockets on the LV, as well as anterior and posterior teeth on the RV reduced. No eye capsules present. A1 5- or 6-segmented (fourth and fifth segments sometimes fused), very slender with fine setae, none transformed into claws. A2 5-segmented, tiny terminal segment carries two claws and is completely fused with penultimate segment. Spinneret seta on A2, more than 3-segmented. Md exopod reduced to a cone-shaped basis and one thick, stick-like, short appendage which distally carry a tuft of setulae. Md palp 4-segmented, without long, comb-like setae. First segment of Md palp ventrally with a pronounced cone-shape extension. Distal segment with two strong claws. Mxl exopod with about 15 vibratory rays and no aberrant seta. Mxl palp reduced, second segment absent, while all three endites present and stout, each carrying strong claws. Thoracopods not sexually dimorphic and increasing in size, L5

than L6, which is larger than L7. Ventral margin of the first segment on all legs with only one seta (this seta very small on L7). Male copulatory limb (hemipenis) simple with triangular distal lobe. UR with two setae. Etymology: The family name is dedicated to Dr Dietmar Keyser (Zoological Museum, Hamburg) as an acknowledgment of his contribution to the study of Cytheroidea and as a thank you for the support he gave to both authors during many years. Type genus: Keysercythere gen. nov. Other genera: Aspidoconcha de Vos, 1953 Genus Keysercythere gen. nov. Diagnosis: Marginal pore canals unbranched and very few. A2 spinneret seta 7-segmented. Terminal segment of A2 and Md palp with two curved serrated claws. Male copulatory limb (hemipenis) with a long ejaculatory tube. Etymology: The genus is named after the family to which it belongs. Gender is feminine. Type species (monotypic): Keysercythere enricoi sp. nov. Geographical distribution: only know from the type locality. Keysercythere enricoi gen. et sp. nov. (Figs. 1–6) 015 Cytheroidea gen. sp., Schwabe et al., Table 2. Material examined: 22 specimens with soft parts. Holotype: male dissected on one slide, shell on the SEM-stub (ZSMA 20145017K-44249). Allotype: female dissected on one slide, shell on the SEM-stub (ZMH K- 44250). Paratypes: 20 specimens with soft parts: one male dissected on one slide, shell destroyed (ZMH K-44249); one male with shell and soft parts on the SEM stub (ZSMA 20145018); one juvenile dissected on one slide, shell on SEM stub (ZSMA 20145019). Additional 7 specimens in alcohol (ZSMA 20145020). Additional 10 specimens in alcohol (ZMH K- 44251). Type locality: Kuril–Kamchatka Trench, KuramBio Expedition (R. V. Sonne, 223rd Expedition), Station 12-05, Agassiz trawl trawled from 39143.47ʹN, 147110.11ʹE, 5229m to 39142.54ʹN, 14719.51ʹE, 5217 m, on the September 1st, 2012. Geographical distribution: only know from the type locality. Description of adult male: Shell elliptical in lateral view (Figs. 1A, B and 4A–C), with inflated medial portion of the shell. L around 0.53 mm. Greatest H situated behind middle L, equaling 35% of total L. Dorsal margin evenly rounded, anterior margin slightly narrower than posterior margin. Ventral margin convex (inflated part of shell), with small cut in front of mouth region, where inflated part meets frontal margin. In dorsal view shell also elliptical (Fig. 1C) with greatest W around middle L, both anterior and posterior ends equally wide. Surface smooth and sparsely covered with sensilla. Only in ventral region several faint longitudinal ridges visible. Some sensilla exit from collared pores (Fig. 1E), some from pores without collar (Figs. 1G and H). Sensilla exiting non-collar pores surrounded with sieve pores; sieve pores clearly arranged in clusters, visible on the inside of the shell. Inner calcified lamella almost equally broad anteriorly and posteriorly (Figs. 1D, 2A, and 4B, C). Around six marginal pore canals present anteriorly and only 2–4 posteriorly. All canals short and simple (unbranched). Muscular scar imprints consist of four vertical scars and one, slightly crescent shaped frontal scar. Several smaller scars present dorsally to main scar pattern. Inside of shell densely covered with sieve pore clusters (Fig. 1F). Each large cluster consists of several smaller clusters. Their distribution on inside surface does not always match sieve pores on outside surface. Hinge is modified merodont with LV carrying small dents in medial part (Fig. 2B and D), posterior part of hinge on LV with relatively prominent teeth (Fig. 2A),while anterior with elongated grove (Fig. 2D). R.V. with corresponding grooves in medial part of hinge, while no prominent teeth or groves present on anterior and

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Fig. 1. Keysercythere enricoi sp. nov., A, B, D–H, SEM; C, light photograph; A, B, E, G, H male, paratype (ZMH X4); C, adult and juvenile in alcohol (ZMH X6); D, F, holotype; H, juvenile (ZMH X5): A, RV external view; B, LV, external view; C, shell dorsal view; D, RV, postero-ventral part from the inside; E, normal pore with collar carrying a sensialla; F, pore cluster from the inside; G, H, normal pores without collar with sensilla, and groups of small pores (pore clusters). Scales ¼A, B, 100 mm; C, scale not included (approximate L of adult 500 mm of juvenile 400 mm); D, 50 mm, E–H, 5 mm.

posterior parts of hinge. This particular hinge structure visible only on high magnification, while under light microscope hinge appears adont. A1 (Fig. 4D and E) 5-segmented with fused 4th and 5th segments. A1 very slender with second segment being especially elongated. First segment bare, second segment with one seta on posterior margin. Third segment with one seta on anterior margin; fused zone of 4th and 5th segments with one seta on each anterior and posterior side. Penultimate segment with one seta anterodistally, and two setae postero-distally. Terminal segment with total of four setae, two proximally fused, and one of the fused setae transformed into aesthetasc. All setae on A1 slender and not particularly long. Segments with patches of setulae, especially on their distal margins.

A2 (Fig. 4F) 5-segmented. Basal segment without any seta, but with row of stiff setulae around medial region. Endopod 4-segmented. First segment with one seta postero-distally and with bunch of long and stiff setulae on medial surface. Second segment with two short setae anteriorly and one short aesthetasc posteriorly. Penultimate segment with only one short seta postero-distally. Terminal segment very short and carrying two spatula-like claws (Fig. 3D). Both claws distally curved and both covered with spines. Separation between terminal and penultimate segment not clear. L ration between first, second and third segment equaling 1.2: 1: 1.1. Spinneret seta very long, and by far exceeding terminal claws. This seta also consisting of seven longer or shorter parts (segments). Md (Figs. 4G and 3E). Coxa shorter than palp and being very stout. Distally carrying around 10 teeth. Coxal seta which are

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Fig. 2. Keysercythere enricoi sp. nov. SEM, A–E, holotype male; F–J, allotype female; A, LV, posterior part of the hinge; B, LV, medial part of the hinge; C, LV, inside view; D, LV, medial part of the hinge, detail; R, anterior part of the hinge; F, RV, anterior part of the hinge; G, RV, inside view; H, RV, detail of the medial part of the hinge; I, RV, muscular scar imprints; J, RV, posterior part of the hinge. Scales ¼A, C, F, G, J, 100 mm; B, E, H, 50 mm; D, 10 mm; I, 500 mm.

situated anteriorly and proximally to terminal teeth very strong and fused with coxa. Md exopod peculiar and consisting of cone shaped part, and one stick-like, short appendage which distally carry a tuft of setulae. Palp 4-segment. First segment internally with two short setae situated on a cone like extension, externally without setae; second segment with total of four longer setae, some pappose, and all situated internally, no setae externally. Following segment with only one seta situated medio-distally on internal side of palp, three short setae postero-distally, and one seta medio-distally. Terminal segment with two peculiar claws,

each curved distally and with pronounced soft, long teeth. One small seta accompanying two claws. Mxl (Fig. 5A) with exopod carrying about 15 rays. All rays turned in same direction, none is reflexed setae or aberrant. Palp without second segment; first segment with three thick-looking setae. All three endites present, and all relatively short and stout but with prominent, often finely serrated claws. L5 (Fig. 5B) 4-segmented. Basal segment with one ventral seta and four dorsal setae: two situated more proximally, two on distal margins. Knee of simple structure. Second segment with one tiny

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Fig. 3. Keysercythere enricoi sp. nov. SEM, A, B, C juvenile (ZMH X5), D–F paratype male (ZMH X4): A, right valve lateral view from the inside; B, normal pores on the surface carrying sensilla and surrounded by pore clusters; C, normal collared pore with bifurcate sensilla; D, A2 distal segment with two claws; E, Md palp with two distal claws; F, male copulatory limb (hemipenis); G, UR, with two setae and caudal seta; H, coiled ejaculatory duct. Scales ¼A, 200 mm; B, 4 mm; C, 5 mm; distal part of A1; B, D, H, 10 mm; E, 20 mm; and F, G, 50 mm.

seta distally. Third segment bare, while 4th carrying thick claw, which armed with strong spines. L6 (Fig. 5C) with one seta ventrally on basal segment and two setae dorsally: one situated more proximally and other on distal end. Second segment with one seta, 3rd without any, and terminal segment with claw similar to L5. L6 longer than L5. L7 (Fig. 5D) longest and most slender of all walking legs, with basal segment carrying two dorsal setae (one more proximal, other on distal end), while ventrally no setae observed. Second segment with one seta, 3rd without any seta, terminal segment with long, distally serrated claw.

Male copulatory limb (hemipenis) (Figs. 3F, H, and 5E) of very simple appearance, with triangular, distally curved distal lobe. No complicated rami attached, copulatory process not clearly distinguishable, but ejaculatory tube very long and coiled when male copulatory limb (hemipenis) not dissected (Fig. 3H), or extended after dissection (Fig. 5E). Skeletal structures on male copulatory limb (hemipenis) present but weak. UR simple (Fig. 3G), with two short setae. Caudal seta prominent exiting from bulbous base. Description of adult female: Shell without sexual dimorphism (Figs. 2F–J and 6A–C). L about 0.5 mm. Females with more

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Fig. 4. Keysercythere enricoi sp. nov. Holotype male: A, RV, lateral view from the outside; B, RV, lateral view from the inside; C, LV, lateral view from the inside; D, E, A1; F, A2; and G, Md. Scales ¼0.1 mm.

marginal pore canals both anteriorly and posteriorly, but structure same as in male. A2 (Fig. 6D) also very similar to male's. L5 same as in male, while L6 with much stouter terminal claw than in male. On L6 small ventral seta on basal segment present (Fig. 6F). Genital field simple and round (Fig. 5F). Description of juveniles: Shell with much straighter dorsal margin than in adults (Fig. 3A) and clusters of pores on the inside not grouped, but rather evenly spread. Some surface sensilla exiting from collared pores bifurcate (Fig. 3C), while pore clusters around sensilla exiting from non-collared pores surrounded with more prominent and wider sieve pore clusters than in adults (Fig. 3B). Etymology: The species is named after Enrico Schwabe from the Bavarian State collection of Zoology (Munich) who sent this

material for examination. The name is to be treated as a noun in the genitive singular.

4. Key to the Recent familes of Cytheroidea 1. A1 slender with thin segments and mostly fine setae…2  A1 different, often with broad segments, sometimes with chelate setae, often some setae transformed into strong claws…13 2. Vertical row of muscular scar imprints on the shell consists of five scars…Bythocytheridae Sars, 1866  Vertical row consists of four scars…3

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Fig. 5. Keysercythere enricoi sp. nov. A–E, holotype male; F, allotype female: A, Mxl; B, L5; C, L6; D, L7; E, Male copulatory limb (hemipenis); and F, UR and caudal seat. Scales ¼ 0.1 mm.

3. All three pairs of thoracopods present…4  Only two pairs of thoracopods present… Parvocytheridae Hartmann, 1959 4. Exopod of Mxl strongly reduce and with only one or two vibratory setae…Kliellidae Schäfer, 1945  Exopod of Mxl not reduced and consisting of many vibratory setae, some of which may be aberrant (reflexed setae)…5 5. Reflexed setae on Mxl exopod present…6  Reflexed setae on Mxl exopod absent…12 6. Md-coxa styliform and/or segments of the Md-palp elongated, with unclear subdivision between segments and with strongly reduced chaetotaxy…Paradoxostomatidae Brady and Norman, 1884

 Md-coxa stout and Md-palp with more robust segments, with clear division between them and with each segment bearing some setae…7 7. Two or three reflexed (or aberrant) setae present on the Mxl exopod…8  One reflexed (or aberrant) seta present on the Mxl exopod…9 8. Shell with posterior extension and thoracopods not sexually dimorphic…Cytheruridae Muller, 1984  Shell without posterior extension, thoracopods sexually dimorphic…Psammocytheridae Klie, 1938 9. Terminal segment of A2 with three claws, or two claws and one seta…10  Terminal segment of A2 with two (sometimes one) claws…11

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Fig. 6. Keysercythere enricoi sp. nov. Allotype female: A, LV, lateral view from the inside; B, RV, lateral view from the inside; C, LV, lateral view from the outside; D, A2; and E, L6; F, L7. Scales ¼0.1 mm.

10. Md exopod with three setae, “xestoleberis” spot on the shell… Xestoleberididae Sars, 1928  No “xestoleberis” spot, Md exopod with one long and one short seta…Microcytheridae Klie, 1938 11. Md exopod with four setae…Loxoconchidae Sars, 1925  Md exopod with one (or two) setae…Paracytherididae Puri, 1974 12. Thoracopods sexually dimorphic, A2 4-segmented…Cobanocytheridae Schornikov, 1975  Thoracopods not sexually dimorphic, A2 5-segmented… Keysercytheridae fam. nov.

13. Md palp with long comb-like setae…14  No comb-like setae present on Md palp…18 14. A1 typically distally curved, penultimate segment carrying chelate seta…Neocytherideidae Puri, 1957  A1 not distally curved…15 15. Spinneret seta on A2 reduced in females…16  Spinneret seta on A2 not reduced in females…17 16. Males with dorso-distal seta on the L5 transformed into claws, Md exopod with five setae…Trachyleberididae Sylvester-Bradley, 1948  Males with normal dorso-distal seta on the L5, Md exopod with three setae…Hemicytheridae Puri, 1953

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17. A1 6-segmented…Cuneocytheridae Mandelstam, 1959  A1 5-segmented…Thaerocytheridae Hazel, 1967 18. Thoracopods sexually dimorphic…19  Thoracopods not sexually dimorphic…21 19. Terminal segment of A2 with three claws…Krithidae Mandelstam, 1958  Terminal segment of A2 with two claws…20 20. Spinneret seta on A2 three segmented…Cushmanidae Puri, 1974  Spinneret seta on A2 two segmented…Cytherideidae Baird, 1850 21. Terminal segment of A2 with three claws…22  Terminal segment of A2 with two claws…23 22. Claw on L7 very long and thin…Australocytherideidae Hartmann, 1980  Claw on L7 similar in L to claws on other thoracopods… Osticytheridae Hartmann, 1980 23. First endite of Mxl reduced (only a knob)…Eucytheridae Puri, 1954  All Mxl endites normally developed…24 24. Marginal pore canals heavily branched and very dense… Leptocytheridae Hanai, 1957  Marginal pore canals not branched and much more sparse…Cytheridae Baird, 1850

5. Taxonomic discussion The new family is characterized by the following combination of characters: (1) smooth shell, covered with normal and sieve pores; (2) highly modified merodont hinge; (3) slender A1; (4) 5segmented A2 with a completely fused terminal segment carrying two claws; (5) similar claws (like on the A2) are present on the Md palp; (7) Md coxa is stout; (8) Md exopod is reduced to a cone; (9) first segment of Md palp ventrally with a pronounced coneshape extension; (10) Mxl palp reduced and 1-segmented; (11) Mxl exopod without reflexed and/or aberrant setae; (12) all thoracopods present and no prominent sexual dimorphism in their morphology; and (13) male copulatory limb (hemipenis) with non-movable and not-subdivided distal lobe. Most of these characters appear in many other families and therefore cannot be considered autapomorhic, with the exception of the peculiarly built A2 and Md. These two appendages seem to be highly specialized morphological adaptations which may be regarded as an autapomorhy of the new family. However, even the combination of all other characters, and in particular those commonly used for cytheroid families identification, make it hard to classify Keysercythere enricoi in any of the existing families. We have therefore erected a new family for it, thereby emphasizing the phylogenetic distance between Keysercytheridae and other cytheroids. Here we also included Aspidoconcha De Vos, 1953 in this new family. The genus was erected to accommodate a species found living commensally on the isopod, Limnoria lignorum (Rathke), which had been collected from a piece of cork washed ashore in The Netherlands. At present Aspidoconcha includes three species, of which only the type species, A. limnoriae De Vos, 1953 is well described based on both shell and soft parts. It is characterized by a slender A1, 5-segmented A2 with completely fused terminal segment carrying two strong claws, Md which has a peculiar conelike extension on the ventral side (enormously described as exopod by De Vos (1953)), 1-segmented Mxl palp, and all thoracopods with strong claws. Interestingly, even the expod of A2 has more than three segments (which is the most found in cytheroids so far). The genus was originally placed in the family Cytheridae. However, at the time the systematics of Cytheroidea was undeveloped, and most of today's families were regarded as subfamilies. De Vos (1953) did not relate this new genus to any of then known

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subfamilies, but later McKenzie (1972) transferred it to the family Xestoleberididae. Aspidoconcha differs from Keysercythere in the L ratio of the A1 segments (the terminal segment in the new genus is very short, while in Aspidoconcha it is as long as predescending segments); claws on both A2 and Md palp are not peculiarly curved; and Aspidoconcha has more numerous pore canals. The copulatory limb (hemipenis) of the males of the two species are different in a sense that in Aspidoconcha lacks the long ejaculatory tube seen in Keysercythere, but appears to be a simple structure with a triangular, non-movable distal lobe. De Vos (1953) stated that the Mxl exopod has a single aberrant seta, which was reiterated by in McKenzie (1972), but the latter's drawing shows a Mxl exopod which is the same as in the new species, i.e., no aberrant or reflexed setae are present. In addition, De Vos (1953) wrongly described the exopod on Md as being cone shaped and with a single seta, but this undoubtedly referred to the ventral conical elongation on the inside of the first segment of the palp. Conversely McKenzie (1972) clear illustration of the Md shows the exopod is in its usual position, and it looking very much like the Md of Keysercythere, except it lacks the stick-like seta. In his redescription of A. limnoriae McKenzie's (1972) states the Mxl-palp is 2-segmented and that it has the so-called “xestoleberis” spot in the eye region, neither of these characters was mentioned in the original description. The spot in the eye region was one of the main reasons for including Aspidoconcha in Xestoleberididae, and it remains an indication that the new family is closely related to Xestoleberididae (see below). It is very likely that the overlapping between endites and segments on the Mxl cased an apparent segmentation, observed by McKenzie (1972). McKenzie (1972) stated that Aspidoconcha has an adont hinge, however, he did not use an SEM which is necessary to observe the peculiar remnants of the merodont hinge type, so this statement needs to be reliablly validated. Keysercytheridae, together with Bythocytheridae, Parvocytheridae, Kliellidae, Paradoxostomatidae, Cytheruridae, Psamocytheridae; Xestoleberididae, Microcytheridae, Loxoconchidae, and Cobanocytheridae (families follow the order from the key) belongs to a group of families where the A1 is slender and carries fine, thin setae. Its appearance of A1 in some families (see comment below for Parvocytheridae) may appear to be intermediate between being slender and stout. However, when such an intermediate A1 is compared with those of families with segments that are stout, broad, and with transformed setae, the differences between slender and stout A1 becomes clear. A slender A1 may be regarded as an adaptation to the interstitial environment, however, in many families that inhabit the shallow littoral the A1 is more slender than in interstitial taxa, such as the family Paradoxostomatidae. On the phylogenetic tree based on the 18S rDNA (Yamaguchi and Endo, 2003) the three families with the slender A1, Paradoxostomatidae, Cytheruridae, and Loxoconchidae, represent more basal branches. However, it seems probable that a slender A1 appeared several times in the evolution of this group, because another two families which today possess a slender A1, Xestoleberididae and Cobanocytheridae, appear phylogenetically closer to families with the stout looking A1 on the same tree. Keysercytheridae seems to be most closely related to Xestoleberididae, but they differ in many details. The most important is the 4-segmented A2, 2-segmented Mxl palp, presence of aberrant setae on the Mxl exopod, and the Md exopod with slender setae (mostly thee setae present) in the latter family. On the other hand, many representatives of Xestoleberididae also have a long ejaculatory tube, but it seems to be inside the male copulatory limb (hemipenis), not coiled outside, like in Keysercythere. A very long tube can also be found in other families, such as Cytheruridae and in some representatives of Cobanocytheridae. Cytheruridae is a very diverse family, with species also having 5-segmented A2. However, the terminal segment of this appendage is prominent,

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and they have reflexed setae on the Mxl exopod. Most of Cytheruridae are, in addition, characterized by a caudal extension and long, often branching marginal pore canals. Nevertheless, Pelecocythere Athersuch, 1979 has a very similar carapace to the new genus, with a prominent lateral extension (Neale, 1988). However, in this genus A2 is 4-segmented, and A1 has stout setae, and therefore clearly differs from the new genus, also having a very isolated position in the family Cytheruridae. Similarly, another Cytheruridae genus, Microcytherura Müller, 1894 has very similar shell to the new genus, and there is a considerable difference between species currently assigned to it (compare Klie, 1938 and Hartmann, 1980), but it may turn out in the future that this genus as well should belong to the new family. Cobanocytheridae is a marine interstitial family (Gottwald, 1983; Higashi and Tsukagoshi, 2011), and it is closely related to the new family not only by the fact that some genera have long ejaculatory tube, but also that the Mxl exopod does not have any reflexed and/or aberrant setae, and the Md exopod is reduced. In some species, such as for example Cobanocythere ikeyai Higashi and Tsukagoshi, 2011, the Md exopod is very similar to the new genus. Cobanocytheridae, on the other hand, have a 4-segmented A2, with clearly developed terminal segment, 2-segmnted Mxl-palp, and the thoracopods are sexually dimorphic. Bythocytheridae is the family with many plesiomorphic characters such as five muscular scar imprints in the vertical row, and thoracopods with ventral branchial plates (Schornikov, 1981). The family inhabits a wide variety of marine environments and can be found from shallow littoral to abyssal depths. Parvocytheridae is a peculiar family inhabiting exclusively marine interstitial with drastic reductions in the number of walking legs, i.e., all species lack the L7 (for example Higashi and Tsukagoshi, 2011). Hartmann (1959) described Parvocytheridae from interstitial waters of El Salvador. Although both species he reported have a 6-segmented A1 and a 4-segmented A2, Hartmann and Puri (1974) stated in the family diagnosis that A1 is 6- or 7-segmented and that A2 is 5segmented. Although in our key we place this family in the group with slender A1, the drawings provided by Hartmann (1959) are dubious in this regard, because the length ratio of the segments, and in particular the very short third segment, may suggest that the A1 in Parvocytheridae is more similar to the second group of families in which the A1 is more stout. However, later reports of this family (Higashi and Tsukagoshi, 2011) show a clearly slender A1. Kliellidae is known after two species from subterranean freshwater (wells) of Greece (Schäfer, 1945), and only after the original description. This family is characterized with an almost complete reduction of Mxl exopod, with only 2–3 setae present. Typical Paradoxostomatidae are very easy to recognize because of a stiliform Md-palp, strongly reduced (mostly missing) Mxl palp, and the reduced number of Mxl endites. However, in the genus Cytherois Müller, 1884 Md coxa is not as stiliform, and carries distal teeth. Unlike the rest of the Paradoxostomatidae, the Mx-palp is also well developed and 2-segmented. Nevertheless, Cytherois has very elongated second segment of the Md palp and may be phylogenetically the most plesiomorphic genus in the family. On the other hand, Nodoconcha Hartmann, 1989, described from the Southern Ocean (Hartmann, 1989), should be excluded from Paradoxostomatidae because this monotypical genus does not share a single synapomorphy with Loxoconchidae. In this genus even the segments of Md palp are stout, and the A1 is not slender. In the same paper where Aspidoconcha was described De Vos (1953) described another two genera: Redekea de Vos, 1953 and Laocoon de Vos, 1953. Both genera were associated with an Isopod species, and found on the cork wood. In the subsequent paper De Vos, Stock (1956) changed the name of the latter taxon into Laocoonella de Vos, 1955. McKenzie (1969) proposed to include these genera into Paradoxostomatidae, which

was accepted for Redekea in subsequent publications (Wouters and de Grave, 1992), but doubted for both genera in McKenzie (1972). In our opinion the two genera should be excluded from Paradoxostomatidae, because they do not have the same reductions on the Mxl and Md. However, their possible placement in other families remains unclear. The family Cytheromatidae Elofson, 1939 currently includes eight genera. The soft parts are known in the type genus, Cytheroma Müller, 1894; Fernandinacythere Gottwald, 1983; Megacytheroma Puri, 1960; Microloxoconcha Hartmann, 1954; Paracytheroma Juday, 1907, and Pontocytheroma Marinov, 1963. Fernandinacythere Gottwald, 1983 is remarkable for apparent absence of Mxl (Gottwald, 1983) and it, along with Microloxoconcha, has a very slender A1. On the other hand, in all other genera the A1 is stout and carrying claws. Other differences include an absence of reflexed setae on Mxl exopod in Microloxoconcha (one in other Cytheromatidae) and peculiar marginal zone in which marginal pore canals are irregular, few, and forming vestibulum. This last character is shared with Pellucistoma Coryell and Fields, 1937, known from the Cenozoic fossil record and subrecent specimens (i.e., empty valves) (e.g., Benson, 1959). In other genera marginal pore canals are relatively dense and evenly distributed along margins. On the other hand, all genera have a similar male copulatory limb (hemipenis) (Gottwald, 1983). Microloxoconcha and Fernandinacythere are known from interstitial environments and therefore, a slender A1 may be an indicator of adaptation to such environments. However, the absence of reflexed setae and the appearance of the marginal zone may bear deeper phylogenetic signal. We do not include the family Cytheromatidae in the key because of many ambiguous characteristics, but most of all because other families where the A1 is slender form relatively tight phylogenetic units. Further revision should shed more light on this peculiar family. Microloxoncha bears some similarities with the new genus (especially the appearance of the Mxl exopod), but the Mxl palp is 2-segmented and A2 is 4-segmented. Nevertheless, the close relationship between Microloxoconcha and Keysercytheridae should not be undermined. This key also does not include the predominantly freshwater family Limnocytheridae Klie, 1938. This diverse family consists of two distinct phylogenetic lineages: Limnocytherinae and Timiriaseviinae. The family belongs to the group with the stout A1, but genera of Timiriaseviinae differ from Limnocytherinae by a prominent brood pouch, and also by a reduced Mxl-palp, and sometimes even reduced number of claws on the A2 (genus Dolekiella Gido, Artheau, Colin, Danielopol and Marmonier, 2007) (for a detailed revision of Timiriaseviinae see Karanovic and Humphreys, 2014). In addition, sexual dimorphism in thoracopods and A2 appears in a couple of genera in both Limnocytherinae and Timiriaseviinae. We strongly believe that the characters of this family should be reassessed to better mirror morphology of the rest of Cytheroidea. From the above discussion it is apparent that many of the Cytheroidea families require revision. This is the main reason why we decided to erect a new family, as the placement of the two genera in any of the existing families would not be possible without substantial diagnosis extension. The fact that the two Keysercytheridae genera have both been collected from the wood habitat may indicate long evolutionary processes which lead to this adaptation. Although Aspidoconcha has been found living commensally on a wood-burrowing isopod, the new genus was collected directly from the wood fall, which also carried a number of isopods (Schwabe et al., 2015), which were not previously known from the wood. Wood seems to be the preferred habitat for the new family, but some characteristics of Keysercythere also appear to be interstitial adaptations as well. It is a well-known that the reduction in size often encountered among interstitial organisms results in the convergent evolution of many characters (Gottwald, 1983). Living commensally

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on other animals also leads to a reduction in the body size, so convergent characters may be shared between ostracods living both interstitially and commensally. Thus, potentially, Keysercythere enricoi can survive on the wood habitats even in the absence of its normal hosts, because it can hide in tiny wood crevices, and the strong claws on the A2 with terminal segment fused, along with curved, strong claws on the Md, provide a powerful structure and may be adaptations to this lifestyle. Future studies of interstitial habitats may either reveal new taxa belonging to Keysercytheridae, or that revisions of known interstitial cytheroids will result in their being re-classified in the new family.

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hydrothermal vents and cold seeps off the coast of Northern and Central America found no genus to be endemic to these chemosynthetic habitats (Degen et al., 2012) whereas many genera, e.g., the ostracod Xylocythere, are known to inhabit oligotrophic, deepsea sediments (Steineck et al., 1990). The occurrence of cosmopolitan fossil assemblages associated with wood and whale falls, hydrothermal vents, and cold seeps (Kaim, 2011; Sirenko, 2013; Kiel et al., 2009) would seem to indicate that many of these organisms had invaded and adapted to such environments long before their apparently first occurrence in the Late Mesozoic. 6.2. Ostracoda from woodfalls and chemosysnthetic environments

6. Biogeography of deep-sea wood fall ostracods, with a short review on ostracods in the deep-sea and chemosynthetic environments 6.1. Wood falls, cold seeps and hydrothermal vents: an overview Wood falls in the deep sea become inhabited by diverse assemblages of species with origins in shallow water, deep-sea or even rarely putative freshwater habitats (e.g., Schwabe et al., 2015; Maddocks and Steineck, 1987; Fig. 7 and Tables 1 and 2). These faunas show clear biogeographical links to the assemblages associated to those exploiting vertebrate carcasses (e.g., whale, fish), hydrothermal vents and cold seeps (e.g., Degen et al., 2012; Cunha et al. 2013). This connection is considered to relate to the enhanced concentrations of reduced inorganic compounds, such as hydrogen sulfide, hydrogen, methane associated with these environments (see Cunha et al., 2013). It is widely accepted that these organic falls represent “stepping stones” for the dispersal of diverse assemblages of organic fall, vent and seep organisms (e.g., Distel et al., 2000). Evidence from experimental wood falls deployed on the continental slope of the Gulf of Cádiz (Northeastern Atlantic) suggests that at family and generic levels all wood fall faunas have elements in common, and they are dominated by substrate-specific taxa (Cunha et al. 2013). The presence in wood falls of both shallow water taxa and typically deep-water organisms (e.g., Schwabe et al., 2015; Maddocks and Steineck, 1987) clearly indicates a biogeographical link between wood fall and shallow water ecosystems, where the wood and possibly also the organisms originated. The occurrence of wood fall assemblages can be traced back in time to at least the Mesozoic (e.g., Kaim, 2011; Sirenko, 2013; Kiel et al., 2009). The earliest record is from the Middle Jurassic of Poland, where Kaim (2011) reported an assemblage lacking a typical xylophagain wood-boring bivalves but including typical leptochitonid polyplacophorans and alleged cocculinoid gastropods. The faunal similarities between organic falls (e.g., whale and fish carcasses and wood) has been recognized for communities dating back to the early Cenozoic; hence these faunas have been exchanging individual species over a long geological period (Kiel and Goedert, 2006a). Modern wood fall assemblages were established at least, as early as the late Eocene (Kiel and Goedert, 2006b), based on a diverse, deep-water, invertebrate assemblage which was reported from fossil wood fragments collected in the Washington State, USA. Kiel and Goedert (2006a) noticed that the fossil wood fall assemblage shared several families but only a few species with fossil whale falls and fossil cold seeps – a pattern seen in the analogous modern environments. The long evolutionary history of the colonization of wood falls by a diverse fauna may explain why most of the taxa above species level are not exclusive to this habitat, but occur also in the “ordinary” deep sea sediments, hydrothermal vents, cold seeps and other organic falls. For example, a comparison of Recent meiofauna collected from

6.2.1. Paleozoic putative hydrothermal vents The earliest record of an ostracod from these extreme habitats, is of a very abundant, monospecific population of Hamaroconcha kornickeri Olempska & Belka, 2010 (Myodocopa) from the Paleozoic (Middle Devonian, Eifelian) found in a putative, deep-sea, hydrothermal vent system in the eastern Anti-Atlas, southern Morocco (Olempska and Belka, 2010) (white dot in Fig. 7a). A more diverse ostracod assemblage was recorded from a probable chemosynthetic community dating from the Lower Carboniferous ( 350 million years) of Newfoundland, Canada (Dewey, 1993) (white dot in Fig. 7a). This environment was a putative shallow, nearshore environment and was inhabited by a quite diverse ostracod assemblage and otherwise by a very abundant but low diversity invertebrate fauna (Dewey, 1993). This ostracod assemblage was dominated by Chamishaella suborculata belonging to the extinct superfamily Paraparchitoidea. Other ostracods were bythocytherid and bairdioid podocopids, amphissitid platycopids, polycopid myodocops, youngiellid palaeocops (Dewey, 1993). However, the Paleozoic fauna (including the ostracods ) is almost completely distinct from the modern fauna, so no dispersion routes for the wood fall fauna can be derived from these early records. 6.2.2. Miocene putative seep There is no known ostracod fauna from wood or other organic falls, seeps or vents from the entire Mesozoic. However, Russo et al. (2012) reported a quite diverse ostracod fauna from a putative cold seep Miocene deposit in the northern Apennines (Italy) (white dot in Fig. 7a). Such rare findings are exciting and of obvious scientific interest, but some important points need to be addressed. The criteria whereby these strata are identified as remnants of cold seeps are based, among others, on the presence of lucinid molluscs. These molluscs are indeed ubiquitous in chemosynthetic habitats, but they are at their most diverse and highest abundant in tropical coral and seagrass habitats of the Atlantic and Indo-West Pacific (Taylor et al., 2014 and references therein). Moreover, Russo et al. (2012) cite three ostracod taxa as being exclusive to seafloors with seepage, namely Abyssocypris sp., Cardobairdia glabra and Buntonia multicostata. However, recently Abyssocypris has been recorded from both ordinary sea floor environments (Maddocks, 1977; Corrège, 1993; Ayress et al., 2004; Alvarez Zarikian et al. 2009) and from deep-sea wood falls (Steineck et al., 1990), but not from cold seeps (Table 1). Cardobairdia species and also Buntonia multicostata are exclusively fossil and the evidence do not indicate that these taxa were endemic to seep environments (e.g., Guernet and Fourcade, 1988; Bonaduce and Barra, 2002). Finally, Russo et al. (2012) cite Xestoleberis sp. as a normally “phytophylous taxa” and its presence in the putative seep environment as an evidence of increase of nutrients in the mounds as “gas seepage” or the presence of wood falls (Russo et al., 2012). However, Xestoleberis is another genus whose species are frequently recorded from oligothrophic deep sea habitats

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Fig. 7. Deep-sea Ostracoda (42000 m, mostly Recent and sub-Recent): (a) All Recent and sub-Recent records and a few hydrothermal vent fossils; (b) Krithe Brady in Crosskey & Robertson, 1874; (c) Argilloecia Sars, 1865;. For the color legend refer to the online version of the present publication. Green: wood fall- asterisk, herein; dots, previous studies (Maddocks and Steineck, 1987; Steineck et al., 1990). Red dots: ordinary, oligotrophic, deep-sea environments (Brandão, unpublished compilation). Yellow dots: hydrothermal vents (Kornicker, 1991; van Harten, 1992; van Harten, 1993; Kornicker and Harrison-Nelson, 2005; Maddocks, 2005; Degen et al., 2012). Blue dots: cold seeps-light blue Recent fauna (Ritt et al., 2010; Degen et al., 2012); dark blue, Subrecent fauna, i.e., dead specimens, empty valves, no soft parts (Coles et al., 1996). White dots: fossil ostracods from vents and seep, i.e. putative Miocene cold seep in Italy (Russo et al., 2012); hydrothermal vent from Eifelian (Middle Devonian) of southern Morocco (Olempska and Belka, 2010); Lower Carboniferous chemosynthetic community from Newfoundland, Canada (Dewey, 1993). Black dots are examples of studies, where Recent, unidentified ostracods have been cited: yellow outline: hydrothermal vents (Fricke et al., 1989; Van Dover et al. 1990; Buckman and Shank, 2004; Zeppilli and Danovaro, 2009); blue outline: seeps (Montagna et al., 1987; Sommer et al., 2007; Van Gaever et al., 2009; Bright et al., 2010). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

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Table 1 Ostracod genera recorded from wood falls, cold seeps and hydrothermal vents. Paleozoic records from putative hydrothermal vents are excluded. Genus

Wood fallsa Recent

Cold seepsb Recent þfossils

Ventsc Recent

oligothrophic deep sead

shallow environmentsd

Propontocypris Thomontocypris Xylocythere Abyssocypris Bythocypris Cytheropteron Echinocythereis Krithe Legitimocythere Paradoxostoma Pseudocythere Sclerochilus Ambocythere Cytherois Jonesia Pelecocythere Polycope Poseidonamicus Retibythere (Bathybythere) Keysercythere Parapontoparta Argilloecia Cytherella Henryhowella Neonesidea Buntonia Parakrithe Quasibuntonia Xestoleberis Palmoconcha Monoceratina Muellerina Paracytherois Thaerocythere Cardobairdia Paleoblitacythereis Bathyconchoecia Euphilomedes Archiconchoecia Polycopetta Prionotoleberis

Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent

Subrecent Recent Recent Fossil Subrecent Subrecent Subrecent Subrecent Recent Subrecent Subrecent Subrecent

Recent Recent Recent

Recent

Recent Recent

Subrecent Recent Subrecent Recent Recent Fossil Fossil Recent Recent Subrecent, Fossil Recent Subrecent Recent Fossil Fossil

Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent Recent

Recent Recent Recent Recent Recent Fossil Fossil Recent

Recent Recent

Recent Recent Recent Recent Recent Recent Recent Recent

Recent Recent Recent Recent Recent

Recent Recent Recent Recent Recent Fossil Fossil

Recent Recent Recent Recent Recent

Recent

Recent

Recent Recent Recent Recent

F, extinct genera; SB, Subrecent (i.e., empty valves, without soft parts); R, Recent (i.e., specimens collected with soft parts). a

Maddocks and Steineck (1987) and Steineck et al. (1990), herein. Coles et al. (1996), Ritt et al., 2010, Degen et al. (2012), and Russo et al. (2012). c Kornicker (1991), Harten (1992, 1993), Kornicker and Harrison-Nelson (2005), Maddocks (2005), and Gollner et al. (2007). d Brandão, unpublished compilation. b

(e.g., Bonaduce et al., 1983; Cronin et al., 1991; Alvarez Zarikian et al. 2009), and although a single individual has been recorded from a cold seep (Nikolov, 2011), none has been reported from wood falls or hydrothermal vents (Table 1). Such misunderstandings illustrate how much more careful evaluation is necessary before using data on ostracod taxa in palaeoenvironmental reconstructions. Special attention is necessary when interpreting data at taxonomic levels higher than species, because most taxa at these higher levels have broad ecological, bathymetrical and geographical ranges. In extreme cases are the genera poorly described and illustrated over than a Century ago, e.g., Argilloecia, Bairdia, Bythocypris, Cytherella, Pontocypris, Xestoleberis (Table 1). These genera include many tens of species and have such broad geographical, stratigraphical and ecological occurrences (Brandão et al., 2014) that their value as indicators is highly questionable.

6.2.3. Quaternary cold seeps A diverse and geographically widespread ostracod assemblage has been reported from bathyal carbonate mounds associated to

gas seepage in the Porcupine Basin, North Atlantic (Coles et al., 1996). Only four taxa have been identified to species level, all are widespread in the North Atlantic, i.e., Cytherella serrulata, Muellerina abyssicola, Neonesidea inflata, Thaerocythere crenulata (Table 2). Other components of this fauna are cosmopolitan genera (unidentified species), some are typically deep-sea inhabitants (Henryhowella, Krithe) (Fig. 7b), while other are eurybathic and occur in both shallow and deep environments (i.e., Argilloecia, Bythocypris, Cytheropteron, Echinocythereis, Monoceratina, Propontocypris, Pseudocythere, Sclerochilus) (Table 1 and Fig. 7c). This assemblage also includes “shallow water” genera, i.e., Paracytherois and Paradoxostoma, which live on the sediment, on detritus and usually associated with macroalgae (e.g., Mueller, 1894) (Table 1). An uncertainty arises from Coles et al. (1996) having based their analysis on subrecent specimens (i.e., empty valves), which had died prior to the sampling and, therefore, could have been transported horizontally after death. Therefore, the composition of the fauna observed and the lack of taxa typically found in cold seeps (see below), e.g., Paradoxostoma, Thomontocypris, Xylocythere, may have been an artifact resulting from transport

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Table 2 Ostracod species recorded from wood falls, cold seeps and hydrothermal vents. Paleozoic records from putative hydrothermal vents are excluded. Species

Wood fallsa

Ambocythere ramosa Cytherois lignincola Cytherois paralignincola Cytheropteron porterae Echinocythereis echinata Keysercythere enricoi gen. et sp. nov. Paradoxostoma turnerae Parapontoparta spicacarens Pelecocythere sylvesterbradleyi Poseidonamicus major Propontocypris excussa Propontocypris repanda Propontocypris sectilis Retibythere (Bathybythere) scaberrima Sclerochilus contortus Sclerochilus turnerae Xylocythere pointillissima Xylocythere rimosa Xylocythere tridentis Xylocythere turnerae

R R R R R R R R R R R R R misid. R R R R R R R

e

Abyssocypris atlantica Legitimocythere acanthoderma Cytherella serrulata Muellerina abyssicola Neonesidea inflata Thaerocythere crenulata

f

misid. R

Cold seepsb

Ventsc

Oligothrophic deep sead

Benthic

x

x x x x x x x x x x x x x x x x x x x x

x x

x x

x x

misid. F misid. SB SB SB SB SB

Archiconchoecia chavturi Bathyconchoecia deeveyae Bathyconchoecia paulula Conchoecinae indet. Euphilomedes climax Polycopetta pax Prionotoleberis styx Thomontocypris brightae Thomontocypris gollnerae Xylocythere vanharteni

x x x x x x R R R R R R R R R R

Benthopelagic

x x x x x x

x x x x

x x x x x x x x x x

misid., misidentification; F, recorded as fossil; SB, Subrecent; R, Recent. All species, except two e and f have only been recorded from a single environment. a

Maddocks and Steineck (1987) and Steineck et al. (1990), herein. Coles et al. (1996), Ritt et al., 2010, Degen et al. (2012), and Russo et al. (2012). Kornicker (1991), Harten (1992, 1993), Kornicker and Harrison-Nelson (2005), Maddocks (2005), and Gollner et al. (2007). d Brandão, unpublished compilation. e Abyssocypris atlantica (Maddocks, 1977) has smooth valves, with subcircular outline. It can be easily misidentified if soft parts are not studied. Therefore, we treat its record from putative fossil cold seeps as a misidentification. f Legitimocythere acanthoderma (Brady, 1880) was misidentified in both the wood falls and fossil cold seeps and has been shown to occur solely in Recent sediments from bathyal environments in the Subantarctic region of the Southern Ocean (Brandão, 2013). b c

exchanging of dead shells between the ordinary deep-sea, oligothrophic sediments and those around the seeps (see also discussion below).

6.2.4. The living ostracods from wood falls, cold seeps and hydrothermal vents: overview Although the Recent, deep-sea, wood fall, vent and seep ostracod faunas are still poorly known, there are recognizable biogeographical links both between them, and with oligotrophic, deep-sea, enviroments (Tables 1 and 2 herein; Degen et al., 2012). Even though deep-sea ostracods assemblages from oligotrophic environments are still undersampled, they are best known. Hundreds of Recent species have been reported worldwide from 836 stations from depths greater than 2000 m (red dots in Fig. 7a, Brandão, unpublished compilation), but of these hundreds of stations, only nine are from wood falls (green dots and asterisk in Fig. 7a) (Maddocks and Steineck, 1987; Steineck et al., 1990; herein), 23 from cold seeps (e.g., Bright et al., 2010; Degen et al., 2012) (blue dots in Fig. 7a) and 18 from hydrothermal vents (yellow dots in Fig. 7a) (e.g., Kornicker, 1991; Harten, 1992, 1993;

Kornicker and Harrison-Nelson, 2005; Maddocks, 2005; Gollner et al., 2007). This low proportion is because studies of these environments seldom address the ostracods despite their importance in geological reconstructions. All the papers cited in the few lines above have been based on the analyses of samples collected off Central and North America. Even then in only 11 of these publications are the ostracods identified to genus or species (e.g., Maddocks and Steineck, 1987; van Harten, 1992; Maddocks, 2005; Gollner et al., 2007; Degen et al., 2012) (yellow, green and blue dots in Fig. 7a). There are other publications reporting on ostracods from hydrothermal vents and cold seeps in other oceanic regions, e.g., the subpolar North Atlantic, off North Iceland, the Mid-Atlantic ridge (  301N), the Northeastern Pacific, and Equatorial Western Pacific (e.g., Fricke et al., 1989; Van Dover et al., 1990; Buckman and Shank, 2004; Zeppilli and Danovaro, 2009) (black dots in Fig. 7a), but without identifying the taxa to a meaningful level. We know of no records of ostracods from wood-falls, vents and seeps in the Indian, Arctic and Southern oceans and from the Mediterranean. Finally, since almost all these studies of recent faunas have been focussed on northern latitudes off Northern and Central America (yellow, black, green and white

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dots in Fig. 7a), no conclusions can be drawn about the global biogeography of these faunas. 6.2.4.1. Recent wood falls. It comes as no surprise that most wood fall ostracods belong to the Cytheroidea, since it is the most diverse Recent ostracod superfamily. The first deep-sea wood-dwelling ostracod assemblage was described from the experimental pieces of wood deployed on the sea floor for at least one year at several locations in the Northeastern Pacific and Northwestern Atlantic at depths ranging from 1830 to 4000 m (Maddocks and Steineck, 1987). These ‘wood islands’ became inhabited by ostracod communities that were quite diverse. Single pieces of wood were colonized by several species, and many of the species colonized wood islands as much as 1000 km apart. In total, 24 ostracod species belonging to 19 genera were reported from deep-sea wood pieces (Maddocks and Steineck, 1987; Steineck et al., 1990). These authors stated that the ostracod assemblages resembled those found living on shallow water algae and marine grass rather than deep-sea habitats. However, we disagree with this statement, since, although there are “shallow water elements” in these assemblages (i.e., Parapontoparta, Paradoxostoma, Cytherois), most the genera reported by these last authors are widely distributed and commonly found in ordinary, deep-sea sediments, i.e. Ambocythere, Bythocypris, Cytheropteron, Echinocythereis, Krithe, Legitimocythere, Pelecocythere, Polycope, Poseidonamicus, Propontocypris, Pseudocythere, Retibythere and Sclerochilus (Table 1 and Fig. 7b, c). The well-defined, but less common genus Abyssocypris Bold, 1974, despite being quite rarely reported in the literature, is known from ordinary, deep-sea sediments in the North and South Atlantic, Southern Ocean and Southwestern Pacific (e.g., Maddocks, 1977; Ayress et al., 2004; Alvarez Zarikian et al., 2009). Even those genera, which are common in shallow water habitats, have also been recorded from oligothrophic, deep-sea sediments, i.e., Cytherois (e.g., Bonaduce et al., 1983; Alvarez Zarikian et al., 2009) and Paradoxostoma (e.g., Didié and Bauch, 2000; Jones et al., 1999). Only Parapontoparta has been only reported from both shallow water environments (e.g., Hartmann, 1955) and from these artificially deployed wood islands (Maddocks and Steineck, 1987). Maddocks and Steineck's (1987) described a new genus, Xylocythere (family Cytheruridae), to accommodate a few species found on these wood pieces. Their presumption that Xylocythere is endemic to wood falls (Steineck et al., 1990) was invalidated when it was reported from hydrothermal vents (van Harten, 1992; Maddocks, 2005; Gollner et al., 2007), cold seeps (Degen et al., 2012) and deepsea, oligothrophic environments (e.g., Corrège, 1993) in the Pacific and Atlantic (Steineck et al., 1990). Paradoxostoma Fischer, 1855 is a genus that was described in the 19th Century and can now be regarded as having an “artificially inflated” diversity, containing 337 species (of which 283 are currently accepted) (Kempf, 1986, 1988, 1994, 1995, 1996, 2000, 2002, 2004, 2008; for an overview see Brandão et al., 2014). The genus has a global distribution and its species are typical of marine and brackish, shallow water environments living on sediments or as epibionts on macroalgae and invertebrates (e.g., corals, amphipods) (e.g., Baker and Wong, 1968; Whatley and Wall, 1975; Horne and Whittaker, 1985) (Table 1). Its species have modified, elongated bucal apparatus, which is considered an evidence for a feeding by sucking on macroalgae, polychaetes, amphipods etc (e.g., Elofson, 1941). Maddocks and Steineck (1987) and later Steineck et al. (1990) postulated that some of the ostracods living on wood are endemic to such habitats, and also that they get transported from one wood island to another by currents and/or other animals. At the generic level, as discussed above, endemicity is non-existent. However, at the species level, several taxa are indeed restricted to wood falls or to hydrothermal vents, in contrast to the widely distributed species which are recorded from cold seeps (Table 2, but see

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discussion below). Xylocythere pointillissima Maddocks and Steineck, 1987, Xylocythere rimosa Maddocks and Steineck, 1987, Xylocythere tridentis Maddocks and Steineck, 1987 and Xylocythere turnerae Maddocks and Steineck, 1987 have only been reported from wood falls. Similarly, Xylocythere vanharteni Maddocks, 2005 and Polycopetta pax Kornicker & Harrison-Nelson, 2005 have only been reported from hydrothermal vents. The endemicity recorded off the American continent differs from previous findings for hydrothermal vents in shallow environments along the subpolar Mid-Atlantic ridge, where the macrofauna and meiofauna species found were also recorded from non-vent areas in the adjacent boreal Atlantic and polar seas (Fricke et al., 1989). As mentioned above (see Section 2.3), the ostracod assemblage recorded from bathyal cold seeps in the Porcupine Basin included no endemic species (Coles et al., 1996). However, this apparent lack of endemicity at seeps may result from methodological artefacts. This is only a single study of cold seeps in which the ostracods were identified to species level (Coles et al., 1996), and then only Subrecent specimens were studied. Conversely, soft parts of living specimens were studied in all wood fall and hydrothermal vent investigations, where ostracods have been identified to species level (e.g., Maddocks and Steineck, 1987; Gollner et al., 2007). There are clear disparities in how ostracodologists morphologically define the species; convergence in evolution inevitably results in studies based solely on shell morphologies giving rise to wider species definitions (and consequent artificially wider geographical and stratigraphical distributions) than those based on soft parts as well as valve morphology (e.g., Jellinek et al., 2006). 6.2.4.2. Recent hydrothermal vents. More studies have been published on the vent ostracods than from wood falls, but it is evident that vent faunas is far less diverse. The following taxa have been reported from a hand full modern, vent areas, which were investigated in detail for ostracods (Kornicker, 1991; Harten, 1992, 1993; Maddocks, 2005; Kornicker and Harrison-Nelson, 2005; Degen et al., 2012). The typical, cosmopolitan, deep-sea genera Krithe and Legitimocythere, the eurybathic Propontocypris, the genera typical of shallower habitats Euphilomedes, Polycopetta, Palmoconcha, Paradoxostoma and Thomontocypris, and, finally, Xylocythere, which occur in wood falls, seeps and vents and also in the oligotrophic deep sea (Tables 1 and 2, Fig. 7b). 6.2.4.3. Recent cold seeps. Ostracods (identified to genus level) were reported from cold seeps in the Gulf of Mexico and in the Marmara Sea, Turkey (light blue dots in Fig. 7a). Similar to hydrothermal vents and wood falls, the cold seep ostracod fauna combines elements prevalent in shallow (Palmoconcha, Paradoxostoma) and deep environments (Krithe, Legitimocythere, Xylocythere) as well as widely distributed taxa (Argilloecia, Propontocypris, Thomontocypris). The genus Argilloecia Sars, 1865 is a ubiquitous taxon with representatives occurring from the littoral to the abyss (Fig. 7c). However, this cosmopolitan distribution is probably an artefact, which results from their lack of morphological characters, i.e. their smooth valves making it virtually impossible to distinguish the species, and the original descriptions being antiquated and inadequate. Smooth valved ostracods are notoriously difficult to identify and consequently their classification tend to be artificial. Hence, many smooth-valved nominal genera (e.g., Pontocypris, Macrocypris and Xestoleberis), tend to be a group of evolutionarily distant lineages. This tendency is exacerbated in genera, like Argilloecia, for which the original descriptions are old, inadequate and poorly illustrated. The systematics of such taxa are so confused and full of errors that any attempt to draw generalization on their ecology and biogeography will be totally misleading. Additionally, the

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assumption that pontocypridids are unusual in the deep sea (Harten, 1992) is unjustified. At least fourteen papers have recorded Propontocypris from the deep sea, only four of these deal with wood fall and hydrothermal vent faunas, the other ten deal with ostracods inhabiting the oligotrophic sediments, most common in the deep sea (e.g., Bonaduce et al., 1983; Jones, et al., 1999; Didié and Bauch, 2000). 6.3. Dispersal strategies and biogeography We conclude that, at the generic level, faunas inhabiting wood falls, seeps and vents are similar, and also include elements common to both shallow and deep habitats. Based on these very limited numbers of studies and species, we suggest that, at the species level, endemism ranges from low to quite high; being zero for cold seeps, 35% for wood falls and 60% for hydrothermal vents (Table 2). Non-endemic species are shared with ostracod assemblages in oligotrophic, deep-sea sediments but not with shallow environments. Also at the generic level, these faunas share more taxa with oligotrophic, deep-sea sediments than with shallow habitats, contrary to previous assumptions. We propose two possible dispersal strategies for wood fall ostracod assemblages (and also vent and seep assemblages). Firstly, as mentioned by previous authors (e.g., Maddocks and Steineck, 1987) by hitchhiking on larger, more motile animals (e.g., fish gills) and, secondly by surviving being ingested and defecated. Ostracods from evolutionary distant groups (i.e., Cytherocopina and Cypridocipina) have been shown either to be able to attach themselves externally to the skin of amphibians and snakes (Lopez et al., 1999), or to be able to survive being passed through the guts of amphibian, mammalian or fish (Lopez et al., 2002, 2005; Vinyard, 1979). Ostracods were thought to be able to survive being ingested by tightly sealing their valves and being able to recover after being defecated (Lopez et al., 2002, 2005; Vinyard, 1979). These wood dwelling ostracods may have developed similar dispersal strategies, be able to reach new wood falls via their “hosts”. However, because of the high endemicity at species level, it seems that the dispersal events between wood falls or between vents and seep sites do occur rarely enough for speciation to take place. Wood, carcasses, seeps and vents on the sea floor represent a great food source so it is not unexpected that many animals use them as refuge (Schwabe et al., 2015). Evidence of fauna submergence for ostracods is available from Kornicker (1991) who reported Euphilomedes climax to be abundant and the sole species in bottom samples collected from the Explorer and Juan de Fuca ridges in the Northeastern Pacific. All the other species of Euphilomedes have only been found at depths shallower than 401 m (Kornicker, 1991). The capability of ostracods to live in marine, brackish, freshwater and terrestrial habitats is well known (Schornikov, 1969; Schornikov and Syrftlanova, 2008). Terrestricythere is typical of terrestrial and semiterrestrial coastal habitats, but it also occurs in zones of gas seepage in the Black Sea (Schornikov and Syrftlanova, 2008). Additionally, ostracods from distinct families (e.g., Entocytheridae, Paradoxostomatidae), are well known as commensals on wood-infesting isopods (e.g., Vos de and Stock, 1956; Wouters and de Grave, 1992) and other invertebrates (e.g., Maddocks, 1987). Ostracods have the flexibility to adapt moving back and forth between environments of different salinities and depths, and this capability allied to the fact that ostracods can live commensally on a wide range of larger organisms, seem to have allowed ostracods to colonize and adapt to ephemeral environments like wood falls, cold seeps and hydrothermal vents. The new genus Keysercythere is very closely related to Aspidoconcha, which is a commensal on wood-burrowing isopod of the genus Limnoria (De Vos, 1953). Their close relationship suggests that the new family probably originated in shallow water and at least one of its representatives

submerged to the deep sea, where it inhabits a comparable environment (e.g., wood falls). Many of the taxa that inhabit vents, seeps and wood falls are widespread. Endemicity on the generic and familial level (e.g., Keysercythere gen. nov. and Keysercytheridae fam. nov.) are also evident in some higher taxa of crustaceans, molluscs and echinoderms (e.g., Baker et al., 1986; Turner, 1981, herein). Despite being quite rare, this is one very interesting aspect of these habitats, hence they may have had a long evolutionary history of adaptation. Finally, the homogeneity of the faunal inhabitants of wood falls, vents, and seeps off the American continent is in marked contrast to the highly endemic fauna described herein from the Northwestern Pacific. Hence, ostracods may show a biogeographical pattern similar to other taxa, in which the faunas found off the American continent are distinct from those in the Western Pacific (e.g., Van Dover et al., 2002; Ramirez-Llodra et al., 2007). However, given very limited data available for ostracods a comprehensive, global biogeographical study of the species inhabiting ephemeral habitats such as wood falls, vents and cold seeps must await the results of new observations.

Acknowledgments This is KuramBio publication # 29. We thank the German Ministry for Science and Education, the chief scientist and the crew of the KuramBio cruise for the logistics and support. We would like to thank Dr Enrico Schwabe for sending us the material. The first author wants to thank Hanyang and Eulji Universities (both in Seoul) for providing the facilities for the taxonomic work. S.N.B. is/was a postdoctoral fellow of CNPq (Processos nos. 400116/ 2013-8 and 374397/2013-9) and of the Alexander von Humboldt Foundation. We are thankful to Martin Angel for improving English, to the editors, Angelika Brandt and Marina Malyutina, and two anonymous referees for positive criticism.

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