Deep-Sea Research I 90 (2014) 91–104

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Deep-Sea Research I

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Serpulids living deep: calcareous tubeworms beyond the abyss$

Elena K. Kupriyanova a,n, Olev Vinn b, Paul D. Taylor c, J. William Schopf d,e,f,g,h, Anatoliy B. Kudryavtsev e,g,h, Julie Bailey-Brock i a The Australian Museum, 6 College Street, Sydney, NSW 2010, b Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia c Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK d Department of Earth, Planetary, and Space Sciences, USA e Center for the Study of Evolution and the Origin of Life, USA f Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA g PennState Astrobiology Research Center, University Park, PA 16802, USA h University of Wisconsin Astrobiology Research Consortium, Madison, WI 53706, USA i Biology Department of Zoology, University of Hawaii at Manoa, 2538 McCarthy Mall, Honolulu, HI 96822, USA article info abstract

Article history: Although the carbonate compensation depth (CCD) for calcite, generally located in the depth range Received 17 December 2013 4000–5000 m, is often proposed as a physiological barrier to deep- colonization, many organisms Received in revised form with calcareous exoskeletons are found in the deepest oceanic trenches. Serpulid inhabiting 11 April 2014 unprotected calcareous tubes are unlikely deep-sea inhabitants, yet, they are found at all oceanic depths Accepted 15 April 2014 from intertidal to hadal. Here we review and revise the published and unpublished records of Available online 24 April 2014 from below 5000 m depth. We also describe tube ultrastructure and mineralogical content of available Keywords: deep-sea serpulid tubes to obtain insights into their biomineralisation. belonging to the genera Polychaeta Bathyditrupa, Bathyvermilia, Hyalopomatus, Pileolaria (spirorbin) and Protis were found at depths from Serpulidae 5020 to 9735 m. However, only specimens of Protis sp. were truly hadal (46000 m) being found at Abyssal 6200–9700 m. Hadal specimens of Protis have irregularly oriented prismatic tube microstructure similar Hadal Carbonate compensation depth to that found in more shallow-water representatives of the . Initial EDX analysis suggested a mostly Tube ultrastructure calcitic composition (i.e., the most stable CaCO3 polymorph) on the basis of high Mg levels. Surprisingly, Mineral composition however, tubes of Bathyditrupa hovei and a species of Protis analysed using the more reliable method of laser Raman spectroscopy were found to be composed of . The compensation depth for this less

stable CaCO3 polymorph in the is usually 2000–3000 m. We found no obvious structural adaptations to life at extreme depths in the studied serpulid tubes and how serpulids are able to biomineralise and maintain their tubes below the CCD remains to be explained. Crown Copyright & 2014 Published by Elsevier Ltd. All rights reserved.

1. Introduction (e.g., holothurians, and soft and organic-walled foraminifera, see Nozawa et al. (2006)). At 4000–5000 m there is the “Carbonate Calcium carbonate is widely used as a structural skeletal Compensation Depth” (CCD) at which calcium carbonate (calcite component by marine invertebrates, such as crustaceans, echino- and aragonite) supply equals the rate of dissolution (e.g., Bickert, derms, foraminiferans, corals and molluscs (e.g., Cuif et al., 2011). 2009). However, although the CCD has been commonly proposed Because carbonate solubility increases with increasing pressure, as a physiological barrier to deep-ocean colonization (e.g., biomineralisation becomes more difficult with increasing depth Blankenship-Williams and Levin, 2009), some bryozoans and and this has been proposed as an explanation (Jamieson et al., molluscs are found below these depths (e.g., Hayward, 1984: 2010) of why some groups with calcareous skeletons (e.g., ophiur- cheilostome bryozoans; Knudsen, 1970: bivalves; Leal and oids and echinoids) tend to be replaced by soft-bodied organisms Harasewych, 1999: cocculinid and pseudococculinid limpets). How species with external calcareous skeletons persist below the CCD remains one of the most intriguing questions of modern ☆Author contributions: EKK wrote most of the first draft of the manuscript, parts deep-sea biology. One obvious explanation is that these calcareous on biomineralisation were also written by OV and PDT, EKK and JBB are responsible exoskeletons do not come into direct contact with seawater, but for diagnoses and illustrations of deep-sea species, OV and PDT did SEM and EDX are protected by thick organic layers, the structure and composi- mineralogical analyses, JWS and AK did Raman mineralogical analyses. n Corresponding author. tion of which vary widely amongst organisms. The calcareous E-mail address: [email protected] (E.K. Kupriyanova). exoskeletons of molluscs typically are externally covered with an http://dx.doi.org/10.1016/j.dsr.2014.04.006 0967-0637/Crown Copyright & 2014 Published by Elsevier Ltd. All rights reserved. 92 E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 organic layer (periostracum) that could protect against carbonate Natural History Museum, London (NHMUK). Back-scattered elec- dissolution (Harper, 1997; Taylor and Kennedy, 1969), and crusta- trons were used to form images of these uncoated tubes. cean carapaces are covered with a thick epicuticle. Molluscs largely exposed to ambient seawater, such as scallops and oysters, 2.3. Mineralogical composition are not found in the lower abyssal zone. For example, the deep-sea oyster Neopycnodonte zibrowii (Gofas et al., 2009) occurs in a The elemental compositions of the deep-sea serpulid tubes were bathymetric range between 350 and 846 m (Van Rooij et al., 2010). determined using an Oxford Instruments X-max EDX detector Serpulid polychaetes inhabiting calcareous tubes that lack any attached to the LEO 1455-VP SEM at the NHMUK. The main objective external protective layers are the most unlikely inhabitants of the was to infer tube mineralogy using Mg and Sr as proxies for calcite deepest parts of the ocean. However, these sedentary suspension and aragonite, respectively. However, because the tubes were not feeders are found from intertidal to abyssal and even hadal depths flat, polished surfaces, these proxies proved to be unreliable. (e.g., Bruun, 1957; ten Hove and Kupriyanova, 2009; Kupriyanova Laser Raman spectroscopy was undertaken at the University of et al., 2011; Levenstein, 1973; Zibrowius, 1977). Vinn and California, Los Angeles (UCLA). Spectroscopic data were obtained Kupriyanova (2011) hypothesised that dense outer layers (DOL) using a T64000 triple-stage laser Raman system (JY Horiba, Edison, giving a smooth shiny appearance to the tube surface evolved as NJ, USA) with macro-Raman and confocal micro-Raman capabil- an adaptation to delay tube dissolution in waters of the deep-sea ities. A Coherent Innova 90 argon ion laser (Santa Clara, CA, USA) under-saturated with respect to calcium carbonate, but this idea provided several laser wavelengths in the blue-green region of the based on a very limited sample size still requires testing. visible spectrum. A single spectral window centred at 1400 cm–1 The deepest parts of the oceans (6000–11,000 m), known as the was employed. For the laser excitation used, at 488 nm, this gave ultra-abyssal (Belyaev, 1989) or hadal zone, are represented almost coverage from 140 to 2650 cm–1, a range containing all of the exclusively by trenches. To date, published records of serpulids major Raman bands of calcite and aragonite. For analysis, speci- from depths below 6000 m are very scarce. Zibrowius (1977), who mens were centred in the path of the laser beam projected reviewed serpulids from depths exceeding 2000 m, listed 25 through an Olympus BX41 microscope (Olympus, Center Valley, species, including only one unidentifiable specimen from the PA, USA). Typical laser power was 1–8 mW over a 1 mm spot, an Kermadec Trench collected at 6620–6730 m (Kirkegaard, 1956). instrumental configuration well below the threshold causing In his influential book on hadal faunas, Belyaev (1989), in addition radiation damage to specimens of the kind studied here. Point to the record of Kirkegaard (1956), listed two unidentified Serpu- spectra were obtained from various parts of the interior and lidae from 6410 to 6757 m (Aleutian Trench) and 9715–9735 m exterior surfaces of the serpulid tubes. (Izu-Bonin Trench), the latter being the deepest record for a serpulid. More recently, Kupriyanova et al. (2011) reviewed all previous reports of abyssal serpulids and provided new records 3. Results based on collections by the R/V “Vityaz”, including Bathyditrupa hovei Kupriyanova, 1993 from 6050 to 6330 m. 3.1. The aims of the current study are to review and revise published and unpublished records of serpulids collected below the CCD The serpulid species found below 5000 m are summarized in (5000 m and deeper), and to address the question whether the tube Table 1. A short taxonomic account of these records with informa- ultrastructure and mineralogy of these calcareous tube-building tion on their tube ultrastructure is given below. polychaetes show functional adaptations to deep-sea habitats. Genus Bathyditrupa Kupriyanova, 1993a

2. Material and methods Remarks. This monotypic genus appears to be closely related to Nogrobs grimaldii (Fauvel, 1909), an unusual serpulid living 2.1. Taxonomic composition unattached in quadrangular in cross-section tubes coiled into tight spirals (hence the original name Spirodiscus) that was originally The serpulids used in this study were mostly collected during collected from lower bathyal depths off the Azores (reviewed in various cruises of the R/V “Vityaz” organized by the P.P. Shirshov Kupriyanova and Nishi (2011)). A worldwide revision of the Bath- Institute of Oceanology (SIO) of the Russian Academy of Sciences yditrupa/Nogrobs (Spirodiscus?) complex is currently underway between 1955 and 1973 and deposited in the research collection of (Kupriyanova and Ippolitov, in preparation). that institution. Two samples from the SIO collection were depos- Bathyditrupa hovei Kupriyanova, 1993a ited at the Netherlands Centre for Biodiversity Naturalis, Leiden Bathyditrupa hovei – Kupriyanova, 1993a:21–23, fig. 1; ten (NCB Naturalis). Material of the spirorbin Pileolaria levensteinae Hove and Kupriyanova, 2009: 29, fig. 9; Kupriyanova et al., 2011: described by one of us (JBB) is deposited in the Smithsonian 46–48, figs. 2 and 3. Institution, DC, USA (USNM). The material was initially Material. SIO, R/V ‘Vityaz’ St. 4370, 6080 m (1 specimen); examined by the senior author (EKK) at SIO and was borrowed for St. 7391, 6330 m (3 specimens); St 5620, 5070 m (11 specimens); detailed examination at the Australian Museum (AM). St. 5622, 5110 m (2 specimens, including the holotype); St. 5624, Selected specimens were photographed with a Nikon 4300 Coolpix 5020 m (2 specimens); St. 6015, 5850 m (1 specimen). camera mounted on a Leica MZ8 stereomicroscope at the AM. Speci- NCB Naturalis, R/V “Vitayz” St. 3151, 5237 m (3 tubes), registra- mens were dehydrated in ethanol, critical-point dried, covered with a tion number ZMA V.Pol. 5326. 20 mm coating of gold and examined under a Leo 435VP scanning Diagnosis. Operculum inverse conical, with brown chitinous electron microscope at the AM. Terminology in taxonomic diagnoses endplate, flat or slightly concave. Opercular ampulla gradually follows that from ten Hove and Kupriyanova (2009). merges into thick, rather triangular in cross-section peduncle with pinnules, but without wings. Peduncle inserted as second 2.2. Tube ultrastructure dorsal on one side. Five thoracic chaetigerous segments, including 4 with uncini. Thoracic membranes ending at 2nd Natural and fractured surfaces of clean serpulid tubes were thoracic segment. Collar chaetae limbate. Apomatus chaetae absent. studied for tube ultrastructure using a Leo 1455-VP SEM at the Thoracic uncini saw-to-rasp-shaped, with up to 4 (?6) teeth in a E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 93

Table 1 Serpulid polychaetes from below 5000 m.

R/V Station Latitude Longitude Depth, m Species Reference

Albatross 342 0110300″N1814000″W 5250–5300 Protis arctica Zibrowius (1969) Albatross 373 2812500″N6110500″W 5500–5987 Bathyvermilia langerhansi Zibrowius (1973) Challenger 244 3512200″N16915300″E 5307 Bathyvermilia challengeri Zibrowius (1973) Challenger 253 3810900″N15612500″W 5719 Serpulidae gen. sp. B Zibrowius (1973) Galathea 650 3212000″S17615400″W 6620–6730 Serpulidae gen. sp. A Zibrowius (1977) Kurchatov 1242A 191006″N8012905″W 6800 Protis sp. Unpublished Vityaz 3114 4814301″N16015505″E 5670 Protis sp. Unpublished Vityaz 3151 4410902″N17010700″E 5237 Bathyditrupa hovei Kupriyanova et al. (2011) Vityaz 3156 3915700″N16510705″E 5535 Bathyvermilia challengeri Kupriyanova et al. (2011) Vityaz 3232 3311800″N14914504″E 6096 Pileolaria levensteinae Bailey-Brock and Knight-Jones (1977) Vityaz 3363 4811404″N16913902″E6272–6282 Protis sp. Unpublished Vityaz 3456 3415100″N14914600″E 6056 Bathyvermilia sp. Unpublished Vityaz 3494 2910902″N14215301″E 9715–9735 Protis sp. Belyaev (1989) Vityaz 3499 2512701″N14312201″E 4892–5022 Bathyvermilia challengeri Kupriyanova et al. (2011) Vityaz 4074 4011900″N17514500″W 6065 Hyalopomatus sp. Bailey-Brock (1974) Vityaz 4074 4011900″N17514500″W 6065 Pileolaria levensteinae Bailey-Brock and Knight-Jones (1977) Vityaz 4370 2610401″N15314902″E 6080 Bathyditrupa hovei Kupriyanova et al. (2011) Vityaz 5620 4414800″N15613300″E 5070 Bathyditrupa hovei Kupriyanova (1993a) Vityaz 5620 4414800″N15613300″E 5070 Protis polyoperculata Kupriyanova (1993a) Vityaz 5622 4511400″N15511500″E5110 Bathyditrupa hovei Kupriyanova (1993a) Vityaz 5622 4511400″N15511500″E5110 Protis polyoperculata Kupriyanova (1993a) Vityaz 5623 4512600″N15415900″E 5045 Protis polyoperculata Kupriyanova (1993a) Vityaz 5624 4512600″N15411200″E 5020 Bathyditrupa hovei Kupriyanova (1993a) Vityaz 5632 4314400″N14915200″E 8240–8345 Protis sp. Unpublished Vityaz 5937 012000″N17915200″W 5480 Pileolaria levensteinae Bailey-Brock and Knight-Jones (1977) Vityaz 6015 2615103″N16513201″E 5850 Bathyditrupa hovei Kupriyanova et al. (2011) Vityaz 6255 3313400″N16812000″E 5581 Pileolaria levensteinae Bailey-Brock and Knight-Jones (1977) Vityaz 6334 1110601″S1591000″W 5240–5300 Bathyvermilia challengeri Kupriyanova et al. (2011) Vityaz 7391 2410802″N14314601″E 6330 Bathyditrupa hovei Kupriyanova et al. (2011) row above peg, with about 15 curved teeth in a row in profile. Diagnosis. Operculum inverted cone covered with simple, Anterior peg flattened gouged. Abdominal chaetae all capillary, almost flat calcareous distal plate; peduncle circular in cross- posterior ones slightly longer; abdominal uncini rasp-shaped. section, smooth, not thicker than other ; slightly enlarged Tubes. White opaque, free, curved, not coiled, rectangular in distally; constriction present. Thoracic membranes ending at 4th cross-section without peristomes. Irregularly oriented prismatic chaetiger. Seven thoracic chaetigers, including six with uncini. microstructure (IOP, Fig. 1A, B) sensu Vinn et al. (2008). Collar chaetae limbate, no special chaetae. Apomatus chaetae Distribution. North and Central Pacific Ocean, abyssal (4104– present in posterior thoracic chaetigers. Uncini saw-shaped with 6330 m). seven teeth, anterior fang simple pointed. Anterior uncini similar Remarks. This abyssal species building very characteristic tusk- to thoracic ones, posterior abdominal uncini rasp-shaped. Abdom- shaped tubes was originally described from 5050 to 5620 m in the inal chaetae flat narrow geniculate with blunt teeth anteriorly, Kurile-Kamchatka Trench and later recorded and redescribed from replaced by long capillary chaetae posteriorly. other abyssal localities of the Pacific Ocean by Kupriyanova et al. Tubes. White opaque, with very regularly closely arranged (2011). smooth ridges (Fig. 1C). The analysed tube fragment had an Genus Bathyvermilia Zibrowius, 1973 angular crystal homogeneous structure microstructure (ACH, Remarks. ten Hove and Kupriyanova (2009) listed five bathyal Fig. 1D, E) sensu Vinn et al. (2008). and abyssal species in the genus, including three (B. challengeri Distribution. Mid-Pacific Ocean, abyssal (4246–5719 m) and Zibrowius, 1973, B. kupriyanovae Bastida-Zavala, 2008, and B. Johnston Atoll (about 1400 km west of Hawaii), 350 m. zibrowiusi Kupriyanova, 1993b) from the Pacific Ocean and two Bathyvermilia langerhansi (Fauvel, 1909) (B. islandica Sanfilippo, 2001, and B. langerhansi (Fauvel, 1909)) langerhansi – Fauvel, 1909:61–62, fig. 6a–d. from the . Kupriyanova and Nishi (2010) added Vermiliopsis sp. – Eliason, 1951: 142, Plate I, figs. 7 and 8. another species from the Gulf of by transferring Vermiliopsis Bathyvermilia langerhansi – Zibrowius, 1973:431–435, fig. 2; (?) eliasoni Zibrowius, 1970 to Bathyvermilia. Zibrowius, 1977: 292 (name only). Bathyvermilia challengeri Zibrowius, 1973 Material. Naturhistoriska Museet, Goteborg,̈ Swedish Deep-Sea Placostegus ornatus – McIntosh, 1885: 522–524, pl. 55, Expedition, R/V “Albatross” St. 373, 5500–5987 m (1 specimen: figs. 5 and 6, pl. 30A, figs. 25–27. anterior fragment and tube fragment, not examined), registration Not Placostegus ornatus (Sowerby MS) Morch,̈ 1863 (fide number NMG 11015. Zibrowius, 1973). Diagnosis (modified from Zibrowius, 1973: 433). Operculum Bathyvermilia challengeri – Zibrowius, 1973: 428–430, fig. 1a–d; inverted cone covered with concave chitinous endplate encrusted Kupriyanova et al., 2011:49–50, fig. 4. with calcareous deposits; peduncle circular in cross-section, Material. SIO, R/V “Vityaz” St. 6334, 5240 m (1 specimen); slightly enlarged distally; constriction present. Thoracic mem- St. 3499, 4892–5,022 m; St. 3156, 5535 m (tube only). branes ending at 3th chaetiger. Seven thoracic chaetigers, includ- Natural History Museum, London, R/V “Challenger” St. 244, ing six with uncini. Collar chaetae limbate, no special chaetae. 5307 m (paratype: 1 specimen and tube fragment, not examined), Apomatus chaetae present in posterior thoracic chaetigers. Uncini registration number BMNH 1885.12.1.411; St. 253, 5719 m (para- saw-shaped with six teeth, anterior fang simple pointed. Anterior type: tube fragment, not examined), registration number BMNH uncini with 6–7 teeth, similar to thoracic ones, posterior abdom- 1885.12.1.412. inal uncini rasp-shaped. Abdominal chaetae flat narrow geniculate 94 E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104

Fig. 1. Tubes of deep-sea serpulid tubes. A – Bathyditrupa hovei (R/V “Vityaz” St. 7391, 6330 m), analysed tube fragment; B – irregularly oriented prismatic (IOP) tube structure, external surface. C – Bathyvermilia challengeri (R/V “Vityaz” St. 6334, 5200 m), analysed tube fragment with typical closely arranged ridges; D – angular crystal homogeneous structure (ACH) tube microstructure of fractured tube wall; E – angular crystal homogeneous structure (ACH) tube microstructure of tube surface. Scale: A, C – 500 mm, B, D – 10 mm, E – 50 mm. with blunt teeth anteriorly, replaced by long capillary chaetae radioles. Seven thoracic chaetigers, including 6 with uncini. Collar posteriorly. chaetae limbate, no special chaetae. Posterior thoracic chaetigers Tubes. White, smooth, thick and hard, with bright surface, sub- (6th and 7th) with Apomatus chaetae. Thoracic uncini with large triangular in cross-section, upper has rather flat and wide, with pointed anterior fang. Abdominal chaetae short with triangular median keel. Not available for analysis of ultrastructure and blade, one per fascicle, replaced by long capillary chaetae poster- mineralogical content. iorly. Length 7.6 mm, including length of branchia 2.6 mm. Distribution. North Atlantic, off Azores, 4020 m; south-east of Tubes. Not available for analysis of ultrastructure and miner- Bermuda, 5500–5985 m. alogical content. Remarks. The specimen was examined and revised by Remarks. Specific attribution is uncertain because the material Zibrowius (1973). is in poor condition and is embedded in permanent slides, making Bathyvermilia sp. SEM examination impossible. Material. SIO, R/V “Vityaz” St. 3456, 6056 m (1 specimen), on Genus Hyalopomatus Marenzeller, 1878 siliceous rock chips. Remarks. The genus comprises 13 species known mainly from Diagnosis. Operculum inverted cone covered with white deli- bathyal and abyssal depths (ten Hove and Kupriyanova, 2009; cate calcareous endplate. Opercular peduncle smooth, non-pinnu- Sanfilippo, 2009). Crenulated uncinal pegs (visible in SEM micro- lated, with numerous constrictions. Nine or ten pairs of branchial graphs) is a clear synapomorphy for the genus Hyalopomatus E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 95

(Kupriyanova et al., 2010). Six thoracic chaetigers and a vesicular limbate and fin-and-blade with distal blade not separated from operculum on smooth (usually thin) peduncle make Hyalopomatus basal denticulate fin by a gap. Apomatus chaetae in posterior relatively easily distinguished from other serpulid genera, but the thoracic chaetigers. Thoracic uncini saw-shaped with 7 teeth; species within the genus Hyalopomatus are very similar abdominal uncini rasp-shaped with 7–9 teeth arranged in 2–3 morphologically. rows. Abdominal chaetae flat geniculate, with finely denticulate Hyalopomatus sp. distal blade. Hyalopomatus marenzelleri–Bailey-Brock, 1974:25–26. Tubes. White, opaque, thick, without peristomes, circular in Material. SIO, R/V “Vityaz”, St. 4074, 6065 m (2 specimens). cross section, with rugose surface; attached to substrate only Diagnosis. Operculum round bladder-like, inner mass visible, basally only, distal part free. Not available for analysis of ultra- situated intermediate between bladder and peduncle. Opercular structure and mineralogical content. peduncle without wings, but obvious middle and lateral parts. Distribution. Kurile-Kamchatka Trench, 4500–5100 m. Radioles long (8 or 7 on each side). Six thoracic segments, Remarks. The species is unique in having multiple soft globular including 5 with uncini. Collar chaetae fin-and-blade plus limbate. opercula on normal radioles. Apomatus chaetae absent. Abdominal chaetae very long with Protis sp. geniculate tip. Thoracic uncini with about 20 teeth, anterior peg Serpulidae gen. sp. – Levenstein, 1973: 130; Belyaev, 1989: 181. crenulated. Material. SIO, R/V “Kurchatov” St. 1242 A, 6800 m (1 specimen). Tubes. Straight, chitinous yellow at origin, becoming calcareous SIO, R/V “Vityaz”, St. 3114, 5670 m (3 specimens); St. 3363, 6272– and of larger diameter distally. Tubes were not available for studies 6,282 m (1 specimen); St. 3494, 9715–9,735 m (1 specimen); of ultrastructure and mineralogy. St. 5632, 8300 m (1 operculum and abdomen). Remarks. Specific attribution is uncertain because the material Tubes. White opaque, circular in cross-section, with indistinct is in poor condition and is embedded in permanent slides, making growth lines. Tubes of all examined specimens have an irregularly SEM examination impossible. oriented prismatic (IOP) microstructure (Figs. 2A–E, 4E, F, 6C, D) Genus Protis Ehlers, 1887 sensu Vinn et al. (2008). Generic diagnosis. Operculum absent or one or more membra- Remarks. Five specimens from depths of 5670–9,700 m are nous globular operculum/a on normal pinnulate radiole. Six or seven briefly characterised and illustrated below. They all fit the diag- thoracic chaetigers, including five or six with uncini respectively. nosis of Protis except for rasp-shaped thoracic uncini of specimen Thoracic membranes ending at mid-thorax to end of thorax, or even C (R/V “Kurchatov” St. 1242 A, 6800 m) and nearly simple limbate forming apron. Collar chaetae fin-and-blade and limbate. Apomatus collar chaetae in the deepest specimen (R/V “Vityaz” St. 3494, chaetae present. Thoracic uncini saw-shaped with about 6–8 teeth, 9700 m). It is unclear whether these specimens belong to the same fang simple pointed. Abdominal chaetae flat narrow geniculate with or several, possibly undescribed species. rounded teeth. Abdominal uncini all rasp-shaped, with 6–8teethin The tiny (2 mm in total length including radioles), likely profile, approximately 6–9 teeth in a row above pointed fang. juvenile, specimen A from R/V “Vityaz” St. 3494, 9700 m is in poor Remarks. The taxonomy of the genus Protis is difficult because condition. Its tube is transparent yellowish, organic, with only the chaetae, uncini, and tubes are very similar and opercula, when distal part calcified (Fig. 2). No details of collar and thoracic present, are mostly undifferentiated. Both operculate and non- membranes are available. Operculum is absent, six thoracic chae- operculate species are found and the latter are often confused with tigerous segments, 5 of which are with uncini (Fig. 3A), and about . ten Hove and Kupriyanova (2009) listed 7(6?) species from 15 abdominal segments. Collar chaetae are nearly simple limbate abyssal and bathyal localities. Most recently, Rzhavsky et al. (2013) (Fig. 3B), thoracic Apomatus chaetae are present (Fig. 3C). Abdom- introduced Protis akvaplani that is clearly distinct in having only inal chaetae are long, nearly capillary, tips with several widely six thoracic chaetigerous segments and short thoracic membranes spaced blunt teeth (Fig. 3E). Thoracic uncini are saw-shaped (some ending after 3rd thoracic chaetiger. As a result, Rzhavsky et al. saw-to-rasp shaped, with a dental formula of F:1:1:1:1:2:2:2) with (2013) emended the diagnosis of Protis given by ten Hove and about 7 teeth (Fig. 3D), abdominal uncini are rasp-shaped and Kupriyanova (2009) to include these features. about 9 teeth in profile and 2–3 rows above pointed anterior fang Protis arctica Hansen, 1882 (Fig. 3F). Protula arctica – Hansen, 1882: 13. Specimen B from R/V “Vityaz” St. 5632, 8300 m has a semi- Protis arctica – Zibrowius, 1969:15–17, fig. 6a and b; Zibrowius, transparent organic tube basally that is covered with a calcareous 1977: 296; Kirkegaard, 1982:257,fig. 2a–c; Ben-Eliahu and Fiege, overlay distally (Fig. 4A, E, F). The body is represented only by the 1996:19–24, figs. 8, 9A, B, and 10c; Kupriyanova and Jirkov, 1997: operculum on a pinnulated peduncle (Fig. 4A) and the abdomen; 221–222, fig. 8, map. 8. therefore, the structures of the thoracic chaetae and membranes, Material. Naturhistoriska Museet, Goteborg,̈ Swedish Deep-Sea as well as the number of thoracic segments, remain unknown. Expedition, R/V “Albatross” St. 342, Romanche Deep, 5250–5300 m Abdominal chaetae and uncini are typical for the genus Protis (1 specimen, not examined). (Fig. 5B–D). Distribution. Arctic to Central Atlantic, Mediterranean. Specimen C from R/V “Kurchatov” St. 1242A, 6800 m lacks the Remarks. The species was re-described in detail by Zibrowius operculum, has seven thoracic chaetigerous segments, including (1969), Ben-Eliahu and Fiege (1996) and Kupriyanova and Jirkov six with uncini (Fig. 5A–C), both simple and fin-and-blade collar (1997). The specimen from Romanche Deep lacking radiolar crown chaetae (Fig. 5D), and Apomatus chaetae starting from 4th thoracic was checked and attributed to P. arctica by (Zibrowius, 1969: 16). chaetiger (Fig. 5C, E). Thoracic membranes end at 4th thoracic Protis polyoperculata Kupriyanova, 1993a chaetiger (Fig. 5A). Thoracic uncini are rasp-shaped, with about Protis polyoperculata–Kupriyanova, 1993a:26–2, fig. 3. 6 teeth in profile, 3–4 rows above pointed fang, abdominal uncini Material. SIO, R/V “Vityaz” St. 5620, 5070 m (3 specimens); St. (Fig. 5F) are also rasp-shaped, about 6 teeth in profile, 3–4rows 5622, 5100 m (5 specimens); St. 5623, 5045 m (2 specimens). above pointed fang. Abdominal chaetae are flat, narrow geniculate Diagnosis (modified from Kupriyanova 1993: 26–27). Up to six with rounded teeth (Fig. 5G). globular, almost transparent opercula borne on normal radioles. Specimen D from R/V “Vityaz” St. 3363, 6300 m (Fig. 6)is Collar trilobed with deep lateral incisions. Thoracic membranes represented by a fragmented calcified tube (Fig. 6A–D) and two reaching end of thorax where forming ventral apron. Seven thoracic and two abdominal fragments, without operculum, the thoracic chaetigers, six of them with uncini. Collar chaetae simple structures of the thoracic chaetae and thoracic membranes, as well 96 E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104

Fig. 2. Tube of Protis sp. A (R/V “Vityaz” St. 3494, 9700 m). A – tube with specimen removed, showing the inner organic transparent layer and the outer partially calcified distally only; B – calcareous tube wall at the tube mouth; C – partially dissolved calcareous tube wall of Protis sp. showing exposed inner organic tube lining; D – tube surface about 900 mm proximal of the mouth; E – tube surface about 900 mm proximal of distal-most tube collar. Scale: A – 1 mm, B – 100 mm, C – 200 mm, D – 10 mm, E – 20 mm. as the number of thoracic segments, remains unknown. Collar rows above pointed fang (Fig. 7H). Abdominal chaetae long, tips flat chaetae are limbate and fin-and-blade (Fig. 6E), thoracic Apomatus with blunt teeth (Fig. 7C), posterior chaetae nearly capillary (Fig. 7F). chaetae are present (Fig. 6F). Thoracic uncini are saw-shaped, with Subfamily Spirorbinae Chamberlin, 1919 about 6 teeth in profile (Fig. 6H). Abdominal are uncini (Fig. 6I) Remarks. Because recent phylogenetic data indicate that the rasp-shaped, about 6 teeth in profile, 2–3 rows above pointed fang. former Spirorbidae is a clade nested inside Serpulidae (e.g., Abdominal chaetae are with flat narrow, slightly geniculate tips Kupriyanova et al., 2006; Lehrke et al., 2007), spirorbins are now with rounded teeth (Fig. 6G). treated as subfamily Spirorbinae and their traditionally recognized The material from St. 3114, 5670 m (Fig. 7) is represented by subfamilies are have been lowered to the tribes Paralaeospirini, three specimens in tubes, which are chitinous yellow at origin, but Spirorbini, Circeini, Romanchellini, Pileolariini, and Januini calcified for most of their length. The specimens lack opercula, with (Rzhavsky et al., 2013). seven thoracic chaetigers, six of which with uncini (Fig. 7A, B). Genus Pileolaria Claparède, 1868 Thoracic membranes extend to 5th chaetiger (Fig. 7B). Collar chaetae Diagnosis. Tube opaque, non-porcellaneous, always sinistral. are fin-and-blade and limbate (Fig. 7D). Apomatus chaetae are Thoracic membranes not fused dorsally. Opercular brood chamber present in posterior thoracic segments (Fig. 7E). Thoracic uncini a deeply invaginated sac totally enclosing embryos except for a saw-shaped with 6–7 teeth and pointed anterior fang (Fig. 7G), pore capable of opening and closing. Collar chaetae fin-and-blade, abdominal uncini rasp-shaped with about 6 teeth in profile, 2–3 with a gap between distal blade and proximal fin. Three thoracic E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 97

Fig. 3. SEM of Protis sp. A (R/V “Vityaz” St. 3494, 9700 m). A – lateral view of thorax; B – collar chaetae; C – thoracic chaetae; D – thoracic uncini; E – abdominal chaetae; F – abdominal uncini; G – ventro-lateral view of the specimen. Scale: A – 50 mm, B, E – 5 mm, C – 10 mm, D, F – 2 mm, G – 100 mm.

chaetigers, including two with uncini. Apomatus chaetae in 3rd Diagnosis (modified from Bailey-Brock and Knight-Jones, thoracic fascicles. Larvae with a single attachment gland. 1977). Operculum with a relatively long thin peduncle up to a Pileolaria levensteinae Bailey-Brock and Knight-Jones, 1977 third of length of . Juvenile opercular endplate slightly Pileolaria levensteinae Bailey-Brock and Knight-Jones, 1977: concave with an eccentric talon. Adult operculum a thin-walled 317–318, fig. 1a–m. lightly calcified cup with a knob-like protrusion on one side. Material. USNM, R/V “Vityaz”, St. 3232, 6096 m (4 specimens, Fin-and-blade collar chaetae. Simple chaetae in second and third including the holotype and paratype); St. 4074, 6010–6,065 m chaetiger and sickle (Apomatus) chaetae in the third. Thoracic (2 specimens); St. 5937, 5480 m (1 specimen); St. 6255, 5581 m uncini with blunt peg and one or two rows of teeth in profile view. (1 specimen). Holotype registration number 53239, paratype 5340, Abdominal chaetae with angular “heel” and coarse serrations, other specimens' registration numbers 53241–53246. uncini small but broad. 98 E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104

Fig. 4. Photographs and SEM of chaetae and tube in hadal Protis sp. B. (R/V “Vityaz” St. 5632, 8240–8,345 m). A – photograph of operculum and partially dissolved tube; B, C – abdominal uncini; D – abdominal chaetae; E – analysed tube fragment; F – irregularly oriented prismatic (IOP) tube microstructure of external surface. Scale: A, E – 500 mm, B, F – 5 mm, C, D – 10 mm.

Tubes. White, sinistrally coiled, with transverse growth lines. referred to any of the recognized genera.” Zibrowius (1977) listed According to (Bailey-Brock and Knight-Jones, 1977: 317), “the it as the deepest serpulid record known at the time. whorls may lie closely attached to the substrate, the coil diameter Serpulidae gen. sp. B then being from 1 to 3 mm, or may coil one upon another, or may finally ascend with helical coiling for up to 6 mm.” Not available Placostegus benthalianus McIntosh, 1885: 524, fig. 7, pl. 30A, for studies of ultrastructure and mineralogy. fig. 28 Serpulidae gen. sp. A Serpulidae indet – Zibrowius, 1973: 435–436. Serpulidae gen. sp. – Kirkegaard, 1956:72;Zibrowius, 1977: 298. Material. Natural History Museum, London, R/V “Challenger” St. Material. Universitetets Zoologiske Museum, Copenhagen 253, 5719 m (several abdominal fragments extracted from tube (UZMC), R/V “Galathea” St. 650, Kermadec Trench, 6620–6,730 m fragments, not examined). (1 specimen, not examined). Remarks. The material was examined by Zibrowius (1973: Remarks. The material was examined by Zibrowius (1977: 436), who stated that “the species is too poorly known to be 298), who stated “tiny specimen, in poor condition, with tube placed in a genus. However, it is evident that it does not belong to fragments: tube white, with smooth surface but not bright, the genus Placostegus. The abdominal setae and uncini rather circular in cross-section and with small simple peristomes evenly closely resemble those of Bathyvermilia challengeri”. spaced out; worm about 2 mm long, tuft without operculum, 5 thoracic chaetigerous segments and about 17–20 abdominal 3.2. Mineralogical composition of tubes segments; thoracic sickle setae present but no special collar chaetae, abdominal setae capillary, not limbate; thoracic and Although EDX results detected an Mg peak in Bathyditrupa abdominal uncini rasp-shaped with about 12 teeth in side view, hovei from the Izu-Bonin Trench (R/V “Vityaz” St. 7391, 6330 m), anterior tooth simple, not bifurcate. The specimen cannot be suggesting calcite, laser Raman spectroscopy showed the tube to E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 99

Fig. 5. SEM of Protis sp. C (R/V “Kurchatov” St. 1242A, 6800 m). A – dorsal view of thorax showing length of thoracic membranes; B – ventral view of thorax; C – lateral view of thorax; D – collar chaetae; E – Apomatus chaetae; F – abdominal uncini; G – abdominal chaeta. Scale: A, B, C – 100 mm, D, E – 10 mm, E – 10 mm, F, G – 5 mm.

be aragonitic (Fig. 8). Another serpulid tube from slightly shal- ribs, valleys between these ribs and the interior of the tube. This is lower than hadal depths, Protis sp. from R/V “Vityaz” St. 3114 important in showing firstly the ability of Raman to detect calcite (5670 m), was also found using Raman to be aragonitic (Fig. 8). The in serpulid tubes as opposed to aragonite, and secondly, in Raman results for the two tubes are conclusive and show aragonite showing that not all deep-sea serpulids biomineralise aragonite. to be the biomineral forming both the inner and outer tube layers. The results of eight spot analyses on tubes belonging to three Lines corresponding to molecular and lattice vibrational modes are species are given in Table 2. well separated in the Raman spectra of calcite and aragonite (see Taylor et al., 2010). High-frequency bands corresponding to vibra- 2– tional modes of the carbonate anion CO3 are conspicuous, being 4. Discussion closely spaced at 1087 cm–1 for both calcite and aragonite, which makes distinction between the two minerals difficult. 4.1. Taxonomic composition of hadal serpulids However, additional bands at 283 cm1 and 717 cm1 for calcite and 208 cm1 and 705 cm1 for aragonite are clearly separated, In total, 29 records of 10 serpulid species are currently known which makes unequivocal a determination of tube mineralogy from depths of below 5000 m. Of these, 11 records representing at (Fig. 8). least 6 species originated from hadal depths of below 6000 m. Raman spectroscopic analysis of Bathyvermilia challengeri Pileolaria levensteinae is the only spirorbin serpulid so far known (Fig. 8) from a depth of 5240 m (R/V “Vityaz” St. 6334) found the from abyssal and upper hadal depths. According to the review by tube to consist of calcite based on spot analyses of the external Kupriyanova et al. (2011), non-spirorbin serpulids from depths 100 E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104

Fig. 6. SEM of Protis sp. D (R/V “Vitayz” St. 3363, 6387 m). A, B – tube fragments; C – middle of tube, external surface; D – fractured wall at tube mouth; E – collar chaetae; F – Apomatus chaetae; G – abdominal chaeta; H – thoracic uncini; I – abdominal uncini. Scale: A, B – 500 mm, C, D – 10 mm, E, H, I – 5 mm, F, G – 10 mm.

exceeding 2000 m belong to the genera Apomatus (Philippi, 1844), and Protis appear to be typical abyssal serpulid groups penetrating Bathyvermilia (Zibrowius, 1973), Bathyditrupa Kupriyanova, 1993, into the upper hadal zone, only formally breaking the 6000 m Hyalopomatus (Marenzeller, 1878), Protis (Ehlers, 1887), and Protula hadal barrier, while two truly hadal serpulid records (below (Risso, 1826). However, operculate Apomatus and non-operculate 7000 m) are those of the Protis specimens diagnosed herein. This Protula are often confused with operculate and non-operculate provides some support for the idea of Wolff (1953), who suggested Protis sp., so that some records of supposed Protula and Apomatus that the upper limit of the hadal zone might better be set at 6800– in the literature might in fact belong to Protis. It is not surprising 7000 m. Moreover, it agrees with the most recent classification that representatives of four of these genera are amongst the (Watling et al., 2013) that defines the hadal zone as starting at deepest-living serpulids. Bathyditrupa, Bathyvermilia, Hyalopomatus, 6500 m. E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 101

Fig. 7. SEM of Protis sp. E (R/V “Vityaz” St 3114, 5670 m.) A – dorso-lateral view of thorax; B – dorsal view of thorax showing thoracic membranes; C – anterior abdominal chaeta; D – collar chaetae; E – Apomatus chaetae; F – posterior abdominal chaetae; G – thoracic uncini; H – abdominal uncini. Scale: A, B – 500 mmC– 5 mm, D, E, F – 50 mm, H – 10 mm. 102 E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104

The tube of Bathyvermilia from 5240 m has a peculiar homo- geneous microstructure of angular crystallites. It is unclear whether this may be an adaptation to life in the deep sea, although the absence of such a microstructure in species of Protis from similar or greater depths does not support this idea.

4.3. Tube mineral composition and CaCO3 dissolution

Serpulids build their tubes of calcite, aragonite or a mixture of these two minerals (Smith et al., 2013; Vinn et al., 2008). Deep

ocean waters are under-saturated with respect to CaCO3 and corrosive to any carbonate skeletons exposed to these waters. Below the carbonate compensation depth (CCD; for calcite varying regionally from about 4000 to 5000 m) dissolution of calcium carbonate is very intense (Thurman and Trujillo, 2003). Of the two

mineral polymorphs of CaCO3 present in serpulids, calcite is the most stable. Indeed, the compensation depth for aragonite ranges between 500 and 3400 m (Berger, 1978), and is therefore sub- Fig. 8. Raman spectra of deep-sea serpulid tubes showing taxa-specific occur- stantially shallower than the CCD. Thus, one would expect to find rences of calcite and aragonite. only calcitic serpulids in the deep sea. Although EDX analyses found Mg peaks pointing to a calcitic composition in the tubes of Table 2 Protis sp. and Bathyditrupa hovei, the more reliable laser Raman Mineralogical composition of tubes of deep-sea serpulids. spectroscopic analysis detected only aragonite in Bathyditrupa hovei. Discovery of aragonite biomineralisation in B. hovei indicates Serpulid species and station Raman Location of analysis Mineralogy that serpulids are able to secrete and maintain this unstable spectrum no. biomineral at hadal depths. Furthermore, a specimen of Protis sp. Bathyditrupa hovei 4031 Tube exterior Aragonite from a slightly shallower depth (5670 m), still well below the CCD, R/V “Vityaz” St. 7391 4032 Tube exterior Aragonite was also found to have an aragonitic tube when analysed using 4033 Tube interior Aragonite laser Raman spectroscopy. (proximal end) The presence of calcareous serpulid worm tubes, and more Protis sp. 4034 Tube exterior Aragonite especially tubes composed of aragonite, in the deep sea below the “ ” R/V Vityaz St. 3114 4035 Tube interior Aragonite CCD poses questions about how these polychaetes are able to Bathyvermilia challengeri 4039 Rib on tube exterior Calcite biomineralise carbonate in such apparently unfavourable environ- R/V “Vityaz” St. 6334 4040 Valley between rib Calcite ments, and also how the tubes, once formed, can be maintained in on tube exterior the corrosive seawater. The deepest serpulid tube (Protis sp. from 4041 Tube interior Calcite 9700 m) is unusual in showing an extremely thin biomineralised layer present only in the distal (youngest) part of the tube (Fig. 2), with the inner organic tube layer being exposed more proximally 4.2. Tube ultrastructure through most of the length of the tube. It is likely that the older parts of the tube were progressively decalcified during the life of

Serpulids have a variety of different tube microstructures that the animal due to intense CaCO3 dissolution (Fig. 2A, C). However, have evolved since the appearance of serpulids in the Middle it remains unexplained as to how the animal succeeded in calci- (Ippolitov et al., 2014; Vinn et al., 2008; Vinn and Mutvei, fying at all at such an extreme depth in the face of the predicted 2009). The primitive serpulid tube microstructure appears to be an high energetic cost. irregularly oriented prismatic structure (IOP) and that is also the The presence of serpulids with mineralised tubes in the hadal most common serpulid tube microstructure. An IOP structure is zone is particularly surprising as their tubes are not externally also characteristic for the genus Protis (Vinn et al., 2008)(Fig. 4F). protected by an organic periostracum as in mollusc shells. Instead, Multilayered serpulid tubes often have an external layer made of the calcite or aragonite of the tube is open to the corrosive water of more compact crystals, forming so called dense outer layers, DOL the hadal zone. The lack of any organic protective outer layer, as sensu Vinn and Kupriyanova (2011). This outer dense layer has well as obvious microstructural adaptations, suggest that the been hypothesised to have a protective function against predators mechanism preventing or delaying tube dissolution is related to in shallow-water serpulids. Vinn and Kupriyanova (2011) also the organic matrix of the tube. Biological calcification is almost speculated that an outer dense layer in deep-sea serpulids may always controlled by polysaccharides or proteins, which act as serve as an adaptation to protect them against CaCO3 dissolution, templates or so-called matrix proteins (Rahman et al., 2011; based on the presence of similar outer tube layer structures in two Weiner and Hood, 1975) or catalyse certain pivotal reactions (e.g. remotely related deep-sea serpulid genera (Laminatubus and carbonic anhydrase (Jackson et al., 2007)). Tanur et al. (2010) Bathyvermilia). However, in the present study we did not find found that most of the soluble organic matrix of serpulid tubes is any peculiarities in tube ultrastructure of hadal specimens of composed of carboxylated and sulfated polysaccharides, whereas Protis. All examined specimens had single-layered tubes with IOP proteins form a minority component. Vinn et al. (2009) proposed a structure similar to shallower water representatives of the genus model of matrix-mediated biomineralisation in serpulids that (Vinn et al., 2008). Like tubes of Protis, examined tubes of suggests how the organic tube matrix (both soluble and insoluble Bathyditrupa hovei also have an IOP ultrastructure. Thus, living in components), synthesized under genetic control, is involved in the hadal conditions appears not to have resulted in any obvious biomineralisation of the inorganic components of the tube. This depth-related structural adaptations in the biomineralised tubes of mechanism is similar to that found in molluscs and arthropods Protis and Bathyditrupa. (e.g., Luquet, 2012; Saunders et al., 2011). E.K. Kupriyanova et al. / Deep-Sea Research I 90 (2014) 91–104 103

We anticipate that a thorough comparative investigation will Kirkegaard, J.B., 1956. Benthic Polychaeta from depths exceeding 6000 m. Galathea reveal important differences in the organic tube matrix of shallow Rep. 2, 63–78. Kirkegaard, J.B., 1982. New records of abyssal benthic polychaetes from the Polar and deep-sea serpulid tubes. Future studies should determine and Sea. Steenstrupia 8, 253–260. map the composition of both soluble and insoluble components of Knudsen, J., 1970. The systematics and biology of abyssal and hadal Bivalvia. the organic matrix in tubes of shallow-water serpulids and Galathea Rep. 11, 1–241. compare them with those from the deep-sea environments. Kupriyanova, E.K., 1993a. Deep-water Serpulidae (Annelida, Polychaeta) from the Kurile-Kamchatka Trench: 2. Genera Bathyditrupa, Bathyvermilia and Protis. A study of probably unique compounds identified in the hadal Zool. Zhur. 72, 21–28 (in Russian). tubes might provide insight into biomineralisation in the deep sea. Kupriyanova, E.K., 1993b. Deep-water Serpulidae (Annelida, Polychaeta) from the Kurile-Kamchatka Trench: 1. Genus Hyalopomatus. Zool. Zh. 72, 145–152 (in Russian). Kupriyanova, E.K., Jirkov, I.A., 1997. Serpulidae (Annelida, Polychaeta) of the Arctic – Acknowledgements Ocean. Sarsia 82, 203 236. Kupriyanova, E.K., Macdonald, T.A., Rouse, G.W., 2006. Phylogenetic relationships within Serpulidae (, Annelida) inferred from molecular and morpho- EKK thanks A.V. Gebruk and A.N. Mironov who hosted her visit logical data. Zool. Scr. 35, 421–439. to P.P. Shirshov Oceanology Institute. S. Lindsey (AM) helped with Kupriyanova, E.K., Nishi, E., 2010. Serpulidae (Annelida, Polychaeta) from Patton- Murray Seamount, Gulf of Alaska, North Pacific Ocean. Zootaxa 2665, 51–68. SEM. OV is indebted to the Sepkoski Grant (Palaeontological Kupriyanova, E.K., Nishi, E., Kawato, M., Fujiwara, Y., 2010. New records of Society), Estonian Science Foundation Grant ETF9064, Estonian Serpulidae (Annelida, Polychaeta) from hydrothermal vents of North Fiji, Pacific – Research Council Grant IUT20-34, and the target-financed project Ocean. Zootaxa 2389, 57 68. Kupriyanova, E.K, Bailey-Brock, J.H., Nishi, E., 2011. New records of abyssal and (from the Estonian Ministry of Education and Science) bathyal Serpulidae (Annelida, Polychaeta) collected by R/V “Vityaz”. Zootaxa SF0180051s08 for financial support. We thank H. ten Hove (the 2871, 43–60. Netherlands Centre for Biodiversity Naturalis, Leiden), Associate Kupriyanova, E.K., Nishi, E., 2011. New records of the deep-sea Nogrobs grimaldii (Serpulidae: Annelida). Mar. Biodiv. Rec. 4 (e74), 1–4. Editor A. Gooday, and an anonymous reviewer for their helpful Leal, J.H., Harasewych, M.G., 1999. Deepest Atlantic molluscs: hadal limpets reviews of the manuscript. (, , Cocculiniformia) from the northern boundary of the Caribbean Plate. Invert. 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