Sea cucumbers (Echinodermata, Holothuroidea) from the JR275 expedition to the eastern Weddell Sea, Antarctica

Abstract Thirty-seven holothuroid species, including six potentially new, are reported from the eastern Weddell Sea in Antarctica. Information regarding sea cucumbers in this dataset is based on Agassiz Trawl (AGT) samples collected during the British Antarctic Survey cruise JR275 on the RRS James Clark Ross in the austral summer of 2012. Species presence by site and an appendix of holothuroid identifications with registrations are included as supplementary material. Species occurrence in the Weddell Sea is updated to include new holothuroids from this expedition.


Introduction
The British Antarctic Survey (BAS) JR275 research cruise on the RRS James Clark Ross visited the Weddell Sea from February to March in 2012 as part of a core EvolHist (Evolutionary History of the Polar Regions) project. Prior to this expedition, the south-eastern Weddell Sea had been a relatively under sampled area on the Antarctic continental shelf, according to a gap analysis carried out by Griffiths et al. (2014). The eastern Weddell Sea is characterized by perennial sea ice cover and very large icebergs. The Filchner Trough is known to be an area responsible for generating the oxygen and nutrient-rich Antarctic Bottom Water (AABW), which helps drive oceanic circulation. By sampling benthic animals from the eastern Weddell Sea continental margin and slope and the deepened shelf basins of the Filchner Trough, the expedition aimed to collect specimens and associated data to investigate patterns of biodiversity and feed into biogeography and phylogeography studies of this important region of the Southern Ocean. Recording current biodiversity in the region is becoming increasingly urgent with the drastic decline in summer sea ice in the Weddell Sea over the last 5 years likely to have major implications for the marine ecosystem (Turner et al. 2020). Echinoids from JR275 were reported by Saucède et al. (2015) and the Asteroidea are included by Moreau et al. (2018).
This dataset reports holothuroid species occurrences and richness for individual Agassiz Trawls (AGTs) during the JR275 expedition and is provided for comparison with and updating of known lists of Weddell Sea and other Antarctic holothuroids.  provided a comprehensive overview of Antarctic sea cucumber species, listing 187 species (including 51 still undescribed at the time of that publication) along with cryptic species and synonymies indicated by mtDNA sequence data.  also reported 37 known species from shelf and slope depths in the Weddell Sea; here we add 11 new known species to this list for comparative depths (Table 5). The Weddell Sea is reported to be one of the most species-rich regions for holothuroids in Antarctica  Gutt et al. (2014) also provided the original dataset for earlier voyages by German research vessel Polarstern to the Weddell Sea, including the holothuroid identifications and distributions published by Gutt (1990Gutt ( , 1991a and subsequently referenced by O'Loughlin (2002), before further examination and revision by . The dataset itself has since been updated by Piepenburg (2019). O'Loughlin et al. (2016) also gave an overview of Antarctic holothuroids collected during the historic Discovery expeditions. This current paper continues to build on our knowledge of Antarctic holothuroids. This is a contribution to the SCAR (Scientific Committee on Antarctic Research) AntEco (State of the Antarctic Ecosystem) Programme.

Design description
The dataset was published through the AntOBIS which is the Antarctic Marine Node of the international OBIS and GBIF, as a contribution to the EU-Lifewatch ERIC (https://www.lifewatch.eu/). Regarding the dataset, the Integrated Publishing Toolkit of the SCAR Antarctic Biodiversity Portal was used (http://ipt.biodiversity.aq/), following the Darwin Core event core. The dataset was uploaded in the AntOBIS (Antarctic Ocean Biogeographic Information System) database, and the taxonomy was matched against the Register of Antarctic Marine Species, using the Taxon Match tool (http://www.marinespecies.org/rams/aphia.php?p=match). The dataset meets the Darwin Core requirements and was designed around this event-core schema.

Material and methods
Collecting equipment used on JR275 included an Agassiz trawl (AGT) and an Epibenthic Sledge (EBS) fitted with camera. This paper reports on the holothuroid specimens collected at 51 of the AGT sampling sites in the eastern Weddell Sea at depths of between ~400 and ~2,000 m, and a single test location at ~280 m depth off the South Orkney Islands (Fig. 1, Table 1). Weddell Sea deployments were mostly conducted along two transects, one running from south to north along the edge of the Filchner Trough and one running from west to east out of the Filchner Trough onto the shallower shelf. Over-deepened basins close to the Brunt Ice shelf were also sampled. At each site, three replicate AGT individual stations were taken and where the substrate was suitable a single EBS trawl was also conducted. EBS samples have not been examined for holothuroids at this stage and are not discussed further here, but this material is currently stored in the BAS collections in Cambridge, UK. The AGT used an inner mesh size of 1 cm, had a mouth width of 2 m, and was trawled at 1 knot for between 2 and 10 minutes depending on depth, substrate, and condition of animals in the initial catch. The deployment protocol was standardized and is outlined in full in the JR275 cruise report, available from the British Oceanographic Data Centre (https://www. bodc.ac.uk/resources/inventories/cruise_inventory/report/10598/). Live or early preservation images of specimens were taken on board the RRS James Clark Ross by Camille Moreau (Institut Universitaire Europeen de la Mer, Brest, France) with assistance from Melanie Mackenzie (Museums Victoria), James Rudd (BAS), and Douglas Hamilton (University of East Anglia) using a digital SLR Nikon D3X with 60 mm lens and flash rigging and Nikon D700 with 60 mm lens.
Preliminary identification of holothuroid material was carried out during the cruise by Melanie Mackenzie. DNA tissue samples (chiefly tentacle or tube foot subsamples) were taken by Melanie Mackenzie with assistance from Stuart MacMillan (BAS) for BOLD barcoding. A total of 190 specimens from 50 AGT stations (~15% of all specimens) were sampled during the cruise. DNA extractions of some Elpidiidae holothuroid specimens were conducted onboard by Jennifer Jackson (BAS) with assistance from Melanie Mackenzie using QIAGEN DNeasy Blood & Tissue molecular kit. Tissues samples of Peniagone specimens were also sent to Pamela Brannock at Auburn University and Rollins College in USA and a sample of Protelpidia was sent  to Akito Ogawa at the National Museum of Nature and Science in Japan for further genetic analysis. Holothuroid specimens were preserved in 96% undenatured and pre-cooled (at −20 °C) ethanol and subsequently transferred to −20 °C freezer for a minimum of 48 hours with rotation of containers to ensure full preservation of material. Material was sent on to Melanie Mackenzie and Mark O'Loughlin at Museums Victoria, in Australia, for further examination and determination using stereo and compound microscopes. New species of Apodida (as Synaptida) specimens from this collection were described in O' Loughlin et al. (2015a) and are reported in Table 5 and Suppl. material 1: Table S1 alongside determinations of the remaining sea cucumber samples from AGT trawls. Specimens were identified to species level where possible, and to higher taxonomic levels where species-level determinations could not be made. Determinations here are based on morpho-taxonomic methods. Future genetic and morphological work may lead to additions or changes.

AntaBIS Antarctic Biodiversity Information System; AntEco
State of the Antarctic Ecosystem; AntOBIS Antarctic Thematic Node of the Ocean Biogeographic Information System; BAS British Antarctic Survey; EvolHist Evolutionary History of the Polar Regions (a BAS core project); NHMUK British Museum of Natural History (registration number prefix NHMUK); NMV Museums Victoria, Australia, used with registration number prefix F.;

SCAR
The Scientific Committee on Antarctic Research.

Taxonomic coverage
Remarks. Miller et al. (2017) assessed and revised the phylogeny of extant Holothuroidea. Apodida was highlighted as a sister to the rest of Holothuroidea, the previously paraphyletic Aspidochirotida was split into Molpadida, Dendrochirotida, and Elasipodida (in part) and a new order, Holothuriida, was erected. For this paper, we follow the taxonomic groups put forward by Miller et al. (2017) Table 3. Presence-only matrix of sea cucumber species in AGT trawls on JR275, Stations 52 to 88 (only stations with holothuroids included).  Peniagone vignoni X X X X X X X X X X X X X X Protelpidia murrayi X X Rhipidothuria racovitzai X X X X X X X X Elpidiidae gen. indet.