Sea spiders (Arthropoda, Pycnogonida) from ten recent research expeditions to the Antarctic Peninsula, Scotia Arc and Weddell Sea - data

Study Extent

The pycnogonids in this study were collected during 10 research cruises, over 13 years, in the area between 110°W - 5°E, and 50°N - 78°S. The samples were collected from different areas in the Southern Ocean, mainly the Weddell sea, South Orkney Islands, and the Western Antarctic Peninsula. Sampling took place during 10 expeditions on the RRS James Clark Ross, RV Polarstern and RRS Discovery. In total 197 stations sampled contained at least one pycnogonid. Sampling took place between 2007 and 2019.

Sampling

Sample Collection: The majority of the specimens were sampled using an Agassiz trawl (AGT) and an epibenthic sledge (EBS) with 165 AGT and 14 EBS deployments. The AGT had a mesh size of 1 cm and a mouth width of 2 m (except for JR17007 where the mouth was 1.25 m). AGTs were deployed to a depth of between 54 and 2279 m. The EBS had a suprabenthic- and an epibenthic net, both with a mesh size of 500 μm (cod-ends 300 μm). The epibenthic net extended from 27 cm to 60 cm above the bottom, with the suprabenthic net extending from 100 cm to 133 cm. The EBS was deployed as described by Brenke (2005) and was fitted with an open-closing mechanism so that the mouth of both nets were closed whenever the EBS was not in contact with the seafloor. EBSs were deployed to depths of between 436 and 5339 m. Both the AGT and EBS were deployed for approximately 10 minutes (trawling time) and at a speed of 1 knot. Pycnogonids were also recovered from Rauschert dredge (RD) deployments, once during PS118 and two occasions during both JR15005 and PS77. During PS118 and PS77 the RD mesh size was 1 mm, while a mesh of 500 μm was used on JR15005. The RD was deployed attached to the AGT with 5 metres of cable. Deployments were between 278.5 – 817 m. A bottom trawl was used during PS77, which was a 130ft trawl with a 10 mm herring codend. This was deployed 12 times at depths of between 223.5 and 486 m. The protocol for deployment of the BT was similar to that of the AGT but with slightly longer trawl times (approx 20 min). A single pycnogonid was recovered from a kelp raft that was recovered from the surface during JR15005.

Quality Control

- All records were validated. - Coordinates were plotted on map to verify the geographical location and locality. - All scientific names were checked for typo and matched to the species information backbone of Worlds Register of Marine Species (http://marinespecies.org/) and LSID were assigned to each taxa as scientificNameID. - Event date and time were converted into ISO 8601

Method steps

1. Sample Processing on deck: EBS – once gear was returned to deck, samples were sieved (300 μm) and/or transferred into precooled (-20°C) 96% ethanol, which were then stored at -20°C for at least 48 hours before further processing to avoid DNA degradation. After at least 48 hours samples were sorted to the lowest taxonomic level possible, counted and stored in 96% ethanol. AGT and BT – once on deck, samples were sorted to the lowest taxonomic level possible, counted, placed in precooled? 96% ethanol and stored at -20°C. All specimens recovered from the trawls during cruises on the RRS James Clark Ross were preserved in this way. It is not known if all specimens were kept on other cruises as sampling may have been selective. RD - The on deck protocol for the RD was the same as that for the EBS, unless specimens were large and immediately obvious, in which case these were separated straight away and transferred to percooled 96% ethanol and stored at -20°C. The kelp sample (Jr15005) was immediately sorted to the lowest taxonomic level possible, counted and stored in precooled 96% ethanol. Specimens remained in -20°C storage until returned to the UK. Once specimens were returned to British Antarctic Survey in Cambridge they were stored at ambient temperature.
2. Treatment of samples: Every specimen was examined using a stereoscope and identified down to the lowest taxonomic rank possible, using the taxonomic keys and original descriptions (e.g. Hodgson, 1907, Gordon, 1938, 1944, Fry &Hedgpeth, Child 1994, 1995). The majority of samples (1019) were identified by J. Maxwell at the University of Ireland Galway, with additional 50 samples identified by J. Domel at both British Antarctic Survey and in Ruhr-Universität Bochum. The online portal World Registry of Marine Species (WoRMS) was used to confirm acceptance of species names and the online Biodiversity Heritage Library was used to source many of the original descriptions. Where identification was inconclusive only genus or family names were assigned. The nomenclature used for these specimens followed Horton, et al. (2021). To further aid in identification, tissue samples were sent to BOLD to be barcoded using COI-5P REGION of the cytochrome C oxidase subunit I gene. These will be made publicly available in the future but if not available at time of reading, they can be requested from the corresponding author.
   All the BAS samples are on long term loan to J Maxwell. All samples from DY099 are stored in the Natural History Museum London. The holotype of any new species discovered within the BAS samples will be sent to the NHM London.

Pycnogonida were identified to at least genus or species.

1. Animalia
   rank: kingdom
2. Annelida
   rank: phylum
3. Arthropoda
   rank: phylum
4. Bryozoa
   rank: phylum
5. Echinodermata
   rank: phylum
6. Foraminifera
   rank: phylum
7. Mollusca
   rank: phylum
8. Platyhelminthes
   rank: phylum
9. Porifera
   rank: phylum
10. Chromista
    rank: kingdom
11. Gastropoda
    rank: class
12. Malacostraca
    rank: class
13. Pycnogonida
    rank: class
14. Thecostraca
    rank: class
15. Bivalvia
    rank: class
16. Crinoidea
    rank: class

The samples were collected from different areas in the Southern Ocean, mainly the Weddell sea, South Orkney Islands, and the Western Antarctic Peninsula.