Rock sponges (lithistid Demospongiae) of the Northeast Atlantic seamounts, with description of ten new species

ABSTRACT Background: Lithistid demosponges, also known as rock sponges, are a polyphyletic group of sponges which are widely distributed. In the Northeast Atlantic (NEA), 17 species are known and the current knowledge on their distribution is mainly restricted to the Macaronesian islands. In the Mediterranean Sea, 14 species are recorded and generally found in marine caves. Methods: Lithistids were sampled in nine NEA seamounts during the scientific expeditions Seamount 1 (1987) and Seamount 2 (1993) organized by the MNHN of Paris. Collected specimens were identified through the analyses of external and internal morphological characters using light and scanning electron microscopy, and compared with material from various museum collections as well as literature records. Results: A total of 68 specimens were analysed and attributed to 17 species across two orders, seven families, and seven genera, representing new records of distribution. Ten of these species are new to science, viz. Neoschrammeniella inaequalis sp. nov., N. piserai sp. nov., N. pomponiae sp. nov., Discodermia arbor sp. nov., D. kellyae sp. nov., Macandrewia schusterae sp. nov., M. minima sp. nov., Exsuperantia levii sp. nov., Leiodermatium tuba sp. nov. and Siphonidium elongatus sp. nov., and are here described and illustrated. New bathymetric records were also found for D. ramifera, D. verrucosa and M. robusta. The Meteor seamount group has a higher species richness (15 species) compared to the Lusitanian seamount group (six species). The majority of the species had their distribution restricted to one seamount, and ten are only known from a single locality, but this can be a result of sample bias. Discussion: The number of species shared between the seamounts and the Macaronesian islands is very reduced. The same pattern repeats between the NEA and Mediterranean Sea. This study demonstrates that NEA seamounts are ecosystems with a higher diversity of lithistids than previously thought, increasing the number of lithistids known to occur in the NEA and Mediterranean Sea from 26 to 36 species.ACKNOWLEDGEMENTS. We dedicate this study to the memory of Hans Tore Rapp, sponge taxonomist and deep- sea explorer, and great colleague and friend of the authors, who sadly passed away before the manuscript publication. We would like to give a special thanks to the chief scientists Philippe Bouchet (Seamount 1) and Serge Gofas (Seamount 2), as well as to the captains, crew and all the scientists onboard of the expeditions Seamount 1 and Seamount 2 for the collection and preservation of the material. To Isabelle Domart-Coulon, curator of the MNHN Paris for hosting JRX and PC in the museum and making the material available for the present study. To Shirley Pomponi from the Harbour Branch Oceanographic Institute (Florida Atlantic University, USA) for sharing some material that was helpful to compare with Seamount 1 and 2 specimens. To Emma Sherlock and Ana Riesgo for hosting FCC at the NHM for the study of the lithistid collection of the museum. To Nicole de Voogd for hosting FCC at the Naturalis Biodiversity Center. To Irene Heggstad and Pedro Ribeiro for the support with the SEM and the map of the study area, respectively. To Christina Nagler and Daniel Kersken for the translations (from German) of several original species descriptions. We also thank the reviewers for their constructive comments to previous version of this manuscript. Lastly, we dedicate this study to all taxonomists and museum curators, who despite the many challenges, dedicate their efforts to discovering, identifying, describing, and documenting the diversity of our planet, and ensure proper archiving of biological specimens and associated scientific knowledge. This output reflects only the authors' views and the Executive Agency for Small and Medium-sized Enterprises (EASME) is not responsible for any use that may be made of the information it contains. FUNDING. The work leading to this publication has received funding from the European Union's Horizon 2020 research and innovation programme through the SponGES project (grant agreement no. 679849), and from the Norwegian Biodiversity Information Centre through the project number 70184219. Joana Xavier research is further supported by national funds through FCT Foundation for Science and Technology within the scope of UIDB/04423/2020 and UIDP/04423/2020. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. GRANT DISCLOSURES. The following grant information was disclosed by the authors: SponGES Project: 679849. Norwegian Biodiversity Information Centre: 70184219. Strategic Funding: UIDB/04423/2020 and UIDP/04423/2020. Foundation for Science and Technology (FCT). AUTHOR CONTRIBUTIONS. Francisca C. Carvalho conceived and designed the experiments, performed the experiments, analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the paper, and approved the final draft. Paco Cárdenas performed the experiments, authored or reviewed drafts of the paper, and approved the final draft. Pilar Ríos performed the experiments, authored or reviewed drafts of the paper, and approved the final draft. Javier Cristobo performed the experiments, authored or reviewed drafts of the paper, and approved the final draft. Hans Tore Rapp performed the experiments, authored or reviewed drafts of the paper, and approved the final draft. Joana R. Xavier conceived and designed the experiments, performed the experiments, analyzed the data, authored or reviewed drafts of the paper, and approved the final draft. DATA AVAILABILITY. The following information was supplied regarding data availability: Data is available at PANGAEA: Carvalho, Francisca C; Cárdenas, Paco; Rios, Pilar; Rapp, Hans Tore; Xavier, Joana R (2018): Lithistids from the Seamounts of the Northeast Atlantic Ocean. PANGAEA, DOI 10.1594/PANGAEA.896492. Specimens examined in this study are stored in the 'zoothèque' of the Muséum National d'Histoire Naturelle of Paris, France (MNHN). Specimen numbers and deposition information are available as a Supplemental File http://dx.doi.org/10.7717/ peerj.8703#supplemental-information. NEW SPECIES REGISTRATION. The following information was supplied regarding the registration of a newly described species: Publication LSID: urn:lsid:zoobank.org:pub:A0DA0236-4579-47A4-8BE4-E68803C2EC8F. Neoschrammeniella inaequalis sp. nov.: Urn:lsid:zoobank.org:act:8A516D9B-5351- 47AF-8EC2-7EBC44166D35. Neoschrammeniella piserai sp. nov.: Urn:lsid:zoobank.org:act:77F1F52E-28C9-43C0- A501-1ADAD03241A5. Neoschrammeniella pomponiae sp. nov.: urn:lsid:zoobank.org:act:2AA76193-B27E- 491E-8E50-FE591786FA26. Discodermia arbor sp. nov.: Urn:lsid:zoobank.org:act:7A732A92-8D8B-4D73-97B1- CD53E9494121. Discodermia kellyae sp. nov.: urn:lsid:zoobank.org:act:E7A06142-4AF7-404E-B369- B30240ADE5F4. Macandrewia schusterae sp. nov.: urn:lsid:zoobank.org:act:2BA2C1EF-8FAB-4C91- 89CB-DCB59DDA61EB. Macandrewia minima sp. nov.: urn:lsid:zoobank.org:act:E405AE49-5636-4778-9B07- ED39E9EBB7BE. Exsuperantia levii sp. nov.: urn:lsid:zoobank.org:act:24B5934A-4767-4429-B172- A649C4CE0D83. Leiodermatium tuba sp. nov.: urn:lsid:zoobank.org:act:041DAB82-B538-4EB9-A43A- 1E3E79B67CF8. Siphonidium elongatus sp. nov.: urn:lsid:zoobank.org:act:26B193F9-2588-4479-ACB2- 27AD1945DEE4