First insights into the biodiversity and biogeography of the Southern Ocean deep sea.

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748-6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment.

Circumantarctic distribution in Southern Ocean benthos? A genetic test using the genus Macroscapha (Crustacea, Ostracoda) as a model.

The ostracod genus Macroscapha is used as a model to test theories predicting circumantarctic distribution of benthic species from the Southern Ocean. Earlier works on Antarctic Ostracoda reported five circumantarctic and/or eurybathic Macroscapha species. However, a recent taxonomic revision used a narrow morphological species definition and subdivided these five species into 20 morphospecies. Most of these narrowly defined species showed restricted depth and geographical distribution. Here, genetic markers are used to investigate the geographic and bathymetric distribution of seven species of the genus Macroscapha. The genetic results (especially COI, but partially also ITS) support more restricted geographical ranges and indicate more restricted depth distributions. Our results therefore corroborate the usefulness of a narrow morphological species definition. Our dataset also indicates that the 'genetic entities' of one species group (i.e. 'Mh. tensa-opaca') are not only geographically but also bathymetrically segregated. For that reason, a re-evaluation of the prevailing theories on the circumantarctic and eurybathic distribution of Southern Ocean benthic species is suggested.

Septemoecia a new genus of halocyprid ostracod (Myodocopa, Halocyprididae, Bathyconchoeciinae) for the seven-spined species formerly attributed to Bathyconchoecia.

The five species with seven large carapace spines that were previously assigned to the genus Bathyconchoecia are re-classified in a new genus Septemoecia. Septemoecia longispinata (Ellis, 1987) (new combination) is designated as the type species. The previously unknown adult female of S. georgei (Kornicker Rudjakov, 2004) (new combination) and adults of S. septemspinosa (Angel, 1970) (new combination) are described. Meristic and zoogeographical data are presented and a key to the species based on external carapace characters is provided.

Biogeography of Abyssocythere and Dutoitella (Ostracoda), with descriptions of three new species.

Ostracods have an extensive fossil record and are widely applied in palaeoenvironmental reconstructions. Here, we investigate the biogeography of two common and widespread genera, Abyssocythere and Dutoitella. Both appeared in the Cretaceous and are widely distributed in modern deep seas, but all species are restricted in distribution. The earliest record of Dutoitella is from shallow water, while the earliest Abyssocythere is from the deep sea. The Southern Ocean/Southern Atlantic seem to have been the area where both genera originated, and from which they eventually colonised other oceans. Dutoitella diversified into at least eleven species during Campanian-Eocene times, and by the end of the Eocene, the genus had spread to the Indian Ocean. This pattern continued after the establishment of the psychrosphere into the Neogene, with the development of numerous Miocene species. Abyssocythere, with 15 species, while also diversifying in the late Cretaceous South Atlantic, appears to have developed fewer species than Dutoitella. Finally, we describe three new species from the Southern Ocean (Abyssocythere bensoni sp. nov., Dutoitella karanovicae sp. nov. and Dutoitella richarddinglei  sp. nov.), re-illustrate the types of Abyssocythere squalidentata (Brady, 1880) and Dutoitella suhmi (Brady, 1880), and study the soft parts of the genus Dutoitella, which were previously undocumented.