Heterobranch Sea Slugs S.L. (Mollusca, Gastropoda) from the Southern Ocean: Biodiversity and Taxonomy

The Southern Ocean, located between Antarctica and the southern tips of South America, Africa and Australia, encompasses an immense area across the southern Atlantic, Pacific and Indian oceans with no clearly defined limits. For the purposes of studying marine heterobranch sea slugs, we consider the Southern Ocean to include all ocean areas located south of latitude 41ºS. South of this latitude we consider different areas and zones: the area of South America (Patagonia/Magellanic area), the island of Tasmania, the southern island of New Zealand, the subantarctic area (Falkland Islands, South Georgia Island, South Orkney Islands, South Sandwich Island, Bouvet Island, the islands of Crozet and Prince Edward, the Kerguelen Islands and Macquarie Island) and the area of Antarctica in which we consider 4 zones (Weddell Sea, West Antarctica, Ross Sea and East Antarctica). Reviewing all available references and unpublished data from the authors, in total, 392 species of Heterobranch sea slugs have been recorded to date in the Southern Ocean > 41ºS, with Nudibranchia standing out with 209 species and Cephalaspidea with 88 species. The marine heterobranchs of Tasmania (154 species) and southern New Zealand (120 species) have been well studied. Sea slug fauna of the Antarctic and Sub-Antarctic regions have been the subject of several partial studies, however there are still many gaps in knowledge across both areas. Eighty eight different species of sea slug have been recorded so far in strictly Antarctic waters (West Antarctica, 43 species; Weddell Sea, 48 species; Ross Sea, 51 species; East Antarctica, 42 species) while in the various subantarctic regions, there are 93 species (36 species from South Georgia, 17 species from South Orkneys, 11 species from south Sandwich, six species from Bouvet, ten species from Prince Edward and Crozet Islands, 15 species from Kerguelen, three species from Macquarie Island, 29 species from Falkland Islands and 71 species from the coast of South America). In the taxonomic section, for each of the species, the location and authors of the records are indicated, and for many of the species, interesting biological, taxonomic or biogeographic observations are also provided. The importance of sampling in underexplored areas is discussed, as well as greaterdepth sampling for a better understanding of the seaslugs of the Southern Ocean.