Brittle stars from Southern Ocean (Echinodermata: Ophiuroidea)

The present biogeographic study on the ophiuroid fauna from the Southern Ocean (SO) contains an updated checklist, based on a compilation of all the published information provided for the Antarctic and sub-Antarctic regions as well as the information available in SCAR-MarBIN database. Faunal composition and geographical and bathymetric distribution are included. So far, 219 species have been recorded, of which 126 are endemic to the SO, 76 are exclusive to Antarctic waters, and 30 are exclusive to sub-Antarctic waters. This study corroborated the circumpolar and eurybathic character of the ophiuroid fauna of the SO, but some differences are discussed when considering shelf and deep-sea fauna in the whole SO, or in the Antarctic and sub-Antarctic regions separately. The biogeographic affinities of 17 areas considered in the SO are revised, based on a presence/absence datamatrix of the 219 species. This similarity analysis shows three main groups, two of them including sub-Antarctic areas and one for Antarctic areas. The faunal movement patterns between the main geographical connections have been based on historical site records of each species. These movements have a level of faunal exchange that exceeds that of other Antarctic benthic groups. Such movements are mainly from Antarctic and sub-Antarctic regions to the subtropical waters of South America, and from New Zealand and southern Australian waters to sub-Antarctic areas. In this context, the origin of the ophiuroid Antarctic fauna is discussed.