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SUMMARY: The Joint Magellan "Victor Hensen" Campaign in 1994 focused on the biogeographic relationships of the Antarctic and Magellan fauna. The Peracarida and Mollusca sampled at 18 stations in the Beagle Channel by means of an epibenthic sledge were compared with the knowledge about the distribution of species data from the Falkland Islands, South Georgia, Antarctica and the Kerguelen. Peracarida were an important fraction of the macrobenthos and sampled in high numbers. About 105,000 individuals were collected with the epibenthic sledge. Until now about 40 species of Amphipoda, about 42 species of Isopoda, 24 species of Cumacea, eight species of Mysidacea, and 16 species of Tanaidacea were found. 118 mollusc taxa were identified, nine species of Aplacophora, 52 of Gastropoda, five of Scaphopoda and 52 of Bivalvia. Although the species present different distribution trends, the zoogeographic comparison for six larger taxa (four Mollusca and two Peracarida) showed that the species similarities decreased from the Magellan region towards the Falkland Islands and from South Georgia to Antarctica. The Magellanic Gastropoda showed similarities with the fauna of the Falkland Islands and South Georgia (31-37 %), whereas the Bivalvia were more similar to the Antarctic fauna (29 %). With regard to Crustacea, 10% of Antarctic Isopoda species were also found in the Magellan region; the Weddell Sea and East Antarctica, and South Georgia and the Antarctic Peninsula shared most species of both Cumacea and Isopoda, whereas the lowest similarities were shown between Bellingshausen and Weddell Sea for the Isopoda, and interestingly between the Magellan region and South Georgia for the Cumacea. The highest degree of endemism of the Isopoda and Cumacea was found in the Magellan region, where as a consequence of the opening of the Drake Passage many new species seem to have evolved in these taxa. -La campaña multidisciplinar realizada en el año 1994 a bordo del "Victor Hensen", se enfocó al estudio de las relaciones biogeográficas entre la fauna de la zona magallánica y la Antártida. Se compararon los datos obtenidos a partir del muestreo de peracáridos y moluscos llevado a cabo en 18 estaciones en el Canal del Beagle mediante un patín epibentónico, con los datos existentes sobre la distribución en las Islas Malvinas, Georgia del Sur, Kerguelen y la Antártida. Los peracáridos representaron una fracción importante del macrobentos y se muestrearon en grandes cantidades. Se colectaron alrededor de 105.000 especímenes con el patín epibentónico. Hasta ahora se han encontrado alrededor de 40 especies de anfípodos, cerca de 42 especies de isópodos, 24 especies de cumáceos, 8 especies de misidáceos y 16 especies de tanaidáceos. Se identificaron 118 taxones de moluscos, 9 especies de aplacóforos, 52 especies de gastrópodos, 5 especies de escafópodos y 52 especies de bivalvos. Aunque las especies presentaron patrones de distribución muy diferentes, la comparación zoogeográfica realizada con 6 taxones (4 moluscos y 2 peracáridos) muestra, en...

Abstract:The global zoogeographic distribution of the most widespread peracarid species occurring in three or more ocean basins below 2000 m is analysed. Basing on the published data we investigated 45 peracarid species, which have a most widespread distribution and most likely are cosmopolitan. Thirty−three species have a wide distribution in the Northern Hemisphere. Most species occur in the North Atlantic, however, 16 of these species occur also in the North Pacific, a more limited number of species occurs in the South Atlantic or South Pacific The Southern Ocean displays some special zoogeographic features and 22 widespread species occur there below 2000 m, including highly eurybathic ones. In total, 11 of the analysed species occur in all oceans. Eucopia australis (Lophogastrida), Munneury− cope murrayi (Isopoda) and Eurythenes gryllus (Amphipoda) are the species with the wid− est distributions. Other peracarids occurring in all oceans are: the isopods Paramunnopsis oceanica and Eurycope sarsi, the mysid Caesaromysis hispida the lophogastrid Eucopia unguiculata, the amphipod Mesopleustes abyssorum and the tanaids Exspina typica, Para− narthura insignis and Pseudotanais nordenskioldi. No cumacean species has been reported with an ocean−wide distribution but Campylaspis glabra occurs in the Atlantic, Indian and Pacific oceans. Among plenty of rare species in each order there are only few species with wide distribution records. There is evidence from molecular genetic studies that some of the widespread peracarids represent several cryptic species, however, some, e.g. Eucopia aus− tralis, seem to be truly cosmopolitan species. Geography of sampling is biasing our view of biogeography. The history and quality of taxonomic work as well as the reliability of geo− graphic records (quality control of large databases) limits our investigations of widespread or cosmopolitan species as much as the limited knowledge of variation within most species causes difficulties in defining morpho−species with certainty.

The following study was the Wrst to describe composition and structure of the peracarid fauna systematically along a latitudinal transect oV Victoria Land (Ross Sea, Antarctica). During the 19th Antarctic expedition of the Italian research vessel "Italica" in February 2004, macrobenthic samples were collected by means of a Rauschert dredge with a mesh size of 500 m at depths between 85 and 515 m. The composition of peracarid crustaceans, especially Cumacea was investigated. Peracarida contributed 63% to the total abundance of the fauna. The peracarid samples were dominated by amphipods (66%), whereas cumaceans were represented with 7%. Previously, only 13 cumacean species were known, now the number of species recorded from the Ross Sea increased to 34. Thus, the cumacean fauna of the Ross Sea, which was regarded as the poorest in terms of species richness, has to be considered as equivalent to that of other high Antarctic areas. Most important cumacean families concerning abundance and species richness were Leuconidae, Nannastacidae, and Diastylidae. Cumacean diversity was lowest at the northernmost area (Cape Adare). At the area oV Coulman Island, which is characterized by muddy sediment, diversity was highest. Diversity and species number were higher at the deeper stations and abundance increased with latitude. A review of the bathymetric distribution of the Cumacea from the Ross Sea reveals that most species distribute across the Antarctic continental shelf and slope. So far, only few deep-sea records justify the assumption of a shallowwater-deep-sea relationship in some species of Ross Sea Cumacea, which is discussed from an evolutionary point of view.