Ascidians (Tunicata, Ascidiacea): species distribution along the Scotia Arc.

TATIÁN, MARCOS; ANTACLI, JULIETA CAROLINA; SAHADE, RICARDO

SCIENTIA MARINA

INST CIENCIAS MAR BARCELONA

Lugar: Barcelona; Año: 2005 p. 205 - 214

0214-8358

Ascidians are found in all the oceans. The Polar Front is considered a strong barrier, especially for benthic organisms, separating the Southern Ocean from other oceans. Its influence on ascidian species present at the boundary of the Magellan and Antarctic regions along the Scotia Arc and on the species composition at each station is inferred from the samples taken during the "LAMPOS" cruise. Ascidians were collected by Agassiz (AGT) and bottom (GSN) trawls, at depths between 250-587 m, on different substrate types. Of 25 identified species/morphospecies one is new, and eight were found in new localities, enlarging the known range of five of these species. Muddy bottoms were found to support higher species richness than hard bottoms, and the South Georgia Islands are found to be the northward limit for Antarctic species and the southern limit for Magellan ones. Affinity between the ascidian fauna from Magellan and Antarctica is slightly stronger than previously considered; there is also a species gradient along the Scotia Arc, which can be viewed as a bridge between both regions.