Ascidians (Tunicata, Ascidiacea): species distribution along the Scotia Arc
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 sp...
| Published in: | Scientia Marina |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Consejo Superior de Investigaciones Científicas
2005
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| Subjects: | |
| Online Access: | https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/325 https://doi.org/10.3989/scimar.2005.69s2205 |
| Summary: | 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 and 587 m on different types of substrate. 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 northern limit for Antarctic species and the southern limit for Magellan ones. Affinity between the ascidian fauna of the Magellan region and the Antarctic is slightly stronger than was previously considered; there is also a species gradient along the Scotia Arc, which can be regarded as a bridge between the two regions. Las ascidias habitan todos los mares. Considerado como una barrera especialmente para los organismos del bentos, el Frente Polar separa al Océano Austral del resto de los océanos. A partir de la composición de especies colectadas en cada estación durante el crucero “LAMPOS”, se infiere la influencia del Frente Polar sobre las especies de ascidias presentes en el límite entre las regiones magallánica y antártica a lo largo del Arco de Scotia. Los ejemplares fueron colectados mediante rastra Agassiz y red de fondo entre 250 y 587 m, en tipos diferentes de sustrato. De un total de 25 especies/morfoespecies identificadas, una es nueva mientras que ocho fueron encontradas en nuevas localidades extendiendo el rango de distribución conocido para cinco de ellas. Se encontró una mayor riqueza de especies sobre fondos lodosos que sobre fondos duros. Las islas Georgias del Sur constituyen el límite norte para las especies antárticas y el límite sur para las magallánicas. Las afinidades entre la ascidiofauna de las regiones magallánica y antártica son ligeramente mayores de lo que se consideraba, existiendo un gradiente a lo largo de las islas del Arco de Scotia, las cuales constituirían un puente biogeográfico entre dichas áreas. |
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