| Summary: | The current thesis covers two important and poorly known aspects of Antarctic bryozoans: biodiversity and chemical ecology. The comparative analyses of diversity carried out here (Chapters 1 and 2) between Antarctica and the last separated fragments of Gondwana support the hypothesis of the sequential separation of Gondwana. We discuss that the high number of species from the Argentine Patagonian (AP) region shared with Antarctica found in our study question the real extent of Antarctic isolation for cheilostome bryozoans. The presence of shared common bryozoan species between these two regions may also be explained by the free migration of marine organisms in and out of the Polar Front, via the deep abyssal plains and the potential passive northwards transport of larvae (or perhaps even adults) to considerable distances, via the branch of the Antarctic Circumpolar Current (ACC) flowing northward along the continental shelf of Argentina, the Falkland/Malvinas Current. The role of the Scotia Arc and other dispersal pathways, like eddies of ACC, and human dispersal mechanisms, may increase the bryozoan connection found between the Antarctica and the AP region. Also, our studies (Chapters 1 and 2) are among the first characterizations of the bryozoan communities, mainly at the slope, from the AP region, and from the Southern Ocean (SO), specially the Weddell Sea. The bathymetric distribution from the AP region and the SO found in our studies fits well with the limits of the continental shelf, the slope and the deep sea. Interestingly, our research also shows an expansion in the known distribution of diverse bryozoan species from the AP region and the SO. Our results stress the importance of taxonomical studies in these scarcely explored regions, reporting a high number of new genera and species, and new records too. Among the new species found in our study, a bryozoan of the genus of Reteporella characterized by rare giant spherical avicularia is described in Chapter 3, leading us to discuss which are the potential ...
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