| Summary: | The Antarctic bottoms harbour rich communities of sponges, which play an important role in structuring benthic habitats. Many Antarctic sponge species have been discovered in the past but most of them were poorly described or incorrectly ascribed to species or genera. Thus, the biodiversity this area is still incompletely explored. However, in the last 20 years the taxonomic and ecological studies of marine benthic invertebrates have benefited from the use of molecular tools, such a mitochondrial and nuclear markers or species-specific markers obtained from sequencing a part of the sponge genome. The present thesis contributed to improve the systematic of an Antarctic sponge group and its phylogenetic relationships with other members of the family (Tetillidae) spread all over the world, and to assess the asexual reproduction rate of an Antarctic sponge species (Stylocordyla chupachups). The phylogeny of Tetillidae has been previously approached using several nuclear and mitochondrial markers but including an incomplete number of Antarctic species. This study, did not resolve completely the family phylogeny and lacked a deep morphological revision of the species sequenced. Hence, in this thesis we performed a new phylogenetic analysis of the family by adding more Antarctic specimens and additional mitochondrial and nuclear markers. Moreover, the morphological characters plus the secondary structure of the (V4) region of the 18S rDNA were analyzed under the principle of maximum parsimony. The resulting trees retrieved seven monophyletic well-supported clades in both the molecular and morphological phylogenies, which correspond to the genera: Cinachyra, Acanthotetilla, Tetilla, Cinachyrella, Craniella, Antarctotetilla and Levantiniella. However, the mitochondrial and nuclear markers used were very conserved and could not discriminate Antarctic species of their corresponding genera (Antarctotetilla and Cinachyra). The revision of the species type of Tethya coactifera and Tethya crassispicula with the COI minibarcode ...
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