Thesis (Ph. D.)--Auburn University. / Abstract. Includes bibliographical references.

Terebeliformes e sabelídeos, são grupos de poliquetas sedentários, bastante abundantes e diversificados em ambientes marinhos. Embora sejam abundantes e geralmente conspícuos, o conhecimento taxonômico sobre esses animais no litoral brasileiro ainda é muito limitado. Entretanto, a maioria dos registros de espécies de poliquetas para o Brasil provém de estudos realizados nas regiões Sudeste e Sul, enquanto em outras regiões, a fauna de poliquetas ainda é praticamente desconhecida, como o litoral nordestino, limitando-se a alguns estudos conduzidos por pesquisadores estrangeiros ao longo da costa brasileira durante a década de 70. Além disso, há muitos habitats praticamente ainda não exploradas ao longo do litoral do Brasil, como bancos de algas calcárias (bancos de rodolitos) e principalmente em ambientes de águas profundas, uma vez que poucos estudos sobre a fauna bentônica foram realizadas na região da plataforma continental (abaixo de 50 m) e menos ainda entre estas e talude continental (∼ 3.000 m). Neste contexto, o presente trabalho é um dos primeiros estudos de cunho taxonômico tratando especificamente dos Terebelliformia (Terebellidae, Thelepodidae, Polycirridae e Trichobranchidae) e Sabellidae que ocorrem ao longo da costa brasileira, abrangendo diversos tipos de substratos, desde consolidados e não consolidados, até substratos biológicos, como recifes de coral e bancos de rodolitos. Além disso, é o primeiro conduzido no país abrangendo também ambientes bentônicos de águas profundas. Foram analisados aproximadamente 5.500 indivíduos, pertencentes a 51 espécies, sendo 6 representantes de Polycirridae, 15 de Terebellidae, 7 de Thelepodidae, 5 de Trichobranchidae, e finalmente, 18 espécies de Sabellidae. Dentre as espécies encontradas, 26 são novas espécies para a ciência, além da ocorrência de dois gêneros de Terebellidae nunca antes registrado em águas brasileiras, Neoleprea e Lanicola. Além disso, material brasileiro anteriormente identificado como pertencente a algumas espécies de Terebelliformia e Sabellidae consideradas cosmopolitas, tais como Loimia grubei, L. medusa, Eupolymnia nebulosa, Pseudopotamilla reniformis, Parasabella microphthalma, Polycirrus plumosus e Amaeana trilobata, foi aqui descrito como diferentes táxons, novos para a ciência. / Terebeliforms and sabelids are sedentary polychaetes, very abundant and diverse in marine environments. Although are abundant, and often conspicuous worms, the knowledge of fauna of terebeliforms and sabellids occurring off the Brazilian coast is still poor. However, those studies are concentrated mostly on the southern/southeastern regions, while in others regions of the Brazilian coast the polychaete fauna occurring there is virtually unknown, as the northeastern coast, with few studies conducted by foreign researchers during the 70s. In addition, there are many habitats virtually still unexplored along the litoral of Brazil, as banks of calcareous algae (rhodolith beds) and mainly in deep-water environments, once few studies on the benthic fauna were conducted in the continental shelf region (below 50 m) and even fewer between the latter and the continental slope (∼3.000 m). In this context, this thesis is one of the first taxonomic studies dealing specifically with Terebelliformia (Terebellidae, Thelepodidae, Polycirridae and Trichobranchidae) and Sabellidae occuring along the Brazilian coast, from Sao Paulo to Paraíba, considering several types of substrates, from consolidated and unconsolidated, to biological substrates such as coral reefs and rhodolith beds. Moreover, it is the first conducted in the country covering terebelliformes and sabellids from deep waters. In total, approximately 5,500 were analyzed, belonging to 51 species, being 6 species of Polycirridae, 15 of Terebellidae, 7 species of Thelepodidae, 5 of Trichobranchidae and finally 18 are Sabellidae species. Among the species found, 26 are new to science, besides the occurrence of two genera of Terebellidae never before recorded in Brazilian waters, Neoleprea and Lanicola. In addition, Brazilian material previously identified as belonging to some species of Terebelliformia and Sabellidae considered cosmopolitan, such as Loimia grubei, L. medusa, Eupolymnia nebulosa, Pseudopotamilla reniformis, Parasabella microphthalma, Polycirrus plumosus and Amaeana trilobata, described herein as different taxa, new to science.

The evolutionary origin and the phylogeny of higher metazoan taxa is still under debate although considerable progress has been made in the past 20 years. Metazoa represents a monophyletic group of highly diverse animals including Bilateria, Cnidaria, Porifera, Ctenophores, and Placozoa. Bilateria comprises the majority of metazoans and consists of three major clades: Deuterostomia, Spiralia (= Lophotrochozoa sensu lato), and Ecdysozoa, whereas the sister group taxa Spiralia and Ecdyzozoa form the monophyletic clade Protostomia. Molecular data have profoundly changed the view of the bilaterian tree of life. One of the main questions concerning bilaterian phylogeny is the on-going debate about the evolution of complexity in Bilateria. It was assumed that the last common ancestor of Deuterostomia, Ecdysozoa and Spiralia had a segmented and coelomate body organization resembling that of an annelid. On the contrary, the traditional view is the evolution of Bilateria from a simple body organization towards more complex forms, assuming that the last common ancestor of Bilateria resembles a platyhelminth-like animal without coelomic cavities and segmentation. To resolve this question, it is necessary to unravel the phylogenetic relationships within Bilateria. By using mitogenomic and phylogenomic data, this thesis had a major contribution to clarify phylogenetic relationships within problematic metazoan taxa: (1) the phylogeny of Deuterostomia, (2) the questionable monophyly of Platyzoa, and first assumptions concerning the phylogeny of Gnathostomulida, Gastrotricha and Polycladida, (3) phylogenetic relationships within annelid taxa, especially Terebelliformia, Diurodrilidae, and Syllidae, with new insights into the evolution of mitochondrial gene order, and (4) new insights into the evolution of annelids, especially the interstitial ones, as well as the colonization of the interstitial realm.