Typescript. Includes vita and abstract. Includes bibliographical references (leaves 134-154). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Vestimentifera inhabit hydrothermal vents, cold-water seeps and other marine reducing habitats. The objectives of this study were to analyse phylogenetic relationships among the extant species and their affinities to perviate and moniliferan Pogonophora and Polychaeta. The phylogeny was reconstructed using morphological characters to test phylogenetic hypotheses based on molecular data. Morphological characters were partly extracted from the literature and partly gained throughout study of gross morphological and anatomical investigations and light, transmission and scanning electron microscopy. Three aspects of morphology were examined in detail in nine vestimentiferan species. The excretory system differs among the vestimentiferan species in the number of excretory pores, absence/presence of excretory papillae and grooves and shape of the excretory ducts. The anatomy of the excretory system resembles that shared by the polychaete families Serpulidae, Sabellidae and Sabellariidae. Chaetal ultrastructure and chaetogenesis show patterns similar to uncini in polychaetes. Contrary to published accounts, the septa dividing the opisthosomal segments only bear musculature on their posterior faces. A rudimentary gut and anus are present in opisthosomes of specimens up to adult size. The blood vascular system includes an intravasal body in the dorsal vessel with ultrastructural characteristics similar to intravasal tissue in Terebellidae, Ampharetidae, Flabelligeridae and Serpulidae, and is probably involved in hemoglobin production. Hemocytes were detected in many blood vessels, most of them attached to the vascular lamina. The sinus valvatus is a specialised region of the anterior ventral vessel, apparently unique to vestimentiferans. The wall of the dorsal vessel is formed by myoepithelial cells, representing a coelomyarian type of double obliquely striated musculature. Phylogenetic analyses including a total of 17 vestimentiferan species and three perviate species as outgroups support molecular interpretations that the vestimentiferan species inhabiting basalt-hosted vents of the Eastern Pacific represent a derived monophyletic clade. According to the reconstructed phylogeny, the ancestral habitat of Vestimentifera was deep-water sedimented vent sites in the Western Pacific. Analysis of the relationships among Pogonophora and six polychaete families placed Pogonophora at the base of a clade including Sabellidae, Serpulidae and Sabellariidae. The Oweniidae represent the sister group to this clade. / Graduate

Atmospheric carbon dioxide (CO2) has increased due to human activity from a pre-industrial value of about 280 ppm to the present level of 399 ppm. The ocean acts as an important natural carbon sink that effectively removes 1/3 of this anthropogenic CO2 from the atmosphere, buffering global warming effects. However, the dissolution of CO2 causes a dramatic change in seawater chemistry and ultimately results in the phenomenon commonly known as "ocean acidification" (OA). As a consequence, the pH value and the saturation states for calcium carbonate decline in the surface seawater, posing a threat to calcareous marine organisms that build their shells using exquisite biomineralization mechanisms. Biological minerals produced by marine organisms are compositionally and structurally more complex than geological minerals. Although changes in biomineral formation in response to OA has been intensively investigated, the features of calcified products in terms of their composition, architectures and mechanical properties have been overlooked in climate change research. The tubeworm is a favourite marine model organism in larval biology. Its life cycle is well understood hence provides a good opportunity to study OA impacts on the stochastic early life. In addition, the model enables comprehensive observation of the sophisticated biomineralization events. In this thesis, four studies on the biomineralization of Hydroides elegans, using a multidisciplinary collaborative approach combining larval biology and material science were conducted. (1) The tube mineral composition at different juvenile stages (4, 11, 18, 25 days) were characterized. (2) The impacts of different predicted OA scenarios (pH 8.1, 7.9, 7.6, and 7.4) on the resultant calcification products were compared. (3) A multiple-stressor investigation of OA (pH 8.1 and 7.8), reduced salinity (33 ‰ and 27 ‰) and increased temperature (25 °C and 29 °C) was conducted to further determine the more environmentally realistic OA impacts. (4) Calcification sites were examined by using a microscopy approach The main findings from each study were: (1) H. elegans produced both calcite and aragonite forms of CaCO3, which have distinctive physical and chemical properties. Thus, the tubeworm serves as an interesting model for studying OA impacts on biomineralization. The early juvenile stages are expected to be more sensitive to OA than the later life stages because the juvenile tubes are rich in aragonite and amorphous calcium carbonate. (2) Under experimental OA conditions, the composition and architecture of the tube structures were adversely affected, ultimately producing tubes with weaker mechanical properties. (3) Warming appeared to strengthen the tube structures and mitigated the adverse OA effects. (4) Calcification sites correlated to regions with higher pH values of 8.5 - 9.0. These regions may be sensitive to OA and should be further analyzed to study the mechanisms of OA impacts on calcification. This series of experiments study biomineralization and larval biology using a variety of modern multidisciplinary approaches provided new insights into the impacts of OA and climate change impacts on marine organisms and also helped us to project which species might adapt or succumb to future scenarios. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

abstract / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / Ecological processes at deep-sea hydrothermal vents on fast-spreading mid-ocean ridges are punctuated by frequent physical disturbance. Larval dispersal among disjunct vent sites facilitates the persistence of sessile invertebrate species in these geologically and chemically dynamic habitats despite local extinction events. Regional population extension and rapid recolonization by the siboglinid tubeworm Riftia pachyptila have been well documented along the East Pacific Rise and the Galápagos Rift. To analyze spatial and temporal population genetic patterns and the processes governing them at ephemeral and disjunct habitats, a suite of 12 highly variable microsatellite DNA markers were developed for this species. Eight of these loci were used to assess the regional and within-ridge genetic structure of recent colonists and resident adults collected from nine sites in the eastern Pacific Ocean over period of three to seven years. A significant seafloor eruption during the seven-year sampling period allowed investigation into the role of local extinction in population genetic diversity at the Tica vent site at 9°N EPR, while collections within two and five years of an eruption that created the Rosebud vent field at 86°W GAR provided insights into genetic diversity input over population establishment. For the first time, this thesis demonstrated significant genetic differences between Riftia populations on the East Pacific Rise and Galápagos Rift. Moreover, the separate treatment of colonist and resident subpopulations revealed a high potential for local larval retention at vent sites. This mechanism for recruitment likely sustains disjunct populations and supports the recolonization of locally extinct areas after disturbance events, while episodic long-distance dispersal maintains genetic coherence of the species. / (cont.) Temporal population genetic consideration at the Tica site on the East Pacific Rise suggests that the 2005-2006 seafloor eruption had little to no discernable effect on local population genetic composition. Yet local populations appear to exhibit a small degree of genetic patchiness, with a high degree of relatedness (half-sibs) among subsets of individuals within both colonist and resident cohorts. This thesis broadens the application of recently developed molecular techniques to study the effect of ridge-crest processes and offers new perspectives into marine dispersal, gene flow, and population differentiation. / by Abigail Jean Fusaro. / Ph.D.