Molecular phylogenetics of the Metazoan clade Lophotrochozoa
Passamaneck, Yale J.
MetadataShow full item record
KeywordMollusks; Phylogeny; Evolution; Genome mapping; Homeobox genes; Recombinant DNA; Cladistic analysis
DNA sequencing and phylogenetic analyses were conducted to investigate evolutionary relationships between taxa within the metazoan clade Lophotrochozoa. Chapter 1 presents an introduction to phylogenetics of the Metazoa and the clade Lophotrochozoa. Chapter 2 analyzes higher level relationships between the major groups within the phylum Mollusca using sequences of the nuclear ribosomal large-subunit RNA gene (LSD rDNA). Results presented provide the first molecular evidence for a close relationship between the Scaphopoda and Cephalopoda. Phylogenetic trees with this topology were found to have likelihood scores significantly better than those for phylogenies constrained to fit the Diasoma hypothesis grouping Scaphopoda and Bivalvia as sister taxa. Chapter 3 utilizes LSU rDNA sequences to analyze relationships between diverse phyla within the clade Lophotrochozoa. LSU rDNA sequences were found to provide greater resolution than has been provided by previous analyses of the nuclear small-subunit ribosomal RNA gene (SSU rDNA). Analysis ofLSU rDNA sequences recovered the monophyly of several phyla, such as Mollusca and Anelida, whose members are found to be paraphyletic using SSU rDNA sequences alone. Results also suggest that the clade Platyzoa, including rotifers and platyhelminthes, may have arisen within the Lophotrochozoa, rather than as a sister group to lophotrochozoans. Chapter 4 investigates the Hox gene complement of the bryozoan Bugula turrita. Six Hox genes were recovered, including an ortholog of the posterior class gene Post2, which is a synapomorphy for the Lophotrochozoa. The identification of a Post2 ortholog provides evidence of a close relationship between the Bryozoa and other lophotrochozoan phyla.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003
Showing items related by title, author, creator and subject.
Involvement of Cytochrome P450 1A in the toxicity of aryl hydrocarbon receptor agonists : alteration arachidonic acid metabolism and production of reactive oxygen species Schlezinger, Jennifer J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998-08)Two cytochrome P4501A-dependent mechanisms of aryl hydrocarbon receptor (AhR) agonist toxicity were examined in the marine teleost scup (Stenotomus chrysops), alteration of arachidonic acid (AA) metabolism and production ...
van der Hoop, Julie (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)Animal movement is motivated in part by energetic constraints, where fitness is maximized by minimizing energy consumption. The energetic cost of movement depends on the resistive forces acting on an animal; changes in ...
McNichol, Jesse C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Chemoautotrophic ecosystems at deep-sea hydrothermal vents were discovered in 1977, but not until 1995 were free-living autotrophic Epsilonproteobacteria identified as important microbial community members. Because the ...