Annelids and Mollusks from Chemosynthetic Environments of the Pacific Ocean

This dissertation utilized molecular methods to reveal new species of annelids and mollusks from chemosynthetic environments in the Pacific Ocean and examined their biogeography and evolutionary history. Sanger sequencing revealed three new species of Bathymodiolus mussels that are partially restricted by depth at seeps along the Costa Rica Margin, and confirmed the presence of B. thermophilus at a seep with molecular data for the first time. New species of the iphionid Thermiphione and vestimentiferan tube worm Lamellibrachia are also described using a combination of Sanger-sequenced molecular data and morphological data. The close relationship of the new Lamellibrachia species with relatives across the Panama Isthmus suggests a vicariant event post-radiation of Lamellibrachia into the Atlantic. Sanger-sequencing also revealed two putative new species of the vestimentiferan tube worm Alaysia. High-throughput sequencing and mitochondrial genome skimming provided the data necessary to place these new species, as well as the vestimentiferan genera Alaysia and Arcovestia into the phylogeny of Vestimentifera for the first time. Additional sequencing of whole mitochondrial genomes in this group provided the data necessary to generate the most complete mitogenomic phylogeny of Vestimentifera to date. The resulting topology suggests the most recent common ancestor of Vestimentifera was a vent-inhabitant of the Pacific Ocean