GOVINDARAJAN, A.F.*; CUNNINGHAM, C.W.; HALANYCH, K.M.; Woods Hole Oceanographic Institution, MA; Duke University, Durham, NC; Woods Hole Oceanographic Institution, MA: Life Cycle Evolution and Systematics of Campanulariid Hydrozoans (Cnidaria)

The goal of this research is to understand evolution of life cycles and systematics in Campanulariid Hydrozoans (Cnidaria). Life cycle diversity is a hallmark of the Hydrozoa, and the Campanulariidae provide an excellent model system in which to study Hydrozoan life cycle evolution. Campanulariids exhibit an extraordinary array of life cycles, ranging from species with a free medusa stage, to those with a reduced or absent medusa stage. Additionally, based on their unique morphology, the medusae of the Campanulariid genus Obelia are hypothesized to have been derived from species lacking medusae, thus representing an example of a rare evolutionary reversal. However, taxonomic confusion has, up to now, prevented verification of this hypothesis. To avoid the pitfalls of a traditional, morphological approach (due, in a large part, to their complex life cycles), a molecular approach was used to resolve Campanulariid relationships, using mitochondrial 16S rDNA and nuclear 18S rDNA sequences to construct a phylogeny of the Campanulariidae. Preliminary analysis corroborates some traditional taxonomic groupings, and contradicts others. Furthermore, results indicate that medusa loss has occurred multiple times.