Meeting Abstract

94.4  Thursday, Jan. 7  The Cephalopod Cornea: Testing for Convergent Evolution using a Supermatrix Phylogeny LINDGREN, AR*; PANKEY, MS; OAKLEY, TH; University of California, Santa Barbara; University of California, Santa Barbara; University of California, Santa Barbara lindgren@lifesci.ucsb.edu

One leading edge question in evolutionary biology is how similar structures can evolve multiple times. Cephalopods possess camera-type eyes similar to humans that are comprised of an iris, lens, retina, and in some lineages a cornea, which is derived from the eyelid, and appears to have evolved independently at least twice, once in octopods and once in squids. Furthermore, several squid lineages possess a cornea, but it is unclear whether this structure is homologous across squids due to conflicting hypotheses on evolutionary relationships. To clarify relationships among cephalopods and test for phylogenetic homology of corneas, we comprised and analyzed a dataset of all available molecular data for approximately 450 taxonomic units. Preliminary results suggest independent origins of a one-part and two-part cornea in the squid and octopod lineages, respectively. Within the octopod lineage, the two-part cornea appears twice, once in the Octopoda and once the cirrate octopod genus Cirrothauma, and differences in corneal morphology between shallow, benthic octopods and deep, benthic octopods require further examination. Within the squid lineage, the presence of a cornea is the ancestral state, with a single loss in the clade consisting of the orders Spirulida, Bathyteuthoidea, and Oegopsida, which possess an eyelid only. To examine the molecular basis for corneal evolution, gene expression data is currently being obtained using 454 pyrosequencing for key taxa in all cephalopod lineages. Results from this study elucidate the molecular changes associated with transitions from eyelids to one and two-part corneas by testing hypotheses of gene parology, duplication, ancestry and character homology.