Evolutionary changes in molluscan opsin repertoire McElroy KE, Serb JM kmcelroy@iastate.edu Iowa State University, Department of Ecology, Evolution and Organismal Biology, Iowa, USA Eyes have evolved numerous times and molluscs have the most varied eye types of any animal phylum. We know very little about how these different molluscan eye types evolved, including the sets of genes recruited to support their development and function. Opsins are the protein component of the photopigment that triggers the visual transduction pathway and fundamental to the genetic architecture of vision. Broadly, we know that mollusks have three groups of opsin families: r-opsins, xenopsins, and tetraopsins, which include neuropsin, Go-opsin, and retinochrome. However, the variation in opsin composition has not been characterized in mollusks due to the previous paucity of assembled molluscan genomes. Now that mollusc genomes are increasingly available in public datasets, we can begin comprehensive phylogenomic comparisons within this diverse phylum. We collected opsin sequences from dozens of molluscan genomes to characterize their opsin repertoires and analyze the history of opsin family evolution across the phylum. We found extensive opsin family expansion and contraction, particularly within r-opsins and xenopsins in a lineage-specific manner; tetraopsin diversification is much rarer in molluscs. The fluctuations in opsin repertoire appear to be limited to bivalve and gastropod lineages, with cephalopods maintaining relatively few opsins and having lost at least two major opsin groups: neuropsins and Go opsins. These results help set the stage for connecting genomic changes, including opsin family expansion and contraction, to patterns of evolution in eye type and vision in molluscs.