show Abstracthide AbstractThe heterokont alga, Vaucheria litorea, is the donor of horizontally transferred genes to the genome of the sacoglossan sea slug, Elysia chlorotica. Upon feeding, the sea slug captures algal chloroplast in specialized cells lining its digestive diverticula where an endosymbiotic relationship is then established. Once captured, the chloroplasts remain photosynthetically active for the remaining part of the slug's life cycle (~10 months) without any additional input of algal food. By sequencing the algal transcriptome we will establish a database of native algal sequence to use to identify additional transferred genes in Elysia chlorotica.