The symbiotic chloroplasts in the sacoglossan Elysia clarki are from several algal species

Abstract. The sacoglossan sea slug Elysia clarki feeds on siphonaceous algae, and intra-cellularly sequesters chloroplasts, which actively photosynthesize for p4 months. We have determined the algal source of chloroplasts in adults of E. clarki from the Florida Keys, using molecular techniques, feeding experiments, and electron microscopy. Our results clearly dem-onstrate that specimens ofE. clarki sequester chloroplasts from four different species of algae, representing two genera: Penicillus lamourouxii, P. capitatus, Halimeda incrassata, and H. monile. In addition, chloroplasts from more than one species of algae are sequestered simultaneously in the same digestive cell. Additional key words: Penicillus, Halimeda, kleptoplasty, feeding, symbiosis Sacoglossans feed on siphonaceous algae; cells lining the digestive diverticulum take up and seques-ter algal chloroplasts from the gut lumen (Trench et al. 1969). In Elysia clarki PIERCE ET AL. 2006, the captured, intracellular plastids retain photosynthetic function for 3–4 months, one of the most persisten