Chloroplasts as symbiotic organelles in the digestive gland of Elysia viridis [Gastropoda: opisthobranchia]

Abstract

An investigation into the histochemistry and ultrastructure of the digestive gland of Elysia viridis has revealed the presence of two types of epithelial cells, one of which contains numerous, structurally intact algal chloroplasts. Chromatographic studies indicate that these chloroplasts are derived from the animal's specific food, the alga Codium tomentosum. Following ingestion by the animal these do not appear to be digested or excreted, but accumulate and are maintained in the digestive cells. Autoradiographic studies suggest that they may be of some benefit to the animal as symbiotic organelles. Such a phenomenon may prove to be widespread among related species of Opisthobranchia.