The sacoglossan sea slug Elysia crispate can be found sunbathing on Caribbean reefs. The slug feeds on green algae but can survive for more than a month without eating. This is because sea slugs store chloroplasts, organelles in the cells of plants and algae that capture energy from sunlight and convert it to chemical energy by photosynthesis, as they ingest different species of green algae. The chloroplasts are stored in the slug’s digestive epithelium and remain active for up to 3-4 months, providing nutrients from photosynthesis, as well as camouflage by making the slug green in color. “Kleptoplasty,” or “stolen plastids,” is the term for the slugs’ remarkable ability. Some marine protists including foraminifera, dinoflagellates, and ciliates are capable of kleptoplasty, but sea slugs are the only animals to exhibit kleptoplasty. They represent a powerful model system for studying the evolution of photosynthesis in eukaryotes through multiple endosymbiotic events.
The downloadable Educator Materials PDF includes background information and implementation suggestions for using the images as phenomena. The Student Handout includes the images and background.