What is the relationship between a sea slug and algae?

Sea slugs, particularly certain types of sacoglossan sea slugs, have a symbiotic relationship with algae. They feed on algae and can incorporate chloroplasts from the algae into their own cells, a process known as kleptoplasty. This allows the sea slugs to utilize the photosynthetic capabilities of the chloroplasts, providing them with additional energy. Thus, the relationship benefits the sea slug by enhancing its nutrition, while the algae serve as a food source.