09/12/2026
Some sea slugs can temporarily keep part of the photosynthetic machinery from the algae they eat.
In a process called kleptoplasty, certain sacoglossan sea slugs consume algal cells but retain functional chloroplasts inside cells of their own digestive tissues instead of immediately digesting them.
These stolen chloroplasts can remain active for varying periods depending on the species. When exposed to light, they can continue photosynthetic activity and produce compounds that may contribute to the slug’s energy and metabolism.
Species such as Costasiella kuroshimae are famous for their leaf-like appearance and association with this remarkable process, although the duration and importance of chloroplast retention vary greatly among sacoglossans.
The slug does not become a plant. Instead, it temporarily preserves functioning cellular machinery taken directly from its food—a remarkable example of one organism borrowing biological equipment from another.