Researchers at Harvard and UC San Diego discovered that 'solar-powered' Elysia crispata sea slugs store stolen algal chloroplasts inside a previously unknown host-derived organelle called the kleptosome. These organelles use ATP-sensitive ion channels (P2X4) to maintain a specialized internal environment that keeps chloroplasts photosynthetically active for months. During prolonged starvation, slugs actively digest stored chloroplasts as a nutrient reserve, explaining their remarkable survival—nearly four months without food versus three to four weeks for non-photosynthetic sea slugs. Similar organellar systems appear to have evolved independently in corals and sea anemones, suggesting convergent evolution of intracellular symbiont integration across photosynthetic animals.
