Sunlight-Eating Sea Slugs: How Sacoglossans Steal Chloroplasts for Photosynthesis

Marine creatures known as sacoglossan sea slugs possess an astonishing ability to harness solar energy, a trait that mirrors elements of science fiction but is firmly rooted in Earth’s oceans. These slugs achieve this by ‘kidnapping’ chloroplasts—the tiny powerhouses of plant cells—from the algae they consume. Once inside the slug’s body, these stolen chloroplasts continue to function, enabling the slug to produce its own energy through photosynthesis.

This remarkable kleptoplasty allows sacoglossans to survive for extended periods on sunlight alone, a feat made possible by their evolved mechanisms for maintaining the functionality of chloroplasts, which typically degrade when separated from their algal host. The phenomenon is so striking that it draws parallels to the fictional ‘astrophage’ from Andy Weir’s novel ‘Project Hail Mary,’ highlighting a real-world example of extreme biological adaptation and an unconventional approach to energy acquisition in the animal kingdom.