Elysia chlorotica, a bright green sea slug native to the Atlantic coast of North America, blurs the line between animal and plant. Early in life, the juvenile slug feeds on the intertidal alga Vaucheria litorea. Instead of digesting the algal cells entirely, the slug executes a remarkable biological theft known as kleptoplasty.
It selectively punctures the algal cells, swallows the contents, and retains intact chloroplasts within the specialized cells lining its extensive digestive tract. What makes Elysia chlorotica truly extraordinary is the incredible longevity of these stolen organelles. While isolated chloroplasts normally degrade within hours outside their host plant cells due to photo-oxidative damage, the chloroplasts inside Elysia chlorotica remain functional for up to nine months.
This enables the slug to survive solely on sunlight and water, effectively functioning as a solar-powered animal. Scientists long debated how an animal cell sustains plant organelles without nuclear algal genes to produce essential repair proteins. Recent biochemical research suggests a combination of unusually resilient algal chloroplast proteins, specialized host animal metabolic stabilization, and precise intracellular chemical environments that protect the plastids from oxidative decay, providing a fascinating window into endosymbiosis and cellular stealing.