Invertebrates
Lettuce Sea Slug
Elysia crispata · also called lettuce sea slugs
A lettuce sea slug drifts slowly across a Caribbean reef, its ruffled, leaf-like body a vivid green sustained partly by chloroplasts stolen from the very algae it eats. For a while after that meal, this animal is doing something remarkably close to photosynthesis.
Overview
The lettuce sea slug, Elysia crispata, is a vividly green, leaf-shaped sea slug native to tropical waters of the western Atlantic and Caribbean. Its ability to steal and temporarily use functioning chloroplasts from algae makes it one of the most genuinely plant-like animals found anywhere in the ocean.
An animal that borrows a plant’s power source
By retaining living chloroplasts from its algal food rather than simply digesting them, the lettuce sea slug gains a temporary solar-powered energy supply few animals anywhere else on Earth are capable of tapping into.
Status
Not Evaluated — no formal conservation assessment completed, with no major documented threats specific to the species.
Lettuce Sea Slug: common questions
How does the lettuce sea slug photosynthesize like a plant?
A lettuce sea slug extracts intact, functioning chloroplasts from the algae it consumes and incorporates them into its own tissue, a process called kleptoplasty, and these stolen chloroplasts continue photosynthesizing for a period of time, allowing the slug to supplement its nutrition with energy produced directly from sunlight.
Why is the lettuce sea slug green?
A lettuce sea slug typically displays a vivid green colouration derived significantly from the chlorophyll-containing chloroplasts it retains within its own tissue after consuming algae, rather than from any pigment the slug produces on its own, making its colour a direct visible sign of its unusual photosynthetic ability.
Can the lettuce sea slug survive without eating for a while?
Yes, because of the ongoing photosynthetic activity from its retained chloroplasts, a lettuce sea slug can survive extended periods with reduced feeding, drawing on solar-powered energy production to supplement its nutritional needs during times when suitable algae may be less available.
Where does the lettuce sea slug live?
The lettuce sea slug is native to tropical and subtropical coastal waters of the western Atlantic, including the Caribbean Sea, generally found among algae-covered reef and rock habitat that provides both food and the specific algae species its unique feeding strategy depends on.