Marine Organism of the Week

Elysia chlorotica, the Eastern Emerald Elysia

Elysia feeding

Elysia feeding on the filamentous alga, Vaucheria.

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Elysia dorsal view

The dorsal parapodia of Elysia as exposed to the sun.

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Elysia chlorotica, or the Eastern Emerald Elysia, is a sea slug that gets much of its energy from the sun via photosynthesis! Sea slugs are a kind of mollusk (related to snails) that normally get their energy from consuming algae, bryozoans, or cnidarians. However, Elysia is a “kleptoplast,” meaning that it “steals” the chloroplasts from the algae that it eats. They feed on the algal species Vaucheria litorea, and as the contents of the algal cells move down its digestive tract, chloroplasts are absorbed (by phagocytosis) into the body of the slug. Elysia have incorporated the genetic material of algae into their genome (read more), so the chloroplasts remain functional inside the slug. These kleptoplasts have evolved parapodia (wings) that give it a large dorsal surface area like a leaf, allowing them to effectively use their chloroplasts to capture energy from the sun.