Solar-Powered Leaf Sheep Sea Slug Tops Invertebrate Year Poll
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- Costasiella kuroshimae (the leaf sheep) is a sea slug about the size of a grain of rice that lives in tropical waters around Japan, Indonesia and the Philippines, grazing on Avrainvillea algae on shallow reefs.
- The leaf sheep performs kleptoplasty — stealing intact chloroplasts from the algae it eats and storing them in leaf-like cerata on its back, which act as solar panels to power the slug via photosynthesis.
- The species also uses its vivid green cerata as chemical defenses and camouflage, locating algae via rhinophore sensory tentacles positioned above its eyes.
- The leaf sheep was first described by science in 1993 and has soared in popularity thanks to advances in underwater and macro photography that revealed its distinctive looks.
- Readers worldwide have nominated the slug for invertebrate of the year 2026, with fans comparing its appearance to Shaun the Sheep and the Pokémon Shaymin.
Why it matters: A rice-grain-sized invertebrate has become a viral favorite for invertebrate of the year because it literally harvests sunlight after stealing chloroplasts from algae — a biological trick that even most plants can't replicate. The story doubles as an accessible primer on kleptoplasty and signals the Guardian's annual reader-driven invertebrate poll, running August 3–12, will lean heavily on charismatic and visually striking nominees.
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