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Adorable “Leaf Sheep” Sea Slugs Look like Cartoon Lambs

By Jenny Zhang on May 1, 2026 (Updated)

Sea slug that looks like a cartoon leafy sheep

Photo: Christian Gloor via Wikimedia Commons (CC BY 2.0)

If you thought sea bunnies were cute, here’s a different species of sea slug that will make you say “aww!” Costasiella kuroshimae (common names including “leaf sheep” and “Shaun the sheep”) is a gastropod species of sacoglossan sea slug whose beady eyes and flat face make it look like an adorable cartoon sheep. Add some droopy feelers and a phosphorescent, leaf-like body, and this little darling may just be the loveliest slug in the ocean!

Costasiella kuroshimae can grow up to 5 millimeters in length and can be found in marine habitats near Japan, Indonesia, and the Philippines. They dwell in shallow waters in coral reef ecosystems. They live, lay their eggs, feed on green algae, and use the chloroplasts from their food to manufacture their own energy in a process called kleptoplasty. Unlike snails, the creature uses its radula to pierce and suck out the chloroplasts from algae. One of the only non-plant organisms in the world that can perform photosynthesis, leaf sheep can survive up to a few months on the energy produced from kleptoplasty.

Their appearance is a defense mechanism used to camouflage themselves into their leafy surroundings to stay safe from predators. Leaf-like tendrils, called cetera, are also functional and act as respiratory surfaces, almost like gills, to provide them with oxygen. Their antennae-like features are sensory organs called rhinophores that help them smell and navigate the waters to find food and avoid toxic compounds.