Name: Leaf sheep, or leaf slug (Costasiella kuroshimae)
Where it lives: Shallow waters across Asia and the Coral Triangle
What it eats: Algae
Why it‘s awesome: These tiny marine creatures are probably better known by their nickname, “Shaun the Sheep” sea slugs, because of their uncanny resemblance to the iconic TV character.
The adorable critters have white faces, small black eyes and two “ears.” These structures are special organs called rhinophores covered in tiny hairs that help the leaf sheep sense chemicals in the water and find food. Their tiny bodies are covered with green structures called cerata, which look like leaves and give them a larger surface area for gas exchange.
Growing to 0.3 inches (8 millimeters) long, leaf sheep were first discovered off Kuroshima Island, Japan, in 1993. They have also been recorded in the Philippines, Indonesia, Singapore and Thailand. Shaun the Sheep sea slugs are found in shallow waters near coral reefs. They live on algae, which also provides them with food.
Solar-powered sea slugs
When leaf sheep munch on algae, they absorb chloroplasts — special structures where photosynthesis takes place. These are filled with chlorophyll, and the green pigment gives the sea slugs’ bodies a leaf-like color. This not only helps them blend in with their surroundings to better hide from predators but also gives them a clever way of generating food.
Related: Blue dragon: The deadly sea slug that steals venom from its prey
The sea slugs steal the chloroplasts through a process called kleptoplasty — from the Greek word for “thief” — and store them in their tissues for up to 10 days. The chloroplasts continue working inside the animals, enabling them to create energy through photosynthesis.
“Imagine you ate a salad and kept the chloroplast from it in your digestive system, so you just need to put yourself under the sun to make food,” Miguel Azcuna, assistant professor of marine natural products chemistry at Batangas State University in the Philippines, told the BBC. “It’s convenient for survival.” Azcuna is an expert in coral reef ecology.
Along with corals, spotted salamanders and giant clams, these solar-powered slugs are among the few animals that can photosynthesize.
