These tiny sea creatures are perhaps best known by their nickname, the “Shaun the Sheep” sea slugs, because they so closely resemble the famous TV character.
These furry creatures have white faces, tiny black eyes and two “ears.” These structures are special organs called rhinophores covered with tiny hairs that help leaf sheep recognize 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 large surface area for gas exchange.
Measuring up to 0.3 inches (8 millimeters) long, leaf sheep were first discovered in 1993 near Japan’s Kuroshima Island. They have also been seen in the Philippines, Indonesia, Singapore and Thailand. Shaun the Sheep sea slugs are found in shallow water near coral reefs. They live on algae, which also provides them with food.
Solar-powered sea slugs
When leaf slugs eat algae, they absorb chloroplasts – special structures where photosynthesis takes place. These are packed with chlorophyll, and the green pigment gives the sea slugs’ bodies their leaf-like colour. This not only helps them blend in with their surroundings to better hide from predators, but also gives them a clever way to make food.
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 to work inside the animals, helping them make energy through photosynthesis.
“Imagine you ate a salad and kept the chloroplasts from it in your digestive system, so you just have to expose yourself to sunlight to make food,” Miguel Azkuna, assistant professor of marine natural products chemistry at Batangas State University in the Philippines, told the BBC. “It’s convenient for survival.” Azkuna 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.