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Leaf sheep sea slug with bright green leafy parapodia crawling over green algae under sunlit blue water

Leaf Sheep Sea Slug: Facts, Photos & Why It’s So Strange

Costasiella kuroshimae

A tiny cartoon sheep that runs on sunlight

It’s about as long as a grain of rice, has a white face with two beady black eyes and looks exactly like a cartoon sheep covered in green leaves. The leaf sheep, also nicknamed the sea sheep, is a sea slug that does something almost no other animal can: it photosynthesises.

Leaf Sheep Sea Slug vs. you

Your height ft in5 ft 7 in

Quick facts

Size
~0.2 in
About 0.2 in (5 mm); up to 0.4 in (1 cm)
Left in the wild
Unknown

Conservation status

Not evaluated

Superpowers

  • Venomous : Is it venomous? No
  • Glows : Does it glow? No

Identity

Scientific name
Costasiella kuroshimae
Class
Mollusk (sea slug)
First described
1993, by M. Ichikawa

Life & family

Diet
Green algae
Gestation
None – it lays eggs
Predators
Unknown

Where to find it

Habitat
Shallow sandy seabeds, living on one kind of green algae
Lives in
Japan, Indonesia and the Philippines
In the wild
Yes – if you’re a diver with a magnifying glass
In zoos
No

Explore similar

Why is this animal unusual?

When it eats algae, it doesn’t digest everything. It keeps the tiny green solar panels from the plant cells and stores them in its own body, where they go on working.

Why does it look like that?

The “ears” are sensors for smelling the water. The “wool” is a coat of leaf-shaped lobes, each filled with stolen green pigment and tipped in pink or white.

Strangest biological feature

Stolen solar power. It’s one of the very few animals on Earth that can get energy from sunlight.

Why is it strange?

Every leaf sheep is both male and female at the same time.

Interesting behavioral facts

It spends its life grazing on a single type of fuzzy green algae, slowly, like a very small sheep in a very small field.

Records held

One of a handful of animals known to keep stolen chloroplasts working inside their own bodies – a trick called kleptoplasty.

White leaf sheep sea slug with green spiky ruffled body and dark tentacles resting on a green leaf underwater

Leaf Sheep Sea Slug: quick answers

Is the leaf sheep real?

Yes. It’s a sea slug called Costasiella kuroshimae, and it really does look like a cartoon sheep. It’s just very small.

Can a leaf sheep really photosynthesise?

It keeps working chloroplasts from the algae it eats, a trick called kleptoplasty. How much energy it actually gets from them is still debated – it still needs to eat.

Where can you see a leaf sheep?

Divers find them in shallow water in Japan, Indonesia and the Philippines. You’ll need sharp eyes or a magnifying lens.

Can you keep a leaf sheep as a pet?

Not realistically. It eats only one kind of algae and is extremely delicate, so it doesn’t do well in home aquariums.

Know someone who needs to see this?

Send them the Leaf Sheep Sea Slug. They'll thank you. Probably.