The leaf sheep is a fascinating slug since it can photosynthesize. That said, there does not seem to be a lot of information about this slug, so let's see what is available and what we can find.
Physical Description and Behavior
The look of this sea slug makes it stand out among anything else around it. This is mainly due to the green dotted spines that pop out of its back, which are akin to leaves. It has two beady eyes and antennae that look similar to that of sheep's ears. It only grows to about 1 inch (2.54 cm), so it is very small.
Its resemblance to a tiny tree is a bit ironic, as the slug can photosynthesize. Through the process of kleptoplasty, it takes the chloroplasts from the algae it eats and incorporates it into their bodies. That said, it is not well understood why and how they do this. Studies have shown that the chloroplasts can survive in some species of Costasiella, but they don't appear to be used as a way to nourish it in times of famine.
More information is needed on this slug. Some experts feel as if this species does not have a firm anatomical description. As a result, many species of the genus Costasiella might be shown as the same species. This can explain why this species seems to come in a variety of colors.
Habitat and Location
These sea slugs were first discovered in Japan; but within 20 years since its discovery, it has been found in other areas as well. Sightings have also been seen in Singapore, Indonesia, Papa New Guinea, Northern Australia, and New Caledonia.
To see this little guy in action, check out the video below. Sadly, it is in Burmese, but you can still see the sea slug in all its glory.