Costasiella kuroshimae, known as leaf sheep, is a type of slug that lives in the sea. They are shell-less marine opisthobranch gastropod mollusks in the family Costasiellidae. These cartoon sea sheep only grow to a length of 5 mm to 1cm. They have two dark eyes and two rhinophores that emerge from the tops of their heads that look not unlike sheep’s ears or insect antennae, hence the common name “leaf sheep.” The rhinophores have fine hairs that sense chemicals in the water, enabling Costasiella kuroshima and other sea slugs to find food sources. They eats green algae in the sea and produce energy from their food’s chloroplasts through a “kleptoplasty” process. These are unique because they are the only organisms in the world that are not plants and can still conduct photosynthesis. They can produce enough energy through this kleptoplasty to stay alive for a couple of months. Kleptoplasty is a chemical process, in which they retain the chloroplasts from algae, which they eat. Absorbing the chloroplasts from algae then enables them to perform photosynthesis. This ability to perform photosynthesis gives them “glow” under water, as they become bioluminescent. It is one of the only creatures in the world that can use algae to photosynthesize. When it consumes green algae, it is only partially digested in its body. Chloroplasts, major double-membrane organelles containing chlorophyll, are left intact. It was discovered in 1993 off the coast of the Japanese island Kuroshima, leaf slugs have been found in the waters near Japan, the Philippines, Indonesia and many places.
Writer: Nabila Rab