Leaf Sheep (Green Thief)

Behold! This is Costasiella kuroshimae, AKA the ‘leaf sheep.”  It isn’t a sheep at all, of course, it’s really a sea slug from the Sarcoglossan clade.  These marine gastropods can be found in the Indo-Pacific off the shores of Indonesia, Japan, and the Philippines. Costasiella kuroshimae scrapes up marine algae and digests it, but the animal then sequesters the living chloroplasts from inside the algae cells into its own tissues.  Chloroplasts, like many other cell plastids, seem to have been independent life forms in the ancient single-cellular dawn of life, but they have since been co-opted and assimilated into the living cells of plants and blue-green algae.  The leaf sheep pulls the same trick–a process known to biologists as kleptoplasty (which is common in protists, but unknown in multicellular creatures except for these slugs).  This is why the leaf sheep glows a glorious living green color.  The slug can keep the chloroplasts alive within its own tissues for extended periods and metabolize the photosynthetic products for its own uses.