Leaf Sheep

Photo Credit: Christian Gloor from Wakatobi Dive Resort, Indonesia

Meet the leaf sheep – it is neither sheep nor leaf. It is a sea slug! And it is likely the most adorable slug you will ever see. But what makes this slug amazing is not its appearance. Leaf sheep are multi-cellular animals that live in the sea. They can also photosynthesize sunlight for food!

This unusual species has beady black eyes and the face of a sheep, albeit a small one – the slugs themselves are only 1 cm long. They also have rhinophores (new word!) on top of their heads that look like ears or horns. These rhinophores give leaf sheep their sense of smell and ability to find food. Their bodies are clad in what looks like leaves, called cerata (new word #2!). These cerata are similar to the leaves of succulent plants, like zebra succulents or aloe.

Okay, but on to the photosynthesizing – here’s how it works. Leaf sheep graze on algae as sheep-sheep would graze on grass. As they do, they take in the chloroplasts from the cells of the algae and store the chloroplasts in the cerata. The chloroplasts are what contain the chlorophyll and allow photosynthesis to take place. So not only do leaf sheep eat algae, they supplement their diet through photosynthesis. The process of taking the chloroplasts from the algae and storing it is called kleptoplasty (another new word!). And yes, the root of this word is “klepto,” from the Greek word for thief. In other words, leaf sheep steal the undigested chloroplasts from the algae. If humans were able to do this, we’d eat a salad, store the chloroplasts in our system, then sit in the sun to make more food. It gives a whole new meaning to the idea of being solar powered.