Tunicates, also known as sea squirts, are a group of over 3,000 marine invertebrate species that live in coastal waters around the world. They can be solitary or colonial, and come in various colors like white, red, brown, yellow and blue. As filter feeders, tunicates draw in water through two siphons to feed on plankton and other particles before expelling the water. While some species have poisonous flesh to deter predators, tunicates also show promise for treating medical conditions and play an important ecological role by providing a food source and regulating plankton levels.