Sea Squirt

The sea squirt, or vase tunicate, is a soft, translucent, tube-shaped animal that lives fixed to rocks and hard surfaces worldwide, growing up to about 20 centimeters and drawing its Latin name from its resemblance to a column of intestine. As an adult it filters plankton from seawater drawn in through one siphon and expelled through another, but its free-swimming, tadpole-like larva shares key traits with vertebrates, a discovery that helped reclassify tunicates as chordates rather than mollusks. It has become an invasive species in many harbors, spreading on boat hulls, pilings, and aquaculture gear, and its small, well-studied genome makes it a widely used model for research into chordate development.