Ciona intestinalis (vase tunicate) is an ascidian (sea squirt), a tunicate with very soft tunic. Its Latin name means, literally, "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock. It is a globally distributed cosmopolitan species. Since Linnaeus described the species, Ciona intestinalis has been used as a model invertebrate chordate in developmental biology and genomics. Recent studies have shown that there are at least two, possibly four, sister species. By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species.