Ciona Intestinalis

Ciona intestinalis (vase tunicate) is a urochordata (sea squirt), a tunicate with very soft tunic, globally distributed cosmopolitan species. Since Linnaeus described the species, Ciona intestinalis has been used as a model invertebrate chordate in developmental biology and genomics. However, 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

Although Linnaeus first categorised this species as a kind of mollusk, Alexander Kowalevsky found a tadpole-like larval stage during development that shows similiarity to vertebrates. Recent molecular phylogenetic studies as well as phylogenomic studies support that sea squirts are the closest invertebrate relatives of vertebrates. Its full genome has been sequenced using a specimen from Moon Bay in California, USA, showing very small genome size, less than 1/20 of human genome, but having almost full sets of genes sharing almost all set of genes but one copy for almost all genes.