Ascidia (Chordata: Tunicata) are exclusively marine organisms. They live attached on substrate and may be solitary or colonial forms and , covered by a tunic consisting of material similar to cellulose. They are hermaphrodites with diverse reproduction strategies - and may or may not incubate larva. The  taxonomy of this group is divided into three main orders: Aplousobronchia (colonial species, body divided into chest and abdomen, simple white basket, without folds or longitudinal vessels) with 13 valid families, Phlebobronchia - solitary or colonial species with simple oral tentacles simple , pharynx without folds and gonads associated with digestive tract - where 10 families and Stolidobronchia - solitary and colonial stupids with branched oral tentacles, folds in the pharynx and gonads associated with body wall, with only four families established as valid.

​