part of part of bounding layer of bounding layer of in taxon composed primarily of (1->4)-beta-D-glucan Tunicata multicellular organism integumental system surface structure adult organism tunicate tunic In some species tunicin occurs in small amounts. Some species calcium salts are deposited as spicules. In ascidians, the tunic is supplied with blood vessels. BSA:0000042 Outer covering of an animal typically consisting primarily of cellulose (tunicin) in addition to varying amounts of water, protein and carbohydrates. The tunicate is a characteristic feature of Tunicata. Wikipedia:Ascidiacea#Anatomy UBERON:0011302