Microscopic features of the tunic in young Styela canopus (Tunicata, Styelidae)

The tunic is a unique tissue in metazoans covering the epidermis of ascidians and other tunicates. The tunic is a multifunctional tissue that provides support, mechanical rigidity, and protection against infection and predation. The outermost surface of it is covered by a thin continuous layer called tunic cuticle. The tunic cuticle density and integrity must be maintained during the growth of the animal after metamorphosis, as it represents the primary body surface barrier preventing the mechanical damage.