Botrylloides violaceus is a colonial ascidian. It is commonly known as the chain tunicate, but has also been called several other common names, including: lined colonial tunicate, orange sheath tunicate, orange tunicate, and violet tunicate. Its native range is in the northwest Pacific from southern China to Japan and Siberia.

Botrylloides violaceus is a colonial tunicate that can vary in color, ranging from purple, light lavender, red, yellow, orange and brown. In all cases the colony is entirely one color. Botrylloides violaceus colonies are encrusting, usually 2 – 3 mm in thickness (Saito et al. 1981) and can be large, up to 200 mm x 20 mm.

Botrylloides violaceus is a colonial sea squirt forming lobed sheets usually 2-3 mm in thickness. Individual colonies are always one colour. The colonies can be different colours, e.g. dark brown, brick red, orange, purple and yellow.

Botrylloides violaceus is a colonial sea squirt that forms flat sheets that are irregular in outline and adhere to the substrate, with large colonies reaching up to a third of a meter or so in diameter.

B. violaceus is a marine colonial tunicate with rapid growth and mat-forming capabilities that colonizes and dominates artificial and natural hard substrata. They form flat sheets and occasionally lobate structures. A colony consists of a number of teardrop-shaped zooids, connected by a common tunic, that are arranged in elongated clusters.