Botrylloides violaceus Oka, 1927
Violet tunicate, Lined compound ascidian
This species is a compound, colonial ascidian, with small, bean-shaped zooids embedded in a common matrix or tunic. The colony grows to form encrusting patches that typically reach 3-4 mm in thickness and 2-30 cm in diameter. Individual zooids are positioned vertically relative to the substrate, and are organized into elongated, meandering systems, each measuring 0.5-1 cm in width. Each zooid grows approximately 3 mm in length. Zooids are characterized by 16 branchial tentacles located on the inside of the oral siphon, and a pharynx with 10-11 rows of stigmata. Each colony is a solid color, either cream, yellow, orange, rose, purple, or brown.
In the Northeast Pacific, Botrylloides violaceus is most similar to B. diegensis Ritter and Forsyth, 1917 and two other non-native botryllid species found in the region, B. perspicuus (Herdman, 1886) and Botryllus schlosseri (Pallas, 1766).
Ecology and Distribution
Botrylloides violaceus has been introduced to the Northeast Pacific, with confirmed records from Alaska to Baja California, Mexico. In addition, this species has been reported from several other locations around the world, including parts of northeast United States and Canada, Great Britain, Europe, the Mediterranean, and Australia. It is native to the Northwest Pacific, with a distribution from Siberia and Japan to southern China.