Styela canopus (Savigny, 1816)
This species is a simple, solitary ascidian, with a tough outer covering or tunic. The body is subglobose in shape, measures < 2 cm in length, and attaches to substrate at its base. The oral and atrial siphons are positioned anteriorly, and the short tips are ringed in alternating light and dark stripes. The tunic is thin and leathery, with distinct warts. Overall colour is usually reddish brown.
In the Northeast Pacific, Styela canopus is most similar to other styelid tunicates, including S. gibbsii (Stimpson, 1864), S. montereyensis (Dall, 1872), S. truncata Ritter, 1901, and two other non-native species found in the region, S. clava Herdman, 1881 and S. plicata (Lesueur, 1823).
Styela canopus has been introduced to the Northeast Pacific, with confirmed records in southern California (Lambert & Lambert, 1998; Lambert & Lambert 2003). In addition, this species has been collected from several other locations around the world, including the North Atlantic (both the United States and Europe), the Caribbean, the South Atlantic (Ascension Island), the Red Sea, the Indo-West Pacific, and Australia. Its native geographical distribution remains uncertain; some workers consider the species native to Asia (Abbott et al. in Carlton, 2007), while others suggest that it is native to the Northwest Atlantic.