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Botrylloides violaceus  Botrylloides violaceus  Botrylloides violaceous  Botrylloides violaceus

  Scientific Name:

Botrylloides violaceus

 Common Name:

Orange sheath tunicate (others: chain sea squirt, red sheath tunicate, colonial sea squirt)

 Native Range:

Coastal southern Siberia through coastal southern China, Japan

 Established Range:

On the East Coast, from northern Maine to Florida

 Established in Rhode Island?

Yes, throughout Narragansett Bay

 Date and Location of Introduction:

1981, New England

 Method of Introduction:

Unknown, but likely through hull fouling or contaminated shellfish stock


Individual zooids of B. violaceus grow together in groups called colonies. Colonies of B. violaceus can be found in the subtidal zone, and occasionally in protected intertidal areas, attached to rocks, boulders, and artifical structures such as pilings, boat hulls, bouys, lines, and floating docks. B. violaceus can also be found growing over seaweeds, eelgrass, shellfish, and other sea squirts. This tunicate can can tolerate temperatures from 8 to 25° Celcius and salinities between 26 and 34 parts per thouand.


B. violaceus is a filter feeder that eats zooplankton, phytoplankton, and detritus.


All B. violaceus zooids are hermaphroditic, and are capable of reproducing sexually and asexually. The breeding period of B. violaceus colonies lasts approximately 4 weeks.


All invasive tunicates, including B. violaceus, pose the same problems. These tunicates are notorious fouling organisms, and can completely cover submerged boat hulls, aquaculture cages, and just about any other surface that they are capable of living on. As a result, they can slow down boats, and have negative impacts on the local environment. Invasive tunicates have been known to smother shellfish and other sessile organisms, and will outcompete native filter feeders for food and space.


There are no known control methods at this time

 Identification Card:

Courtesy of Salem Sound Coastwatch


 Works Cited:

Cohen, Andrew N. 2005 Guide to the Exotic Species of San Francisco Bay. San Francisco Estuary Institute, Oakland, CA,

Pam Fuller. 2010. Botrylloides  violaceus. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.

Gittenberger, A. 2010. Botrylloides violaceus Oka, 1927. World Register of Marine Species.