Photographer:Lorne Curran Source:www.bugwood.org Copyright: CC BY-NC 3.0
The chain tunicate is a sessile and colonial sea squirt consisting of many individuals (zooids) arranged in elongated clusters and chains. The zooids are about .1 in long and the largest colonies can be up to 1 ft. in diameter. All the zooids in a given colony are the same color: red, orange, yellow, purple or tan.
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 out-compete native filter feeders for food and space.
The colonial Botrylloides violaceus zooids are hermaphroditic and create larvae internally by the fertilization of its eggs from male gametes of nearby colonies. It then releases the planktonic larvae into the water column where it eventually settles on a firm surface. From there it metamorphoses into a zooid and then buds off to the sides asexually to form the multiple systems that make up a colony. The larvae are very short lived, but fragments from a colony can survive indefinitely, reproducing asexually while drifting, or traveling within ship ballast water to colonize new areas. The breeding period lasts about 4 weeks.
In 1973 this tunicate was identified off of the San Francisco Bay. By 1981 Botrylloides violaceus was found in Great Bay, New Hampshire then Chesapeake Bay in 2000. 1997 it was found off of Washington near Puget Sound, demonstrating a simultaneous invasion of both the West and East coasts. Dispersal to new areas along the coasts of North America may occur by contaminated oyster boat hulls or rafting on debris. Since the planktonic larvae is so brief it is unlikely that is spreads far in the ballast water.
East Asia from Siberia to Southern China and Japan
U.S. Habitat: Protected marine waters and can reproduce rapidly, fouling ship hulls, docks, piers and shellfish aquacultures. It can be found on any substrate, including gravel, seabed, metal, plastic, rope, fiberglass, wood, and shellfish.
U.S. Present: AL, CA, DE, FL, GA, MA, ME, NC, NH, OR, RI, VA, VT, WA
Like most invasive marine species eradication measures are unlikely to succeed. Regardless, there are no management procedures for this tunicate at this time.
Bock, D. G., Zhan, A., Lejeusne, C., MacIsaac, H. J., & Cristescu, M. E. 2011. Looking at both sides of the invasion: patterns of colonization in the violet tunicate Botrylloides violaceus. Molecular ecology, 20(3):503-516.
Carver, C. E., Mallet, A. L., & Vercaemer, B. 2006. Biological Synopsis of the Colonial Tunicates (Botryllus Schlosseri and Botrylloides Violaceus). Bedford Institute of Oceanography.
Cohen, Andrew N. 2005. Guide to the Exotic Species of San Francisco Bay. San Francisco Estuary Institute, Oakland, CA.
Fuller, Pam. 2010. Botrylloides violaceus. USGS Nonindigenous Aquatic Species Database, Gainesville,FL.
Woodward, Susan L., and Joyce Ann. Quinn. 2011. Chain Tunicate. Encyclopedia of Invasive Species: From Africanized Honey Bees to Zebra Mussels. Santa Barbara, CA: Greenwood. 39-41. Print.