About Didemnum

The invasive ascidian, Didemnum sp. (right) was first documented in New England off the coast of Maine in 1993. This ascidian, also called a sea squirt because it often squirts when removed from the water, also occupies an expanding region from Maine to Connecticut, including Georges Bank off the coast of Massachusetts, Narragansett Bay and most recently in Long Island Sound in 2002 (below). There is a great deal of uncertainty as to the origin of the invader, and significant research is currently underway to better understand its taxonomy. In addition to being identified in the northeast, Didemnum has also been documented in California and Washington, British Columbia, New Zealand and Europe.

Distribution of Didemnum throughout the New England area (Bullard et al., in press, Journal of Experimental Marine Biology and Ecology)

• Description: cream to white in color; colonial tunicate where microscopic individuals form large colonies (up to 45 cm long) with finger-like projections; juveniles present from July to November
• Pathway: introduced, exact vector unknown, likely from hull fouling
• Current East Coast Distribution: Maine to New York, including Georges Banks off New England coast
• Impact: fouling organisms, attaches to rocks, docks, pilings; forms encrusting mats on seafloor, overgrowing benthic habitat
  

For a excellent overview of the biology, history and likelihood of future invasion by Didemnum see the summary of Bryon Daley and Don Scavia: "An integrated assessment of the potential for further invasion of the colonial ascidian, Didemnum sp. in large marine ecosystems of the United States"

An excellent link to learn more about Didemnum, including a great index and links to other sites can be found at:

http://woodshole.er.usgs.gov/project-pages/stellwagen/didemnum/index.htm

To learn more about the research of Robert Whitlatch and invasive species ecology see:

http://www.marinesciences.uconn.edu/teamb/Pages/Team Benthos.htm