Sea Squirt

Scientific name: Didemnum vexillum Kott, 2002

Common names: Sea squirt, ascidian, colonial tunicate, compound sea squirt, carpet sea squirt

Native To: Unknown, possibly Japan (Lambert 2009)

Date of U.S. Introduction: First confirmed sighting in 1993 (Lambert 2009)

Identification of this species has been problematic. For more information, see:

• Genetic conspecificity of the worldwide populations of Didemnum vexillum Kott, 2002 (PDF | 1.5 MB)
  Aquatic Invasions (2009) Volume 4, Issue 1: 29-44.
• Adventures of a sea squirt sleuth: unraveling the identity of Didemnum vexillum, a global ascidian invader (PDF | 1.5 MB)
  Aquatic Invasions (2009) Volume 4, Issue 1: 5-28.

Images: Google

Video: Great Britain Non-Native Species Secretariat - Carpet Sea Squirt (or click Play button below)

Means of Introduction: Introductions likely due to shipping (either via hull or sea chest fouling) (Lambert 2009)

Impact: Forms dense colonies that can smother native species (Bullard et al. 2007)

Management Plans: Aquatic Species

Selected Internet Resources:

• Federal Government
• State Government
• University/Academic
• International
• Organizations

Invasive Marine Species Found on Georges Bank (Nov 19, 2003)
DOC. National Oceanic and Atmospheric Administration.
Identification/Description; Distribution; Dispersion

Didemnum vexillum - Rhode Island Marine & Estuarine Invasive Species Site
DOC. NOAA. National Estuarine Research Reserve System. Narragansett Bay Research Reserve. Coastal Training Program.
Photographs; Introduction History; Impacts; Life Cycle; Habitat; Distribution

Have You Seen This Tunicate?
DOC. NOAA. Northeast Fisheries Science Center; DOI. United States Geological Survey.
Identification/Description; Photographs

Marine Invasive Species: Didemnum vexillum (PDF | 555 KB)
DOI. NPS. Natural Resource Program Center.
Photographs; Impacts; Distribution; Dispersion

Invasive Sea Squirt Alive and Well on Georges Bank (Nov 19, 2004)
DOI. United States Geological Survey.
Identification/Description; Introduction History; Distribution; Dispersion

Wanted… Sea Squirt (Nov 21, 2003)
DOI. United States Geological Survey.
Identification/Description; Impacts

Genus Didemnum - Marine Invasive Species
DOI. USGS. Woods Hole Science Center.
Taxonomy; Photographs; Impacts; Habitat; Distribution

Didemnum vexillum Article Citation Search - AGRICOLA Database
USDA. National Agricultural Library.
Research; Special Note: NAL Catalog Search (resources)

State Government

Didemnum vexillum - Invasive Species of the Month
Oregon Invasive Species Council.
Identification/Description; Photographs; Impacts; Habitat; Distribution

Didemnum vexillum (Colonial sea squirt)
Washington Department of Fish and Wildlife.
Taxonomy; Identification/Description; Photographs; Habitat; Dispersion

University/Academic

Sea Squirt (Didemnum sp.) - Introduced Species Summary Project
Columbia University. Center for Environmental Research and Conservation.
Taxonomy; Identification/Description; Photographs; Introduction History; Impacts; Life Cycle; Habitat; Controls

Didemnum vexillum - Invasive Species Compendium
Centre for Agricultural Bioscience International (CABI).
Taxonomy; Identification/Description; Impacts; Life Cycle; Habitat; Distribution; Controls

Didemnum spp. (tunicate) - ISSG Global Invasive Species Database
World Conservation Union. Invasive Species Specialist Group.
Identification/Description; Impacts; Life Cycle; Habitat; Distribution; Dispersion; Controls

The Dutch Ascidians Homepage
Ascidians.com.
Photographs

Sea squirt (Didemnum vexillum)
Northeast Aquatic Nuisance Species Panel.
Identification/Description; Photographs; Impacts; Habitat; Distribution

Invasive Tunicate in Washington State
Reef Environmental Education Foundation.
Photographs; Impacts; Distribution; Controls

Didemnum sp. - Guide to Marine Invaders in the Gulf of Maine (PDF | 592 KB)
Salem Sound Coastwatch. Marine Introduced Species Monitoring Resource Center.
Identification/Description; Illustrations; Introduction History; Impacts; Habitat; Distribution

Didemnum sp. A - Guide to the Exotic Species of San Francisco Bay
San Francisco Estuary Institute.
Identification/Description; Photographs; Impacts; Habitat; Distribution; Dispersion

Citations

Bullard, S.G., G. Lambert, M.R. Carman, J. Byrnes, R.B. Whitlatch, G. Ruiz, R.J. Miller, L. Harris, P.C. Valentine, J.S. Collie, J. Pederson, D.C. McNaught, A.N. Cohen, R.G. Asch, J. Dijkstra, and K. Heinonen. 2007. The colonial ascidian Didemnum sp. A: Current distribution, basic biology and potential threat to marine communities of the northeast and west coasts of North America. Journal of Experimental Marine Biology and Ecology 342(1):99-108.

Lambert, G. 2009. Adventures of a sea squirt sleuth: unraveling the identity of Didemnum vexillum, a global ascidian invader. Aquatic Invasions 4(1):5-28.