Sea Squirt

Scientific name: Didemnum vexillum Kott, 2002

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

Native To: Unknown

Date of U.S. Introduction: 1993 in Maine (documented)

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)

Impact: Forms dense colonies which smother native species

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

Didemnum vexillum - Nonindigenous Aquatic Species Database
DOI. USGS. Southeast Ecological Science Center.
Identification/Description; Photographs; Introduction History; Impacts; Distribution; Special Note: Distribution maps and collection information (State and County)

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
CAB International.
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