Sea Squirt

Scientific name: Didemnum vexillum Kott, 2002

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

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

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

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)

Didemnum sp. (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

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