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Colonial Sea Squirt

Scientific Name

Didemnum vexillum Kott, 2002 (Stefaniak et al. 2009)

Common Name

Colonial 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)

Means of Introduction

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


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

Current U.S. Distribution

Coastal New England, Coastal Pacific Northwest

Sea squirt
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Sea squirt, adult


Photo by U.S. Geological Survey

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Selected Resources

The section below contains highly relevant resources for this species, organized by source.

Council or Task Force
Federal Government
International Government
State and Local Government