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Sea squirt (Didemnum vexillum) Credit: A. Pappal

sea squirt
Didemnum vexillum

Characteristics:

• Cream, white, tan, or yellow
• Dense colonies of microscopic, individual animals (zooids)
• Colonies grow up to 12-18 in (30-46 cm) long
• In slow-moving waters, may form long, ropey, or beard-like colonies that commonly hang from hard substrates such as docks, lines, and ship hulls
• In faster-moving waters, may form low, undulating mats that encrust and drape rocky seabeds (pebbles, cobbles, boulders, and rock outcrops)

Habitat:

• Hard surfaces such as docks, pilings, moorings, ship hulls, rocks, and seafloor
• Primarily below the low-tide line to continental shelf depths of 210 ft (65m)

Known Distribution:

• Northeastern U.S. (New Jersey, New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, Maine)
• Covers much of Georges Bank and Gulf of Maine

Impacts:

• Alters marine habitats and threatens to interfere with fishing, aquaculture, and other coastal and offshore activities
• Grows over organisms such as tunicates, sponges, seaweeds, hydroids, anemones, bryozoans, scallops, mussels, and oysters
• Covers siphons of shellfish living in the seabed
• Blocks bottom-feeding fish from reaching their prey

Common Vector(s):
Shipping: Ballast waterShipping: Fouling

Sea squirt (Didemnum vexillum) Credit: L. Stefaniak, UConn

Sea squirt (Didemnum vexillum) Credit: L. Stefaniak, UConn

Sea squirt (Didemnum vexillum) Credit: Bostwick

Sea squirt (Didemnum vexillum) Credit: Becca Toppin (UNH)

Sea squirt (Didemnum vexillum) Credit: A. Pappal

Sea squirt (Didemnum vexillum) covering rocks, mussels, and barnacles in Harpswell, Maine Credit: Bostwick

Sea squirt (Didemnum vexillum) Credit: A. Pappal