D. vexillum grows into lobed, smothering colonies. It is generally whitish to tan, sometimes yellowish according to sources outside southeast Alaska. When growing in rocky shorelines, it tends to colonize the undersides of rocks more thoroughly than their sides which are exposed to the sunlight.
The species has large calcareous spicules, which are somewhat visible with the naked eye as white grains in the tunic, and very dramatic under the microscope. The spicules look like spiked balls.
In Whiting Harbor near Sitka, Stearn's ear-shell (Marsenina stearnsii) and the Two-spotted keyhole limpet (Fissurellidea bimaculata) are apparent predators.
- SERC Marine invasions lab page for Didemnum vexillum
- Alaska invasive species working group page for Didemnum vexillum
- Biological synopsis of the invasive tunicate Didemnum vexillum page for Didemnum vexillum
- Urochordata - Stanford page for Didemnum vexillum
- WoRMS Page for Didemnum vexillum
- Search Arctos Database for Didemnum vexillum (Southeast only)
- Search Arctos Database for Didemnum vexillum (entire database)
- Encyclopedia of Life search for Didemnum vexillum
- iNaturalist Observations for Didemnum vexillum in Southeast Alaska