Didemnum vexillum

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Marine vomit:
Marine vomit (Didemnum vexillum): This is an invasive tunicate species of great concern. All regional sightings outside Whiting Harbor should be reported to the Alaska Department of Fish and Game as soon as possible.

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.

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