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Bluebell tunicates

Colonies of tunicate Botrylloides violaceus. Note new zooid buds within colonies and along margins of colonies.

Colony of Botryllus.

Tunicates (sea squirts or Urochordata) are a subphylum of the Chordates.

They are sea filter-feeders: they live mainly on plankton. They are called tunicates because the adult form is covered by a leathery tunic. This tunic supports and protects the animal. The adults are sessile, stuck to rocks.

Many tunicates are colonial or semi-colonial in their adult stage. They are quite a large group, containing about 3,000 species. The adults live mostly on the sea floor, in the littoral zone.