Tunicates, also known as ascidians or sea-squirts, are marine invertebrates belonging to the phylum Chordata and sub-phylum Urochordata. They are found throughout the world's oceans, from the tropics to the poles and from shallow water to the deep sea. Although most tunicates are found attached to hard benthic substrates, some have the ability to live within subtidal soft sediments and others (salps and larvaceans) drift in the plankton. All of the exotic tunicates in NEMESIS are permanently attached (sessile) filter feeders that grow in either solitary or colonial forms. Exotic tunicates are most often introduced through hull fouling on commercial and recreational boats, as well as accidental transfers on aquaculture shipments. While some may be recent world hitchhiking travelers, many have been moved around for decades or centuries. The impacts of exotic tunicates vary across time, place, and species, but some of the most detrimental invaders are those that have had negative effects on shellfish aquaculture. Some exotic tunicates can overgrow shellfish stock and foul infrastructure causing large scale shellfish mortality, reducing shellfish growth and dramatically increasing processing costs.

Schematic of the generalized anatomy of a solitary tunicate. Reprinted by request from Heidi Gartner and Melissa Frey, Royal BC Museum Digital Tunicates Key (http://taxonomy.royalbcmuseum.bc.ca/Taxonomy/viewer/BC_Tunicates.aspx).

Species List

Ascidia sp. A
Ascidia sydneiensis
Ascidia zara
Ascidiella aspersa
Bostrichobranchus pilularis
Botrylloides giganteus
Botrylloides violaceus
Botryllus planus
Botryllus schlosseri
Ciona robusta
Ciona savignyi
Clavelina lepadiformis
Corella inflata
Didemnum perlucidum
Didemnum psammatodes
Didemnum vexillum
Diplosoma aff. spongiforme
Diplosoma listerianum
Ecteinascidia turbinata
Lissoclinum fragile
Microcosmus exasperatus
Microcosmus squamiger
Molgula citrina
Molgula ficus
Molgula manhattensis
Perophora japonica
Polyandrocarpa sagamiensis
Polyandrocarpa zorritensis
Polyclinum constellatum
Styela canopus
Styela clava
Styela plicata
Symplegma brakenhielmi
Symplegma reptans
Databases Overview| Chesapeake Bay | National Database |