Vase Tunicate, Ciona intestinalis

The Vase Tunicate (Ciona intestinalis) is a species of sea squirt widely distributed in Northern European waters. It has also spread to other parts of the world, where it is considered invasive. It grows in dense aggregations on any floating or submerged substrate, especially on artificial structures like pilings, aquaculture gear, floats and boat hulls. It is found in the lower intertidal and subtidal zones.

Sea squirts have been long recognized as being possibly the closest invertebrate relative of humans. Its full genome has been sequenced, and has been found to share nearly 80 percent of its genes with humans. Because of this, it has become a key experimental model for developmental biologists.

The Vase Tunicate is a solitary tunicate with a cylindrical, gelatinous body, about 5.5 inches long. The soft, smooth, translucent outer skin (tunic) is pale yellow or green in color with orange body parts visible through the tunic. The body is bag-like and is attached at a permanent base located at the posterior part, and the opposite bears two openings, the oral and atrial siphons. Water is drawn into the ascidian through the oral siphon and leaves the atrium through the atrial siphon. In their immature tadpole form, they resemble vertebrates.

This tunicate is a hermaphroditic broadcast spawner but cannot self-fertilize. Eggs and sperm, when released, can stay in the water column for 1 to 2 days while larvae are free-swimming for 2 to 10 days.

This species is believed to be spread to new areas mainly through hull fouling. Since larvae can live up to 10 days this species may also be transferred through release of bilge and ballast water. It often grows with or on other fouling organisms. To avoid spreading this organism fish harvesters should avoid transferring harvested shellfish and fishing gear to other areas. Gear should be thoroughly dried before transfer. Boat hulls should be inspected and, if necessary, thoroughly cleaned and disinfected with bleach or vinegar and dried before moving to other areas. Any organisms removed from boat hulls or gear should be disposed of on land. Bilge water should be released on land or disinfected.

Image Caption: Vase Tunicate, Ciona intestinalis. Credit: Wikipedia(CC BY-SA 3.0)