Introduced Species

For other chordates:

Kingdom Animalia

Phylum Chordata

Class Ascidiacea

There are many varied and beautifully coloured ascidians in Tasmanian waters. They may stand upright or be encrusting, may be solitary individuals or colonies. All have two 'holes' or siphons, one in which water is drawn into the body (inhalent siphon), the other through which water is expelled from the body (exhalent siphon). With the water comes plankton, which is extracted in the net-like stomach before the water is expelled. These animals are therefore filter feeders. The external skin is quite tough and called the tunic. Ascideans have a rudimentary backbone or notochord in the larval stage, therefore relating ascideans to vertebrates such as fish instead of invertebrates.

Because of the variety of ascideans found around Tasmania, it is difficult to describe all that could be found at the Marine Discovery Centre. Here are a couple of common ascideans collected:

Ascidia sydneiensis - Sea Squirt (Edgar, 1997)

Habitat: Mud, sand; 2-50 m depth Distribution: Around Australia and Tasmania. Maximum Size: Height to 200 mm Diet: Plankton (filter feeder) Comments: This is one of the largest ascideans and is often coated in mud.

Sycozoa pulchra - Ascidean (Edgar, 1997)

Habitat: Sheltered sand, silt; 5 - 15 m depth Distribution: WA to QLD and around Tasmania Maximum Size: Height to 330 mm Diet: Plankton (filter feeder) Comments:  This has a long narrow stalk with a cylindrical head. This species is common and is important to the Spotted Handfish, which uses the stalk to lay it's eggs around. This species is heavily predated on by the Introduced Northern Pacific Sea Star (Asterias amurensis), creating reduced breeding success for the Endangered Spotted Handfish.