Sea vase

Sea vase

Ciona intestinalis

Common name:

Sea vase

Scientific name:

Ciona intestinalis

Alternative common names:


Sea vase is highly competitive species that is a major pest of shellfish aquaculture production. Indigenous to the northern Atlantic Ocean, it has been recorded as an invader of harbours in both temperate and tropical climates. In South Africa, it has been recorded in harbours ranging from Saldanha Bay to Durban.

Additional Information

Where does this species come from?

Northern Atlantic Ocean.

What is its invasive status in South Africa?

NEMBA Category 3.

Where in South Africa is it a problem?

Western Cape, Eastern Cape and KwaZulu-Natal.

How does it spread?

Sea vase is spread primarily as a hull fouling species on commercial vessels or it is associated with aquaculture transfers.

Why is it a problem?

It is known to reduce the amount of food available in shallow waters and can outcompete indigenous species for space and food. It is also a nuisance in aquaculture farms around the world due to its high fouling tendencies.

What does it look like?

Description: Sea vase is a cylindrical, translucent ascidian, ending in a cone-shaped siphon. The opening of the siphon may be bordered in yellow and have orange or red spots, and the body wall is a pale yellow-green with clearly visible muscle bands. The body is usually soft and is commonly 100-150mm in length.

Habitat: Sea vase lives attached to submerged rocks or other hard surfaces, such as ropes, chains and boat hulls. It has a cosmopolitan distribution and tolerates organic pollution and a wide range of environmental conditions. It is abundant in ports and marinas all over the world.

Breeding: Sea vase is hermaphroditic like many ascidians, making it capable of self-fertilisation, and is also known to exhibit broadcast spawning. Each adult is capable of spawning once a day during the spawning period and can release up to 500 eggs per day. These eggs are released in mucus strings that float and become tangled around other nearby adults or other protrusions.

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