Biodiversity & Conservation

A sea squirt - Styela clava

Styela clava

Image Keith Hiscock - Styela clava attached to rock. Firestone Bay, Plymouth. Image width ca 8 cm.
Image copyright information

  • #
  • #
  • #
  • #
  • #
  • #
  • #
  • #
  • #
Distribution map

Styela clava recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

Sightings Have you seen Styela clava?
If so please submit your record.

Styela clava is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Chordata Sea squirts, fish, reptiles, birds and mammals
Class Ascidiacea Sea squirts
Authority Herdman, 1882
Recent synonyms Styela mammiculata
Map icon Recorded Distribution in Britain and Ireland Styela clava is distributed on the south and west coasts of England as far north as Cumbria. It has also been found in Loch Ryan and Androssan marina, Scotland, in Cork and Fenit Harbours, Ireland, and the Channel Isles.
Habitat information icon Habitat information Styela clava is found in shallow water on hard surfaces and occurs abundantly in sheltered warm water docks and harbour installations.
Text page icon Description A solitary sea squirt with a long club-shaped body, tapering to a slender and tough stalk. The overall height of the sea squirt can reach 12cm and the stalk can be a 1/3 of the total length. The surface of the sea squirt can be leathery with folds and swellings. The siphons at the top (anterior) end are close together.
Identifying features
  • Body long, narrow and club-shaped.
  • Slender tough stalk can be 1/3 of total length.
  • Total length up to 12 cm.
  • Surface leathery with folds and swellings.
  • Siphons at anterior end close together.
  • 2-4 gonads on left-side and 5-8 on right, each with a long narrow ovary surrounded by male follicles.
Additional information icon Additional information Styela clava is a non native marine species originally from the north western Pacific. It was found in Plymouth Devon in 1953 (Carlisle, 1954) and was possibly introduced on the hulls of war ships following the end of the Korean war in 1951. Styela clava is a fouling pest on ships hulls and oyster beds, and the transport of oysters and any movement of ships probably aided its rapid dispersal (Eno et al., 1997). The distribution of Styela clava was examined recently by Davis & Davis (2004). They reported another 40 new records of this species in European harbours, including new records in the Channel Isles, France and Spain. A similar sea squirt, Styela gelatinosa has only been found in one location and is easily separated from Styela clava by its narrow base or slight stalk.

This review can be cited as follows:

Anna Neish 2007. Styela clava. A sea squirt. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/11/2015]. Available from: <>