Taxonomy
Styela clava | Leathery Sea Squirt
Distribution
Status
Conservation status
Not Assessed
Legal status
Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted). Listed as a schedule 9 species under Articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).
Native status
Non-native
First reported in the wild
1971
Invasiveness
Invasive species - risk of High Impact
Irish status
Established
Introduction pathways - 1
Transport Stowaway
Introduction pathways subclass - 1
Ship/boat ballast water
Introduction pathways - 2
Transport Contaminant
Introduction pathways subclass - 2
Contaminant on animals
Invasive score
19
NAPRA Ireland risk assessed
No
Species Biology
Identification
Unitary sea squirt, club shaped, with a long oval body attaching to the substrate via a tapered peduncle, chocolate brown with a 'leathery' appearance, maximum length 150mm (Lutzen, 1999).
Ecology
Competes for space with native species and 'bio-fouls' by growing densely on pontoons, ropes, boats and marinas (Nunn & Minchin, 2009).
Habitat
Marine
Reproduction
Hermaphrodite, larvae brooded internally.
Pathway and vector description
Likely introduced to Ireland with Pacific oyster (Crassostrea gigas) or on leisure craft, as most locations in Ireland where it has been recorded to date have oyster cultures or/and a marina (Nunn & Minchin, 2009). Subsequent spread is likely by leisure craft, as larva in ballast water or adults attached to sheltered parts of the hull (Minchin et al., 2006).
Mechanism of impact
Competition, Bio-fouling
Broad environment
Marine
Habitat description
Low tidal to sub-tidal species in sheltered habitats with low wave action, such as inlets, bays, harbours and marinas (Lutzen, 1999). Attaches to various objects including rocks, stones, shells or live or dead bivalves, Saccharina latissima and Sargassum muticum, as well as a variety of man made objects (Lutzen, 1999).
Species group
Vertebrate
Native region
Temperate Asia
Distribution
World distribution(GBIF)
Irish distribution
Established - Widespread. Likely under recorded.
Native distribution
Native to the Sea of Okhotsh, Sea of Japan and the coasts of Japan, Korea and northern China as far south as Shanghai (Abbott & Johnson, 1972).
Temporal change
Date of first record category
1971-1980
Fifty year date category
1951-2000
Records submitted to Data Centre in 2024
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
Report any sightings to the National Biodiversity Data Centre.
Further information
Delivering Alien Invasive Species In Europe (DAISIE) project list this as one of the 100 Worst Invaders in Europe.
References
Publications
Guiry, G. M., & Guiry, M. D. (1973). Spread of an introduced ascidian to Ireland. Marine Pollution Bulletin, 4(8), 127. Nunn, J. D., & Minchin, D. (2009). Further expansions of the Asian tunicate Styela clava Herdman 1882 in Ireland. Aquatic Invasions, 4(4), 591-596.Minchin, D., Davis, M. H., & Davis, M. E. (2006). Spread of the Asian tunicate Styela clava Herdman, 1882 to the east and south-west coasts of Ireland. Aquatic Invasions, 1(2), 91-96. Minchin, D. (2007). A checklist of alien and cryptogenic aquatic species in Ireland. Aquatic Invasions, 2(4), 341-366. Lützen, J. (1998). Styela clava Herdman (Urochordata, Ascidiacea), a successful immigrant to North West Europe: ecology, propagation and chronology of spread. Helgoländer Meeresuntersuchungen, 52(3-4), 383-391. Abbott, D P. & Johnson, J. V. (1972) The Ascidians Styela barnharti, S. plicata, S. clava, and S. montereyensis in Californian Waters. Bulletin of the Southern California Academy of Sciences.71(2)
Relevant links
Global Invasive Species Database