Ascidiella aspersa (European sea squirt)
Datasheet Type: Invasive species
Abstract
This datasheet on Ascidiella aspersa covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Impacts, Prevention/Control, Further Information.
Identity
- Preferred Scientific Name
- Ascidiella aspersa
- Preferred Common Name
- European sea squirt
- Other Scientific Names
- Acidia expansa (Kiaer, 1893)
- Ascidia aculeata (Alder, 1863)
- Ascidia affinis (Hancock, 1870)
- Ascidia albida (Alder & Hancock, 1848)
- Ascidia aspersa (Müller, 1776)
- Ascidia elliptica (Alder & Hancock, 1848)
- Ascidia minuta (Kiaer, 1893)
- Ascidia normanni (Alder & Hancock, 1870)
- Ascidia opalina (Macgillivray, 1843)
- Ascidia patula (Müller, 1776)
- Ascidia pedunculata (Hoffman, 1829)
- Ascidia pellucida (Alder & Hancock, 1848)
- Ascidia pustulosa (Alder, 1863)
- Ascidia scabra (Müller, 1776)
- Ascidia sordida (Alder & Hancock, 1848)
- Ascidia triangularis (Herdman, 1881)
- Ascidia truncata (Herdman, 1881)
- Ascidiella aspersa (Kiaer, 1893)
- Ascidiella cristata (Roule, 1884)
- Phallusia aspersa (Traustedt, 1883)
- Phallusia cristata (Risso, 1826)
- International Common Names
- Englishdirty sea squirt
- Frenchascidie sale
- Local Common Names
- GermanySpritz-Ascidie
- Netherlandsruwe zakpijpvuilwitte zakpijp
Summary of Invasiveness
Ascidella aspersa (European sea squirt) is a solitary marine and estuarine tunicate that is native from Norway to the Mediterranean. It is a suspension filter-feeder and was introduced via foulling on the hulls of ships to the northwest coast of the Atlantic, India, Australia and New Zealand. Commonly called the European sea squirt, it has become a moderate to serious threat by displacing native fauna.
Taxonomic Tree
Description
Ascidiella aspersa (European sea squirt) is a marine organism classified as a tunicate. The classification comes from a transparent, thick and rough (Curtis, 2005) cartilaginous tunic that covers the body of the adult organism (de Kluijver, 2004). The surface of the tunicate is rough and finely papillated (de Kluijver, 2004), greyish-black to brown (Curtis, 2005) with two siphons, a terminal brachial siphon, and an atrial siphon located up to one-third the length of the body away from the terminal siphon (de Kluijver, 2004). The brachial siphon is 6-8 lobed, while the atrial siphon is 6 lobed (de Kluijver, 2004). The siphons may be frilled (Curtis, 2005). The intestinal gut is located to the left of the brachial sac with numerous rows of straight stigmata (de Kluijver, 2004).
Distribution
Native range: Norway, Baltic Sea, Irish Sea, English Channel, Mediterranean Sea, northwest African coasts (Currie, 1998; de Kluijver, 2004; NIMPIS, 2010).
Known introduced range: United States (Maine, Massachusetts, Rhode Island, Conneticut), New Zealand, Southern Australia, Tasmania, India (NIMPIS, 2010; Currie, 1998; Pederson et al. 2003; Osman, undated).
Known introduced range: United States (Maine, Massachusetts, Rhode Island, Conneticut), New Zealand, Southern Australia, Tasmania, India (NIMPIS, 2010; Currie, 1998; Pederson et al. 2003; Osman, undated).
Distribution Map
Distribution Table
Means of Movement and Dispersal
Introduction pathways to new locations
Aquaculture: Ascidiella aspersa (European sea squirt) could have been accidentaly introduced through aquaculture materials (Carlton, 2003).
Ship ballast water: Ship ballast water is also considered a potential pathway for Ascidiella aspersa (European sea squirt) introduction into the New England area (Carlton, 2003).
Ship/boat hull fouling:Ascidiella aspersa (European sea squirt) was first detected in New England in the 1980s, introduced by hull foulling (Carlton, 2003).
Local dispersal methods
Water currents:Ascidiella aspersa (European sea squirt) releases its gametes into the water column where fertilization occurs. While in the water column local tidal forces and ocean currents can transport these free-swimming gametes to new locations (Hewitt et al 2002).
Aquaculture: Ascidiella aspersa (European sea squirt) could have been accidentaly introduced through aquaculture materials (Carlton, 2003).
Ship ballast water: Ship ballast water is also considered a potential pathway for Ascidiella aspersa (European sea squirt) introduction into the New England area (Carlton, 2003).
Ship/boat hull fouling:Ascidiella aspersa (European sea squirt) was first detected in New England in the 1980s, introduced by hull foulling (Carlton, 2003).
Local dispersal methods
Water currents:Ascidiella aspersa (European sea squirt) releases its gametes into the water column where fertilization occurs. While in the water column local tidal forces and ocean currents can transport these free-swimming gametes to new locations (Hewitt et al 2002).
Pathway Causes
| Pathway cause | Notes | Long distance | Local | References |
|---|---|---|---|---|
| Aquaculture (pathway cause) | Yes | |||
| Hitchhiker (pathway cause) | Yes | Yes |
Pathway Vectors
| Pathway vector | Notes | Long distance | Local | References |
|---|---|---|---|---|
| Ship ballast water and sediment (pathway vector) | Yes | |||
| Ship hull fouling (pathway vector) | Yes | Yes | ||
| Water (pathway vector) | Yes |
Similarities to Other Species/Conditions
Ascidiella scabra in some of the literature is considered to be identical to A. aspersa, however in one account differences between the two have been recorded. The size of A. scabra at maturity is much smaller than A. aspersa, reaching only a maximum length of 5 cm. A. scabra has reddish coloration that is diffuse through the tunic, while in A. aspersa the reddish coloration is localized near the siphons. The siphons in A. scabra are also closer together in length than in A. aspersa. The size at which A. scabra becomes sexually mature is much smaller at 2 cm when compared with A. aspersa at a size of 5 cm (Berrill, undated). ascidie jaune (French), cione (French), doorschijnende zakpijp (Dutch), gelbe seescheide (German), sea vase (English), vase tunicate (English), yellow sea squirt (English)Molgula spp. may be mistaken for A. aspersa juveniles, but Molgula spp. are more spherical in shape, do not get as large as A. aspersa at maturity and have both siphons at the apex (Salem Sound Coastwatch, undated).
Ciona intestinalis is more slender than A. aspersa and has yellow markings at the siphons which A. aspersa does not (Salem Sound Coastwatch, undated).
The best identification difference between Styela clava and A. aspersa is that the latter has one siphon located at the terminal end and the third one-third the length down its body, while S. clava has both siphons located on its apex (Salem Sound Coastwatch, undated).
Habitat
A. aspersa (European sea squirt) is a solitary tunicate but often forms unfused colonies in close association with each other (Curtis, 2005). It can tolerate salinities from 18-40 ppt (NIMPIS, 2010). This species establishes in subtidal and low water depth, with maximum settlement depth of 90m (de Kluijver, 2004). It can establish on soft muds but is commonly found associated with hard subtrates, like pier pylons (Currie, 1998), rocks, docks, etc. (Pederson, 2003). A. aspersa is found in low energy habitats, like estuaries, harbours and semi-enclosed embayments that protect them from strong currents and tidal forces (NIMPIS, 2010). Establishment is not inhibited by native fauna for substrate sites (Osman, undated). The establishment of A aspersa is increasing as global and ocean water temperatures increase (Stachowicz, 2002).
Habitat List
| Category | Sub category | Habitat | Presence | Status |
|---|---|---|---|---|
| Multiple | ||||
| Littoral | Coastal areas | Present, no further details | Harmful (pest or invasive) | |
| Brackish | Estuaries | Present, no further details | Harmful (pest or invasive) | |
| Marine | Present, no further details | Harmful (pest or invasive) |
Biology and Ecology
Nutrition
Ascidiella aspersa (European sea squirt) is a filter-feeding organism (Currie, 1998) with a brachial siphon that regulates inflowing water and an atrial siphon that controls water release (de Kluijver, 2004).
Ascidiella aspersa (European sea squirt) is a filter-feeding organism (Currie, 1998) with a brachial siphon that regulates inflowing water and an atrial siphon that controls water release (de Kluijver, 2004).
Reproduction
Ascidiella aspersa (European sea squirt) is hemaphroditic, containing both male and female sex organs, although the male sex organs develop first (Millar, 1952). In spring to early summer both male and female gametes are released into the water column where fertilisation takes place (NIMPIS, 2010). Chemotaxis interactions occur between sperm and egg, with homospecific chemical signalling of the egg, increasing sperm activity in the water column (Bolton, 1996). Larva go through a brief free-swimming stage and then quickly metamorphosise into a juvenile and begin settlement (NIMPIS, 2010).
Ascidiella aspersa (European sea squirt) is hemaphroditic, containing both male and female sex organs, although the male sex organs develop first (Millar, 1952). In spring to early summer both male and female gametes are released into the water column where fertilisation takes place (NIMPIS, 2010). Chemotaxis interactions occur between sperm and egg, with homospecific chemical signalling of the egg, increasing sperm activity in the water column (Bolton, 1996). Larva go through a brief free-swimming stage and then quickly metamorphosise into a juvenile and begin settlement (NIMPIS, 2010).
Lifecycle stages
Ascidiella aspersa (European sea squirt) has a lifespan of 18 months, from mid-summer to the following year's winter (Millar, 1952). In early to mid-summer larval settlement and metamorphosis occurs and takes approximately 24 hours at 20°C (NIMPIS, 2010). Growth is continued through the fall and into the winter, although growth in winter is reduced. Upon reaching a size of 30mm, the male sexual organs begin to fill with sperm and at a much bigger size the female eggs begin to fill the oviducts. At a size of 40mm, both sex organs are fully mature (Millar, 1952). One spawning season occurs, usually one year after larval settlement (Millar, 1952). Under laboratory conditions (Bolton, 1996), there was an observed synchronous response to light in the spawning of ascidians.
Ascidiella aspersa (European sea squirt) has a lifespan of 18 months, from mid-summer to the following year's winter (Millar, 1952). In early to mid-summer larval settlement and metamorphosis occurs and takes approximately 24 hours at 20°C (NIMPIS, 2010). Growth is continued through the fall and into the winter, although growth in winter is reduced. Upon reaching a size of 30mm, the male sexual organs begin to fill with sperm and at a much bigger size the female eggs begin to fill the oviducts. At a size of 40mm, both sex organs are fully mature (Millar, 1952). One spawning season occurs, usually one year after larval settlement (Millar, 1952). Under laboratory conditions (Bolton, 1996), there was an observed synchronous response to light in the spawning of ascidians.
Impact Summary
| Category | Impact |
|---|---|
| Biodiversity (generally) | Negative |
Impact
General Impacts
Compiled by IUCN SSC Invasive Species Specialist Group (ISSG)
Ascidiella aspersa
(European sea squirt) has several impacts on the environment, mainly in the form of affecting the native fauna. The tunicate can form large populations and subsequent high amounts of biomass (Pederson et al. 2003), which redirects energy pathways to decomposers and not to higher trophic communities because it lacks many predators (Currie, 1998). It also directly competes with other native filter-feeding fauna of economic importance like scallops, mussels and oysters (Currie, 1998).
Risk and Impact Factors
Invasiveness
Proved invasive outside its native range
Has high reproductive potential
Impact outcomes
Altered trophic level
Negatively impacts aquaculture/fisheries
Threat to/ loss of native species
Impact mechanisms
Competition - monopolizing resources
Prevention and Control
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Management Information
Compiled by IUCN SSC Invasive Species Specialist Group (ISSG)
Chemical: Copper based anti-fouling paints have minimal affect on Ascidiella aspersa (European sea squirt). The use of copper compounds is not cost effective under broad applications and is nonspecific, so open sea applications is both illegal and not recommended (McEnnulty et al. 2001).
Links to Websites
| Name | URL | Comment |
|---|---|---|
| GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gateway | https://doi.org/10.5061/dryad.m93f6 | Data source for updated system data added to species habitat list. |
| Global register of Introduced and Invasive species (GRIIS) | http://griis.org/ | Data source for updated system data added to species habitat list. |
Bibliography
Berrill, N.J., undated, The Identification and Validity of Certain Species of Ascidians, Journal of the Marine Biological Association of the United Kingdom, pp.159-175. http://sabella.mba.ac.uk/579/01/The_identification_and_validity_of_certain_species_af_ascidians.pdf
Bolton, T.F., & Havenhand, J.N., June, 1996, Chemical Mediation of Sperm Activity and Longevity in the Solitary Ascidians Ciona intestinalis and Ascidiella aspersa, Biol. Bull., 190, pp. 329-335. http://www.biolbull.org/cgi/reprint/190/3/329.pdf
Carlton, J.T., 2003, Community assembly and historical biogeography in the North Atlantic Ocean: the potential role of human-mediated dispersal vectors, Hydrobiologia, 503, pp.1-8.
Centre for Environment, Fisheries & Aquaculture Science (CEFAS)., 2008. Decision support tools-Identifying potentially invasive non-native marine and freshwater species: fish, invertebrates, amphibians. http://www.cefas.co.uk/projects/risks-and-impacts-of-non-native-species/decision-support-tools.aspx
Connecticut Aquatic Nuisance Species Working Group, 2005. Connecticut Aquatic Nuisance Species Management Plan. http://www.ctiwr.uconn.edu/ProjANS/SubmittedMaterial2005/Material200601/ANS%20Plan%20Final%20Draft121905.pdf
Costello, M.J., Bouchet, P., Boxshall, G., Emblow, C., Vanden Berghe, E., 2004, European Register of Marine Species, [online database]. http://www.marbef.org/data/aphia.php?p=taxdetails&id=103718
Currie, D.R., McArthur, M.A., & Cohen, B.F., Sept. 1998, Exotic Marine Pests in the Port of Geelong, Victoria, Marine and Freshwater Resources Institute, Report no. 8.
Curtis, L., 2005, Ascidiella aspersa, A sea squirt. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [online]. Plymouth: Marine Biological Association of the United Kingdom. http://www.marlin.ac.uk/species/Ascidiellaaspersa.htm
de Kluijver, M.J., & Ingalsuo S.S., Feb. 4, 2004, Macrobenthos of the North Sea-Tunicata, Zoological Museum, University of Amsterdam
McEnnulty, F.R., Jones, T.E., & Bax, N.J., June 2001, Copper Compounds, Wed-Based Rapid response Toolbox, Web-publication, [online]. http://www.marine.csiro.au/crimp/NIMPIS/controlDetail.asp?ID=87
Millar, R.H., 1952, The Annual Growth and Reproductive Cycle in Four Ascidians, Journal of the Marine Biological Association of the United Kingdom, vol. 31, no. 1, pp. 41-61. http://sabella.mba.ac.uk/1498/01/The_annual_growth_and_reproductive_cycle_in_four_ascidians.pdf
NIMPIS, 2010. Ascidiella aspersa general information. National Introduced Marine Pest Information System. http://adl.brs.gov.au/marinepests/index.cfm?fa=main.spDetailsDB&sp=6000005711#generalInfo
Osman, R.W. & Whitlatch, R.B. 1999. Ecological interactions of invading ascidians within epifaunal communities of Southern New England. In Abstracts: First National Conference on Marine Bioinvasions, January 24 -27, 1999. Massachusetts Institute of Technology, Cambridge, MA http://massbay.mit.edu/publications/marinebioinvasions/mbi1_abstracts.pdf
Osman, R.W. & Whitlatch, R.B., undated, Ecological factors controlling the successful invasion of three species of ascidians into marine subtidal habitats of New England, CSA Illumina.
Pederson, J., & Adams, C., April 12, 2003, MIT Sea Grant, Center for Coastal Resources, Ascidiella aspersa. http://massbay.mit.edu/exoticspecies/exoticmaps/descriptions_intro.html
Pederson, J., Bullock, R.,Carlton, J., Dijkstra, J., Dobroski, N., Dyrynda, P., Fisher, R., Harris, L., Hobbs, N., Lambert, G., Lazo-Wasem, E., Mathieson, A., Miglietta, M-P., Smith, J., Smith III, J., & Tyrrell, M., August 3-9, 2003, Marine Invaders in the Northeast, Rapid Assessment Survey of Non-native and Native Marine Species of Floating Dock Communities.
Salem Sound Coastwatch, undated, MA Executive Office of Environmental Affairs, Office of Coastal Zone Management, U.S. Fish and Wildlife Service. http://www.mass.gov/czm/invasives/docs/invaders/a_aspersa.pdf
Stachowicz, J.J., Terwin, J.R., Whitlatch, R.B., & Osman, R.W., Nov. 26, 2002, Linking climate change and biological invasions: Ocean warming facilitates nonindigenous species invasions, PNAS, vol. 99, no. 24, pp. 15497-15500. http://www.pubmedcentral.nih.gov/picrender.fcgi?tool=pmcentrez&blobtype=pdf&artid=137745
Whitlatch, R.B. and Osman, R.W. 1999. Geographical distributions and organism-habitat associations of shallow-water introduced marine fauna in New England. In Abstracts: First National Conference on Marine Bioinvasions, January 24 -27, 1999. Massachusetts Institute of Technology, Cambridge, MA http://massbay.mit.edu/publications/marinebioinvasions/mbi1_abstracts.pdf
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References
ISSG, 2011. Global Invasive Species Database (GISD). Invasive Species Specialist Group of the IUCN Species Survival Commission. http://www.issg.org/database
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Published online: 10 March 2010
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