Ciona intestinalis (sea vase)

Pictures

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Invasive habit

This SETL-plate, i.e. a PVC-plate attached to a brick on a rope, was completely overgrown by Ciona intestinalis specimens within three months of submersion.

Adriaan Gittenberger/GiMaRIS

Specimens attached to artificial substrate

Ciona intestinalis specimens are often found attached to floating docks or other artificial substrates. Massachusetts, USA.

Adriaan Gittenberger/GiMaRIS

Specimens growing on a mussel rope

Two specimens of Ciona intestinalis growing on a mussel rope in The Netherlands

Adriaan Gittenberger/GiMaRIS

Identity

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Preferred Scientific Name

Ciona intestinalis (Linnaeus, 1767)

Preferred Common Name

sea vase

Other Scientific Names

Ascidia canina Mueller, 1776
Ascidia corrugata Mueller, 1776
Ascidia diaphanea Quoy & Gaimard, 1834
Ascidia intestinalis Linnaeus, 1767
Ascidia membranosa Renier, 1807
Ascidia ocellata Agassiz, 1850
Ascidia pulchella Alder, 1863
Ascidia tenella Stimpson, 1852
Ascidia virens Fabricius, 1779
Ascidia virescens Pennant, 1812
Ascidia viridiscens Brugiere, 1792
Ciona canina Mueller, 1776
Ciona diaphanea Quoy & Gaimard, 1834
Ciona ocellata Agassiz, 1850
Ciona pulchella Alder, 1863
Ciona robusta Hoshino & Tokioka, 1967
Ciona roulei Lahille, 1887
Ciona sociabilis Gunnerus, 1765
Ciona tenella Stimpson, 1852
Phallusia intestinalis Linnaeus, 1767
Tethyum sociabile Gunnerus, 1765

International Common Names

English: transparent sea squirt; yellow sea squirt

Summary of Invasiveness

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C. intestinalis can grow, reproduce and spread quickly (Ramsay et al., 2009), and can alter benthic communities by either smothering other species (Blum et al., 2007), competing with other suspension-feeders for food (Petersen, 2007; Daigle and Herbinger, 2009) or heavily grazing phytoplankton (Petersen and Riisgård, 1992). The native range of C. intestinalis is currently unresolved, and it is formally considered cryptogenic throughout the northern Atlantic. However, its abundance has increased considerably in the Gulf of St Lawrence and New England, so this species can be considered invasive, and likely exotic, to these areas (Locke, 2009). C. intestinalis invasions often exhibit dramatic boom-bust cycles, but it has established persistent populations in some areas (e.g. in southern California for at least a century (Lambert and Lambert, 1998). C. intestinalis poses a significant economic threat to bivalve aquaculture, and has been documented growing in these areas in Hong Kong, New Zealand, Japan, Canada, Spain, South Africa and Chile (Rocha et al., 2009).

Taxonomic Tree

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Domain: Eukaryota
Kingdom: Metazoa
Phylum: Chordata
Subphylum: Tunicata
Class: Ascidiacea
Order: Enterogona
Suborder: Aplousobranchia
Family: Cionidae
Genus: Ciona
Species: Ciona intestinalis

Notes on Taxonomy and Nomenclature

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There are about 15 species within the genus Ciona. Ciona intestinalis is a widespread, morphologically variable species that had been frequently misidentified in the past. Further adding confusion, recent molecular studies have identified at least two cryptic C. intestinalis species, formally referred to as type A and type B. Type A is widely distributed in the Mediterranean and the Pacific and type B is widely distributed throughout the northern Atlantic. Although the two types do coexist in part of their range, they are partially reproductively isolated: crosses of type B eggs with type A sperm result in normal fertilization rates, but reciprocal crosses yield very low fertilization rates (Lambert et al., 1990; Suzuki et al., 2005). See Suzuki et al. (2005), Caputi et al. (2007), Iannelli et al. (2007), and Nydam and Harrison (2007) for further information on the C. intestinalis cryptic species complex.

Description

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C. intestinalis is a solitary, translucent ascidian that can have a pale yellow or pale green hue. If individuals are not fouled by algae or invertebrates, ten muscle bands that run the length of the body are visible, and pale orange internal organs are seen through the translucent body. The brachial siphon has eight lobes and the atrial siphon has six lobes. Both siphons may have yellow or orange margins.

C. intestinalis is most common in enclosed or semi-enclosed shallow embayments, though individuals have been found at depths up to 100 m (Runnström, 1936). Individuals can grow up to 14 cm in length and become sexually mature ~4 cm (Dybern, 1965). Adults are hermaphrodites but do not self-fertilize (Morgan, 1910; Niermann-Kerekenberg and Hofmann, 1989). Both male and female gametes are spawned into the water column and can persist there for 1-2 days. Fertilization results in free-swimming tadpole larvae that can persist from 2-10 days in the water column. As adults, C. intestinalis individuals are sessile suspension-feeders and can form dense aggregations with >5000 individuals/m² (Millar, 1971).

Distribution

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C. intestinalis is now a cosmopolitan species inhabiting sub-arctic, temperate and tropical waters. It is considered to be primarily a cold-water species, but temporary or transient populations have been observed in tropical waters.

C. intestinalis is widely believed to be native to the northern Atlantic; however, it is considered non-indigenous in northern Atlantic Canada (Locke, 2009). Molecular studies have identified two cryptic species, formally called type A and type B (Suzuki et al., 2005; Caputi et al., 2007; Iannelli et al., 2007; Nydam and Harrison, 2007). Type A is now widely distributed in the Mediterranean and the Pacific, type B is widely distributed in the northern Atlantic, with both coexisting in the UK (Caputi et al., 2007).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 17 Dec 2021

Continent/Country/Region	Distribution	Origin	First Reported	Invasive	Reference	Notes
Africa
South Africa	Present	Introduced	1955		Seebens et al. (2017)
Europe
Iceland	Present	Introduced	2007		Seebens et al. (2017)
North America
Canada	Present	Introduced			Seebens et al. (2017)	First reported: 1850 - 1859
United States	Present	Introduced	1917		Seebens et al. (2017)
-Hawaii	Present	Introduced	1933		Seebens et al. (2017)
Oceania
Australia	Present	Introduced	1958		Seebens et al. (2017)
Sea Areas
Arctic Sea	Present	Native			Hartmeyer (1924) Kott (1952)	Denmark Strait, Barents Sea
Atlantic - Eastern Central	Present				Hartmeyer (1924) Pérès (1951)	Cap Verde, east Africa
Atlantic - Northeast	Present, Widespread	Native			Linnaeus (1758) Orton (1914) Runnström (1927)	Sweden, Denmark, Norway, Germany, United Kingdom, Spain
Atlantic - Northwest	Present	Native			LeGresley et al. (2008) Name (1945) Gosner (1978) Carman et al. (2009)	Bay of Fundy
Atlantic - Southeast	Present	Introduced			Millar (1962) Robinson et al. (2005)	South Africa
Atlantic - Southwest	Present	Introduced			Millar (1958) Marins et al. (2009)	Brazil
Indian Ocean - Eastern	Present	Introduced			Kott (1952) McDonald (2004)	Papua New Guinea, Western Australia
Mediterranean and Black Sea	Present, Widespread	Native			Jordan (1908) Lo Bianci (1909) Kott (1952)
Pacific - Eastern Central	Present, Widespread	Introduced		Invasive	Ritter and Forsyth (1917) Lambert and Lambert (1998) Blum et al. (2007)	California (San Diego, San Francisco)
Pacific - Northeast	Present	Introduced			Huntsman (1912) Ritter and Forsyth (1917)	Alaska, British Columbia, Washington
Pacific - Northwest	Present				Yamaguchi (1971) Kang et al. (1978) Blum et al. (2007)	China, Japan, Korea
Pacific - Southeast	Present	Introduced		Invasive	Uribe and Etchepare (2002) Castilla et al. (2005)	Chile
Pacific - Southwest	Present	Introduced			Brewin (1950) Kott (1952)	New Zealand, Southeast Australia
Pacific - Western Central	Present	Introduced			Hartmeyer (1924) Dawydoff (1952) Kott (1997)	Indonessia
South America
Brazil	Present	Introduced	1958		Seebens et al. (2017)
Peru	Present	Introduced	1885		Seebens et al. (2017)

History of Introduction and Spread

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C. intestinalis was introduced to non-native ranges of southern California, South Africa and Brazil at least as early as the twentieth century. The main vector of dispersal is widely believed to be ship fouling, including via sea chests (Lambert and Lambert, 2003). Persistent taxonomic confusion and poor early records prevent more detailed understanding of the history of its introduction and spread. Recently, C. intestinalis has become a nuisance species to aquaculture industries in northern Atlantic Canada and in Chile (Uribe and Etchepare, 2002; Carver et al., 2003).

Introductions

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Introduced to	Introduced from	Year	Reason	Introduced by	Established in wild through		References	Notes
Introduced to	Introduced from	Year	Reason	Introduced by	Natural reproduction	Continuous restocking	References	Notes
Atlantic, Northwest		2004	Aquaculture (pathway cause); Hitchhiker (pathway cause)		Yes		Locke et al. (2009b)	Brundell River, Prince Edward Island, Canada
Pacific, Eastern Central		1917onwards			Yes		Lambert and Lambert (1998); Ritter and Forsyth (1917)	San Diego, CA

Risk of Introduction

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The risk of introduction of C. intestinalis is high. It has a broad temperature and salinity, fast growth rate and high fecundity (Dybern, 1965) and can quickly form dense aggregations (Lambert and Lambert, 1998). C. intestinalis can exclude native species (Blum et al., 2007) and reduce the productivity of aquaculture industries (Uribe and Etchepare, 2002; Carver et al., 2003; Ramsay et al., 2009). Total eradication of C. intestinalis would be costly and has never been attempted (Edwards and Leung, 2009), but rapid-response strategies to reduce population sizes and prevent spread have proven successful (Locke et al., 2009b). Anthropogenic dispersal appears to be common, most likely via hull-fouling and transportation of aquaculture and fishing gear (Lambert and Lambert, 1998). Natural long-distance dispersal is rare because adults are sessile and the dispersive larval stage is short (Petersen and Svane, 1995), although long-distance natural dispersal via rafting on eelgrass or kelp is possible (Havenhand and Svane, 1991).

Habitat

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C. intestinalis grows on submerged substrates including rock, eelgrass and kelp, and on anthropogenic substrates such as wood, metal or concrete docks, pilings and aquaculture gear (Dybern, 1963; 1965; Yamaguchi, 1971; McDonald, 2004). One study found that C. intestinalis was more abundant on vertical surfaces (Costelloe et al., 1986), but it is unclear if this is due to preferential larval settlement, preferential growth rates or higher biotic resistance at other orientations. C. intestinalis is most abundant in enclosed or semi-enclosed embayments, but has been found at depths up to 100 m (Dybern, 1965).

Habitat List

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Category	Habitat	Presence
Littoral	Coastal areas	Present, no further details
Marine
Marine	Inshore marine	Present, no further details
Marine	Benthic zone	Present, no further details

Hosts/Species Affected

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C. intestinalis can quickly form dense aggregations, which can smother and eventually exclude other fouling species and exert heavy grazing pressure on the local phytoplankton and bacterial communities (Peterson and Riisgård, 1992; Lambert and Lambert, 1998; Riisgård et al., 1998; Blum et al., 2007; Petersen, 2007). In Tasmania, C. intestinalis was found to harbour the amoeba, Neoparamoeba pemaquidensis, which is responsible for amoebic gill disease in farmed salmon (Tan et al., 2002).

Biology and Ecology

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Genetics

C. intestinalis is an important experimental model organism for developmental biologists (Chabry, 1887; Morgan, 1910; Minganti, 1948; Sordino et al., 2000). The genome of C. intestinalis was sequenced and published in 2002 (Dehal et al., 2002), thus providing an important tool to study the evolutionary origins of chordates. C. intestinalis has 14 pairs of chromosomes and ~14,000 genes (Shoguchi et al., 2001; Dehal et al., 2002).

Reproductive Biology

Adult C. intestinalis individuals are hermaphrodites that cannot self-fertilize (Morgan, 1910; Niermann-Kerekenberg and Hofmann, 1989). Both male and female gametes are spawned into the water column; however, eggs are released within a sticky mucous string that remain attached to or nearby the parent (Havenhand and Svane, 1991). Eggs are relatively small, 150-200 nm, (Yamaguchi, 1975; Svane, 1983), and fecundity is estimated to be between 5,000-10,000 eggs per individual (Petersen and Svane, 1995). Spawned gametes can persist for 1-2 days, and fertilized eggs develop into free-swimming tadpole larvae that can persist 2-10 days in the water column. Gametogenesis and development rates are both dependent on temperature (Dybern, 1965; Gulliksen, 1972).

C. intestinalis will continuously produce gametes as long as environmental conditions are suitable, with spawning occurring only when temperatures exceed 8°C (Dybern, 1965; Carver et al., 2006).

Physiology and Phenology

C. intestinalis can survive a broad range of temperatures (-1°C to 30°C) (Dybern, 1965; Carver et al., 2003) and salinities (Dybern, 1967). However, survival, growth and filtration rates are reduced at extreme temperatures (Dybern, 1965). Mortality increases at <10°C and filtration rates reduce at >21°C (Petersen et al., 1999) and it appears that this species cannot withstand extended periods with salinity <11 ppt (Dybern, 1967).

C. intestinalis exhibits considerable variation in generation time and spawning phenology across its range, and this variation is believed to be driven by temperature regime (Dybern, 1965). In sub-arctic or deep waters that are cold throughout the year, C. intestinalis can live up to two years and will spawn continuously throughout the year. In waters that exhibit strong seasonal differences in temperature, C. intestinalis lives ~ 1 year and spawns at temperatures >8°C, and in continuously warm waters generation time is short <1 year) and spawning is continuous throughout the year.

Nutrition

C. intestinalis is a suspension-feeder, and uses ciliary action to pump water through its branchial basket, where small particles (0.5-5 µm) including phytoplankton and bacteria are trapped on a mucous sheet (Lambert, 2005, see Petersen, 2007 for a detailed review of feeding anatomy and feeding rates).

Associations

A variety of parasitic or commensal copepods belonging to the order Doropygidae have been found in C. intestinalis and are described in Millar (1971). Three species are known to inhabit the branchial sac: Pachypygus gibber, Hermanilla rostrata (Becheikh et al., 1996) and Lichomolgus carai (Pastore, 2001) and one is documented from the intestines (Ooishi and O’Reilly, 2004).

In Tasmania, C. intestinalis was found to harbour the amoeba responsible for amoebic gill disease, Neoparamoeba pemaquidasis (Tan et al., 2002). The amoeba’s effect on C. intestinalis is unknown.

Environmental Requirements

C. intestinalis has a wide temperature and salinity tolerance, with adults being more tolerant than larvae. Adults can survive temperatures ranging from -1 to 30°C (Dybern, 1965; Carver et al., 2003) and salinities ranging from 8-40 ppt (Dybern, 1967). However, C. intestinalis does not appear to be able to survive salinities persistently below 11 ppt (Dybern, 1967), and growth and filtration rates are reduced at temperature extremes (Dybern, 1965; Petersen and Riisgård, 1992; Riisgård et al., 1996; Petersen et al., 1999).

Development of fertilized eggs into larvae can occur between 6-24°C, but normal metamorphosis is reduced at the extremes of this range (Dybern, 1965; Gulliksen, 1972) and spawning occurs only after water temperature exceeds 8°C (Dybern, 1965; Gulliksen, 1972). Development rates from zygote-larva and from larva-adult correlate positively with temperature.

Water Tolerances

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Parameter	Minimum Value	Maximum Value	Status	Notes
Depth (m b.s.l.)			Optimum	1-100 tolerated
Salinity (part per thousand)	8	42	Optimum	34-42 optimal for embryogenesis (Bellas et al., 2003)
Velocity (cm/h)			Optimum	Prefers semi-protected embayments with good water flow
Water pH (pH)	7	9	Optimum	(Bellas et al., 2003)
Water temperature (ºC temperature)	10	20	Optimum	-1-30 tolerated (Dybern, 1965)

Natural enemies

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Natural enemy	Type	Life stages	Specificity
Asterias rubens	Predator	Aquatic\|Adult	not specific
Aurelia aurita	Predator	Aquatic\|Larval	not specific
Cancer irroratus	Predator	Aquatic\|Adult	not specific
Carcinus maenas	Predator	Aquatic\|Adult	not specific
Hydrobia	Predator	Aquatic\|Adult
Littorina	Predator	Aquatic\|Adult
Mitrella	Predator	Aquatic\|Adult

Notes on Natural Enemies

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Natural enemies include a variety of fish (Yamaguchi, 1971; 1975; Petersen and Svane, 1995), crabs (Carver et al., 2003), seastars (Gulliksen and Skjæveland, 1973; Svane, 1983) and small snails (Mitrella) (Whitlatch and Osman, 2009); Hydrobia and Littorina (Petersen and Svane, 1995) all of which consume adult or newly-settled C. intestinalis. Petersen and Svane (1995) also demonstrated that the jellyfish Aurelia aurita consume substantial amounts of C. intestinalis eggs and larvae.

Means of Movement and Dispersal

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Adults are sessile, so natural dispersal occurs primarily by passive drifting of eggs/egg-strings and active swimming by larvae, although dispersal of adults rafting on eelgrass blades and kelp fronds can occur. The major anthropogenic vectors of adult C. intestinalis are widely believed to be boat hulls and aquaculture equipment (Lambert and Lambert, 1998).

Natural Dispersal (Non-Biotic)

Natural dispersal is very short (0-3 m) and occurs primarily by drifting eggs/egg-strings and swimming larvae. When spawned, eggs are secreted in a sticky mucous string that remains close to the parent, thus promoting spatial aggregation (Svane and Havenhand, 1993). However, ~50% of larvae may escape this mucous string, thereby enabling them to swim short distances away from parents. Dispersal of adults can occur by rafting on eelgrass or kelp (Svane and Havenhand, 1993).

Vector Transmission (Biotic)

Adults can be transported via boat hulls and aquaculture or fishing gear (Lambert and Lambert, 1998). Larvae can be transported in ballast water.

Accidental Introduction

C. intestinalis currently has no commercial or aesthetic values, so all introductions are assumed to be accidental.

Pathway Causes

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Cause	Long Distance	Local
Aquaculture	Yes	Yes
Interconnected waterways		Yes
Research		Yes

Pathway Vectors

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Vector	Notes	Long Distance	Local
Aquaculture stock		Yes	Yes
Floating vegetation and debris	Adult stage, infrequent	Yes	Yes
Ship ballast water and sediment		Yes	Yes
Ship bilge water		Yes	Yes
Ship hull fouling		Yes	Yes

Impact Summary

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Category	Impact
Economic/livelihood	Negative
Environment (generally)	Negative

Economic Impact

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C. intestinalis can reduce the productivity of bivalve aquaculture (Uribe and Etchepare, 2002; Carver et al., 2003; Ramsay et al., 2009) either by fouling aquaculture gear (Yamaguchi, 1975;Kang et al., 1978; Castilla et al., 2005), smothering shellfish or competing with shellfish for food (Daigle and Herbinger, 2009). Edwards and Leung (2009) estimated that fouling by invasive ascidians costs the aquaculture industry on Prince Edward Island approximately Canadian $5 million annually.

Environmental Impact

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C. intestinalis can significantly alter marine benthic communities by competing with native benthic species for space and food and by consuming phytoplankton and possibly invertebrate larvae. C. intestinalis has been demonstrated to exclude sessile marine invertebrates and reduce native biodiversity (Blum et al., 2007), compete with other suspension-feeding species for food (Daigle and Herbinger, 2009), and its relatively high clearance rate (Petersen and Riisgärd, 1992) indicates that it has the potential to significantly alter the phytoplankton community. Furthermore, solitary ascidians species are known to consume invertebrate larvae (Bingham and Walters, 1989) although this has not yet been demonstrated for C. intestinalis specifically.

Impact on Habitats

C. intestinalis can form dense aggregations that can provide a new substrate for fouling organisms. Ciona intestinalis also has the ability to filter a large amount of water, which could alter phytoplankton communities.

Impact on Biodiversity

C. intestinalis reduce the richness of native sessile invertebrate communities (Blum et al., 2007) and can also exert heavy grazing pressure on phytoplankton (Peterson and Riisgård, 1992), potentially altering the diversity of these phytoplankton assemblages.

Risk and Impact Factors

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Invasiveness

Proved invasive outside its native range
Highly adaptable to different environments
Pioneering in disturbed areas
Tolerant of shade
Has high reproductive potential

Impact outcomes

Ecosystem change/ habitat alteration
Host damage
Infrastructure damage
Modification of natural benthic communities
Monoculture formation
Negatively impacts livelihoods
Negatively impacts aquaculture/fisheries
Reduced native biodiversity
Threat to/ loss of native species

Impact mechanisms

Competition - monopolizing resources
Competition - smothering
Pest and disease transmission
Filtration
Fouling
Rapid growth

Uses

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C. intestinalis is used a model organism (Corbo et al., 2001).

Environmental Services

The high clearance rates of C. intestinalis (Peterson and Riisgård, 1992) could help reduce phytoplankton abundance in embayments suffering from nutrient loading. C. intestinalis could also be used as a quick and inexpensive indicator of marine pollution; Bellas et al. (2001, 2003) have developed a C. intestinalis embryonic-larval bioassay protocol for toxic heavy metals.

Uses List

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General

Laboratory use
Research model

Similarities to Other Species/Conditions

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Recent molecular studies have identified at least two cryptogenic species within C. intestinalis: type A which is distributed in the Mediterranean and Pacific and type B which is distributed in the north Atlantic (Suzuki et al., 2005; Caputi et al., 2007; Iannelli et al., 2007; Nydam and Harrison, 2007). There are no obvious morphological differences between these two types, although Caputi et al. (2007) suggest that the two forms can be distinguished by looking at spermiduct pigmentation. With one exception, they found that papillae at the end of the vas deferens (which is located inside the atrial siphon just below the anus) of C. intestinalis type A had bright orange pigmentation whereas the remainder of the duct remained uncoloured. In C. intestinalis type B, bright orange pigmentation is confined to the duct only. Caputi et al. (2007) also report molecular characters that can be used to identify the two types.

C. intestinalis is similar to Ciona savignyi, but can be distinguish by two morphological characters: C. intestinalis has a red dot at the end of its sperm duct that is not present in C. savigyni and C. intestinalis lacks white pigment flecks in its body wall that are present in C. savigyni (Hoshino and Nishikawa, 1985). C. savignyi is believed to be native to Japan. See Hoshino and Nishikawa (1985) for a more detailed description of Ciona species.

Prevention and Control

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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.

Prevention

A C. intestinalis prevention strategy should focus on reducing anthropogenic transport of this species. The main vectors are boat-hulls and aquaculture gear, which should be cleared before transportation from infested areas. On Prince Edward Island (PEI), the Introduction and Transfers committee (I&T) composed of federal and provincial resources managers, academic and governmental scientists, and mussel aquaculture industry representatives enforce aquaculture containment and equipment cleaning laws to prevent the spread of invasive solitary ascidians within the region. These laws were very successful at limiting the spread of another solitary ascidian, Styela clava, but only modestly successful in limiting the spread of C. intestinalis (Locke et al., 2009b).

Rapid response

Locke et al. (2009b) present a superb review of rapid response efforts against four different ascidian species, including C. intestinalis, in Prince Edward Islands, Canada.

Public awareness

Increasing boat-owner awareness is required so that they regularly inspect and clean their boats which is crucial for preventing further spread of not just C. intestinalis, but many other invasive species. Recreational SCUBA divers can also be trained and enlisted in monitoring sites for marine invaders (see the Pacific Northwest REEF Critter-Watcher programme at http://www.pnwscuba.com/critterwatchers/index.htm).

Eradication

No eradication methods are totally effective, but hand-removal, chemical treatments and power-hosing methods continue to be developed and tested. A high-powered hose that can pierce C. intestinalis’ thin tunic has been used to remove it from mussel ropes in Canada and New Zealand. Thoroughly cleaning, drying and washing a substrate in acetic acid is 100% effective at killing C. intestinalis but unfeasible in many situations.

Containment/Zoning

C. intestinalis adults are sessile and larvae have a short dispersal potential, so this species should not spread rapidly by itself. To avoid anthropogenic transfer, boat hulls, aquaculture gear and shellfish should be inspected and if necessary thoroughly dried, cleaned or disinfected with 5% acetic acid before moving to new areas. Any individuals removed should be disposed of on land. Bilge water should also either be released on land or disinfected.

Control

Cultural control and sanitary measures

Recreational boat users should regularly check their boat’s hull, and thoroughly dry and sanitize the hull if C. intestinalis is found. Bilge water should also be either released on land or disinfected.

Physical/mechanical control

Adult C. intestinalis can be removed by hand, but this is a time-consuming and expensive endeavour that is unlikely to eradicate the entire population, especially if it consists of many small individuals. If attempted, hand-removal should be performed right before and a few weeks after the reproductive season, so as to maximize the diver’s ability to see individuals. Alternatively, an underwater vacuuming device has been developed to quickly remove colonial ascidians (Coutts, 2002), and this could theoretically be applied to C. intestinalis removal, although it would likely miss small individuals that are stuck firmly to the substrate. Prolonged exposure to air will kill C. intestinalis, and this method could be used to clear any substrate that can be removed from the water.

Movement control

Anthropogenic transport of adult C. intestinalis individuals can be prevented by thoroughly checking and cleaning boat hulls, aquaculture gear and shellfish before transport.

Chemical control

Exposure to 5% acetic acid is 100% effective against C. intestinalis after 1 minute of exposure, and was found to be a more effective than hydrated lime, saturated brine, or hypochlorite solution treatments (Carver et al., 2003; Locke et al., 2009a).

Monitoring and Surveillance

SCUBA divers surveys are the only known monitoring and surveillance method for C. intestinalis.

Mitigation

In the Prince Edward Islands (PEI), Canada, the regulation of aquaculture transport and harvests has been modestly successful at containing the spread of C. intestinalis. Aquaculture transport, harvest and equipment cleaning regulations were mandated by the PEI Introductions and Transfer Committee under section 55 of Canada’s federal Fishing General Regulations in 2001 and 2002 (Locke et al., 2009). These regulations were actually developed to prevent the spread of an earlier invasive solitary tunicate, Styela clava, and were already in place when C. intestinalis invaded in 2004. Since 2004, C. intestinalis has spread to other rivers and bays in PEI, but it is believed that these regulations have helped slow the invasion.

Ecosystem Restoration

There is currently little to no baseline data concerning pre-invasion ecosystems, thus hindering our ability to assess restoration efforts. At this time, all eradication and management efforts have focused on aquaculture facilities and non-natural habitats.

Gaps in Knowledge/Research Needs

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In contrast to many other invasive marine species, the biology and ecology of C. intestinalis is well known (Berrill, 1947; Dybern, 1965; Dybern, 1967; Lambert and Brandt, 1967; Gulliksen, 1972; Petersen and Svane, Blum et al., 2007; Daigle et al., 2009).

A large-scale molecular study is needed to resolve the distributions of C. intestinalis type A and type B. Further lab and field studies are also needed to determine whether there are any differences in environmental tolerances, growth rates and reproduction of these two types.

References

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Becheikh S; Thomas F; Raibaut A; Renaud F, 1996. Some aspects of the ecology of Pachypygus gibber (Copepoda), an associated organism of Ciona intestinalis (Urochordata). Parasite, 3:247-252.

Bellas J; Beiras R; Vázquez E, 2003. A standardisation of Ciona intestinalis (Chordata, Ascidiacea) embryo-larval bioassay for ecotoxicological studies. Water Research, 37:4613-4622.

Bellas J; Vázquez E; Beiras R, 2001. Toxicity of Hg, Cu, Cd, and Cr on early developmental stages of Ciona intestinalis (Chordata, Ascidiacea) with potential application in marine water quality assessment. Water Research, 35:2905-2912.

Bingham BL; Walters LJ, 1989. Solitary ascidians as predators of invertebrate larvae: evidence from gut analysis and plankton samples. Journal of Experimental Marine Biology and Ecology, 342:5-14.

Blum JC; Chang AL; Liljeshröm M; Schenk ME; Steinberg MK; Ruiz GM, 2007. The non-native Ciona intestinalis (L.) depresses species richness. Journal of Experimental Marine Biology and Ecology, 342:5-14.

Brewin BL, 1950. Ascidians of New Zealand. Part IV: Ascidians in the vicinity of Christchurch. Transactions of the Royal Society of New Zealand, 78:344-353.

Caputi L; ; reakis N; Mastrototaro F; Cirino P; Vassillo M; Sordino P, 2007. Cryptic speciation in a model invertebrate chordate. Proceedings of the National Academy of Sciences,USA, 104:9364-9369.

Carman MR; Hoagland KE; Green-Beach E; Grunden DW, 2009. Tunicate faunas of two North Atlantic-New England islands: Martha's Vineyard Massachusetts and Black Island, Rhode Island. Aquatic Invasions, 4:65-70.

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Kang PA; Bae PA; Pyen CK, 1978. Studies on the suspended culture of oyster, Crassostrea gigas in Korean coastal waters. On the fouling organisms associated with culturing oysters at the oyster culture farms in Chungmu. Bulletin of Fisheries Research and Development Agency, 20:121-127.

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Lo Bianci S, 1909. [English title not available]. (Notizie biologiche riguardanti specialmente il periodic di maturita sessuale degli animali del golfo di Napoli) Mittheilungen aus der Zoologischen Staatsinst zu Neapel, 19:513-761.

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Pérès JM, 1951. Nouvelle contribution à l'éude des ascidies de la côte occidentale d'Afrique. Bulletin de la Institute France Afrique Noir, 13.

Petersen JK, 2007. Ascidian suspension feeding. Journal of Experimental Marine Biology and Ecology, 342:127-137.

Petersen JK; Mayer S; Knudson MA, 1999. Beat frequency of cilia in the branchial basket of the ascidian Ciona intestinalis in relation to temperature and algal cell concentration. Marine Biology, 133:185-192.

Petersen JK; Svane I, 1995. Larval dispersal in the ascidian Ciona intestinalis (L.). Evidence for closed dispersal. Journal of Experimental Marine Biology and Ecology, 186:89-102.

Peterson JK; Riisgard HU, 1992. Filtration capacity of the ascidian Ciona intestinalis and its grazing impact in a shallow fjord. Marine Ecology Progress Series, 88:9-17.

Piola RF; Johnston EL, 2008. Pollution reduces native diversity and increases invader dominance in marine hard-substrate communities. Diversity and Distributions, 14:329-342.

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Yamaguchi M, 1975. Growth and reproductive cycles of the marine fouling ascidians Ciona intestinalis, Styela plicata, Botrylloides violaceus and Leptoclinum mitsukurii at Aburatsubo-Moroiso inlet (Central Japan). Marine Biology, 29:253-259.

Distribution References

Blum J C, Chang A L, Liljeshröm M, Schenk M E, Steinberg M K, Ruiz G M, 2007. The non-native Ciona intestinalis (L.) depresses species richness. Journal of Experimental Marine Biology and Ecology. 5-14.

Brewin B L, 1950. Ascidians of New Zealand. Part IV: Ascidians in the vicinity of Christchurch. Transactions of the Royal Society of New Zealand. 344-353.

CABI, Undated. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Carman M R, Hoagland K E, Green-Beach E, Grunden D W, 2009. Tunicate faunas of two North Atlantic - New England islands: Martha's Vineyard Massachusetts and Black Island, Rhode Island. Aquatic Invasions. 65-70.

Castilla J C, Uribe M, Bahamonde N, Clarke M, Desqueyroux-Faúndez R, Kong I, Moyano H, Rozbaczylo N, Santelices B, Valdovinos C, Zavala P, 2005. Down under the southeastern Pacific: marine non-indigenous species in Chile. Biological Invasions. 213-232.

Dawydoff C, 1952. Bulletin Biologique de France Belgique,

Gosner K L, 1978. A field guide to the Atlantic seashore. Boston, MA, USA: Houghton Mifflin Company. 329.

Hartmeyer R, 1924. Ascidiacea, Pt. 2. In: Danish Ingolf Expedition, Vol. 2, 1-278.

Huntsman A G, 1912. Ascidians from the coasts of Canada. Transactions of Canadian Institutes. 11-148.

Jordan H, 1908. About reflex-poor animals. A contribution to comparative physiology of the central nervous system, primarily on the basis of experiments on Ciona intestinalis and octopuses. (Über reflezarme tiere. Ein Beitrag zur vergleichende physiologie des zentralen nervensystems, vornehmlich auf grund von versuche an Ciona intestinalis und Oktopoden.). Zeitschrift für Allgemeine Microbiologie. 86-135.

Kang P A, Bae P A, Pyen C K, 1978. Studies on the suspended culture of oyster, Crassostrea gigas in Korean coastal waters. On the fouling organisms associated with culturing oysters at the oyster culture farms in Chungmu. Bulletin of Fisheries Research and Development Agency. 121-127.

Kott P, 1952. The ascidians of Australia. Australian Journal of Marine and Freshwater Research. 206-233.

Kott P, 1997. The Tunicates. In: Marine Invertebrates of Southern Australia, Part I. [ed. by Shepherd S A, Thomas I M]. Adelaide, South Australia, Australia: Government Printer. 1092-1255.

Lambert C C, Lambert G, 1998. Non-indigenous ascidians in southern California harbors and marinas. Marine Biology. 675-688.

LeGresley M, Marin J L, McCurdy P, Thrope B, Chang B D, 2008. Non-indigenous tunicate species in the Bay of Fundy, eastern Canada. ICES Journal of Marine Science. 770-774.

Linnaeus C, 1758. [English title not available]. (Systema Naturae per Regna Tria Naturae, Secundum classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. Tomus I. ed. X.). In: Systema Naturae per Regna Tria Naturae, Secundum classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. Tomus I. ed. X.

Lo Bianci S, 1909. Biological information regarding the frequency of sexual maturity of animals in the Gulf of Naples. (Notizie biologiche riguardanti specialmente il periodic di maturita sessuale degli animali del golfo di Napoli.). Mittheilungen aus der Zoologischen Staatsinst zu Neapel. 513-761.

Marins F D O, Oliviera C D S, Maciel N M V, Skinner L F, 2009. Reinclusion of Ciona intestinalis (Ascidiacea: Cionidae) in Brazil - a methodological view. JMBA2- Biodiversity Records.

McDonald J, 2004. The invasive pest species Ciona intestinalis (Linnaeus 1767) reported in a harbour in southern Western Australia. Marine Pollution Bulletin. 868-870.

Millar R H, 1958. Some ascidian from Brazil. Annals and Magazine of Natural History. 497-514.

Millar R H, 1962. Further descriptions of South African ascidians. Annals of the South African Museum. 113-221.

Name W G Van, 1945. Bulletin of the American Museum of Natural History, 84, 1-476.

Orton J H, 1914. Preliminary account of a contribution to an evaluation of the sea. Journal of the Marine Biological Association. 312-326.

Pérès J M, 1951. A new contribution to the study of the ascidians of the coast of West Africa. (Nouvelle contribution à l'éude des ascidies de la côte occidentale d'Afrique.). In: Bulletin de la Institute France Afrique Noir.

Ritter W E, Forsyth R A, 1917. Ascidians of the littoral zone of southern California. University of California Publications in Zoology. 439-512.

Robinson T B, Griffiths C L, McQuaid C D, Rius M, 2005. Marine alien species of South Africa - status and impacts. South African Journal of Marine Science. 297-306.

Runnström S, 1927. Effects of temperature on the reproduction and development of marine animals. (Über die Thermopathie der Fortpflanzung und Entwicklung Mariner Tiere.). Bergens Museum Arbok. 1-67.

Seebens H, Blackburn T M, Dyer E E, Genovesi P, Hulme P E, Jeschke J M, Pagad S, Pyšek P, Winter M, Arianoutsou M, Bacher S, Blasius B, Brundu G, Capinha C, Celesti-Grapow L, Dawson W, Dullinger S, Fuentes N, Jäger H, Kartesz J, Kenis M, Kreft H, Kühn I, Lenzner B, Liebhold A, Mosena A (et al), 2017. No saturation in the accumulation of alien species worldwide. Nature Communications. 8 (2), 14435. http://www.nature.com/articles/ncomms14435

Uribe E, Etchepare I, 2002. Effects of biofouling by Ciona intestinalis on suspended aquaculture of Agropecten purpuratus in Bahia Inglesa, Chile. Bulletin of the Aquaculture Association of Canada. 93-95.

Yamaguchi M, 1971. Natural substrata of marine fouling animals. Scientific Reports of the Yokosuka Cy Museum. 110-121.

Links to Websites

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Website	URL	Comment
Genome Project Ciona intestinalis	http://genome.jgi-psf.org/Cioin2/Cioin2.home.html
MarineSpecies.org	http://www.marinespecies.org
NIMPIS 2011	http://www.marinepests.gov.au/nimpis	Balanus improvisus general information, National Introduced Marine Pest Information System,

Organizations

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Canada: Department of Fisheries and Aquaculture, Department of Fisheries, Aqualculture and Rural Development Fifth Floor, Jones Building, 11 Kent St, PO Box 2000, Charlottetown, PEI

Ontario: Department of Fisheries and Ocean - Canada, Fisheries and Oceans Canada Communications Branch 200 Kent Street, 13th Floor, Station 13E228, Ottawa, http://www.dfo-mpo.gc.ca

Contributors

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19/06/09 Original text by:

Erin Grey, University of Chicago, USA

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Ciona intestinalis (sea vase)

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