Botrylloides violaceus (violet tunicate)
Index
- Pictures
- Identity
- Summary of Invasiveness
- Taxonomic Tree
- Description
- Distribution
- Distribution Table
- Introductions
- Habitat
- Habitat List
- Biology and Ecology
- Water Tolerances
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact
- Risk and Impact Factors
- References
- Contributors
- Distribution Maps
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Top of page| Picture | Title | Caption | Copyright |
|---|---|---|---|
| Colour morphs | Botrylloides violaceus colonies occur in many colours and can overgrow large areas. Netherlands coast. | Adriaan Gittenberger/GiMaRIS | |
| Invasive habit | The reddish Botrylloides violaceus colonies overgrow and potentially suffocate the mussels. Massachusetts coast, USA. | Adriaan Gittenberger/GiMaRIS | |
| Invasive habit | The purple and reddish Botrylloides violaceus colonies overgrow and potentially suffocate the mussels. Massachusetts coast, USA. | Adriaan Gittenberger/GiMaRIS | |
| Colonising habit | The reddish colonies have only just settled and consist of one to several individuals. The white Botrylloides colony is a few weeks older. Massachusetts coast, USA. | Adriaan Gittenberger/GiMaRIS | |
| Colonising habit and a natural enemy | The small red patches are the recently settled Botrylloides violaceus colonies. They are Massachusetts coast, USA. | Adriaan Gittenberger/GiMaRIS | |
| Colonising habit and a natural enemy | The small red patches are the recently settled Botrylloides violaceus colonies. They are threatened by grazers like sea-urchins. Massachusetts coast, USA. | Adriaan Gittenberger/GiMaRIS |
Identity
Top of pagePreferred Scientific Name
- Botrylloides violaceus Oka, 1927
Preferred Common Name
- violet tunicate
International Common Names
- English: orange sheath tunicate
Local Common Names
- Netherlands: slingerzakpijp
Summary of Invasiveness
Top of pageB. violaceus is a compound ascidian (tunicate or sea squirt) and belongs to the subfamily Botryllinae. It is made up of individual genetically identical zooids and ampullae that are connected by an internal vascular system. Like all colonial ascidians, it has two types of reproduction: asexual reproduction, a process known as blastogenesis, and sexual reproduction.
It is native to the west Pacific, and is now found in the Northeast Pacific (Alaska, British Columbia to Ensenada, Baja California; Lambert and Sanamyan, 2001; Cohen et al., 2005), Sydney Harbour, Australia, the Venetian Lagoon, the Netherlands, and the coast of Japan. It can tolerate a wide range of environmental factors including temperature, salinity and nutrients (Carman et al., 2007; Dijkstra et al., 2008). B. violaceus overgrows shellfish (e.g. mussels) and other sessile invertebrate species. It is a pest to mussel farmers and must be removed either manually or by innovative engineering.
Taxonomic Tree
Top of page- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Chordata
- Subphylum: Tunicata
- Class: Ascidiacea
- Suborder: Stolidobranchia
- Family: Styelidae
- Genus: Botrylloides
- Species: Botrylloides violaceus
Description
Top of pageB. violaceus is a compound ascidian (tunicate or sea squirt) and belongs to the subfamily Botryllinae. It is made up of individual genetically identical zooids (measuring ~2 mm in diameter) and ampullae that are connected by an internal vascular system. Zooids are arranged in loose circles or rows and are embedded in a transparent tunic.
Distribution
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Distribution Table
Top of pageThe 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.
| Continent/Country/Region | Distribution | Last Reported | Origin | First Reported | Invasive | Reference | Notes | |
|---|---|---|---|---|---|---|---|---|
Sea Areas | ||||||||
| Atlantic, Northwest | Widespread | Stachowicz et al., 2002; Pederson et al., 2005; Dijkstra et al., 2007 | New York (NY) to Eastport (ME), introduced to Gulf of Maine in the 1970s | |||||
| Mediterranean and Black Sea | Present | Introduced | Invasive | Zaniolo et al., 1998 | Venetian Lagoon | |||
| Pacific, Northeast | Widespread | Invasive | Lambert and Lambert, 1998; Lambert and Sanamyan, 2001; Cohen et al., 2005 | Coast off Alaska, from British Columbia to Ensenada, Baja California | ||||
| Pacific, Northwest | Present | Bock et al., 2011 | ||||||
North America | ||||||||
| Canada | Present | Introduced | Lejeusne et al., 2011 | |||||
| -Newfoundland and Labrador | Present | Introduced | Callahan et al., 2010 | |||||
| -Prince Edward Island | Present | Gittenberger, 2009 | ||||||
| USA | Present | Introduced | Lejeusne et al., 2011 | |||||
| -California | Present | Introduced | Davidson et al., 2010 | |||||
Europe | ||||||||
| Ireland | Present | Minchin, 2007 | ||||||
| Italy | Present | DAISIE, 2011 | ||||||
| Netherlands | Present | Gittenberger, 2007 | ||||||
Introductions
Top of page| Introduced to | Introduced from | Year | Reason | Introduced by | Established in wild through | References | Notes | |
|---|---|---|---|---|---|---|---|---|
| Natural reproduction | Continuous restocking | |||||||
| North America | Japan | Hitchhiker (pathway cause) | Lejeusne et al. (2011) | Likely introduced as a hitchhiker in the shellfish aquaculture trade | ||||
Habitat
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Habitat List
Top of page| Category | Sub-Category | Habitat | Presence | Status |
|---|---|---|---|---|
| Brackish | ||||
| Inland saline areas | Present, no further details | Natural | ||
| Estuaries | Secondary/tolerated habitat | Natural | ||
| Marine | ||||
| Inshore marine | Present, no further details | Natural | ||
| Benthic zone | Secondary/tolerated habitat | Natural |
Biology and Ecology
Top of pageGenetics
For information on the genetics of this species see Lejeusne et al. (2011).
Reproductive Biology
Like all colonial ascidians, B. violaceus has two types of reproduction: asexual reproduction, a process known as blastogenesis, and sexual reproduction. Asexual reproduction occurs through budding which produces colonies of genetically identical zooids. Studies have shown that small substrates limit asexual reproduction and induce sexual reproduction. B. violaceus is a hermaphrodite that undergoes sexual reproduction between 10 and 12°C. Sexual reproduction begins when the gonads of both sexes develop on either side of the zooid with the ovary situated behind the testis. The egg is ovulated in a brood pouch that forms as an outgrowth of the body wall. Within the brood pouch, the egg is fertilized and develops until the larva escapes. The brooding period depends on several factors including temperature, salinity and number of asexual reproductive cycles (Sabbadin, 1955; Millar, 1971). More on growth and reproductive cycles can be found in Yamaguchi (1975). Brown et al. (2009) report further on whole body regeneration in this species.
Larvae, when release, are relatively large (0.01-0.02 mm) and are brightly coloured. They are lecithotrophic and spend less than 24 hours in the water column before settling on suitable substrate and metamorphosing into adult colonies. During metamorphosis, the larvae sticks to the substrate and begins to form a circle of ampullae. All Botrylliodes of the same generation appear, grow, and die synchronously. Both the zooids bearing embryos and the sterile zooids of the oldest generation begin to disintegrate and are eventually reabsorbed into the common vascular system.
Environmental Requirements
B. violaceus can tolerate a wide range of environmental factors including temperature, salinity and nutrients (Carman et al., 2007; Dijkstra et al., 2008).
Associations
B. violaceus overgrows shellfish (e.g., mussels) and other sessile invertebrate species.
Water Tolerances
Top of page| Parameter | Minimum Value | Maximum Value | Typical Value | Status | Life Stage | Notes |
|---|---|---|---|---|---|---|
| Depth (m b.s.l.) | 0 | 7 | Optimum | 0-15 tolerated | ||
| Salinity (part per thousand) | 33 | Optimum | 15-33 tolerated | |||
| Turbidity (JTU turbidity) | Optimum | B. violaceus is a filter feeder and as such doesn't tolerate a silty environment | ||||
| Water pH (pH) | Optimum | 7.0 tolerated | ||||
| Water temperature (ºC temperature) | -1 | 27 | Optimum | -1-27 tolerated; optimal temperatures yet to be determined |
Notes on Natural Enemies
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Means of Movement and Dispersal
Top of pageAt least three potential mechanisms account for the introduction of colonial ascidians to the Gulf of Maine: 1) hull fouling, 2) ballast water, and 3) aquaculture. Because colonial ascidians produce lecithotrophic larvae that have an abbreviated planktonic stage (Lambert, 1968; Olson, 1985; Svane and Young, 1989), the likelihood of larvae surviving in ballast water is very low (Carlton and Geller, 1993). Thus, the most likely vectors for transport are hull fouling, aquaculture or rafting. Rafting on broken leaves and other debris to which they are attached can transport colonies both long and short distances. Some studies show evidence that rafting events occur frequently, and thus may have a substantial effect on population dynamics.Dijkstra et al. (2007) found bivalve aquaculture to the likely mechanism of long-distance (trans-oceanic) spread for this species. Other vectors include sea chests (Coutts and Forrest, 2007). Once transported to a site, further introduction to sites in the region (kms apart) can be from hull fouling of recreational or commercial vessels.
Impact
Top of page
Risk and Impact Factors
Top of page Invasiveness- Proved invasive outside its native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Pioneering in disturbed areas
- Tolerant of shade
- Fast growing
- Has high reproductive potential
- Reproduces asexually
- Ecosystem change/ habitat alteration
- Modification of natural benthic communities
- Modification of successional patterns
- Monoculture formation
- Negatively impacts aquaculture/fisheries
- Competition - monopolizing resources
- Competition - smothering
- Filtration
- Fouling
- Interaction with other invasive species
- Rapid growth
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
- Difficult/costly to control
References
Top of pageBrown FD; Keeling EL; ADLe; Swalla BJ, 2009. Whole body regeneration in a colonial ascidian, Botrylloides violaceus. Journal of Experimental Zoology, 312B(8):885-900.
DAISIE, 2011. European Invasive Alien Species Gateway. http://www.europe-aliens.org/
Distribution Maps
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