Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Diplosoma listerianum



Diplosoma listerianum


  • Last modified
  • 25 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Diplosoma listerianum
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Tunicata
  •         Class: Ascidiacea
  • Summary of Invasiveness
  • D. listerianum is a cosmopolitan species. It is found on the coasts of the Netherlands, Madagascar, South Africa, Tanzania, Chile, Brazil, Panama, the USA (both east and west coasts), and England. Within these...

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Preferred Scientific Name

  • Diplosoma listerianum (Milne-Edwards, 1841)

Summary of Invasiveness

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D. listerianum is a cosmopolitan species. It is found on the coasts of the Netherlands, Madagascar, South Africa, Tanzania, Chile, Brazil, Panama, the USA (both east and west coasts), and England. Within these habitats, D.listerianum occupies both primary and secondary substrates. It is found to overgrow shellfish (e.g. mussels) and other sessile invertebrate species as well as macroalgae (e.g. Codium fragile subsp. tomentosoides, Ulva lactuta). It is unclear if other species are negatively affected by overgrowth of D.listerianum

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Tunicata
  •                 Class: Ascidiacea
  •                     Order: Enterogona
  •                         Suborder: Aplousobranchia
  •                             Family: Didemnidae
  •                                 Genus: Diplosoma
  •                                     Species: Diplosoma listerianum


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D. listerianum is native to the northeast Atlantic and has a cosmopolitan distribution. It is observed in both tropical and temperate waters. D. listerianum is currently found in the Caribbean (Rocha et al., 2005), the Pacific (Carman and Grunden, 2010), Australia (Kott, 2001), southern Brazil (Rocha et al., 2005; Rocha et al., 2009), the Gulf of Maine (Dijkstra et al., 2007a), south of Cape Cod (Osman and Whitlatch, 1995), the Mediterranean (Brunetti et al., 1988), South Africa (Millar, 1955) and Madagascar (Millar, 1988). In temperate offshore areas, D.listerianum can be abundant and appear healthy throughout the year (LG Harris, University of New Hampshire, USA, personal communication, 2009). In contrast, colonies of D. listerianum experience seasonal die-back at coastal sites. Fluctuations in population size along coastal sites are likely related to the seasonally colder waters that delay reproduction and growth of this species (Stachowicz et al., 2002). Like all colonial ascidians, it overgrows shellfish (e.g. mussels) and other sessile invertebrate species and subtidal macroalgae (J Dijkstra, University of New Hampshire, USA, personal communication, 2009).


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.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Sea Areas

Atlantic, NortheastWidespread Invasive Monniot, 2001The Netherlands, England and France
Atlantic, NorthwestWidespreadNativeDijkstra et al., 2007a; Whitlatch et al., 1995New York, NY to Casco Bay, ME
Indian Ocean, Eastern Invasive Marshall et al., 2003; Kott and Esnal, 2009Many locations around Australia
Pacific, NortheastWidespread Invasive Grey, 2009British Columbia to Ensenada, Baja California

North America

CanadaPresentPresent based on regional distribution.
-QuebecPresentIntroduced2008Willis et al., 2011
USAPresentIntroducedOsman and Whitlatch, 2007; Carman and Grunden, 2010New England
-MainePresentDijkstra et al., 2007a
-MassachusettsPresentIntroducedAgius, 2007; Carman et al., 2007; Carman and Grunden, 2010Lake Tashmoo
-New HampshirePresentDijkstra et al., 2007b
-WashingtonPresentIntroducedGrey, 2009


CroatiaPresentIgac, 1994
NetherlandsPresentIntroducedGittenberger, 2007

Habitat List

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Inland saline areas Present, no further details Natural
Estuaries Secondary/tolerated habitat Natural
Lagoons Present, no further details Natural
Coastal areas Present, no further details Natural
Mangroves Present, no further details Natural
Inshore marine Present, no further details Natural
Coral reefs Present, no further details Natural
Benthic zone Present, no further details Natural

Biology and Ecology

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D. listerianum is an aplousobranch ascidian of the family Didemnidae. Colony formation is similar to Botryllids. It forms patches or sheets of small zooids enclosed in a matrix of the tunic (fibrous tunicin). The tunic forms a thin-walled sac enclosing an extensive water-filled cloacal space in which the zooids are suspended (Berrill, 1950; Mackie and Singla, 1987). Unlike Botryllid ascidians, blood vessels of different zooids are not interconnected, but are independent of one another and connected by the common tunic only.

Like all colonial ascidians, D. listerianum has two types of reproduction: sexual and asexual reproduction. Asexual reproduction occurs through budding which produces colonies of genetically identical zooids. D. listerianum is a hermaphrodite that undergoes sexual reproduction in which ovulating eggs detach themselves from the ovary wall and segregate in the tunic without exposure to seawater (Burighel and Martinucci, 1994). Likely brooding period depends on several factors including temperature, salinity and number of asexual reproductive cycles (Sabbadin, 1955; Millar, 1971). Each zooid has a testis and ovary and the oocytes mature in the ovary (Martinucci et al., 1988). Zooids in a colony bud and reproduce independently of each other (Bishop and Sommerfeldt, 1999), resulting in rapid growth and development. Each zooid can produce two descendants. Rapid growth coupled with large numbers of offspring can lead to a build-up in local abundance.
Colonies of this species are loosely organized lending it to movement and sometimes fragmentation and splitting (Marshall and Keough, 2005; J Dijkstra, University of New Hampshire, USA, personal communication, 2009). Movement of zooids can take place over hours or days. Interestingly, individual zooids appear to change their relative position within the matrix of the tunic (Bishop and Ryland, 1991). Each zooid has an oral siphon and are connected to an atrial siphon via a common cloacal aperture (Mackie and Singla, 1987).
Larvae, when released, are relatively small. 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 stick to the substrate.
Once established, D. listerianum occupies a wide variety of habitats, including fouling and benthic surfaces on both vertical and horizontal surfaces. Very few species settle on the tunic of living colonies as it can be acidic. Its rapid growth and acidic tunic reduces the availability of space for settlement and their short larval dispersal allows them to build up local populations.
D. listerianum has provided a new source of prey for some species including the snails, Mitrella lunata and Anachis lafrashnayi (Osman and Whitlatch, 1995; 2004) and the blood star Henricia sanguinolenta (Dijkstra et al., 2007a).


Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Salinity (part per thousand) Optimum 25-34 tolerated. Optimal salinities are yet to be determined, most often found in waters between 30 and 33 psu
Turbidity (JTU turbidity) Optimum D. listerianum has been observed as deep as 15m
Water temperature (ºC temperature) Optimum 0-28 tolerated. Prefers warmer waters. Optimal temperatures are yet to be determined

Means of Movement and Dispersal

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At least three potential mechanisms account for the introduction of colonial ascidians: 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, seagrass 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. Bivalve aquaculture and sea chests are likely mechanisms of long-distance (trans-oceanic) spread for this species (Coutts et al., 2003; Coutts and Forrest, 2007; Dijkstra et al., 2007a). Once transported to a site, further introduction to sites in the region (kms apart) can be from hull fouling of recreational or commercial vessels.


Environmental Impact

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Ecological knowledge gained from studies on this species and other similar species suggest that D. listerianum may become a permanent member of the community. It is unclear whether it will replace resident species. Monitoring is necessary to determine the range and size of the population, but management and/or eradication of the species may not be necessary in natural communities.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Is a habitat generalist
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Fast growing
  • Has high reproductive potential
  • Reproduces asexually
Impact outcomes
  • Modification of natural benthic communities
  • Monoculture formation
  • Threat to/ loss of native species
Impact mechanisms
  • Filtration
  • Fouling
  • Interaction with other invasive species
  • Rapid growth
Likelihood of entry/control
  • 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

Detection and Inspection

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Grey (2009) describes methods for surveying exotic ascidians such as D. listerianum, and recommends a visual inspection of floating docks. Willis et al. (2011) have designed a PCR assay to detect D. listerianum in water samples.


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Agius BP, 2007. Spatial and temporal effects of pre-seeding plates with invasive ascidians: growth, recruitment and community composition. Journal of Experimental Marine Biology and Ecology [Proceedings of the 1st International Invasive Sea Squirt Conference, Woods Hole, Massachusetts, USA, April 21-22, 2005.], 342(1):30-39.

Berrill NJ, 1950. The Tunicata with an account of the British Species. London: Ray Society, 354 pp.

Bishop JD; Sommerfeldt AD, 1999. Not like Botryllus: indiscriminate postmetamorphic fusion in a compound ascidian. Proc. Soc. Lond. B, 266:241-248.

Bishop JDD; Ryland JS, 1991. Storage of exogenous sperm by the compound ascidian Diplosoma listerianum. Mar. Biol, 108:111-118.

Brunetti R; Bressan M; Marin MG; Libralato M, 1988. On the ecology and biology of Diplosoma listerianum (Milne Edwards, 1841) (Ascidiacea, Didemnidae). Vie et Milieu, 38:123-131.

Burighel P; Martinucci GB, 1994. Sexual reproduction in the compound ascidian Diplosoma listerianum (Tunicata). I. Metamorphosis, storage and phagocytosis of sperm in female duct. Marine Biology, 118:489-498.

Carlton JT; Geller JB, 1993. Ecological roulette: the global transport of nonindigenous marine organisms. Science, 261:78-82.

Carman MR; Bullard SG; Donnelly JP, 2007. Water quality, nitrogen pollution, and ascidian diversity in coastal waters of southern Massachusetts, USA. Journal of Experimental Marine Biology and Ecology, 342(1):175-178.

Carman MR; Grunden DW, 2010. First occurrence of the invasive tunicate Didemnum vexillum in eelgrass habitat. Aquatic Invasions [Proceedings of the 16th International Conference on Aquatic Invasive Species, Montreal, Canada, 19-23 April 2009.], 5(1):23-29.

Coutts ADM; Forrest BM, 2007. Development and application of tools for incursion response: lessons learned from the management of the fouling pest Didemnum vexillum. Journal of Experimental Marine Biology and Ecology, 342(1):154-162.

Coutts ADM; Moore KM; Hewitt CL, 2003. Ships' sea-chests: an overlooked transfer mechanism for non-indigenous marine species? Marine Pollution Bulletin, 46:1504-1515.

Dijkstra J; Harris LG; Westerman E, 2007. Distribution and long-term temporal patterns of four invasive colonial ascidians in the Gulf of Maine. Journal of Experimental Marine Biology and Ecology, 342(1):61-68.

Dijkstra J; Sherman H; Harris LG, 2007. The role of colonial ascidians in altering biodiversity in marine fouling communities. Journal of Experimental Marine Biology and Ecology, 342(1):169-171.

Gittenberger A, 2007. Recent population expansions of non-native ascidians in The Netherlands. Journal of Experimental Marine Biology and Ecology [Proceedings of the 1st International Invasive Sea Squirt Conference, Woods Hole, Massachusetts, USA, April 21-22, 2005.], 342(1):122-126.

Grey E, 2009. Ascidians of Washington State: Native and introduced.

Grey EK, 2009. Do we need to jump in? A comparison of two survey methods of exotic ascidians on docks. Aquatic Invasions [Proceedings of the 2nd International Invasive Sea Squirt Conference, Prince Edward Island, Canada, 2-4 October 2007.], 4(1):81-86.

Igac L, 1994. Fouling as an indicator of municipal pollution in the area of Rovinj (northeastern adriatic). Bollettino del Museo Civico di Storia Naturale di Venezia, 43:157-178.

Kott P, 2001. The Australian Ascidiacea, Part 4, Aplousobranchia (3). Didemnidae. Memoirs of the Queensland Museum, 47:1-407.

Kott P; Esnal G, 2009. New Zealand Inventory of Biodiversity. In: Tunicata, Volume One: Kingdom Animalia [ed. by Gordon, D. P.]. 584.

Lambert G, 1968. The general ecology and growth of a solitary ascidian, Corella willmeriana. Biological Bulletin Woods Hole, 135:296-307.

Lambert G, 2007. Invasive sea squirts: A growing global problem. Journal of Experimental Marine Biology and Ecology, 342:3-4.

Mackie GO; Singla CL, 1987. Impulse propagation and contraction in the tunic of a compound ascidian. Biol. Bull, 173:188-204.

Marshall D; Keough M, 2005. Offspring size effects in the marine environment: A field test for a colonial invertebrate. Ecology, 30:275-280.

Marshall D; Pechenik J; Keough M, 2003. Larval activity levels and delayed metamorphosis affect post-larval performance in the colonial, ascidian Diplosoma listerianum. Marine Ecology Progress Series, 246:153-162.

Martinucci GB; Burighel P; Zaniolo G; Brunetti R, 1988. Ovulation and egg segregation in the tunic of a colonial ascidian, Diplosoma listerianum (Tunicata, Ascidiacea). Zoomorph, 08:219-227.

Millar RH, 1955. On a collection of ascidians from South Africa. Proc. Zool. Soc. Lond, 125:169-221.

Millar RH, 1971. The biology of ascidians. In: Advances in marine biology, Vol 9 [ed. by Russell FS, Youge CM] London, : Academic Press, 1-100.

Millar RH, 1988. Ascidians collected during the International Indian Ocean Expedition. J. Nat. Hist, 22:823-848.

Monniot C, 2001. European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels. In: Ascidiacea & Sorberacea, 50 [ed. by Costello MJea]. 352-355.

Olson RR, 1985. The consequences of short-distance larval dispersal in a sessile marine invertebrate. Ecology, 66:30-39.

Osman RW; Whitlatch RB, 1995. Predation on early ontogenic life stages and its effect on recruitment into a marine epifaunal community. Marine Ecology-Progress Series, 117:111-126.

Osman RW; Whitlatch RB, 2004. The control of the development of a marine benthic community by predation on recruits. Journal Of Experimental Marine Biology and Ecology, 311:117-145.

Osman RW; Whitlatch RB, 2007. Variation in the ability of Didemnum sp. to invade established communities. Journal of Experimental Marine Biology and Ecology, 342(1):40-53.

Pederson J; Bullock R; Carlton JT; Dijkstra J; Dobroski N; Dyrynda P; Fisher R; Harris L; Hobbs N; Lambert G; Lazo-Wasem E; Mathieson AC; Miglietta MP; Smith J; Smith IIIJ; Tyrrell M, 2005. Marine invaders of the Northeast, Rapid Assessment Survey of Non-native and Native Marine Species of Floating Dock Communities. Massachussetts Institute of Technology.

Rocha RM; Faria SB; Moreno TR, 2005. Ascidians from Bocas del Toro, Panama. Biodiversity. Caribbean Journal of Science, 41:600-612.

Rocha RM; Kremer LP; Baptista MS; Metri R, 2009. Bivalve cultures provide habitat for exotic tunicates in southern Brazil. Aquatic Invasions, 4:195-205.

Ruiz GM; Fofonoff PW; Carlton JT; Wonham MJ; Hines AH, 2000. Invasion of coastal marine communities in North America: apparent patterns, processes and biases. Annual Review of Ecology and Systematics, 31:481-531.

Sabbadin A, 1955. [English title not available]. (Osservazioni sullo sviluppo, l'accrescimento e la riproduzione di Botryllus schlosseri (Pallas) in condizioni di laboratorio.) Bollettino di Zoologia, 22:243-263.

Stachowicz JJ; Terwin JR; Whitlatch RB; Osman RW, 2002. Linking climate change and biological invasions: Ocean warming facilitates nonindigenous species invasions. Proceedings of the National Academy of Sciences of the United States of America, 99:15497-15500.

Svane I; Young CM, 1989. The ecology and behaviour of ascidian larvae. Oceanography of Marine Biology Annual Review, 27:45-90.

Whitlatch RB; Osman RW; Frese A, 1995. The ecology of two introduced marine ascidians and their effects of epifaunal organisms in Long Island Sound. In: Proceedings of the Northeast Conference on Non-Indigenous Aquatic Nuisance Species: a regional conference. 29-48.

Willis JE; Stewart-Clark S; Greenwood SJ; Davidson J; Quijon P, 2011. A PCR-based assay to facilitate early detection of Diplosoma listerianum in Atlantic Canada. Aquatic Invasions, 6(1):7-16.

Links to Websites

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Ascidians of Washington State: Native & Introduced by Erin Grey
Dutch ascidians homepage


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15/12/09 Original text by:

Jenn Dijkstra, University of New Hampshire, USA

Distribution Maps

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