Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Polyandrocarpa zorritensis



Polyandrocarpa zorritensis


  • Last modified
  • 06 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Polyandrocarpa zorritensis
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Tunicata
  •         Class: Ascidiacea
  • Summary of Invasiveness
  • P. zorritensis is a fast-growing, conspicuous shallow water ascidian.It is a declared invasive species found in different harbours and lagoons of the Pacific Ocean (California, Japan, Hawaii), the Atlantic Ocean...

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Preferred Scientific Name

  • Polyandrocarpa zorritensis (Van Name, 1931)

Other Scientific Names

  • Stolonica zorritensis Van Name, 1931

Summary of Invasiveness

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P. zorritensis is a fast-growing, conspicuous shallow water ascidian.It is a declared invasive species found in different harbours and lagoons of the Pacific Ocean (California, Japan, Hawaii), the Atlantic Ocean (Ruppert in Lambert and Lambert, 1998) and the Mediterranean Sea (Italy, Spain). P. zorritensis is known to be an aggressive invader, tolerant of large fluctuations in temperature (8-30.5°C) and salinity (22.7-38 ppm) (Lambert and Lambert, 1988; Brunetti and Mastrototaro, 2004). The aggressive invasion of this species could be due to its budding which makes possible the rebuilding of the colony even in the absence of adult zooids (Brunetti and Mastrototaro, 2004).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Tunicata
  •                 Class: Ascidiacea
  •                     Suborder: Stolidobranchia
  •                         Family: Styelidae
  •                             Genus: Polyandrocarpa
  •                                 Species: Polyandrocarpa zorritensis

Notes on Taxonomy and Nomenclature

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The genus Polyandrocarpa (family Styelidae) is generally accepted as containing 43 species (Monniot, 2009). Polyandrocarpa zorritensis (Van Name, 1931) was first named as Stolonica zorritensis by Van Name (1931). The genus Polyandrocarpa as the genus Polycarpa is characterized by small hermaphroditic gonads irregularly scattered on the surface of the body wall. Moreover in Polyandrocarpa genus the zooids produce buds and form colonies and each gonad contains several testes (Van Name, 1945).


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P. zorritensis is a colonial Styelidae of the subfamily Polyzoinae. The colony appears as a group of zooids of various sizes closely crowded together, but without the tests merging them. The basal portion of the colony is formed by a tangle of stolons along which there are orange globular bodies (buds) which will be transformed in new zooids. Adult zooids are sub cylindrical, yellow-green in colour, with the oral siphon apical and the cloacal one slightly eccentric. Both siphons are four-lobed with two dark, almost black, bands per lobe. The test is thin and leathery. The well developed zooids, without test, range in height from 9-10 to 12-13 mm. The body wall has a delicate musculature, longitudinal and transversal fibres are of the same size and regularly arranged. According the zooid size there are from 20 to 30 simple tentacles of two lengths. The dorsal tubercle has a transversal wavy split-shaped opening. The dorsal lamina is flat and has a smooth edge. The branchial sac has four few prominent folds per side. The intestinal tube, entirely located to the left of the branchial sac, is formed by a short oesophageal tract followed by a trapezoid stomach with a plicated wall (generally 10-15 folds in addition to typhlosole). From the posterior external ventral corner of the stomach comes out a gastric caecum finger shape with a spherical tip. Its presence is hidden by an endocarp located in the intestinal loop. The gonads are oval polycarps lying in a row on each side of the endostyle, in general 9 on the right and 6 on the left, although up to 10 on the right and 8 on the left. All ovarian apertures are directed towards the dorsal side. The sexually ripe zooids have several embryos in the peribranchial cavity. The larval trunk, at the developmental stage in which the tail completely surrounds it, is about 530 µm in length. The three adhesive organs are included in a sessile frontal process from which at the metamorphosis take the origin of three clusters of ampullae (Brunetti and Mastrototaro, 2004).

P. zorritensis is a shallow water species that for its size and colonial habit it is difficult to think that might be escaped to the attention of the observers. Thus it is reasonable to think that the new records of the species out of its natural range represent stages of a biological invasion.


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P. zorritensis is considered a native of the South Pacific (Zorritos, Perù) (Turon and Perera, 1988). It is present along the coast of Brazil (Millar, 1958), and has also been recorded in California (Lambert and Lambert, 1998), Texas (Lambert et al., 2005), Florida (Vàzquez and Young, 1996), Hawaii (Abbott et al., 1997), Japan (Nishikawa et al. 1993) and in the Mediterranean Sea: in Italy (Brunetti, 1978-1979; Brunetti and Mastrototaro, 2004) and Spain (Turon and Perera, 1988).


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


JapanPresentIntroduced Invasive Nishikawa et al., 1993

North America

USAPresentPresent based on regional distribution.
-CaliforniaWidespreadIntroduced1994 Invasive Lambert and Lambert, 1998; Lambert and Lambert, 2003; Cohen et al., 2005Southern California harbours and marinas (Mission and San Diego Bays)
-FloridaPresentIntroduced Invasive Vázquez and Young, 1996Jim Island (Ft. Pierce Inlet in the Indian River Lagoon - Florida)
-HawaiiPresentIntroduced Invasive Abbot et al., 1997Pearl Harbour, Coconut Island in Kane 'ohe Bay, Kewalo Bay (Oahu)
-TexasWidespreadIntroduced2004 Invasive Lambert et al., 2005South Padre Island Texas, Port Isabel deep water docks, Billy Kenan's dock

South America

BrazilPresentPresent based on regional distribution.
-Sao PauloWidespread Not invasive Millar, 1958Sabtos; Itacurussa (Cananeia)
PeruPresentNativeTuron and Perera, 1988


ItalyWidespreadIntroduced1974 Not invasive Brunetti, 1978; Brunetti and Mastrototaro, 2004Harbour of La Spezia (North Tyrrenean Sea - Mediterranean Sea)
SpainWidespreadIntroduced Invasive Turon and Perera, 1988Delta of Ebro River, salt-wedge estuaries in Mediterranean Sea

History of Introduction and Spread

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The species is spreading in the Atlantic (Ruppert in Lambert and Lambert, 1998) and also the Pacific Ocean (Japan (Nishikawa et al., 1993; 1994), South California (Lambert and Lambert, 1998) Hawaii (Abbott et al., 1997). At the moment the main cause of this (and that of other species) expansion is considered to be the warming of the ocean waters (Brunetti and Mastrototaro, 2004). According to Lambert and Lambert (2003), the stolidobranch ascidians “both solitary and colonial survive long-range anthropogenic transport better than do other types of ascidians”. Moreover the aggressive invasion of P. zorritensis might also be due to its budding modality. The vascular budding allows the rebuilding of the colony in the absence of adult zooids (Brunetti and Mastrototaro, 2004).

P. zorritensis has been found in lagoons, harbours and eutrophic basins often associated with mussel farms.


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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Brazil 1958 Yes Millar (1958) fouling
California 1994 Yes Lambert and Lambert (1998) fouling
Florida 1994 Aquaculture (pathway cause) Yes Vázquez and Young (1996)
Hawaii 1997 Yes Abbot et al. (1997)
Italy 1978 Yes Brunetti (1978) fouling
Spain 1988 Yes Turon and Perera (1988) fouling
Texas 2004 Yes Lambert et al. (2005) fouling

Risk of Introduction

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P. zorritensis is accidentally introduced in many countries as an epibiotic species on the shells of oysters and mussels breeding in mussel farms.


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P. zorritensis colonizes all hard substrata present in the shallow water down to 2 m depth. In particular, extended colonies may be found under iron buoys, on mussel breeding piles and on the steel wires connecting them. Colonies were also present on detritus of the bottom. The species seems to prefer harbour environments, that is with eutrophic waters, where the colonies develop rapidly by an intense vegetative replication, while the zooids produce an high number of larvae, which showing a positive phototaxis (Vázquez and Young, 1998), and colonize every hard substrata in shallow waters.

Habitat List

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Inland saline areas Principal habitat Natural
Estuaries Secondary/tolerated habitat Productive/non-natural
Lagoons Secondary/tolerated habitat Productive/non-natural
Inshore marine Principal habitat Natural
Benthic zone Principal habitat Natural

Biology and Ecology

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The phylogeny of the Styelidae, inferred from mitochondrial and nuclear DNA sequences, has been studied by Perez-Portela et al. (2009). 

Reproductive Biology

P. zorritensis develop rapidly by prolific asexual replication; moreover the ripe zooids produce a larger number of larvae (Brunetti and Mastrototaro, 2004).
P. zorritensis is a shallow water species that grows with other ascidians common in eutrophic habitats such as Ciona intestinalis and Styela plicata.
Environmental Requirements
The species seems to prefer harbour environments with eutrophic waters, where the colonies develop rapidly.


Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Depth (m b.s.l.) 0.5 2 Optimum 0.5-5 tolerated
Salinity (part per thousand) Optimum 35-39 tolerated
Water temperature (ºC temperature) Optimum 8-30 tolerated

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

By planktonic larvae and transport as a fouling species.
Accidental Introduction
This species may be transported as epibiotic species on the shells of non-indigenous oysters or mussels imported alive to mussel farms.
Intentional Introduction
There are no recorded cases of the intentional introduction of P. zorritensis.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Aquaculture Yes Mastrototaro et al., 2008

Impact Summary

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Environment (generally) Negative

Economic Impact

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P. zorritensis may have a negative impact on artificial structures present in the shallow waters. P. zorritensis colonizes all artificial hard substrates includes buoys and iron ropes used in mussel farms.

Environmental Impact

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Reduction of the availability of hard substrates.

Impact on Biodiversity
P. zorritensis can form dense populations, which outcompete native species.

Social Impact

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See Impact: Economic for impacts on mussel farms. 


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
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Benefits from human association (i.e. it is a human commensal)
  • Fast growing
  • Has high reproductive potential
  • Gregarious
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
Impact outcomes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Host damage
  • Infrastructure damage
  • Modification of natural benthic communities
  • Modification of nutrient regime
  • Modification of successional patterns
  • Monoculture formation
  • Negatively impacts aquaculture/fisheries
  • Reduced native biodiversity
  • Threat to/ loss of native species
  • Negatively impacts animal/plant collections
  • Damages animal/plant products
Impact mechanisms
  • Antagonistic (micro-organisms)
  • Competition - smothering
  • Competition
  • 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

Prevention and Control

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To prevent spread it is necessary to check and eliminate epibiotic species on living mollusc shells.


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Abbot PD; Newberry AT; Morris KM, 1997. Reef and Shore Fauna of Hawaii. Section 6B: Ascidians (Urochordata). Bishop Museum Special Publication, 64(6B) [ed. by Lambert, G.]. Honolulu, Hawaii 43-48.

Brunetti R, 1978. Polyandrocarpa zorritensis (Van Name, 1931). A colonial ascidian new to the Mediterranean record. Vie Milieu, 28-29:647-652.

Brunetti R; Mastrototaro F, 2004. The non-indigenous stolidobrach ascidian Polyandrocarpa zorritensis in the Mediterranean: description, larval morphology and pattern of vascular budding. Zootaxa, 528:1-8.

Cohen AN; Harris LH; Bingham BL; Carlton JT; Chapman JW; Lambert CC; Lambert G; Ljubenkov JC; Murray SN; Rao LC; Reardon K; Schwindt E, 2005. Rapid Assessment Survey for exotic organisms in southern California bays and harbors, and abundance in port and non-port areas. Biological Invasions, 7(6):995-1002.

Izquierdo-Muñoz A; Díaz-Valdés M; Ramos-Esplá AA, 2009. Recent non-indigenous ascidians in the Mediterranean Sea. Aquatic Invasions [Proceedings of the 2nd International Invasive Sea Squirt Conference, Prince Edward Island, Canada, 2-4 October 2007.], 4(1):59-64.

Kott P, 1985. The Australian Ascidiacea part 1, Phlebobranchia and Stolidobranchia. Memoirs of the Queensland Museum, 23:1-440.

Lambert CC; Lambert G, 1998. Non indigenous ascidian in southern California harbors and marinas. Marine Biology, 130:675-688.

Lambert CC; Lambert G, 2003. Persistence and differential distribution of nonindigenous ascidians in harbors of the Southern Californian Bight. Marine Ecology Progress Series, 259:145-161.

Lambert G; Zen F; Lambert CC; Scofield VL, 2005. Ascidians of South Padre Island, Texas, with a key to species. The Texas Journal of Science, 57(3):251-262.

Mastrototaro F; D'Onghia G; Tursi A, 2008. Spatial and sesonal distribution of ascidians in a semi-enclosed basin of the Mediterranean Sea. Journal of the Marine Biological Association of the United Kingdom, 88(5):1053-1061.

Millar RH, 1958. Some ascidians from Brazil. Annals and Magazine of Natural History, 13(I):497-514.

Monniot C, 2009. Polyandrocarpa Michaelsen, 1904. World Register of Marine Species.

Name WGVan, 1931. New North and South American ascidians. Bull. Mus. Nat. Hist, 61:207-225.

Name WGVan, 1945. The North and South American ascidians. Bulletin of the American Museum of Natural History, 84:1-476.

Nishikawa T; Kajiwara Y; Kawamura K, 1993. Probable introduction of Polyandrocarpa zorritensis (Van Name) to Kitakyushu and Kochi, Japan. Zoological Science, Suppl 10:176.

Perez-Portela R; Bishop JD; Davis AR; Turon X, 2009. Phylogeny of the families Pyuridae and Styelidae (Stolidobranchiata, Ascidiacea) inferred from mitochondrial and nuclear DNA sequences. Mol. Phylogenet. Evol, 50(3):560-570.

Turon X; Perera M, 1988. [English title not available]. (Las ascidias del delta del Ebro. Aspectos faunisticos y cuantitativos.) P. Dept. Zool. Barcellona, 14:81-90.

Vázquez E; Young CM, 1996. Response of compound ascidian larvae to haloclines. Marine Ecology Progress Series, 133:179-190.

Vázquez E; Young CM, 1998. Ontogenic changes in phototaxis during larval life of ascidians Polyandrocarpa zorritensis (Van Name, 1931). Journal of Experimental Marine Biology and Ecology, 231:267-277.


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03/12/09 Original text by:

Francesco Mastrototaro, University of Bari, Department of Zoology, Via Orabona, 4, 70125, Bari, Italy

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