Invasion History

First Non-native North American Tidal Record: 2000
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 2000

General Invasion History:

Diplosoma aff. spongiforme is native to the Northeast Atlantic from Scotland south to the Atlantic coast of Spain and the Mediterranean Sea (Hayward et al. 1990; Turon and Bercerro 1992; Vazquez et al. 1994). In 2002, a colonial tunicate closely resembling D. aff. spongiforme was found on Smithsonian Environmental Research Center (SERC) fouling plates in Tampa Bay and Miami Harbor (Gretchen Lambert, personal communication; Ruiz et al., unpublished data). In 2007, the same form was found on fouling plates in Puerto Rico (Ruiz et al., unpublished). Similar spongiforme-like tunicates have been reported from the Currais Islands, Parana, Brazil by da Rocha and de Faria (2007), and from the Hawaiian islands (Pearl Harbor and Keehi Lagoon, Oahu) (Coles et al. 2009, cited by Carlton and Eldredge 2015). However, detailed comparisons of the Brazil, Florida, Puerto Rico, and European tunicates have not been made.

North American Invasion History:

Invasion History on the East Coast:

A colonial tunicate closely resembling Diplosoma aff. spongiforme was found on fouling plates in Miami Harbor, Florida in 2002 (Gretchen Lambert, personal communication; Ruiz et al., unpublished data). The fouling plates were part of a survey conducted by the Marine Invasions Lab at the Smithsonian Environmental Research Center (SERC).

Invasion History on the Gulf Coast:

A colonial tunicate closely resembling Diplosoma aff. spongiforme was found on fouling plates in Tampa Bay, Florida in 2002 (Gretchen Lambert, personal communication; Ruiz et al., unpublished data). 

Invasion History in Hawaii:

Diplosoma aff. spongiforme was found in 2008 in Pearl Harbor and Ke‘ehi Lagoon on Oahu (Coles et al. 2009, cited by Carlton and Eldredge 2015).


Diplosoma aff. spongiforme is a colonial species forming extensive thick, tough, but soft and loosely attached sheets. It grows on rock faces and associated fouling organisms, but rarely on algae. Colonies are ~6 mm thick and can occupy up to 0.25 m2. They are grayish-white in color, and may contain white non-calcareous bodies, while the zooids have black speckles. The tunic is more opaque than that of D. listerianum. The surface and basal test of the colony are connected by strands which enclose the zooids in clusters of 4-6 around a parent zooid. Zooids are ~ 1.5 mm long. The atrial opening is large. The ovary contains a single egg at a time. The larvae are large, with a trunk 0.6-8 mm long, 3-8 fixatory papillae and 2-7 pairs of ampullae (LaFargue 1975; Hayward and Ryland 1990). The wide range in papilla and ampulla numbers indicates that several species may have been combined in the authors' descriptions (Gretchen Lambert, personal communication 2012).

The tropical colonial tunicate Diplosoma aff. spongiforme is morphologically close to the temperate Northeast Atlantic D. spongiforme (Girard 1872) (da Rocha et al. 2005; Gretchen Lambert 2005). Genetic analysis is needed to determine its identiity.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Chordata
Subphylum:   Tunicata
Class:   Ascidiacea
Order:   Aplousobranchia
Family:   Didemnidae
Genus:   Diplosoma
Species:   aff. spongiforme


Astellium spongiforme (Giard, 1872)
Diplosoma chamaelon (Von Drasche, 1883)
Lissoclinum cupuliferum (Kott, 1952)
Diplosoma cupuliferum (LaFargue, 1968)

Potentially Misidentified Species

Diplosoma listerianum



Life History- A colonial tunicate consists of many zooids, bearing most or all of the organs of a solitary tunicate, but modified to varying degrees for colonial life. Colonial tunicates of the family Didemnidae have small zooids, completely embedded in an encrusting and thin tunic. Each zooid has an oral siphon and an atrial aperture which opens to a shared cloacal chamber. Water is pumped into the oral siphon, through finely meshed ciliated gills on the pharynx, where phytoplankton and detritus is filtered, and passed on mucus strings to the stomach and intestines. Excess waste is expelled in the outgoing atrial water (Van Name 1945; Barnes 1983).

Colonial tunicates reproduce both asexually by budding and sexually from fertilized eggs that develop into larvae. Buds can form from the body wall of the zooids. Colonies vary in size ranging from small clusters of zooids to huge spreading masses. The zooids are hermaphroditic, which means both eggs and sperm are released into the atrial chamber. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but some species have a partial block to self-fertilization. Fertilized eggs are brooded within the tunic until they hatch into lecithotrophic (non-feeding, yolk-dependent) tadpole larvae. The larva has a muscular tail and a notochord, eyespots, and a set of adhesive papillae. The larvae are expelled upon hatching and swim briefly before settlement. Swimming periods are usually less than a day, but some larvae settle immediately after release or swim for longer periods if the water temperature is low. On settlement the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Van Name 1945; Barnes 1983).


Phytoplankton; Detritus

Trophic Status:

Suspension Feeder



General HabitatMarinas & DocksNone
General HabitatRockyNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone

Life History

Tolerances and Life History Parameters

Broad Temperature RangeNoneCold temperate-Warm temeprate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Impacts of introduced populations of Diplosoma aff. spongiforme have not been reported.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
CAR-I Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida 2002 Def Estab
S200 Biscayne Bay 2004 Def Estab
NEA-III None 0 Native Estab
NEA-V None 0 Native Estab
NEA-IV None 0 Native Estab
MED-I None 0 Native Estab
MED-II None 0 Native Estab
MED-VII None 0 Native Estab
SA-II None 2002 Def Estab
G070 Tampa Bay 2000 Def Estab
S190 Indian River 2004 Def Estab
CAR-IV None 2007 Def Estab
MED-IV None 0 Native Estab
MED-VI None 0 Native Estab
SEP-H None 2008 Def Estab
CAR-III None 2008 Def Estab
SP-XXI None 2008 Def Estab
PAN_PAC Panama Pacific Coast 2008 Def Estab
PAN_CAR Panama Caribbean Coast 2008 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Carlton, James T.; Eldredge, Lucius G. (2015) Update and revisions of the marine bioinvasions of Hawai‘i: The introduced and cryptogenic marine and estuarine animals and plants of the Hawaiian archipelago, Bishop Museum Bulletin in Cultural and Environmental Studies 9: 25-47

da Rocha, Rosana Moreira; de Faria, Suzana Barros (2005) Ascidians at Currais islands, Paraná, Brazil: Taxonomy and distribution., Biota Neotropica 5(2): 1-20

Espla, A. A. Ramos; Buencuerpo, V.; Vazquez, E.; Lafargue, F. (1992) Some biogeographical remarks about the ascidian littoral fauna of the straits of Gibraltar (Iberian sector), Bulletin de l'Institut Océanographique 9 (special): 125-131

Hayward, P.J.; Ryland, J. S. (1990) <missing title>, 2 Clarendon Press, Oxford. Pp. <missing location>

Koukouras, Athanasios; Voultisiado-Koukoura, Eleni; Kevrekidis, Theodoros; Vafidis, Dimitri (1995) Ascidian fauna of the Aegean Sea with a checklist of the Mediterranean and Black Sea species, Annales de l Institut Oceanographique, Paris 71(1): 19-34

LaFargue Françoise (1975) Révision taxonomique des Didemnidae a des cotes de France (Ascidies composees). Description des especes de banyuls-sur-mer. Genre Lissoclinum. Genre Diplosoma., Vie et Milieu 25(ser. 2A): 289-309

LaFargue, F.; Tursi, A. (1975) Contribution a la connaissance des didemnidae (ascides composees) des cotes des pouilles (mer ionienne et mer adriatique), Vie et Milieu 25(1B): 33-48

Lafargue, Francois (1968) Les peuplements sessiles de L'archipel de Glenan, Vie et Milieu 19: 353-446

Naranjo, S. A.; Carballo, J. C.; Garcia-Gomez, J. C. (1996) Effects of environmental stress on ascidian populations in Algeciras Bay (southern Spain)., Marine Ecology Progress Series 144: 119-131

Simkanin, Christina; Fofonoff, Paul W.; Larson, Kriste; Lambert, Gretchen; Dijkstra, Jennifer A.; Ruiz, Gregory M. (2016) Spatial and temporal dynamics of ascidian invasions in the continental United States and Alaska, Marine Biology 163: Published online

Turon, X.; Becerro, M. A. (1992) Growth and survival of several ascidian species from the northwestern Mediterranean, Marine Ecology Progress Series 82: 235-247

Turon, Xavier (1990) Distribution and abundance of ascidians from a locality on the northeast coast of Spain, Marine Ecology 11(4): 391-408

Van Name, Willard G. (1945) The North and South American ascidians, Bulletin of the American Museum of Natural History 84: 1-462

Vazquez, Lafargue, Elsa; Francoise ; Urgorri, Vicotia (1994) Nuevos datos sobre distribucion de tres especies de la familia Didmenidae (Tunicata, Ascidiacea) de la costas ibericas., Boletin de la Real Sociedad Espaniola de Historia Natural 91(1-4): 219-224.