Invasion History

First Non-native North American Tidal Record: 1994
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1994

General Invasion History:

Botryllus planus is native to warm waters of the western Atlantic, from North Carolina and Bermuda to Panama, Curaçao, Colombia, and Venezuela (Van Name 1945; Monniot 1972; US National Museum of Natural History 2011). Da Rocha and Kremer (2005) considered B. planus native to Brazil, with a fairly continuous distribution, but noted a comparatively late first record (1969) in Rio de Janeiro province, and frequent occurrences with cultured oysters. In Brazil, this tunicate is found from the state of Ceara to the state of Sao Paulo (Da Rocha and Kremer 2005). In 1994, B. planus was collected in Chincoteague, Virginia, however information on its establishment in this area is unknown, suggesting that it was a failed invasion.

North American Invasion History:

Invasion History on the East Coast:

One record of Botryllus planus, from Chincoteague, Virginia, in 1994 (USNM 20714, US National Museum of Natural History 2011) appears to be an apparent introduction. This probably represents transport of a fouling organism by recreational boats moving up the coast. Its establishment in Chincoteague Bay is unknown. Several other disjunct records of subtropical organisms probably transported by boats, for instance the tunicate Ecteinascidia turbinata and the gastropod Eupleura sulcidentata, are also known from this estuary (Prezant et al. 2002).

Invasion History Elsewhere in the World:

Botryllus planus has been collected from Panama Bay, at the Pacific entrance to the Panama Canal. It is not known whether colonies could survive transport through the canal, or were introduced by another route or vector (in 2009, Carman et al. 2010).


Botryllus planus is a colonial tunicate with encrusting colonies. Colonies are often irregular in shape and several centimeters in greatest diameter. They are frequently so thin that the zooids are sometimes nearly parallel to the colonies surface, but in other cases, colonies are thicker and the zooids nearly upright. The color is very variable during life. Zooids range from orange, dark purple, purplish brown, or blackish with a white, pale green, or golden yellow area surrounding the branchial orifice of each zooid. The colonies' light colors fade after death to purple or brownish purple. 'Some specimens collected at Bermuda were bright orange when alive, this color suffusing the tunic as well as the zooids. The young zooids produced by budding are in many colonies differently colored than the adult ones from which they developed (Van Name 1945).

Zooids are smaller than 1.5 to 1.75 mm in length when preserved. Zooids have eight or fewer tentacles, and usually 11 to 13 rows of stigmata. 'The reproductive and digestive organs furnish the easiest means of distinguishing this species. The male organs consist of a single testis on each side of the body, situated posterior to the middle and so deeply cleft into numerous (10 to 20) rounded lobes that it appears like a rosette shaped mass of small separate glands. The female organs, at least in the adult state, consist of a single ovary on each side, each containing a large egg situated close, and directly anterior, to the testis. The stomach is oblong or barrel shaped though tapering somewhat more toward the pyloric end. The stomach has about nine complete glandular folds and one incomplete one, which increase gradually in prominence toward the esophageal end, and a very long tubular curved pyloric caecum that is slightly enlarged at the extreme end.' (Van Name 1945).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Chordata
Subphylum:   Tunicata
Class:   Ascidiacea
Order:   Stolidobranchia
Family:   Styelidae
Genus:   Botryllus
Species:   planus


Botrylloides nigrum planum (Van Name, 1902)

Potentially Misidentified Species

Botrylloides niger



Life History- A colonial (or compound) tunicate consists of many, small zooids, bearing most or all of the organs of a solitary tunicate, but modified to varying degrees for colonial life. Colonial ascidians of the genera Botryllus and Botrylloides have small, flattened and curved zooids, arranged in systems, with groups of zooids having atrial canals opening into a common cloacal chamber. The zooids are embedded in a mass of tunic material. Each zooid has an oral siphon and an atrial canal, an opening to a shared cloacal chamber. The thorax contains an elaborate gill basket, and below it, a compressed abdomen, which contains the stomach, intestine, ovaries, testis, and heart.. The intestine leads back to the thorax and to the atrial opening. The abdomen ends in stolons, which are attached to the substrate and neighboring zooids. Water is pumped through the oral siphon, through finely meshed ciliated gills, where it is filtered and expelled through the oral siphon. Phytoplankton and detritus is filtered by the gills and passed on mucus strings to the stomach and intestines where waste is expelled in the outgoing atrial water (Van Name 1945; Barnes 1983).

Colonial ascidians reproduce both asexually, by budding, and sexually, from fertilized eggs developing into larvae. Buds can form from the body wall of the zooid. Colonies vary in size and can range from small clusters of zooids to huge spreading masses. The zooids are hermaphroditic, with eggs and sperm being produced by a single individual. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but many species have a partial block to self-fertilization. Depending on the life-history of the species, eggs may be externally or internally fertilized. Fertilized eggs hatch into a tadpole larva with a muscular tail, notochord, eyespots, and a set of adhesive papillae. The lecithotrophic (non-feeding, yolk-dependent) larva swims briefly before settlement. Swimming periods are usually less than a day, and some larvae can settle immediately after release, but the larval period can be longer at lower temperatures. Once settled, the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Van Name 1945; Barnes 1983).

Botryllus planus is found in tropical and subtropical environments from North Carolina to Brazil (da Rocha and Kremer 2005; US National Museum of Natural History 2010; Lord et al. 2015). Botryllus planus is found in polyhaline and euhaline saliiities (Dijkstra et al. 2016). Botryllus planus is known from a wide range of natural and artificial surfaces, including rocks, mangroves coral reefs, oyster beds, marinas,floats and vessel hulls. It often grows on other organisms (Van Nsme 1945; Woods Hole Oceanographic Institution and United States Navy Department1952; Rodrigues and da Rocha 1993). Pr


Phytoplankton, detritus

Trophic Status:

Suspension Feeder



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

Tolerances and Life History Parameters

Maximum Temperature (ºC)29.7Field, US East & West Coast marinas (Lord et al. 2015)
Minimum Salinity (‰)24Experimental. Specimens did show reduced heart rates, and some showed expanded clocae, a sign of stress, (Dijkstra and Simkanin 2016).
Broad Temperature RangeNoneWarm Temperate-Tropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Impacts of introduced Botryllus planus 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 0 Native Estab
CAR-III None 0 Native Estab
S050 Cape Fear River 0 Native Estab
CAR-VII Cape Hatteras to Mid-East Florida 0 Native Estab
CAR-II None 0 Native Estab
NA-ET3 Cape Cod to Cape Hatteras 1994 Def Unk
M120 Chincoteague Bay 1994 Def Unk
NA-ET4 Bermuda 0 Native Estab
SA-II None 1969 Native Estab
SA-III None 0 Native Estab
CAR-IV None 0 Native Estab
SEP-H None 2009 Def Estab
PAN_PAC Panama Pacific Coast 2009 Def Estab
PAN_CAR Panama Caribbean Coast 0 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Carman, Mary R. and 7 authors 2010 Ascidians at the Pacific and Atlantic entrances to the Panama Canal. <missing URL>

Carman, Mary, and 8 authors (2011) Ascidians at the Pacific and Atlantic entrances to the Panama Canal, Aquatic Invasions 6(4): 371-380

da Rocha, Rosana M.; Faria, Suzana B.; Moreno, Tatiane R. (2005) Ascidians from Bocas del Toro, Panama, Caribbean Journal of Science 41(3): 600-612

da Rocha, Rosana M.; Kremer, Laura P. (2005) Introduced ascidians in Paranagua Bay, Parana, southern Brazil., Revista Brasileira da Zoologia 22(4): 1170-1184

Dalby, James E. Jr.; Young, Craig M. (1992) Role of early post-settlement mortality in setting the upper depth limit of ascidians in Florida epifaunal communities, Marine Ecology Progress Series 80: 221-228,

Dijkstra, Jennifer A.; Simkanin, Christina (2016) Intraspecific response of colonial ascidians to variable salinity stress in an era of global change, Marine Ecology Progress Series 551: 215-225,

Lord, Joshua P.; Calini, Jeremy M.; Whitlatch, Robert B. (2015) Influence of seawater temperature and shipping on the spread and establishment of marine fouling species, Marine Biology 162: 2481-2492

Monniot, C.; Monniot, F. (1985) [Littoral ascidians of Guadeloupe Island: IX. Characteristics of populations, ecology, relationships with the world fauna] (French), Tethys 11(3-4): 203-213

Monniot, Claude (1972) [Stolidobranch Ascidians of Bermuda[ (French), Bulletin du Museum National d'Histoire Naturelle. 4e Serie. Section A. Zoologie, Biologie et Ecologie Animales 43: 617-643

Mook, David (1983) Indian River fouling organisms, a review, Florida Scientist 26(3/4): 162-167

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database.

Van Name, Willard G. (1921) Ascidians of the West Indian region and southeastern United States., Bulletin of the American Museum of Natural History 44: 283-494

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