Invasion History

First Non-native North American Tidal Record: 1997
First Non-native West Coast Tidal Record: 1997
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

The colonial tunicate Botrylloides giganteus was first described from Senegal in 1949. In the 1980s, it was found in Brazil, over a limited range from Sao Paulo to Vittorio (Aron and Sole-Cava 1991, Rodrigues and da Rocha 1993, Da Rocha and Costa 2005). In 1997, a colonial tunicate, first identified as B. perspicuum, was found on the coast of southern California (Lambert and Lambert 2003). Recent morphological and genetic studies (in preparation) indicate that the Southern California form was conspecific with B. giganteus and with a colonial tunicate described from the Gulf of Taranto, Italy, B. pizoni (Brunetti and Mastrotaro 2012). It has also been identified in New Zealand (Riding et al. 2014, Ministry of Primary Studies 2015, Rocha et al. 2019). The native and introduced ranges of this tunicate are unresolved. 

North American Invasion History:

Invasion History on the West Coast:

Botrylloides giganteum was first collected in the Eastern Pacific in 1997 at the Naval Station in San Diego Bay, California. Since then, it has been collected at several sites in San Diego and Mission Bay and appears to have extended its range from the initial sites of collection in both locations (Lambert and Lambert 2003). In 2003, it was collected in Alamitos Bay and Huntington Harbor, south of Los Angeles (Ruiz et al., unpublished data) and in BahiáSan Quintín, on the Pacific Coast of Baja California in 2005 (Rodriguez and Ibarra-Obando 2008).

Invasion History Elsewhere in the World:

The native range of Botrylloides giganteus is unknown. The type locality was Senegal (Peres 1949, cited by (Aron and Sole-Cava 1991), but it was subsequently found on the Indian Ocean coast of South Africa and Mozambique (Millar 1955, Millar 1961, Millar 1963, cited by Monniot et al. 2001; Rocha et al. 2019). In Brazil, it was first found in 1986, and is known largely from artificial substrates, and is especially abundant in mussel cultures. It was not seen in previous surveys and is considered introduced and established in Brazil (da Rocha et al. 2009; Rocha et al. 2019; Oricchio et al. 2019). In 2014, B. giganteus was found in Whangarei Harbor, New Zealand (Riding et al. 2014; Rocha et al. 2019), and on Santa Cruz and Baltra Islands, in the Galapagos Archipelago, in 2015 (Lambert 2009; Rocha et al 2019).


Botrylloides giganteus is a colonial tunicate. Colonial tunicates are communities of individuals, called zooids, which share a protective cellulose layer called a tunic. Each zooid is an individual, but they are such an intricate part of the colony that they cannot be separated from it. In fact, the zooids are connected to one another by a network of blood vessels and work together to make the colony function like a single animal.

The colonies of B. giganteus are 2-5 mm thick, translucent, and variable in size and shape, ranging from 30 to 150 mm in diameter. They can grow on algae or other debris. Botrylloides giganteus has linear systems of zooids, which are visible through the tunic. The colonies are red to orange or violet in color. The body walls of its zooids are very delicate and transparent and lack longitudinal or circular musculature. The oral siphon is round, with a smooth margin. There are 24 branchial tentacles in mature zooids. On the branchial sac there are 11-17 pairs (usually 14) of stigmata. The atrial siphon develops a languet, a tongue-like structure, which varies in shape and length. The esophagus is short and curved, and the stomach has 9-10 longitudinal folds. A mature zooid can have a single developing embryo. Description based on: Rodrigues and da Rocha 1993, and da Rocha and Costa 2005.

This tunicate, discovered in Southern California, was initially identified as B. perspicuum (1997, Lambert and Lambert 2003). Recent observations indicate that it is actually B. giganteus (Gretchen Lambert and Rosana da Rocha, personal communications). We are in the process of revising the morphological description and biogeographical history of this species (Rodriques and da Rocha 1993; da Rocha and Costa 2005; Rocha et al. 2019).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Chordata
Subphylum:   Tunicata
Class:   Ascidiacea
Order:   Stolidobranchia
Family:   Styelidae
Genus:   Botrylloides
Species:   giganteus


Botryllus giganteus (Aron & Sole Cava, 1991)
Botrylloides niger var. giganteum (Pérès, 1949)
Botrylloides giganteum (Ryland, 2015)
Botrylloides pizoni (Brunetti and Mastrotaro, 2012)

Potentially Misidentified Species

Botrylloides conchyliatus
Rocha et al. 2919, new species, described from Queesland, Australia

Botrylloides leachii
Kott 1972, cited by Kott 1985

Botrylloides nigrum
Michaelson 1919, cited by Kott 1985

Botrylloides perspicuus

This tunicate was initially identified as Botrylloides perspicuum (1997, Lambert and Lambert 2003). Recent observations suggested that it is actually B. giganteum (Gretchen Lambert, Rosana da Rocha, personal communications, 2013–2015).

Botyrllus firmus
Monniot and Monniot 2001



Life History- A colonial (or compound) 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 genera Botrylloides have small zooids, usually not organized in systems, and fully embedded in a mass of tunic material. Each zooid has an oral siphon and an atrial canal, opening 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 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. Eggs are internally fertilized, and embryos are incubated in a brood pouch. Once they are mature, 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). 




fishes, crabs

Trophic Status:

Suspension Feeder



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

Life History

Tolerances and Life History Parameters

Broad Temperature RangeNoneWarm temperate-Tropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Competition: The colonial tunicate Botrylloides giganteus (then identified as B. perspicuum) covered extensive areas crowding out other species. This was seen in San Diego Bay in 1997 (Lambert and Lambert 2003).

Regional Impacts

NEP-VIPt. Conception to Southern Baja CaliforniaEcological ImpactCompetition
The colonial tunicate Botrylloides giganteum is a recent invader of two locations in southern California, in Mission Bay and San Diego Bay. From 1994-2000 strong competition was noted at some locations where the tunicate grew over extensive areas (100% cover) (Lambert and Lambert 2003).
P020San Diego BayEcological ImpactCompetition
The colonial tunicate Botrylloides giganteum is a recent invader of San Diego Bay. At one location (24th street), in 1997, it covered extensive areas up to 100% cover, indicating strong competitive ability (Lambert and Lambert 2003).
P030Mission BayEcological ImpactCompetition
The colonial tunicate Botrylloides giganteum is a recent invader of Mission Bay. Strong competition was noted at some locations where the tunicate grew over extensive areas (100% cover) (Lambert and Lambert 2003).
CACaliforniaEcological ImpactCompetition
The colonial tunicate Botrylloides giganteum is a recent invader of San Diego Bay. At one location (24th street), in 1997, it covered extensive areas up to 100% cover, indicating strong competitive ability (Lambert and Lambert 2003)., The colonial tunicate Botrylloides giganteum is a recent invader of Mission Bay. Strong competition was noted at some locations where the tunicate grew over extensive areas (100% cover) (Lambert and Lambert 2003).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-VI Pt. Conception to Southern Baja California 1997 Def Estab
P050 San Pedro Bay 2003 Def Estab
P020 San Diego Bay 1997 Def Estab
P030 Mission Bay 1998 Def Estab
SA-II None 1986 Def Estab
SA-III None 1991 Def Estab
WA-I None 0 Crypto Estab
WA-II None 1949 Crypto Estab
NZ-IV None 2014 Def Estab
MED-IV None 2001 Def Estab
WA-V None 1955 Crypto Estab
EA-IV None 1961 Crypto Estab
WA-IV None 2010 Crypto Estab
CAR-I Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida 2008 Crypto Estab
SEP-Z None 2015 Def Estab
P064 _CDA_P064 (Ventura) 2013 Def Estab
P062 _CDA_P062 (Calleguas) 2013 Def Estab
P060 Santa Monica Bay 2013 Def Estab
SEP-C None 2011 Def Estab
P065 _CDA_P065 (Santa Barbara Channel) 2020 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
4441 Lambert and Lambert 2003 1997 1997-05-01 Naval Station, San Diego Def 32.7347 -117.2164
4442 Lambert and Lambert 2003 1998 1998-05-01 Shelter Island, San Diego Def 32.7100 -117.2342
4443 de Rivera et al. 2005 2003 2003-08-01 Chula Vista Marina San Diego Def 32.6244 -117.1038
4444 de Rivera et al. 2005 2003 2003-08-01 Dana Point Marina Def 32.7675 -117.2365
4445 de Rivera et al. 2005 2003 2003-08-01 Seaforth Marina, Def 32.7630 -117.2373
4447 Ruiz et al., unpublished data 2003 2003-06-06 Peters Landing Marina, Huntington Harbor Def 33.7211 -118.0641
4448 Goodbody 2004 1996 1996-01-01 Twin Cays Def 16.8167 -88.1000
4449 Goodbody 2000 1993 1993-01-01 Pelican Cays Def 16.6500 -88.2000
4450 Goodbody 2000 2000 2000-01-01 South Water Cay Def 16.8000 -88.0833
5921 Rodriguez et al. 2008 2005 2005-01-21 Bahia San Quintin Def 30.4500 -116.0000


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