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The non-native striped barnacle, Balanus amphitrite. Photograph courtesy SFEI, Photograpger Andrew N. Cohen.

B. amphitrite. Photograph courtesy SFEI, Photograpger Andrew N. Cohen.

Species Name: Balanus amphitrite Darwin, 1854
Common Name: Striped Barnacle
Purple Acorn Barnacle
Amphitrite's Rock Barnacle
Synonymy: Darwin originally described 9 morphologically distinct Balanus amphitrite subspecies, but numerous subsequent revisions including genetic alalysis by Flowerdew (1985) currently recognize only a single subspecies worldwide.

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Arthropoda Maxillopoda Sessilia Balanidae Balanus

    Species Description

    The striped barnacle, Balanus amphitrite, is a medium-sized surface-fouling, sessile barnacle with distinct vertical bands of purple stripes on it's protective rigid housing plates, known as capitulum plates. It is conical in appearance and largest at the base, with a diamond-shaped opening protected by a movable opercular lid composed of two symmetrical triangular halves. Each of these halves contains two plates, the tergum and the scutum. The operculum opens when is the lid halves are flexed out to the sides (Cohen 2005).

    B. amphitrite is an acorn barnacle (Suborder Balanomorpha). Like all members of the taxon, it resides within a protective wall of rigid plates and is attached by its base directly to solid substrata. In contrast, goose barnacles attach by means of slender, flexible stalks (Cohen 2005).

    Potentially Misidentified Species

    The IRL native ivory barnacle (Balanus eburneus) is somewhat similar in appearance but the white plates lack stripes and it is slightly larger (9.5-24.5 mm) than Balanus amphitrite. B. amphitrtie. is also larger than the star barnacle Chthamalus stellatus Two other probable non-native congeners, B. reticulatus and B. trigonus, are also common in Florida fouling communities, but the striped barnacle can be readily distinguished from these (Carlton and Ruckelschaus 1997). The non-native barnacle Megabalanus coccopoma, recently discovered in Florida waters, has plates that are distinctly pink in color and is considerably larger than the other acorn barnacles found in Florida.


    Regional Occurrence

    Balanus amphitrite is a common, broadly distributed coastal and estuarine biofouling organism found on hard natural surfaces such as rocks, in oyster beds, red mangrove (Rhizophora mangle) prop roots and mollusc shells. It is also found on artificial substrates like ship hulls, pilings, riprap, and seawalls.

    The native range of B. amphitrite is uncertain, but may be located in the Indian Ocean to the southwestern Pacific, based on its presence in the Pleistocene fossil record (Cohen 2005). It is now a dominant fouling organism found in warm and temperate waters worldwide (Desai et al. 2006).

    USGS collection information lists B. amphitrite as established in Florida coastal waters by 1975 (Henry and McLaughlin 1975, Carlton and Ruckelshaus 1997), but the initial introduction most likely occurred much earlier and the first reports of the species in Florida date to at least the 1940s.

    IRL Distribution

    Mook (1983) reported Balanus amphitrite and B. trigonus as occurring in lesser abundances than B. eburneus is IRL settlement studies conducted in 1977-1978 in Fort Pierce in the vicinity of Harbor Branch Oceanographic. Boudreaux and Walters (2005) suggest B. amphitrite and the native B. eburneus are abundant in the Mosquito Lagoon portion of the estuary.


    Age, Size, Lifespan

    The maximum basal length of Balanus amphitrite is reported to be around 20 mm (Anderson 1986, Cohen 2005).

    Research conducted in the Mediterranean suggests a mean lifespan of 77 days and a maximum lifespan of 1.26-1.40 years, and a somewjhat longer mean lifespan of 22 months and maximum lifespan of 5-6 years in South Africa and Argentina (Calcagno et al. 1997, 1998).


    Matias et al. (2003) proclaim Balanus amphitrite to be the predominant barnacle of ports worldwide and noted that the global distribution was likely the result of ship-facilitated introductions occurring centuries earlier.

    Settlement densities can be quite high. Boudreaux and Walters (2005) indicated that over 300 individual B. amphitrite and B. eburneus were counted on a single oyster (Crassostrea virginica) shell in the Mosquito Lagoon basin of the IRL.


    Like most balanomorph barnacles, Balanus amphitrite is hermaphroditic. Reproductive individuals are general capable of simultaneous production of male and female gametes. However, outcrossing with neighboring individuals, occuring through the deposit of sperm into the mantle cavities of adjacent animals via a long intromittent tube and subsequent internal fertilization of eggs, is the general rule. Self-fertilization is also reported to occur, however (Charnov 1987, Furman and Yule 1990, El-Komi and Kajihara 1991, Desai et al 2006).

    Spawning seasonality varies by location. B. amphitrite populations in temperate areas exhibit spawning peaks in the spring and/or summer, while those in more subtropical areas may spawn throughout the year (Costlow and Bookhout 1958, Pillai, 1958, Egan and Anderson 1986).

    Individuals reach reproductive maturity at around 5.0 mm in length (Egan and Anderson 1986). Individuals can release 1,000-10,000 eggs/ brood and produce as many as 24 broods/year (El-Komi and Kajihara 1991).


    Fertilized eggs are brooded within the mantle cavity for up to several months before free-swimming planktonic larvae are released to the water column (Hawaii Biological Survey 2002).

    Habitat settlement selectivity in settlement stage Balanus amphitrite cyprids has been shown to vary with age. Experimental work by Miron et al. (2000) revealed that fewer young cyprids (0-5 days old) spent less time than older individuals (6-12 days old) exploring suboptimal substrata. The authors reported that the physical condition of cyprids decreased significantly with age, suggesting that substratum selectivity decreases in older individuals as the period of metamorphic competence nears its end. The settlement-stage cypris cements itself to a suitable hard substratum using a matrix of adhesive proteins secreted by the cypris antennae.



    Balanus amphitrite is eurythermal in nature. Individuals can survive water temperatures as low as 12°C, but will will not breed in water colder than 15-18°C (Cohen 2005, Desai et al. 2006). Bishop (1950) reported that low temperature reproductive limits defined the northermost extent of B. amphitrite distribution in England, while Vaas (1978) notes that it survives in colder waters in Britain and the Netherlands at sites bathed in heated power plant effluent. Experimental work by Anil et al. (1995) suggest an optimum temperature near 23°C.

    Embryonic development is accelerated B. amphitrite by temperature increase (Anil and Kurian 1996, Desai et al. 2006).


    Balanus amphitrite is considered to be a euryhaline species. It survives in tropical estuaries where seasonal monssons can drive salinity to as little as 4 ppt (Desai et al. 2006). Higher salinities of at least 10-15 ppt are likely required for breeding to occur (Vaas 1978).


    Trophic Mode

    Like other acorn barnacles, Balanus amphitrite filter feeds when submerged by means of a set of extensible sieving appendages called cirri (barnacles belong to infraclass Cirripedia). The extended cirri are oriented perpendicular to the general flow direction and varying food concentrations and water velocities can elicit different patterns and rates of movement of the cirri to maximize particle intake (LaBarbera 1984, Crisp and Bourget 1985).

    Associated Species

    Balanus amphitrite occur alongside a number of different animal and algal taxa that comprise hard fouling intertidal communities, although none of these associations are likely to be obligate.


    Invasion History

    Zullo (1963) indicates that Balanus amphitrite occurs worldwide in warm and temperate seas. The cosmopolitan distribution is attributable to the early date at which human-facilitated spread of the species began. Like other well-known ship-fouling organisms such as shipworm (e.g, Teredo navalis) and certain tunicates (e.g., Styela plicata), man has likely been unintentionally transporting B. amphitrite across wide expanses of ocean for as long as sailing ships have been in existence. Darwin himself in 1854 recognized that the broad geographic ranges inhabited by B. amphitrite and certain other barnacles, "which seem to range over nearly the whole world (excepting the colder seas)," were probably due in part to accidental transport as fouling organisms on ship hulls (Cohen 2005).

    The first records of B. amphitrite in and around various shipping centers in the United States confirm the early dates of introduction. In 1883 it was collected from North Carolina, from Los Angeles Harbor in 1914, from Hawaii in 1902, and from Florida by the 1940s. As early as the 1920s, the species was present on 20% of ship hulls examined (Cohen 2005). Although hull fouling (and possibly also dry ballast) is the most likely mechanism of transport in most introductions, particularly the earliest instances, B. amphitrite may in some cases also have been introduced to new locations as naupliar and cypris larvae in ballast water, or in live oyster shipments (Cohen 2005).

    On the east coast of the U.S. B. amphitrite presently occurs from Florida north to Massachusetts (Zullo 1963).

    Potential to Compete With Natives

    Space competition is likely to occur among Balanus amphitrite and other barnacle species, and among B. amphitrite and other hard fouling taxa as well. However, Boudreaux and Walters (2005) report that B. amphitrite and the native congener B. eburneus are capable of persisting side-by-side, at least for a period of time. Vertical zonation of barnacles and other rocky shoreline taxa probably moderates competition somewhat.

    Possible Economic Consequences of Invasion

    The striped barnacle is a prevalent biofouler of ships and harbor sturctures (Brankevich et al. 1984). Balanus amphitrite cements itself onto hard surfaces with a matrix of proteins (Saroyan et al. 1970). Hulls of ships, buoys, and inflow pipes of desalination plants become covered with the barnacles (Mangum et al. 1972, Starostin 1968) which eventually causes corrosion of the metals and increased maintenance costs. Barnacle aggregations also increase friction between the surface of ships' bottoms and surrounding water, thus travel costs are increased and efficiency decreased, i.e., it requires additional energy to move the ship at the same speed (London 1972).


    Anil A.C., Chiba K., Okamoto K., and H. Kurokura. 1995. Influence of temperature and salinity on larval development of Balanus amphitrite: Implications in fouling ecology. Marine Ecology Progress Series 118:159-166.

    Anil, A. C. ; And J. Kurian. 1996. Influence of food concentration, temperature, and salinity on the larval development of Balanus amphitrite. Marine Biology 127:115-124.

    Bishop M.W.H. 1950. Distribution of Balanus amphitrite Darwin var. denticulata (Broch). Nature 165:409.

    Boudreaux M.L., and L.J. Walters. 2005. Competition between oysters and barnacles: The impact of native and invasive barnacle density on native oyster settlement, growth, and survivorship. Poster presented at the 18th Biennial Conference of the Estuarine Research Federation (ERF) Norfolk VA, October 16-21 2005.

    Calcagno J.A., Lopez Gappa J., and A. Tablado. 1997. Growth and production of the barnacle Balanus amphitrite in an intertidal area affected by sewage pollution. Journal of Crustacean Biology 17:417-423.

    Calcagno J.A., Gappa J.L., and A. Tablado. 1998. Population dynamics of the barnacle Balanus amphitrite in an intertidal area affected by sewage pollution. Journal Of Crustacean Biology 18:128-137.

    Carlton J.T. and M.H. Ruckelshaus. 1997. Nonindigenous marine invertebrates and algae. Pp 187-201 in: Simberloff D., Schmitz D.C., and T.C. Brown (eds). Strangers in Paradise. Island Press, Washington, D.C. 467 p.

    Charnov E.L. 1987. Sexuality and hermaphroditism in barnacles: a natural selection approach. pp: 89-104 in: Southward A.J. (Ed.). Crustacean Issues 5. Barnacle Biology. AA Balkema, Rotterdam.

    Cohen A.N. 2005 Guide to the Exotic Species of San Francisco Bay. San Francisco Estuary Institute, Oakland, CA. Available online.

    Costlow J.D. and C.G. Bookhout. 1958. Larval development of Balanus amphitrite Var. denticulate Broach reared in the laboratory. Biological Bulletin 114:284-295.

    Crisp D.J. and E. Bourget. 1985. Growth In barnacles. Advances In Marine Biology 22:199-244.

    Desai D., Anil A., and K. Venkat. 2006. Reproduction in Balanus amphitrite Darwin (Cirripedia: Thoracica): influence of temperature and food concentration. Marine Biology 149:1431-1441.

    Egan E.A. and D.T. Anderson. 1986. Larval development of Balanus amphitrite Darwin and Balanus variegates Darwin (Cirripedia, Balanidae) from New South Wales, Australia. Crustaceana 51:188-207.

    El-Komi M.M. and T. Kajihara. 1991. Breeding And moulting of barnacles under rearing conditions. Marine Biology 108:83-89.

    Furman E.R. and A.B. Yule. 1990. Self-fertilisation in Balanus improvisus Darwin. Journal of Experimental Marine Biology and Ecology 144:235-239.

    Hawaii Biological Survey. 2002. Striped barnacle (Balanus amphitrite). Bishop Museum and University of Hawaii Guidebook of Introduced Marine Species of Hawaii. Available online.

    Hayward, P.J., & Ryland, J.S., eds. 1990. The marine fauna of the British Isles and north-west Europe. 2 vols. Oxford, Clarendon Press.

    Henry D.A., and P.A. McLaughlin. 1975. The barnacles of the Balanus amphitrite complex (Cirripedia, Thoracica). Zoologische Verhandlingen (Leiden) 141:1-254.

    LaBarbera M. 1984. Feeding currents and particle capture mechanisms in suspension feeding animals. American Zoology 24:71-84.

    Matias J.R., Rabenhorst J., Mary A., and A.A. Lorilla. 2003. Marine biofouling testing of experimental marine paints: Technical considerations on methods, site selection and dynamic tests. Proceedings of the SSPC 2003 Industrial Protective Coatings Conference and Exhibit in New Orleans, Louisiana.

    Miron G., Walters L.J., Tremblay R., and E. Bourget. 2000. Physiological condition and barnacle larval behavior: a preliminary look at the relationship between TAG/DNA ratio and larval substratum exploration in Balanus amphitrite. Marine Ecology Progress Series 198:303-310.

    Mook D. 1983. Responses of common fouling organisms in the Indian River, Florida, to various predation and disturbance intensities. Estuaries 6:372-379.

    Pillai K.N. 1958. Development of Balanus amphitrite, with a note on the early larvae of Chelonibia testudinaria. Bull. Central Res. Inst. Kerala 6:117-130.

    Vaas K.F. 1978. Immigrants among the animals of the delta-area of the SW. Netherlands. Hydrological Bulletin 9:114-119.

    Zullo, V. A. 1963. A Preliminary Report On Systematics And Distribution Of Barnacles (Cirripedia) Of Cape Cod Region. Systematics-Ecology Program, Marine Biology Laboratory, Woods Hole, Massachusetts, 33 p.

Report by: J. Masterson, Smithsonian Marine Station
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Page last updated: October 5, 2007

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