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The non-native titan acorn barnacle, Megabalanus coccopoma. Photograph courtesy South Carolina DNR.

M. coccopoma present in the hard-fouling community at Mayport Naval Station Beach, Jacksonville, FLorida. Photograph courtesy

Species Name: Megabalanus coccopoma Darwin,1854
Common Name: Titan Acorn Barnacle
Synonymy: Studies are ongoing to determine if Megabalanmus coccopoma and the Asian-Pacific species M. rosa are the same species (Powers et al. 2006). If so, the native range and introduced distribution of the species will need to be reassessed.

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Arthopoda Maxillopoda Sessilia Balanidae Megabalanus

    Species Description

    The titan acorn barnacle Megabalanmus coccopoma, is not native to the Atlantic but now occurs along the U.S. Atlantic coast and in the Gulf of Mexico. It is a very large balanid (acorn barnacle family), pink in color and growing to over 5 cm in height and width (Kerckhof 2002, Jaxshells).

    Potentially Misidentified Species

    A number of non-native balanid barnacles occur in Florida and have introduced ranges that potentially overlap that of Megabalanmus coccopoma. The Mediterranean barnacle Megabalanus antillensis (= Balanus tintinnabulum) and the Pacific barnacle Balanus trigonus are two such species that are similar in color to M. coccopoma. Balanus trigonus is distinguishable by size, only growing to around 8 mm, while differentiating between Megabalanus species may require taxonomic expertise beyond that of most amateur naturalists. In the IRL region, however, M. coccopoma appears thus far to occur primarily to the extreme northern part of the system while M. antillensis has been found primarily at the southern end of the IRL region, i.e., in the Loxahatchee River Estuary (McPherson et al. 1984). M. coccopoma was reported from Port St. Lucie in 2006, however (Florida Wildlife 2007). If this report is valid, then the IRL distribution of the two non-native Megabalanus species may overlap.


    Regional Occurrence

    Megabalanus coccopoma is native to the Pacific coast of the Americas from southern California to Ecuador. The animal now occurs in the Gulf of Mexico and along the southeastern U.S coast from northern Florida to southern North Carolina.

    IRL Distribution

    Megabalanus coccopoma was first collected from the Cape Canaveral area in 2006. Several specimens have also been collected around Ponce De Leon Inlet at the northern end of the IRL system. The USGS Nonindigenous Aquatic Species (NAS) program considers M. coccopoma to be established in the Volusia County portions of the system.


    Age, Size, Lifespan

    Megabalanus coccopoma grows to around 5 cm in height and width. Tibbetts (2007) reports that non-native M. coccopoma from South Carolina attain a body mass 100 times greater than that of native barnacle species.


    Collection information reported from Florida to date do not yet indicate the presence of Megabalanus coccopoma in large numbers.


    Details on reproduction in Megabalanus coccopoma remain unpublished. Reproduction in nearly all barnacles employs outcrossing of neighboring adult individuals as the norm, with individual animals occurring as simultaneous hermaphrodites. Fertilization is internal, occurring through the deposit of sperm into the mantle cavities of adjacent animals via an elongated intromittent tube.


    Details on larval development in Megabalanus coccopoma remain unpublished. As with other barnacle species, M. coccopoma larvae progress through several sequential nauplius stages and one cypris larval stages prior to settling to suitable hard substrata to spend the rest of their lives as sessile animals.



    Cool water temperatures appear capable of limiting the distribution of this tropical species. A 1982-1983 El Niño event allowed a brief northern range expansion along the southern California coast into ephemeral warm water off of San Diego (Newman and McConnaughey 1987).


    Megabalanus coccopoma appears to favor high salinity conditions (Kerckhof 2002). If 2006 reports of the species from estuarine waters near Port St. Lucie, Florida, are valid, however, then M. coccopoma also appears capable of inhabiting more brackish environments.


    Trophic Mode

    Like other acorn barnacles, Megabalanus coccopoma 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

    Megabalanus coccopoma 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

    Megabalanus coccopoma is native to the eastern Pacific, historically known to occur from Baja California (occassionally as far north as San Diego) through Central and South America southern Equador.

    M. coccopoma was reported as a non-native species established in southern Brazil in the late 1980s and along the coast of Belgium in 2002 (Newman and McConnaughey 1987, Kerckhof 2002). The species was found in Louisiana in 2002, and from Florida, Georgia, and South Carolina in 2006.

    Ship hull fouling and ballast water transport are the most probable introduction vectors.

    Potential to Compete With Natives

    If Megabalanus coccopoma begins to occur in consistently large numbers within its non-native range in Florida and elsewhere, it would be expected to compete with other intertidal hardbottom organisms for space and also possibly with a variety of filter-feeding animals for food.

    Young (1994) suggests M. coccopoma, now established along southern Brazil, may outcompete the native congeneric barnacle, M. tintinnabulum.

    Possible Economic Consequences of Invasion

    Boat hulls props, and drive shafts, coastal navigation buoys, and other submerged man-made hard surfaces are readily colonized by settling Megabalanus coccopoma (Kerckhof, 2002). If the species becomes established, costs associated with removing animals from such structures may be significant.

    Factors such as gregarious settlement, rapid growth, and large size suggest M. coccopoma has the potential to become an economically important nuisance species in Florida.


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

    Florida Wildlife. 2007. New, bigger barnacle discovered on Florida's East Coast. Florida Wildlife 2007:13.

    Kerckhof, F. 2002. Barnacles (Cirripedia, Balanomorpha) in Belgian waters: an overview of the species and recent evolutions, with emphasis on exotic species. Bulletin van het Koninklijk Belgisch Instituut voor Natuurwetenschappen. Biologie 72(Suppl.):93-104.

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

    McPherson B.F., Sonntag W.H., and M. Sabanskas. 1984. Fouling Community of the Loxahatchee River Estuary, Florida, 1980-81. Estuaries 7:149-157.

    Newman, W.A., and R.R. McConnaughey. 1987. A tropical eastern Pacific barnacle, Megabalanus coccopoma (Darwin), in southern California, following El Ni—o 1982-83. Pacific Science 41:31-36.

    Powers A., Mitchell M., Walker R., Posey M., Alphin T., and C. Belcher. 2006. Baseline Port Surveys for Introduced Marine Molluskan, Crustacean and Polychaete Species in the South Atlantic Bight . NOAA's National Sea Grant Aquatic Nuisance Species Program. Project Number R/HAB-15; Grant number NA06RG0029. 310 pgs.

    Tibbetts J.H. 2007. Knocking Back Biological Invaders. Coastal Heritage, South Carolina Sea Grant Consortium 21:3-11. Available online.

    Young P. S.1994 The Balanoidea (Cirripedia) from the Brazilian coast. Bolm. Mus. Nac., sŽrie Zoologia, 356:1-36.

Report by: J. Masterson, Smithsonian Marine Station
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Page last updated: December 1, 2007

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