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Close-up of a small group of ivory barnacles, Balanus eburneus. Photo L. Holly Sweat, Smithsonian Marine Station at Fort Pierce.

A large aggregation of B. eburneus and other barnacle species on a dock piling at Ponce de Leon Inlet, Florida. Photo L. Holly Sweat, Smithsonian Marine Station at Fort Pierce.

Species Name: Balanus Eburneus Gould, 1841
Common Name: Ivory Barnacle
Synonymy: None

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

    Species Description

    The ivory barnacle, Balanus eburneus, is a medium-sized sessile barnacle belonging to the class Cirripedia. This group contains approximately 900 described species, about two-thirds of which are free-living barnacles that foul or attach to rocks and other hard intertidal and submerged surfaces (Ruppert & Barnes 1994). Like other members of the suborder Balanomorpha, the soft tissue of B. eburneus is protected within a series of rigid plates, known as capitular plates. The solid white plates of the ivory barnacle form a conical appearance that is largest at the base, with a diamond-shaped opening guarded by a movable opercular lid composed of two symmetrical triangular halves (eg. Gosner 1978). Each of these halves contains two plates, the tergum and the scutum. During feeding, excretion, larval release and copulation, the operculum opens as the terga and scuta are flexed out to the sides.

    Potentially Misidentified Species

    Several species of acorn or balanoid barnacles inhabit the waters in and around the IRL. Probably the most commonly confused species with B. eburneus is the white bay barnacle, Balanus improvisus. This species is usually smaller than B. eburneus, at a maximum height of about 0.6 cm (Kaplan 1988). Definitive identification between species of acorn barnacles similar in appearance usually requires examination of the shape of the terga and scuta through dissection.

    The striped acorn barnacle, Balanus amphitrite, is similar in size and shape, but bears pink vertical stripes on the capitular plates. The non-native titan acorn barnacle, Megabalanus coccopoma, recently discovered in Florida waters as of the date of this text, has plates that are distinctly pink in color. The average size of most M. coccopoma is considerably larger than the other acorn barnacles found in Florida.


    Regional Occurrence & Habitat Preference

    The range of the ivory barnacle is extensive, probably due in part to introductions of the species via the ballast water and hull fouling of ships (eg. Hawaii, Matsui et al. 1964). The native distribution of B. eburneus extends from Nova Scotia to Florida, the Caribbean and Gulf of Mexico (Kaplan 1988). Large aggregations of the barnacle can be found on a variety of hard surfaces at or below the low tide line to a depth of about 37 m (Voss 1980), including: rocks; oysters, mussels and other mollusk shells; pilings; buoys; seawalls and prop roots of the red mangrove, Rhizophora mangle (Kaplan 1988, Ruppert & Fox 1988, Voss 1980, Zullo 1979).

    IRL Distribution

    The ivory barnacle is considered one of the most common fouling organisms found in the IRL (Hoskin & Courtney 1983, Mook 1976). Single individuals to large aggregations can be found in all intertidal IRL habitats.


    Age, Size and Lifespan

    The maximum age of B. eburneus is unknown, and the lifespan can vary with food availability and environmental factors. The maximum reported height and diameter for the ivory barnacle is about 2.5 cm (Gosner 1978, Kaplan 1988), though most specimens are much smaller.


    The ivory barnacle is gregarious like many other balanoid species (Toonen 2005). Occasional solitary individuals can be found on mangrove roots or pilings, but most larvae settle near others to produce large aggregations of several thousand individuals, covering the substrate and often growing on top of one another.


    Like most other free-living barnacles, B. eburneus is hermaphroditic. However, populations reproduce via cross-fertilization. The penis of B. eburneus is quite long, and can be protruded out of the body and into the mantle cavity of nearby individuals where sperm is deposited on the first cirri of the recipient before penetrating the ovisac and reaching the lamellae or egg mass (Ruppert & Barnes 1994). The eggs are brooded in the mantle cavity and released as swimming larvae once development is complete.


    Once they are released from the parent, larvae of B. eburneus pass through six naupliar stages and one cypris stage (Costlow & Bookhout 1957). The first nauplius is a non-feeding stage, but larvae in the following five developmental stages feed on phytoplankton. The non-feeding cyprid is the final larval stage, subsisting on lipid (fat) reserves accrued through naupliar feeding. The primary goal of this stage is to find suitable habitat on which to settle and metamorphose into a juvenile barnacle, usually after a total planktonic duration of 7-13 days (Costlow & Bookhout 1957). Several cues such as the presence of other B. eburneus, and the texture and biofilm (slime layer) composition of the substrate can influence cyprid settlement (eg. Dineen & Hines 1994, O'Connor & Richardson 1994). Once an appropriate site has been found, cyprids attach to the substrate as they are metamorphosing by secreting an adhesive substance from cement glands at the base of the 1st antennae (Ruppert & Barnes 1994).



    Based on the range and distribution of B. eburneus throughout temperate to tropical latitudes, the thermal tolerance of the ivory barnacle is likely quite large.


    The ivory barnacle is a euryhaline species, capable of withstanding a wide range of salinities. Large populations are commonly found in the field in waters from 5-30 ppt (Bacon 1971). In the laboratory, cypris larvae of B. eburneus settled at salinities ranging from 2 to 35 ppt, although the highest settlement occurred between 15 and 20 ppt (Dineen & Hines 1994).


    Trophic Mode

    Barnacles are filter feeders, extending their long feeding appendages (cirri) to remove zooplankton and microalgae from the water column. During feeding, the paired scuta and terga open and six pairs of cirri unroll and extend through the aperture (Ruppert & Barnes 1994). Long setae, or hair-like projections, cover the cirri to form a basket-shaped netting apparatus which strokes through the water to collect plankton.


    Few predators are recorded for B. eburneus, but individuals are likely preyed upon by a variety of fishes and invertebrates.

    Associated Species

    No known obligate associations exist for B. eburneus. However, ivory barnacles are associated with several organisms common to intertidal areas. For extensive lists of other species found in the habitats in which B. eburneus occurs, please refer to the "Habitats of the IRL" link at the left of this page.


    Special Status


    Economic & Ecological Importance

    Like other species of barnacles, B. eburneus poses an economic threat to several marine-associated industries. Adults and juveniles can attach to ship hulls, creating drag and increasing fuel costs. In addition, intakes of marine-cooled nuclear power plants can become fouled, requiring costly removal. In regions where the ivory barnacle is invasive, B. eburneus can alter food webs and have other devastating impacts on local ecosystems. However, in their native habitat, ivory barnacles and their associated fouling organisms can form extensive fouling communities that provide a home and food source for a variety of coastal fishes and invertebrates.


    Bacon, PR. 1971. The maintenance of a resident population of B. eburneus (Gould) in relation to salinity fluctuation in a Trinidad mangrove swamp. J. Exp. Mar. Biol. Ecol. 6: 187-198.

    Boudreaux, ML, Walters, LJ & D Rittschof. 2009. Interactions between native barnacles, non-native barnacles, and the eastern oyster Crassostrea virginica. Bull. Mar. Sci. 84: 43-57.

    Costlow, JD & CG Bookhout. 1957. Larval development of Balanus eburneus in the laboratory. Biol. Bull. 112: 313-324.

    Dineen, JF, Jr. & AH Hines. 1994. Larval recruitment of the polyhaline barnacle Balanus eburneus (Gould): Cue interactions and comparisons with estuarine congeners. J. Exp. Mar. Biol. Ecol. 179: 223-234.

    Gosner, KL. 1978. A field guide to the Atlantic seashore: Invertebrates and seaweeds of the Atlantic coast from the Bay of Fundy to Cape Hatteras. Houghton Mifflin Co. Boston, MA. USA. 329 pp.

    Henry, DP & PA McLaughlin. 1975. The barnacles of the Balanus amphitrite complex (Cirripedia, Thoracica). Zool. Verh. Leiden. 141: 3-254.

    Hoskin, CM & D Courtney. 1983. Biodeposition by a fouling community in the Indian River, Florida. Estuar. Coast. 6: 243-246.

    Kaplan, EH. 1988. A field guide to southeastern and Caribbean seashores: Cape Hatteras to the Gulf coast, Florida, and the Caribbean. Houghton Mifflin Co. Boston, MA. USA. 425 pp.

    Leibovitz, L & S Koulish. 1989. A viral disease of the ivory barnacle, Balanus eburneus, Gould (Crustacea, Cirripedia). Biol. Bull. 176: 301-307.

    Matsui, T, Shane, G & W Newman. 1964. On Balanus eburneus Gould (Cirripedia, Thoracica) in Hawaii. Crustaceana. 7: 141-145.

    Mook, D. 1976. Studies of fouling invertebrates in the Indian River. Bull. Mar. Sci. 26: 610-615.

    Norris, DR. 1991. Recruitment, growth, and survivorship of Balanus eburneus with respect to settlement, surface, and season. J. Elisha Mitchell Sci. Soc. 107: 123-130.

    O'Connor, NJ & DL Richardson. 1994. Comparative attachment of barnacle cyprids (Balanus amphitrite Darwin, 1854; B. improvisus Darwin, 1854; B. eburneus Gould, 1841) to polystyrene and glass substrata. J. Exp. Mar. Biol. Ecol. 183: 213-225.

    Páez-Osuna, F, Bójorquez-Leyva, H & J Ruelas-Inzunza. 1999. Regional variations of heavy metal concentrations in tissues of barnacles from the subtropical pacific coast of Mexico. Environ. Intern. 25: 647-654.

    Ruppert, EE & RD Barnes. Invertebrate zoology, 6th edition. Saunders College Publishing. Orlando, FL. USA. 1056 pp.

    Ruppert, EE. & RS Fox. 1988. Seashore animals of the Southeast: A guide to common shallow-water invertebrates of the southeastern Atlantic coast. University of SC Press. Columbia, SC. USA. 429 pp.

    Scheltema, RS & IP Williams. 1982. Significance of temperature to larval survival and length of development in Balanus eburneus (Crustacea: Cirripedia). Mar. Ecol. Prog. Ser. 9: 43-49.

    Toonen, RJ. 2005. Foundations of gregariousness in barnacles. J. Exp. Biol. 208: 1773-1774.

    Voss, GL. Seashore life of Florida and the Caribbean. Dover Publications, Inc. Mineola, NY. USA. 199 pp.

    Weis, JS & P Weis. 1992. Construction materials in estuaries: reduction in the epibiotic community on chromate copper arsenate (CCA) treated wood. Mar. Ecol. Prog. Ser. 83: 45-53.

    Zullo, VA. 1979. Marine flora and fauna of the northeastern United States. Arthropoda: Cirripedia. NOAA Tech. Rep. NMFS. Circ. 425. 29 pp.

Report by: LH Sweat, Smithsonian Marine Station at Fort Pierce
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Page last updated: 21 August 2009

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