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
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.
HABITAT AND DISTRIBUTION
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.
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
LIFE HISTORY AND POPULATION BIOLOGY
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).
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).
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.
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).
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