"Ivory barnacle American acorn barnacle"

Type Description

The ivory barnacle is a medium-sized, cone-shaped sessile barnacle with a white test composed of fused plates. It has a diamond-shaped operculum protected by a hinged lid formed from two triangular halves each consisting of two plates, a tergum and a scutum. It can grow to a height of 2.5 cm (0.98 in) but most individuals are much smaller. This barnacle can be confused with the white bay barnacle (Balanus improvisus) but that species is smaller, only growing to a height of 6 mm (0.24 in). Another similar species is the striped barnacle (Balanus amphitrite) but that has vertical pink lines on the test.

Habitat

The native range of the ivory barnacle extends from Nova Scotia to the Caribbean Sea and Gulf of Mexico but it has extended this range as a result of fouling the bottoms of ships and because its larvae are sometimes transported in ballast water. It was first seen in Pearl Harbor, Hawaii in 1929 and is now common in all the main islands. It is found, sometimes in great numbers, from low tide mark to depths of 37 m (121 ft) attached to hard surfaces including rocks, mollusc shells, pilings, jetties and other man-made structures, ships' hulls and the roots of the red mangrove (Rhizophora mangle).

Reproductive Information

Lifecycle

Ivory barnacles tend to aggregate with others and form dense populations. Each one is a hermaphrodite but cross fertilisation takes place when an individual protrudes its long penis and inserts it into the operculum of an adjoining individual where eggs have already developed. Sperm is deposited there, and the fertilised eggs are brooded in the mantle cavity. On hatching, the larvae are expelled into the water column and become planktonic. They pass through six naupliar stages and one cyprid stage over the course of one to two weeks. The nauplii feed on phytoplankton but the cyprid larvae do not feed. They search out sites for settlement, possibly following chemical cues from already established adults or testing the substrate for suitability. Once settled, they cement themselves by their heads to the surface and undergo metamorphosis into juvenile barnacles.

Nutrition Information

Phytoplankton

General Impact Information

"Economic Impacts

We have not found specific reports of economic impacts for Amphibalanus eburneus. However, A. eburneus is an abundant fouling species in its native range on the East and Gulf Coasts of the U.S. (Visscher 1927; Moore and Frue 1959; Utinomi 1970; Relini and Matricardi 1999; Kocak and Kucuksezgin 2001) and it can be a major contributor to growth/biofouling on the surfaces of ships and harbor structures. It is also a common fouling organism in oyster beds, and a potential competitor with oysters for space and food (White and Wilson 1996). Hull fouling by barnacles and other organisms has costly impacts for shipping lines by increasing fuel costs, decreasing maneuverability, and clogging internal seawater piping (Visscher 1927; Haderlie 1984). Barnacles also greatly contribute to fouling of navigational buoys and coastal power station intakes (Haderlie 1984).

Ecological Impacts

In its native waters on the Atlantic and Gulf coasts, A. eburneus is considered a potential fouling organism and competitor of the Eastern Oyster (Crassostrea virginica) (White and Wilson 1996). In the southern Caspian Sea, a mass population boom of A. eburneus is reported to have adversely affected molluscs and hydroids, due to competition for space and planktonic food (Zaitsev and Ozturk 2001)."

General Management Information

General Pathway Information

Notes

References