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Order SESSILIA
Amphibalanus improvisus - Bay Barnacle
Morphology: Characterized by 6 smooth shell plates surrounding the body; diamond-shaped center; calcareous base with radial pattern that remains on the substrate after the animal is removed. Usually less than 10 mm in diameter, but can reach 20 mm.Distribution: Worldwide - considered non-native or invasive in the Baltic, Black, and Caspian Seas; the west coast of the US; and Japan.Habitat: Attaches to any hard substrate in coastal and estuarine waters. Highly euryhaline and eurythermal.Life History: Filter-feeding, cross-fertilizing hermaphrodites. Exhibit rapid growth - newly metamorphosed young may grow up to 5 mm in 3 weeks.Reference and picture: NOBANIS - European Network on Invasive Alien Species
Balanus amphitrite - Striped Barnacle
Morphology: Medium-sized barnacle. Purple stripes run vertically on calcareous plates. Conical in shape, with diamond-shaped opening. Reaches maximum basal length of 20 mm.Distribution: Found worldwide, although native habitat probably in Indian Ocean or southwestern Pacific Ocean.Habitat: Coastal and estuarine intertidal habitats. Attaches to hard substrates.Life History: Filter-feeder. Hermaphroditic. Worldwide invasive species, believed to have been spread through ships.Reference: Smithsonian Marine Station at Ft. Pierce; Gosner plate 18.
Balanus eburneu - Ivory Barnacle
Morphology: Small, white, conical with longitudinal stripes. Up to 2 cm in diameter; test plates are smooth; the tergum has a short broad spur and rounded tip.
Distribution: From Maine to South America, and Atlantic Europe.
Habitat: Low intertidal zone as well as on ship hulls, buoys, and oyster reefs. They range from the low tide line to 37m deep with a large temperature tolerance and salinities anywhere from 5-30 ppt.
Life History: Filter feeders use cirri as a scoop net that is then scraped in the mouth. Hermaphrodites with cross-fertilization. planktonic larvae settle 7-13 days and undergo metamorphosis.
Reference: Smithsonian Marine Station at Ft. Pierce
Chthamalus fragilis - Little Gray Barnacle
Morphology: Dark colored shell with no calcarious base. The opercular plates fill the dorsal surface and the end plates of the shell are overlapped by adjacent lateral plates. Both the scutum and tergum are clearly visible.
Distribution: Texas to Cape Cod and Caribbean.
Habitat: Most common barnacle species of the US Atlantic coast. Most desiccation tolerant of barnacle species in its range, so it is usually found in the upper intertidal zone on hard surfaces (rocks, walls, pilings, marsh grass, other animals, etc.).
Life History: Suspension feed, mostly on plankton and detritus. Each individual is hermaphroditic, but they cannot self fertilize. Spawning by internal fertilization occurs in the mid to late spring. Free swimming larvae are released into the water column and soon settle on a hard substrate.
Reference: Seashore Animals of the Southeast, Chesapeake Bay Program
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