Pacific barnacle
Balanus glandula
Common name:
Pacific barnacleScientific name:
Balanus glandulaAlternative common names:
Acorn barnacle.
The Pacific barnacle is an acorn barnacle, occurring in the high-mid intertidal zone of rocky coastlines. Here it can be one of the most abundant solitary animals, reaching densities of more than 70 000 individuals per square metre.
Additional Info
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Where does this species come from?
Pacific coast of North America.What is its invasive status in South Africa?
NEMBA Category 3.Where in South Africa is it a problem?
Cape Town in the Western Cape.How does it spread?
Spread via larvae in shipping ballast water or hull-fouling.Why is it a problem?
It invades rocky shores. It out-competes the indigenous African chthamalus species - Chthamalus dentatus - and as a result this species is currently rare on the Atlantic South African shores.What does it look like?
Description: It is a small barnacle, up to 8mm in diameter. The shell is brown-grey in colour and smooth. The operculum (gill cover) is oval. Habitat: Mainly on intertidal rocks, in the open ocean and protected waters. Breeding: Mothers brood eggs, which are released into the water as larvae. These planktonic larvae undergo five moults to become a non-feeding cypris with six pairs of legs. Cyprids attach to a suitable substrate (avoiding potential predators or competitors) and metamorphose into adult form. They reach adult size in about two years.