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Semibalanus balanoides    


Cirripedia: Barnacles

Semibalanus balanoides

Barnacles are marine sessile or parasitic crustaceans many of which are encrusting on hard substrates primarily in shallow intertidal waters. They range in side from a few millimeters to more than 10 cm.

Their morphology is highly modified relative to other crustaceans in that the free-living barnacles live inside a six-plate shell and suspension-feed with modified legs. Eggs hatch into a mobile planktonic nauplius similar to other crustaceans, then pass through a non-feeding "cyrid" stage that looks for a suitabel place to settle. They attach to the substratum by cement glands in their antennae, meaning the adult barnacles are fixed to the substrate with their ‘foreheads’ and kick food toward their mouth with their legs.

They are often exposed to desiccation by tides, thus have plates that tightly close off their aperture. There are 2 major body-forms, the one shown above and the goose-neck "stocked" form where a more laterally compressed body is on the end of a semi-flexible peduncle or "stem"

Worldwide, about 1220 species are currently known with only 13 species known from the Arctic.

Page Author: Bodil Bluhm
Created: September 20, 2010

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