Barnacles belong to a group of highly specialised crustaceans called the Cirripedia.

Two kinds of barnacles

Many people still assume barnacles are related to molluscs, but inside the interlocking shell plates is an animal similar to an upside down shrimp. While adults are strange in appearance, barnacle eggs hatch into unmistakeably crustacean larvae.

Barnacles mostly feed on suspended particles in the water by opening the top plates of the shell and protruding their feathery legs (cirri) which trap microorganisms from the water flowing past.

While most species live attached to inanimate hard substrates, some attach to other living objects, and can actually be embedded in sponge, sea-fan and coral hosts, and even bury into the flesh of whales and turtles. One extraordinary group, the Rhizocephala, live as internal parasites of crabs 

Seventy-three barnacle species have so far been found in south-eastern Queensland.

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