Barnacles

There are about 100 species of barnacle from more than 50 genera living on the Great Barrier Reef.

Barnacles are marine and estuarine crustaceans. Not all crustaceans move around. Once a barnacle has found space to live, it stays put. Pushing its legs out through a central hole in its cone-shaped shell, it spends its life lying on its back kicking food into its mouth.

The two largest groups of barnacles found in the reef, goose barnacles and acorn barnacles.

Goose barnacles / Lepas anserifera / Subclass Cirripedia

Barnacle physiology

Goose barnacles have a distinct stalk connecting the body to the substrate. The plates surrounding the body are white in colour, with spaces between the valves a dull orange-brown, purple-brown or yellow grey. The edge may be scarlet, bright orange or lemon-yellow.

Acorn barnacles do not have a stalk and they attach themselves directly to hard surfaces. Acorn barnacles are greyish to white inn colour. Most acorn barnacles can be seen on rocks in open coastal areas. This species is never found in estuarine conditions or on wood.

Habitat

Barnacles live on hard surfaces including rocks, boat hulls, jetty piles, and other crustaceans and even hitch a rides on turtles and whales.

Reproduction

Barnacles are both male and female. Cross-fertilisation is via the long penis on one individual. This individual acts a the male to another which acts as a female.

Feeding

Barnacles feed with its cirri, modified feathery legs used to sweep the water like sieves, collecting particles of food, especially plankton.