Barnacle: Difference between revisions

The outermost layer of a barnacle is its shell.  The shell of the adult barnacle is usually composed of four to eight Calcereous plates which form a shape that resembles a triangle with a hole at the top.[http://www.mesa.edu.au/friends/seashores/barnacles.html] This hole is also covered by two calcereous plates which can pull back to reveal six thoracic legs.[http://museumvictoria.com.au/crust/barnbiol.html]  These plates will grow and expand by adding more material to itself.

These legs are used for filter feeding and are the main source of response in class cirripedia.  The legs are extended into the water by the barnacle in order to catch whatever food it can.[http://www.cb1.com/~john/research/barnacle.html] The legs are then retracted and whatever particles the legs have caught are brought to the mouth.  The particles enter the stomach after passing through the esophagus and then flow to the small intestine.  After the nutrients have been absorbed the waste is filtered out the penis and back into the ocean.[http://webs.lander.edu/rsfox/invertebrates/balanus.html]