Semibalanus cariosus (thatched barnacle)

Found all over the mussel beds.

Thomas Huxley described barnacles as rude fellows who stand on their heads and kick food into their mouths with their heels. That picture is a bit unfair. Barnacles are graceful and have a very clever means of protection. Most people think of barnacles as white encrustations on surfaces. Barnacles go through various states. When first released they are free swimmers. Then they find a location and settle down. They molt (shed their enclosures) a few times until they reach adulthood. Finding the free swimming molted barnacle provides a vision of water ballet. While intent on observing a green shrimp, two free swimming barnacles were discovered in the water. The cirripeda (feet) propel the barnacle backwards through the water in a similar fashion to the movement of jellyfish. Below is a picture of the two free swimmers. I don’t know which species of barnacles these were.

Semibalanus cariosus is a fascinating barnacle. These thatched barnacles are numerous on rocks and shells on the beach. They are large and have layers of what look like grass skirts. Size is an advantage to these barnacles. Once the shell exceeds the size of acorn barnacles they are fairly free from attack by snails and starfish. If you pop this barnacle off the surface where it is attached, jelly-like tissue will be found on the rock. You need to leave them planted where they are.