Northern Rock Barnacle - Semibalanus balanoides
Barnacles are sessile filter feeders. The use feathery, thoracic appendages, called cirri, to capture plankton and detritus from the water column.
When there is a current, the barnacles hold their cirri stiffly into the flow. But, when there is no current, the barnacles pulse their cirri rhythmically, in and out of their shell. Their cirri are also used as gills to extract oxygen from the water.
Habitat: Encrusted on rocks and starting to feed again as the tide was starting to come back in.
''Semibalanus balanoides'' is a common and widespread boreo-arctic species of acorn barnacle. It is common on rocks and other substrates in the intertidal zone of north-western Europe and both coasts of North America.