ENCRUSTING ANIMALS cover a lot of the pilings and floats in the bay. They come in many sizes and shapes, and represent many completely different kinds of animals! The barnacles are crustaceans like the crabs and shrimp, but they attach themselves to rocks and pilings when they are small and never leave. Others are soft-bodied, like the tunicates or “sea squirts,” which have a simple central nervous system and are very distant ancestors of fish, birds, mammals, and people!
Acorn barnacle
Balanus glandula
Round shells composed of several plates
Plates are smooth and folded at the seams
Look for a large, feathery foot that kicks!
Individuals rarely more than a half-inch wide
Forms large colonies
Red sea squirt 
Cnemidocarpa finmarkiensis
Bulbous with smooth, shiny red to orange skin
Look for two distinct siphons or “chimneys”
Usually solitary and small (up to 2 inches)
Club tunicate 
Styela clava
Thick, leathery brown and warty, on a narrow stalk
Look for two distinct yellowish siphons
Solitary or in small groups, up to 2 inches
This sea squirt is an invasive species!
Friday Harbor Marine Health Observatory 