Mussel with community of organisms on its shell
Bay Mussel; on shell: Scallop and Dwarf Calcareous Tube Worm and Moss Animal
Mytilus trossulus; Chlamys sp. and Subfamily Spirobinae and Phylum Bryozoa
Friday Harbor Marine Laboratories, University of Washington
San Juan Island, Washington
Archival Pigment Print
Like coral reefs in the tropics, intertidal mussel beds on temperate shores harbor diverse communities. Hundreds of species have been recorded from beds along the North American west coast. The mussels in a bed can be layers thick, their shells providing vast areas of hard surface for other animals to occupy, as well as a variety of microhabitats between and beneath them. On this bay mussel, we see tiny worms that live in coiled tubes and even tinier moss animals that form encrusting colonies; both live cemented to the mussel shell and extend crowns of tentacles (pink in the worms, microscopic in the moss animals) to capture plankton. The juvenile scallop is temporarily anchored to the mussel; it can swim away.