Pear-shaped, these bivalves typically attach to the surfaces of surf-beaten rocks. A strong byssus near the hinge fastens the mussel to rock, where the surf brings ample oxygen and food. However numerous genera have adapted to other habitats, including sand burrows. Many genera in this family have continued down from the Paleozoic era essentially unchanged. Two major groupings within this family are the Modiolus and Mytilis genera. Looked at on-edge, both genera are distinguished by a beak; near the hinge for Mytilis. The beak is somewhat distant from the hinge for Modiolus.
A principal food worldwide, mussels aggregate in large colonies. They are periodically rendered poisonous by the "red tide"
i.e., microscopic one-celled protozoans that bloom during warm temperature regimes. The dinoflagellates are filtered out into the mussel's gill cavities, by which people who later eat the mussel can be poisoned. The poison is not destroyed by cooking. Mussel colonies are usually preyed upon by starfish (an echinoderm, not a mollusk) and by
gastropods in the
typically attach to small stones with mutliple byssus threads, while
bury in peat or coarse sediments also using byssus threads.
Falcate Swamp Mussel