- 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" dinoflagellates; 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 Thais gastropods in the Murex family.
The genera, Pinna and Atrina typically attach to small stones with
mutliple byssus threads, while Modiolus and Geukensia bury in peat or coarse
sediments also using byssus threads.
Mytilus californianus (Conrad, 1837)
Mytella falcata (Orbigny, 1846)
Falcate Swamp Mussel