The Remarkable Existence of Mussels
Mike Kozuch. [November, 2015]
Many of us have seen mussels on the beach as clusters of dark shells attached to rocks in the intertidal zone. These seemingly nondescript creatures are a remarkable example of how animals can adapt to a very distinct and harsh marine environments.
Cluster of mussels in the intertidal zone. (Photo M Kozuch).
Mussels are not only found in intertidal zones where they have to deal with surviving exposure to air associated with low tides, but you may find them in the extreme environment of hydrothermal vent systems. Some species are also found in freshwater lakes where their numbers can grow to be a nuisance.
Mussels are a type of Mollusc, a phylum of the Animal (or Metazoa) Kingdom. Within the molluscs are the Bivalve class. It is in this class of bivalves that we find our mussels.
Mussels are soft-bodied but have an outer shell to protect them. The shell halves are held together by a tough muscle that adheres to the inside surface of the shells. In some species the interior of the shells may have a slight mother-of-pearl iridescence.
The feeding of mussels is somewhat peculiar in that they use a siphon to draw water into their shell. Little hairs (called cilia) located on their gills move the water around and any trapped plankton particles are drawn into their mouth.
Bilateral symmetry is a feature of mussel bivalves as well as the mother-of-pearl appearance on the inside of the shell. (Photo M Kozuch)
Taxonomists refer to bivalves as having bilateral symmetry where the shells are mirror opposites of one another. If one opens the shells at the hinge, the bilateral symmetry is apparent. (see image).
Culinary Delicacy
Mussels are a food fit for human consumption and are most often steamed until they open. They can be served with a dipping sauce with melted butter, garlic or lemon.
Mussels also provide a good source of nutrients such as selenium and vitamin B12 as well as zinc and folate.
Like most shellfish, mussels should be avoided during red tides since these organisms can actually concentrate the toxic effects of a particular kind of plankton called dinoflagellates.
Some species of mussels have a remarkable adaptability to both air and ocean environments and you will find muscles attached to rocks at the low tide mark on coastal areas. By retreating into their shell they do not dry out at low tide when they are exposed to air. Huddling in clusters helps them preserve water as well.
One of the remarkable features of mussels are the very strong fibers or “beard” that is actually a cluster of byssal threads that they use to attach to rocks or a solid surface.
Closeup of the byssal threads that enable mussels to adhere to rocky surfaces. (Photo M Kozuch)
The sheer strength of the glue and fibrous hairs that mussels use to adhere onto a surface has caught the interest of researchers that are exploring how the sticking properties can be used in various industrial and surgical applications such as medical adhesives.
Mussels aren’t always attached to rocks, however. Using their foot they are able to move around on the ocean floor until they find a site that is suitable for anchoring.
Like many other seemingly simple creatures that blend into the background, mussels make you wonder how many other animals there are with similarly remarkable properties or abilities.
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