The Blue Mussel (Mytilus edulis)

Not all muscles are mussels....there are more than just muscles on the local beaches. Mussels, everyone knows what they are, but have you ever really thought about the tenacity of these animals as you walk across them when the tide is out?

The Mussels are in the Phylum Mollusca (the molluscs), Class Bivalvia (the Bivalves), Subclass Pteridomorphia, Family Mytilidae. From an ecological perspective, they are sometimes referred to as living surface dwellers. They attach to their chosen substrate by byssal threads, these are tough protein threads that the mussel secreted by its foot They have a groove that runs from a deep byssus gland to the anterior tip of the foot and the byssus is formed by a mixture of secretions produced by several glands along the length of the groove. The mussel flexes the foot outwards to the substrate and pushes the byssus secretion out along the groove until it touches the surface of whatever it wants to attach to. It retracts the foot and the sticky thread hardens quickly, leaving the mussel firmly anchored to the substrate. The mussel has a byssus retractor muscle that it can use to pull against the anchorage.

The mussels are widely distributed and can be found in great numbers on wharf pilings, rocky shores, and of course....on the bottom of your boat! If you are a seafood addict, you think of Prince Edward Island when you think of mussels. Sweet, tender PEI mussels are a staple on the menu of any decent seafood restaurant. PEI mussels are cultured on long lines in the maritimes (PEI mostly...who woulda thunk?). We have a couple of species of mussels around our area. While there are many common intertidal and some less common subtidal mussels on the Pacific coast, the two main ones you will come across, depending on where you are, are the California mussel and the Pacific blue mussel.

The Pacific blue mussel (more appropriately known as Mytilus edulis) is that common pest that you are scraping off the bottom of your boat every year. It is also the one that you will commonly find on local sheltered shores at low tide. Not as sweet as the PEI mussel, these are still edible....as long as you are careful about where you harvest them of course. They are generally small, but can reach up to 6 inches (15 cm) and range from the Arctic to Mexico. While they are generally blue to black in colour, they can also be shades of reddish brown to brown. The blue mussel in our region of the world lives for about 2 years.

The California mussel (Mytilus californiensis) is quite easily distinguished from the blue mussel. They grow to 10 inches (25 cm) and have a thicker shell that has strong radial ribs. The inside of the shells are blue-grey with an iridescent edge and the meat is bright orange. Native populations once used these for food. They are found in more exposed areas than the littler blue mussel and form dense mats on surf exposed rocks, pilings, and wharves. They are found from Alaska to Baja.

Mussels are an important food source for so many creatures. Those massive flocks of scoters that swoop across the sea will fly in and decimate populations of mussels at low tide. It helps fuel them for their migrations. When the tide rolls back in they aren't safe though. Small fish, like tidepool sculpins thrive on mussels that have been damaged by wave action or hungry birds. They swoop in and pick off all the scraps. Want to make friends with fish in tidepools? Grab a couple of mussels and break them open and drop them into the pool and watch the feast begin!

Blue mussels live in intertidal areas attached to rocks and other hard substrates by those strong (and somewhat elastic) thread-like byssal threads. But unlike thread, these things are tough! When they are secreted, it only takes about one minute for the viscous substance to harden into a tether that enables the mussel to anchor to rocks and pilings in turbulent areas where food and oxygen are more abundant. Just grab a handful of the things and try and pry them off. For something so small they sure have a grip on the rocks (and the bottom of your boat) don't they!

In fact, this stuff is so darned tough that when the U.S. military was looking for a strong waterproof adhesive, scientists at a Department of Energy laboratory in Idaho went straight to the experts -- mussels - I mean really, think about it, they've been clinging to rocks in pounding seas for millennia! The "feet" of the small shellfish produce an epoxy with adhesive-like properties that rivals any "super" glue on the market. Unfortunately, it takes about 10,000 mussels to produce just one gram of adhesive, resulting in a prohibitive cost, not only in dollars but to the mussel population as well.

Blue mussels are highly prized and very successfully cultured species and are an important commercial commodity. They are cultured on long lines hanging above the sea floor to ensure that they get the best possible water flow and pick up lots of natural food before they are harvested.

Another cool fact? How about this! In the summer, these animals are submerged for part of the day and exposed for part. So? Well, think about it for a moment, in the heat of the summer, these aquatic animals are exposed to temperatures in excess of 30 degrees C...they're literally stewing in their own juices! How do they survive? Literally by the threads that hold them on the rocks. They actually gasp for air! You know how you can hear those odd noises when you walk down near the rocks at low tide? That's the sound of mussels opening and closing their shells to cool themselves off!

Last growth spurt on February 12, 2008