Mytilus edulis
blue mussel
(Also: edible blue mussel)

Mytilus edulis is found in coastal areas of the northern Atlantic Ocean, including North America, Europe, and the northern Palearctic. They are found from the White Sea in Russia to southern France, throughout the British Isles, with large commercial beds in the Wash, Morecambe Bay, Conway Bay and southwest England, north Wales, and west Scotland. In the west Atlantic, M. edulis occupies the southern Canadian Maritime provinces to North Carolina. (FAO Inland Water Resources and Aquaculture Service (FIRI), 2006)

Mytilus edulis is eurythermal and are able to withstand freezing conditions for several months. Blue mussels are well acclimated to a 5 to 20 °C temperature range, with an upper sustained thermal tolerance limit of about 29 °C for adults. Blue mussels do not thrive in salinities of less than 15%, but can withstand wide environmental fluctuations. Their depth ranges from 5 to 10 meters. Usually, M. edulis is found in subtidal and intertidal beds on rocky shores, and remain permanently attached there. The range of Mytilus edulis is limited by the movement of drifting larval and juvenile stages. (FAO Inland Water Resources and Aquaculture Service (FIRI), 2006; Tyler-Walters and Seed, 2006)

Mytilus edulis is characterized by a smooth inequilateral shell, usually purple, blue, or dark brown, which features concentric growth lines emanating from the hinge. The interior of the shell is pearl-white. Internally the mantle has a whitish/yellow color, with a posterior adductor scar significantly larger than its anterior adductor scar. Extending from the closed shell are fibrous brown byssal threads for attachment to a surface. (Tyler-Walters and Seed, 2006)

After the egg is fertilized it turns into a ciliated trocophore larva. The trochophore larva then becomes a veliger, which persists 1 to 1.5 months. In this phase, the larva bears ciliated fan-like protrusions and filter feeds before becoming a juvenile and finding a primary settlement location. The primary settlement location is often located in openings in the substrata, or amongst bryozoans or other filamentous structures and often situated away from mature mussels, presumably to decrease competition. After weeks there, the juvenile has doubled in size and detaches to drift again and find a permanent substrate to which to attach. The young adult will attach to the sea floor with a byssus thread or, if such open substrate is not stable, may attach to another mussel, creating a mussel bed. (Nordsieck, 2006; Tyler-Walters and Seed, 2006)

The lifespan of Mytilus edulis may vary considerably depending on attachment location. Settline in more exposed coastal areas make individuals significantly more vulnerable to predation, in large part avian. Quality and stability of the substrate also plays a role in the lifespan. Mussels that settle in exposed locations can experience mortality up to 98% per year. Drifting larval and juvenile stages suffer the highest mortality rates. (Nordsieck, 2006; Tyler-Walters and Seed, 2006)

Mytilus edulis is a sessile species, permanently settling on substrates as adults. In loose substrates blue mussels settle together in beds, with younger individuals smothering the older individuals on which they settle. (Nordsieck, 2006; Tyler-Walters and Seed, 2006)

Blue mussels have statocysts to aid in geo-positioning and orientation. Blue mussels have chemoreceptors capable of detecting the release of gametes. These chemoreceptors also help juvenile blue mussels avoid settling temporarily on substrata near mature blue mussle, presumably to decrease competition for food. (Conservation Management Institute, 2001; Nordsieck, 2006; Tyler-Walters and Seed, 2006)

The diet of Mytilus edulis consists of phytoplankton, dinoflagellates, small diatoms, zoospores, flagellates, other protozoans, various unicellular algae, and detritus filtered from the surrounding water. Blue mussels are suspension filter feeders and are considered scavengers, collecting anything in the water column that is small enough to ingest. (Conservation Management Institute, 2001; Tyler-Walters and Seed, 2006)

Blue mussels are most often found in large mussel beds, where they are somewhat protected from predation by virtue of their numbers. The shell of Mytilus edulis acts as a protective layer, though some predator species are able to crush the shell. (Nordsieck, 2006; Tyler-Walters and Seed, 2006)

Some predators of M. edulis wait until the mussel is forced to open its valves to breathe. The predator then pushes the mussel's siphon into the gap, wedging the mussel open so it can be eaten. (Nordsieck, 2006)

Mytilus edulis has a high tolerance for increased sediment levels and help to remove sediments from the water column. Large blue mussel beds provide habitat and prey for other animals and act as a substrate for algal attachment, increasing local diversity. Blue mussel larvae are an important food source for plantivorous animals as well. (FAO Inland Water Resources and Aquaculture Service (FIRI), 2006; Tyler-Walters and Seed, 2006)

There are no known adverse effects of Mytilus edulis on humans.

People harvest blue mussels as food and they are used in commercial aquaculture. Blue mussels are considered an important food source in some coastal areas and the shells are used in jewelry manufacturing. Blue mussels also help limit algae growth, which has become problematic in the Mediterranean Sea and elsewhere. (Conservation Management Institute, 2001; Nordsieck, 2006; Tyler-Walters and Seed, 2006)

Mytilus edulis is fairly common and is abundant in many coastal areas and has therefore not been placed on any conservation list or given any special status.