A mussel is a bivalve shellfish that can be found in lakes, rivers, creeks, intertidal areas, and throughout the ocean. The saltwater mussels (family Mytilidae) and freshwater mussels (family Unionidae) are not thought to be closely related, and are grouped in different subclasses, despite considerable similarities in appearance. Cooked mussels are a popular seafood item.

Characteristics

External anatomy

The mussel’s external shell is composed of two valves that protect it from predators and desiccation. Protruding from a valve is an enlarged structure called the umbo, which indicates the dorsal surface of the mussel.

Feeding

Mussels are filter feeders that feed on microscopic organisms called plankton. They do so by sucking in water through their incurrent siphon. The inhaled water is then brought into the branchial chamber by the actions of the cilia located on the gills for cilliary-mucus feeding. The left over water exits out the excurrent siphon. The labial palps finally funnel the food into the mouth where digestion can continue.

One species, the European zebra mussel (Dreissena polymorpha), is causing a serious problem in North America. From its first discovery in American waters in 1988 it has spread to a large number of waterways disrupting the ecosystem, displacing the local unoinoida mussels and damaging harbours, boats, power plants etc.

Freshwater mussels are used as the host animal for the cultivation of freshwater pearls. A species of marine mussel, the Blue Mussel (Mytilus edulis), is also cultivated as a source of food.

Protection

Mussels are usually found clumping together with one another to hold in water. Those mussels found in the middle will have less water loss, due to water capture by the clump.

Growing mussels

There are a variety of techniques for growing mussels.

• Intertidal growth technique, or bouchot technique: pilings, known in French as bouchots, are planted at sea; ropes, on which the mussels grow, are tied in a spiral are the pilings; some mesh netting prevents the mussels from falling away. This method needs an extended tidal zone.

Mussels as edibles

Mussels can be prepared boiled or steamed. As for all shellfish, mussels should be alive just before they are cooked. A simple criterion is that live mussels, when in the air, are tightly shut; open mussels are dead and should be discarded. Mussels open by themselves when cooked.