Mussel

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{{Taxobox | color = pink | name = Mussel | image = Mussels.jpeg | image_width = 240px | image_caption = Mussels | regnum = Animalia | phylum = Mollusca | classis = Bivalvia | subdivision_ranks = Subclasses | subdivision = Heterodonta
Palaeoheterodonta }}

A mussel is a bivalve mollusk 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.

1 Characteristics
2 Cultivation
3 Mussels as food
4 See also
5 External links and references

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Characteristics

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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.

Like most bivalves, mussels have a large organ referred to as a foot, which is tongue-like in shape with a groove on the ventral surface, which is continuous with the byssus pit. In this pit a viscous secretion is poured out which enters the groove and hardens gradually when it comes into contact with sea water. This forms an extremely tough byssus thread that secures the mussel to its substrate.

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Feeding

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

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

Living mussels are a favored source of food for muskrats, otters, raccoons and other mammals.

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Reproduction

Mussels reproduce sexually or asexually. Sperm released by the male directly into the water enters the female via the incurrent siphon. After fertilization, the eggs develop into the larval stage called glochidia. The glochidia grow in the gills of the female where they are constantly flushed with oxygen-rich water. For a time, these glochidia are parasitic on fish, attaching themselves to the fish's fins or gills. They grow and then break free from the host and drop to the bottom of the water. If they land in a place that suits their needs, they will continue their development and begin their independent life.

Mussel glochidia are generally species-specific and will only live if they find the correct host.

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Distribution

Marine mussels are abundant in the low and mid intertidal zone in temperate seas of the northern and southern hemispheres. Within their geographic range, some species prefer salt marshes or quiet bays, while others thrive in pounding surf, completely covering exposed wave-washed rocks. In addition, some species have colonized abyssal depths in the vicinity of hydrothermal vents. Freshwater mussels inhabit permanent lakes, rivers and streams throught the world in all but polar regions. They require a constant source of water and are more abundant if it is non-acidic and has a substantial mineral content.

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Cultivation

Image:Bouchots DSC04101.jpg

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

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 on the pilings; some mesh netting prevents the mussels from falling away. This method needs an extended tidal zone.

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Mussels as food

Cooked mussels are a popular seafood item.

Image:Cooked mussels DSC09244.JPG

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. The mussel shells open by themselves when cooked.

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