Editing Mussel (section)

{{Short description|Type of bivalve mollusc}}
{{Paraphyletic group
| auto = yes
| image = CornishMussels.JPG
| image_caption = A bed of blue mussels, ''[[Mytilus edulis]]'', in the [[intertidal zone]] in [[Cornwall]], England
| parent = Bivalvia
| includes_text = Subclasses
| includes = 
[[Pteriomorphia]] (marine mussels)<br/>
[[Palaeoheterodonta]] (freshwater mussels)<br/>
[[Heterodonta]] ([[zebra mussel]]s)
}}

'''Mussel''' ({{IPAc-en|ˈ|m|ʌ|s|ə|l}}) is the [[common name]] used for members of several families of [[bivalve]] [[mollusc]]s, from saltwater and [[Freshwater bivalve|freshwater]] habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.

The word "mussel" is frequently used to mean the bivalves of the marine family [[Mytilidae]], most of which live on exposed shores in the intertidal zone, attached by means of their strong [[Byssus|byssal threads]] ("beard") to a firm substrate.<ref name=":0">{{Cite encyclopedia |entry-url=https://www.britannica.com/animal/mussel |entry=Mussel |date=22 May 2009 |encyclopedia=Encyclopædia Britannica}}</ref> A few species (in the genus ''[[Bathymodiolus]]'') have colonised [[hydrothermal vent]]s associated with deep ocean ridges.

In most marine mussels the shell is longer than it is wide, being wedge-shaped or asymmetrical. The external colour of the shell is often dark blue, blackish, or brown, while the interior is silvery and somewhat [[nacre]]ous.

The common name "mussel" is also used for many freshwater bivalves, including the [[freshwater pearl mussel]]s. Freshwater mussel species inhabit lakes, ponds, rivers, creeks, canals, and they are classified in a different [[Subclass (biology)|subclass]] of bivalves, despite some very superficial similarities in appearance.

Freshwater [[zebra mussels]] and their relatives in the family [[Dreissenidae]] are not related to previously mentioned groups, even though they resemble many ''Mytilus'' species in shape, and live attached to rocks and other hard surfaces in a similar manner, using a byssus. They are classified with the [[Heterodonta]], the taxonomic group which includes most of the bivalves commonly referred to as "clams".