ANATOMY OF UNIONID MUSSELS

These illustrations are from the booklet
"A Pocket Guide to Kansas Freshwater Mussels".
They are reproduced here with the kind permission of the artist, Karen Couch.

Parts of a mussel shell

External anatomy of a mussel shell

Fluting – repeated ridges and valleys alternately arranged
Hinge – the edge of the shell where the two valves are physically connected
Lateral teeth – the elongate, interlocking ridges on the hinge line of each valve
Mantle – the fleshy tissue that is attached to the nacre and envelops a mussel’s soft parts
Nacre – the pearly interior of a mussel shell that may vary in color
Pallial line – the indented groove on the inner shell surface, roughly parallel to the ventral edge, that marks where the mantle was formerly attached
Periostracum – the outermost external layer of a shell
Pseudocardinal teeth – the interlocking tooth-like structures located near the umbo
Pustule – a small bump or knob
Rays – a solid or broken stripe on the periostracum that usually radiates from the umbo
Sculpture – raised portions on the shell exterior that form lines, ridges or pustules
Sulcus – a narrow shallow shell depression extending from umbo to ventral margin
Umbo – the area of the shell first to form (sometimes called the beak)
Valve – one of the halves of a shell
Wing – a thin posterior extension of the shell most notable on heelsplitters

Internal anatomy of a mussel shell

Internal anatomy

Soft anatomy of a mussel

This simplified illustration shows the arrangement of the soft tissue body parts of a freshwater mussel. The adductor muscles function to close the two halves of the shell. The mantle surrounds the visceral mass and covers the interior surface of the shell. The mantle also manufactures the shell itself, which is mostly composed of calcium carbonate. Water enters the mantle cavity through the incurrent siphon. Mucus secreted by the gills traps food which moves to the palps, is passed to the mouth and is digested in the stomach. The intestines continue to the anus, where waste is carried out the excurrent siphon. Water circulation also provides oxygen exchange in the gill tubes and on the gill’s outer surface. Mussels have two pairs of gills; one pair rests in each shell valve. Other organs of the mussel include the hepatopancreas, gonad, kidney and a 2-chambered heart. The nervous system consists of ganglia. The foot extends from between the two shell halves and is used for movement and to anchor the animal in the substrate.

Go back to the Mussel Bed!

Mussel Bed
Text: Ed Miller, Karen Couch and Jim Mason
Range Maps & Web Design: Jim Mason
Questions or comments?  Send Email to Jim Mason Spidey
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Great Plains Nature Center
6232 E. 29th Street North
Wichita, KS 67220-2200             Call:  316-683-5499            Fax:  316-688-9555