above shows a preserved, dissected freshwater mussel. Note the conspicuous fold
of tissue called the mantle (1). In molluscs the mantle is a sheath of skin that
hangs down in two folds around the soft body and encloses a mantle cavity, which
performs many of the same functions as a coelom in other animals. The outer side
of the mantle secretes the shell while the inner side is ciliated, and along
with gills (2), participates in gas exchange.
prominent anterior adductor muscle (3) and posterior adductor muscle (4) that
draw the two valves together to enclose and protect the animal from predators.
The lateral hinge teeth (5) that help the valves to securely interlock can also
be seen in this image. Observe the heart (6), which is contained within
the pericardial cavity (7) located in a dorsal position just below the lateral
hinge teeth (5). In molluscs, this cavity represents the remains of a
much-reduced coelom. Note the conspicuous, hatchet-shaped foot (8) that is used
for burrowing. In the image shown, a portion of the foot has been removed to
reveal the greenish digestive gland (9) and gonad (10).